Order Iniomi (Myctophiformes): Part 7 9781933789309

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Fishes of the \\festern North Atlantic

PUBLICATIONS OF THE SEARS FOUNDATION FOR MARINE RESEARCH, YALE UNIVERSITY The Sears Foundation for Marine Research at Yale University was established in 1937 by Albert E. Parr/ director of Yale's Bingharn Oceanographic Laboratory/ through a gift from Henry Sears/ to promote research and publication in marine sciences. The Foundation's Memoirs/ inaugurated in 1948/ remain important references. In 1959 the Bingharn Oceanographic Collection was incorporated into the Yale Peabody Museum of Natural History. Distributed by Yale University Press www.yalebooks.com I yalebooks.co.uk MEMOIR I FISHES OF THE WESTERN NORTH ATLANTIC Part One Lancelets/ Cyclostomes/ Sharks Part Two Sawfishes/ Guitarfishes, Skates and Rays/ Chimaeroids Part Three Soft-rayed Bony Fishes: Orders Acipenseroidei/ Lepisostei/ and Isospondyli Sturgeons/ Gars/ Tarpon/ Ladyfish/ Bonefish/ Salmon/ Charrs/ Anchovies/ Herring/ Shads/ Smelt/ Capelin/ et al. Part Four Soft-rayed Bony Fishes: Orders Isospondyli and Giganturoidei Argent ino ids/ Stomiatoids/ Pickerels/ Bathylaconids/ Gig ant ur ids Part Five Orders Iniomi and Lyomeri Lizardfishes/ Other Iniomi/ Deepsea Gulpers Part Six Orders Heteromi (Notacanthiformes)/ Berycomorphi (Beryciformes)/ Xenoberyces (Stephanoberyciformes)/ Anacanthini (Gadiformes) Halosauriforms/ Killifishes/ SquirreIrishes and Other Beiyciforms/ Stephanobeiyciforms/ Grenadiers Part Seven Order Iniomi (Myctophiformes) Neoscopelids/ Lanternfishes/ and Atlantic Mesopelagic Zoogeography Part Eight Order Gasterosteiformes Pipefishes and Seahorses Part Nine/ Volume One Orders Anguilliformes and Saccopharyngiformes Part Nine/ Volume Two Leptocephali Part Ten Order Beloniformes Needlefishes/ Sauries/ Halfbeaks/ and Flyingfishes MEMOIR II THE ELEMENTARY CHEMICAL COMPOSITION OF MARINE ORGANISMS by A. P. Vinogradov

MEMOIR SEARS FOUNDATION FOR MARINE RESEARCH Number I

Fishes of the Western North Atlantic

PART SEVEN

Order Iniomi (Myctophiformes) NEOSCOPELIDAE AND MYCTOPHIDAE and ATLANTIC MESOPELAGIC ZOOGEOGRAPHY

NEW HAVEN SEARS FOUNDATION FOR MARINE RESEARCH, YALE UNIVERSITY

Yale ISBN 978-1-933789-17-0 (pbk.) ISBN 978-1-933789-30-9 (e-book) Issued in paperback by the Peabody Museum of Natural History, Yale University, New Haven, Connecticut 06511 USA Part Seven first published in hardcover in 1977 by the Sears Foundation for Marine Research, Yale University ISBN 978-0-912532-88-2 (cloth) Library of Congress Control Number: 49000120 Distributed by Yale University Press NEW HAVEN AND LONDON Printed in the United States of America Printed on acid-free paper

Fishes of the Western North Atlantic

Authors BASIL G. NAFPAKTITIS University of Southern California

RICHARD H. BACKUS JAMES E. CRADDOCK RICHARD L. HAEDRICH BRUCE H. ROBISON Woods Hole Oceanographic Institution

CHARLES

KARNELLA

Smithsonian Institution

NEW HAVEN SEARS FOUNDATION FOR MARINE RESEARCH, YALE UNIVERSITY

Editorial Board Editor-in-Chief

ROBERT H. GIBBS, JR. Smithsonian Institution, Washington, D. C.

WILLIAM N. ESCHMEYER

FREDERICK H. BERRY

California Academy of Sciences San Francisco, California

National Marine Fisheries Service Miami, Florida

GILES W. MEAD

JAMES E. BOHLKE

Academy of Natural Sciences Philadelphia, Pennsylvania

Los Angeles County Museum Los Angeles, CaUfomia

DANIEL MERRIMAN

DANIEL M. COHEN

Sears Foundation for Marine Research New Haven, Connecticut

National Marine Fisheries Service Washington, D. C.

THEODORE W. PIETSCH

BRUCE B. COLLETTE

National Marine Fisheries Service Washington, D. C.

California State University Long Beach, California

Editor Emeritus ALBERT E. PARR Hamden, Connecticut VI

Table of Contents INTRODUCTION

xiii

Family Neoscopelidae. By BASIL G. NAFPAKTITIS General Characters Dentition Skeletal Characters Luminous Organs Swimbladder Development Diversity and Range Remarks Key to the Genera of Neoscopelidae Genus Scopelengys S. tristis Genus Neoscopelus N. macrolepidotus N. microchir N. porosus Literature Cited Family Myctophidae. By BASIL G. NAFPAKTITIS, RICHARD H. BACKUS, JAMES E. CRADDOCK, RICHARD L. HAEDRICH, BRUCE H. ROBISON, and CHARLES KARNELLA General Characters Dentition Skeletal Characters Luminous Organs and Sexual Dimorphism Swimbladder Vertical Distribution and Migrations Food Diversity and Range Commercial Value Systematics North Atlantic Genera and Species Terminology and Methods vii

1 1 1 1 1 2 2 2 3 4 4 4 6 6 9 11 11

13 14 14 15 15 18 18 21 21 21 22 23 24

viii

Table of Contents Key to the North Atlantic and Mediterranean Genera Genus Protomyctophum Subgenus Protomyctophum Subgenus Hierops Protomyctophum arcticum Genus Electrona E. risso Genus Hygophum Key to the North Atlantic Species of Hygophum H. benoiti H. reinhardtii H. hygomii H. macroctnr H. taaningi Genus Benthosema Key to the North Atlantic Species of Benthosema B. glaciate B. suborbitale Genus Dhgenichthys Key to the Species of Diogenichthys D. atlanticus Genus Myctophum Key to the North Atlantic Species of Myctophum M. punctatum

Genus Genus Genus Genus Genus Genus

26 29 29 29 30 33 34 35 36 36 39 42 44 47 49 50 50 53 56 56 56 59 60 60

M. 0j0m?

62

M. nitidulum M. asperum M. obtusirostre M. selenops Symbolophorus S. veranyi S. rufinus L&weina L. rora L. interrupta Gonichthys G. rorro Centrobranchus C. nigroocellatus Notolychnus N. valdiviae Lobianchia

65 6g 70 72 7j 7g 7g

gj 81

gj «x gx g^ QQ

91 92 g.

Table of Contents Key to the North Atlantic Species of Lobianchia L. dofleini L. gemellarii

ix 95 96 99

Genus Diaphus Key to the North Atlantic Species of Diaphus D. dumerilii D. garmani D. problematic™ D. adenomus D. splendidus D. taaningi D. bertelseni D. luetkeni D. termophilus D. minax D. lucidus D. fragilis D. perspicillatus D. effulgens D. roei D. metopoclampus D. vanhoeffeni D. rafinesquii D. mollis D. holti D. subtilis D. brachycephalus D. anderseni

102 103 113 116 119 121 123 126 128 131 133 136 138 140 143 146 149 150 153 156 159 161 164 167 169

Genus Lampadena Key to the Atlantic Species of Lampadena L. luminosa L. uropbaos atlantica L. speculigera L. pontifex L. charesi L. anomala

171 172 173 176 178 180 182 184

Genus Taaningichthys Key to the Species of Taaningichthys T. minimus T. bathyphilus T. paurolychnus

186 187 187 189 191

x

Table of Contents Genus Lampanyctus Key to the North Atlantic and Mediterranean Species of Lampanyctus L. macdonaldi L. cuprarius L. lineatus L. JJ/KfCJI

I. *ter

L. crocodilus L. intricarius L. photonotus L. »0&/J5 L. festivus L. tenuiformis L. /W5J//W5 L. 0/0/U5 Genus Lepidophanes L. guentheri L. gaussi Genus Bolinichthys Key to the North Atlantic Species of Bolinichthys B. supralateralis B. distofax B. photothorax B. indicus Genus Ceratoscopelus C. maderensis C. warmingii Genus Notoscopelus Key to the North Atlantic and Mediterranean Species of Notoscopelus Subgenus Notoscopelus N. caudispinosus N. resplendens N. elongatus kroeyerii N. elongatus elongatus Subgenus Pareiophus N. ^o/i»i . Literature Cited

193 194 195 197 199 201

203

206 209 211 214 216 218 221 223 226 226 228 231 231 232 234 236 238 241 241 244 247

247 248 24g 2JQ 253 255 2Jj oc , /)o 2«

Table of Contents

xi

Atlantic Mesopelagic Zoogeography. By RICHARD H. BACKUS, JAMES E. CRADDOCK, RICHARD L. HAEDRICH, and BRUCE H. ROBISON

266

The Collections Area Covered Methods of Study The Zoogeographic System The Atlantic Subarctic Region The North Atlantic Temperate Region The North and South Atlantic Subtropical Regions The Atlantic Tropical Region Mauri tanian Up welling Gulf of Mexico Distribution Patterns Literature Cited INDEX

266 268 269 272 276 279 280 283 284 284 284 286 288

In memory of Rolf L. Bolin, who set the standards in lanternfish taxonomy.

Introduction HpHIS seventh part of FISHES OF THE WESTERN NORTH ATLANTIC includes ac•*" counts of two iniomous (myctophiform) families for which short interim accounts have previously appeared in Part Five. These are the Neoscopelidae, which has few genera and species, and the Myctophidae, which has many genera and several hundred species in the world's oceans and is exceedingly important in the economy of the open sea. Also included is a special contribution on Atlantic Mesopelagic Zoogeography, based primarily on the species of Myctophidae. This section synthesizes a large amount of data to provide a scheme for relating fish distributions to characteristics of the Atlantic Ocean. These accounts were to have been written by Rolf Bolin, who was unquestionably the leading authority on lanternfishes. Rolf is no longer with us, and we miss him. This volume is dedicated to him. Recent years have seen a great surge in the exploration of the open sea. As a result, the study of deep-sea fishes is receiving more attention than ever before. Lanternfishes are so abundant and speciose that they must be taken into account in any consideration of the dynamics and energetics of biological communities in oceanic midwaters. We have been fortunate, therefore, in enlisting the efforts of several leading scientists in preparing this volume, which we hope will be a guide and inspiration to others. There is still a great deal to be learned. Users of this volume will notice that several names of species are spelled slightly differently than in much of the most recent literature. Some of the revised spellings are reversions to the original spelling, as used in the description of the species by the author who first named it. This follows a recent decision by the International Commission on Zoological Nomenclature, which had previously ruled that singular male patronyms should end in a single i, whether the original author used none, one, or two. The names so changed here, correctly spelled, are: Electron* risso Hygophum reinhardtii Hygophum bygomii Gonichthys cocco

Lobianchia gemellarii Diaphus rafinesquii Notoscopelus kroeyerii Ceratoscopelus warmingii Diaphus dumerilii

The use of diacritical marks in a scientific name is not accepted by the International Code of Zoological Nomenclature, and letters that originally employed an umlaut are to be transliterated (for example, ii becomes ue). This rule has been followed by some workers, but not by others. The names involved here are: Diaphus luetkeni Lepidophanes guentheri Notoscopelus kroeyerii XIII

xiv

Introduction

One other name has been changed here from the spelling currently in use. Myctophum obtusirostre employs the correct neuter adjectival ending. The Synonyms and References sections in this volume are limited to those names and references that were considered most important. For much fuller synonymies, readers should refer to the work by Krefft and Bekker (1973). Two species names that have appeared in the literature recently, one of them having been in use for a long time, are herein newly relegated to the synonymy of an earlier-named species: Myctophum selenoides Wisner is placed in the synonymy of Myctophum selenops TSning. Diaphus elucens (Brauer) is placed in the synonymy of Diaphus perspicillatus (Ogilby). The following abbreviations have been used throughout in order to avoid repetition of the names of natural history collections housing the preserved specimens upon which the accounts have been based. AMS — Australian Museum, Sydney BMNH — British Museum (Natural History), London BOC — Bingham Oceanographic Collection, Yale University, New Haven CAS(SU) — Stanford University collections, now at California Academy of Sciences, San Francisco ISH — Institut f iir Seefischerei, Hamburg LACM — Los Angeles County Museum of Natural History MCZ — Museum of Comparative Zoology, Harvard University MMF — Museu Municipal do Funchal, Madeira MOM — Musee Oceanographique, Monaco NMFS — National Marine Fisheries Service NRMG — Naturhistoriska Riksmuseet, Goteborg RMNH — Rijksmuseum van Natuurlijke Historic, Leiden ROM — Royal Ontario Museum of Zoology, Toronto SIO — Scripps Institution of Oceanography, La Jolla USNM — National Museum of Natural History, Washington WHOI — Woods Hole Oceanographic Institution ZMHU — Zoologisches Museum der Humboldt Universit'at, Berlin ZMO — Zoologisk Museum, Oslo ZMUC — Zoological Museum, University of Copenhagen Other often used abbreviations are: TL — total length SL — standard length hi — head length m.w. or m.w.o. — meters of wire out f.w.o. — feet of wire out

xv

Introduction

The editors are grateful to the authors for their contributions and to the home institutions of the authors for supporting their work. We also thank the several agencies and foundations that have supported the authors in many ways, as the authors have noted in their acknowledgments. The museum community deserves special appreciation, for without their cooperation, good and comprehensive studies as exemplified by this series would be impossible. Finally, we renew our thanks to the Sears Foundation for the publication of this volume. The Editor-in-Chief points out the many services provided by the Smithsonian Institution during preparation of this volume and thanks Mrs. Jane Shaw for her diligence and hard work in preparing the manuscript for the printer and seeing it through to publication. December, 1976 Washington, D. C.

ROBERT H. GIBBS, JR. Editor-in-Chief

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Family Neoscopelida< BASIL G.

NAFPAKTITIS

Department of Biological Sciences and Allan Hancock Foundation University of Southern California, Los Angeles

Acknowledgments. I thank the following for providing me with specimens and information: Victor G. Springer, United States National Museum; John L. Butler and Elbert H. Ahlstrom, National Marine Fisheries Service, La Jolla, California; Elizabeth N. Shore and Robert L. Wisner, ScHpps Institution of Oceanography, La Jolla, California. I also thank Mary Nafpaktitis for typing the manuscript and for editorial assistance. This study received financial support through a grant (GB 13389) from the National Science Foundation.

General Characters. Deep-sea pelagic and benthopelagic fishes with compressed bodies and heads. Eyes lateral, small in Scopelengys and Solivomer, large in Neoscopelus. Mouth large, terminal; upper jaw extending to or beyond vertical through posterior margin of orbit; maxillary greatly expanded and truncate posteriorly, toothless and completely excluded from the gape by the premaxillary. Dorsal fin well in advance of anal fin. Adipose fin present. Lateral-line organs weakly developed. Scales large, deciduous and cycloid, except in Solivomer arenidens, which has ctenoid scales on body and cycloid ones on head (Miller, 1947). Luminous organs present in Neoscopelus only.

Dentition. In general, premaxillaries and dentaries with closely set villiform teeth; a band of small teeth on each palatine and similar ones on vomer and basibranchials. Skeletal Characters. Six circumorbital bones. Subocular shelf absent. A long slender supramaxillary present along dorsal margin of posterior part of maxillary. Branchiostegals 8 in Scopelengys, 8-9 in Neoscopelus9 and 10 (911) in Solivomer. Gill rakers well developed. Vertebrae 29-3 5. Three ventral and 4 dorsal hypurals; 3 epurals. Six to 8 dorsal and 5-7 ventral, soft procurrent caudal-fin rays; principal caudal-fin rays 10 (9) dorsal and 9 ( 8 ) ventral. Pelvic-fin rays 8. A small, spinelike splint at base of 1st dorsal-, 1st anal-, uppermost pectoral-, and outermost pelvic-fin ray in Neoscopelus; the same element is either very soft or absent altogether in Scopelengys. Luminous Organs. The species of Neoscopelus have numerous photophores arranged linearly in horizontal series on the ventral part of the body and along the periphery of the tongue (Fig. 1). The photophores are superficial, oval in shape with a rim of black pigment along their dorsal and posterior margins. Their

2

Memoir I, Part 7—Sears foundation for Marine Research

°O o o o o O o o o o o o o

FIGURE 1. Arrangement of photophores in Neoscopelus. Terminology follows Matsubara (1943). Am, anteromedian; Av, anteroventral; AVO, accessory ventral; Bp, basipectoral; Ca, circumanal; Is, isthmus organs; LO, lateral; Pm, posteromedian; PO, thoracic; PVO, prepectoral; TO, tongue organs; Vc, ventrocaudal.

anteroventral margins are often indistinct, the reflective layer fading into the surrounding silver of the lower half of the body. The small mass of photogenic tissue is restricted to the posterodorsal or posterior part of each organ. The scales overlying the photophores are not modified into lenses. No other luminous organs or luminous tissue are evident on the bodies and heads of these fishes. Swimbladder. A swimbladder is present in the monotypic Solivomer (Miller, 1947) and in Neoscopelus. The organ is absent in Scopelengys. The swimbladder of Neoscopelus macrolepidotus was found by Marshall (1960: 42) to be capacious, with a gas gland that covers

some two-thirds of its floor and supplied by 5 massive retia mirabilia. Marshall was able to find no trace of an oval or of any specialized region that might function in gas resorption. Development. The larvae of Scopelengys have been studied by Moser and Ahlstrom (1970: 142) and found to bear a striking resemblance to certain myctophid larvae, especially those of the genus Lampanyctus. In their recent review of the genus Scopelengys, Butler and Ahlstrom (1976) described and illustrated a 13.9-mm larva of Scopelengys tristis and a 15.2-mm larva of a new species of this genus from the central North Pacific Ocean. Diversity and Range. The Neoscopelidae are

Fishes of the Western North Atlantic distributed in tropical and subtropical regions of all three major oceans. The family includes three genera: Scopelengys, with two species, inhabits deep, oceanic midwaters; the three species of Neoscopelus are benthopelagic and occur in the proximity of land masses; the third, monotypic genus Solivomer has been known in the past only from the holotype and 30 paratypes of S. arenidens, all collected in the vicinity of the Philippine Islands. Recently, Robert L. Wisner of SIO sent me seven additional specimens of S. arenidens which had been made available to him by J0rgen Nielsen of the ZMUC. The specimens (71-175 mm) were all taken off Mindanao (08°48'N, 124* WE) during the GALATHEA Expedition, 1950-52. Re-marks. Originally, neoscopelids were included in the family Myctophidae. Their relationships with the lanternfishes were discussed by Regan (1911). Changes in the systematic picture began with Fowler's (1925) division of the family into the subfamilies Myctophinae and Neoscopelinae, the latter to include the genus Neoscopelus alone. Three years later, Parr (1928), on the basis of external characters, concluded that the forms included by Regan (1911) in the Myctophidae represented "three different types or stages of differentiation" each deserving a subfamilial status. He thus divided the family into the "Scopelengyni" with the single genus Scopelengys, the "Neoscopelini" with Neoscopelus and, "provisionally," Scopelopsis, and the "Myctophini" with most of the mytophids (sensu stricto). Following an examination of Scopelengys and Neoscopelus, Fraser-Brunner (1949: 1021) became convinced that the two had more in common with each other than with the Myctophinae, in spite of the presence of photophores only in Neoscopelus. He therefore placed the two genera, as well as Solivomer Miller, 1947, in the same subfamily, Neoscopelinae. He further showed that Scopelopsis belonged with the Myctophinae rather than with the Neoscopelinae, a relationship that obviously was not noticed by Smith

3

(1949) who, without any explanation whatsoever, placed this genus along with Neoscopelus in a family of their own, the Neoscopelidae. Apart from the Scopelopsis question, Smith's action of according Neoscopelus full familial status proved to be correct and support for it came from Marshall (1955: 306 and, especially, 1960: 55) whose studies led him to suggest that it might be better to put Neoscopelus into a separate family (Neoscopelidae) together with the genera Scopelengys and Solivomer. Subsequent major systematic studies have all recognized the family Neoscopelidae. Of the three neoscopelid genera, Neoscopelus with its large eyes, silvery, fusiform body, firm musculature, well-ossified skeleton, numerous photophores, and large swimbladder stands in sharp contrast to the small-eyed, dark brown Scopelengys with its flabby musculature, weakly ossified skeleton, lack of photophores and swimbladder. However, these striking differences are explainable if they are seen as reflecting adaptations to two different environments. Scopelengys inhabits the deep oceanic midwaters. In this food-poor environment the cost of maintaining highly complex organizations is prohibitive. On the other hand, the richer food resources available near and on the bottom over continental and island slopes provide the benthopelagic Neoscopelus with sufficient energy to maintain the features that make it so distinct from its midwater relative. One is tempted to speculate that Scopelengys was derived from a Neoscopelus-like, benthopelagic ancestor which invaded the deep oceanic waters. In doing so, it had to evolve all the necessary adaptations (i.e., loss of certain organs and reduction of others) in response to the intense selective pressures of its new, midwater environment. Concerning the little-known, monotypic Solivomer, FraserBrunner (1949: 1021) noted, and I agree, that, in some morphological characters, it seems to be intermediate between the other two neoscopelid genera.

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Memoir 1, Part 7—Sears Foundation for Marine Research

Key to the Genera of Neoscopelidae la. Photophores present; upper jaw extending to or slightly beyond vertical through posterior margin of orbit; pseudobranchia well developed. Neoscopelus Johnson 1863 Ib. Photophores absent; upper jaw extending at least one eye diameter behind vertical through posterior margin of orbit; pseudobranchia rudimentary 2 2a. Vomerine teeth in one transverse patch; mesopterygoid teeth present; scales on trunk ctenoid. Solivomer Miller 1947 Known only from the Philippine Islands

2b. Vomerine teeth in two separate patches, one on each side of vomer; mesopterygoid teeth absent; scales on trunk cycloid. Scopelengys Alcock 1890

FIGURE 2. Scopelengys tristis, young, 129 mm, from the eastern North Pacific.

Genus Scopelengys Alcock 1890 Scopelengys Alcock, 1890: 302 (type-species Scopelengys tristis Alcock 1890, by monotypy).

Characters. Body moderately slender, elongate. Dorsal profile of head straight or somewhat concave. Eye small, its diameter more than 7 times in hi. Mouth large, terminal, oblique; upper jaw extending at least one eye diameter behind vertical through posterior margin of orbit; premaxillaries and dentaries with closely set villif orm teeth on their outer surfaces and enlarged, sharp, posteriorly and medially depressible ones on their inner surfaces; small teeth in long narrow bands on palatines; similar teeth in two patches, one on each side of vomer, the two patches separated by a median, naked area; no teeth on mesopterygoids. Base of anal fin nearly equal in length to that of dorsal fin. Base of adipose fin over posterior half of base of anal fin. No luminous organs. Scales large, thin, cycloid

and highly deciduous. Pseudobranchia rudimentary. Swimbladder absent. Size. Members of this genus grow to a size of about 200 mm. Range. Tropical and subtropical waters of all three major oceans. Absent or rare in the western parts of the Pacific and Atlantic Oceans. Species. The genus contains two species: S. tristisy known from all three major oceans, and a second species recently described by Butler and Ahlstrom (1976) from the central North Pacific (see Remarks under S. tristis). Scopelengys tristis Alcock 1890 Figure 2 Study Material. ATLANTIS II, 10' IKMT stations: RHB 2051, 16°50'N, 18°50'W, 0-730 m, 1 ( 5 5 ) ; RHB 2059, 16°14'N, 20°44'W, 0-650 m, 1 (38); RHB 2075, 14°43/N, 25°27'W, 0-720 m, 1 (50), in LACM. Narragansett Marine Laboratory, U. Rhode Island, sta. MWT-5 TR-023, 10°N, 30°W, 0-1370 m,

Fishes of the Western North Atlantic 10' IKMT, 1 (153), in LACM. USNM 206789, 07° 32'N, 20°S4'W, 0-1300 m, 1600-mesh Engel midwater trawl, 5 (152-164). VELERO IV, 10' IKMT stations: 15521, 33°14'N, 118°36'W, 0^50 m, 2 (130-157); 18762, San Pedro Basin, 0^00 m, 1 (129), in LACM. ANTON BRUUN western Indian Ocean cruises 3 and 6, 91 (22.5-194), from 18 stations between 16°N and 20°S, in LACM.

Description. Fin rays: dorsal 11-12 (13); anal 13 (1214); pectoral 15-16 (14^17). Gill rakers: 1 + 1 + 7 (6-8), total 9 (810) in North Atlantic and Indian Ocean material; 1 + 1 + 5-6, total 7-8 in eastern North Pacific specimens. These counts do not include the toothed tubercles of which there are 3 on the upper and, usually, 2 on the lower limb of the 1st gill arch. Vertebrae: 30-31 (32). The following measurements are in percent of SL and are based on 7 specimens 130-164 mm: Eye diameter: 3.1-3.8. Length of upper jaw: 15.0-16.2. Length of head: 27.2-29.8. Least depth of caudal peduncle: 6.7-7.6. Tip of snout to: base of pectoral fin 28.530; base of pelvic fin 39.7-42.1; origin of dorsal fin 41.6-42.4; origin of anal fin 65.3-66.6; anterior end of base of adipose fin 79.0-81.5. Head. Dorsal profile of head concave; hi 3.4-3.8 in SL. Mouth large, oblique, with lower jaw slightly projecting; maximum width of maxillary greater than diameter of eye; length of upper jaw about 1.8 in hi and 6.26.6 in SL; a long, narrow band of small but sharp, posteromedially depressible teeth on each palatine; an oval patch of similar, posteriorly depressible teeth on each side of vomer. Eye small, its diameter 4.2-5 in length of upper jaw, 7.6-9.2 in hi, and 28-31 in SL. Fins. Origin of dorsal fin approximately over base of pelvic fin. Pectoral fins long, extending about to vertical through end of base of dorsal fin. Pelvic fins also long, ex-

5

tending to or somewhat beyond anus but not reaching origin of anal fin. Base of adipose fin over posterior Y$ of base of anal fin. Size. The largest specimen examined measured 194 mm. Ripe females ranging from 152 to 180 mm were found in both the North Atlantic and Indian Ocean material. Development. Butler and Ahlstrom (1976) have described a 13.9-mm larva of this species. The larva is characterized by a horizontal bar of pigment that extends from the snout through the eye and on to the operculum. No pigment is apparent elsewhere on the body or head of the larva. Range. S. tristis is found in tropical and subtropical waters of all three major oceans. The species is known mainly from the eastern North Atlantic, east of about 30°W, and between the equator and approximately 33°N. It is very rare in the western North Atlantic. In fact, the only two records reported so far are both from the Caribbean Sea off Venezuela (Mead, 1963; Devany, 1969). The species is known also from the eastern South Atlantic. The distributional pattern of S. tristis in the Pacific Ocean is similar to that in the Atlantic Ocean. It is relatively common in the eastern Pacific off the Americas and between approximately 33°N and 20°S, with the latitudinal range and abundance tapering westward. No records are available from the waters west of about 170°W. The species has repeatedly been taken in the western Indian Ocean between approximately 16°N and 20°S. Features such as weakly ossified skeleton, flaccid musculature, small eyes, and absence of a swimbladder reflect a pelagic existence in deep oceanic waters. Indeed, available capture data indicate that young (less than 100 mm) S. tristis frequent depths between about 500 and 800 m, whereas adults tend to occur deeper than 1000 m. The species does not seem to migrate vertically. Remarks. In their review of the genus Sco-

Memoir I, Part 7—Sean Foundation for Marine Research

6

pelengys, Butler and Ahlstrom (1976) described a new species, S. clarkei, from the central North Pacific. The new form differs from S. tristis in having a lower number of pectoral-fin rays (12-13 vs. 14-17), a higher number of vertebrae (34-35 vs. 29-32), a deeper caudal peduncle (8.3-10.2% of SL vs. 5.6-8.3%), and a narrower maxilla (width 22.3-27.1% of its length vs. 29.9-36.7%). Further, a 15.2-mm larva belonging to the new species shows extensive pigment on the operculum and on the lower jaw. Pigment is also present on top of the head, in front of the pectoral-fin base, and on the nape immediately behind the head. The rest of the trunk and fins are devoid of pigment. Synonyms and References: Scopelengys tristis Alcock, 1890: 303 (Orig. descr., 11°12'47"N, 74°25'30"E, 1,000 fms; Zool. Surv. of India, Calcutta, F 12873); Bblin, 1939: 94, Fig. 2 (descr. from £ N Pac.); Fraser-Brunner, 1949: 1040, Fig. (in key); Bussing, 1965: 200 (records from off Peru) ; Berry and Perkins, 1966: 655 (records from off southern Calif, and Baja Calif.); Kotthaus, 1967: 80 (record from Indian Ocean, 15°28'N, 69°26'E; char., photo of otol.); Nellen, 1973: 47 (records of larvae from W Ind. Ocean); Nieben, 1973: 170 (synon., ref.; northernmost Atl. record 32°47'N, 16°24'W). Scopelengys dispar Carman, 1899: 254, PL 54, Fig. 2 (Orig. descr., Gulf of Panama; holotype MCZ 28508). Scopelengys who* Mead, 1963: 255, Fig. 1 (Orig. descr., 12°Ol'N, 65°Ol'W, 400-600 m; holotype MCZ 41638); Devany, 1969: 127 (record from off Venezuela) *

Genus Neoscopelus Johnson 1863 Neoscopelus Johnson, 1863: 44 (type-species Neoscopelus macrolepidotus Johnson 1863, by mono-

typy).

Characters. Body fusiform, compressed. Head conical, its dorsal profile straight or slightly concave. Eye large, its diameter 5 times or less in hi. Mouth large, terminal, oblique; upper jaw extending to or slightly behind vertical through posterior margin of orbit; premaxillaries and dentaries with closely

set, blunt, villiform teeth on their outer surfaces and enlarged, conical, sharp, posteriorly and medially depressible ones on their inner surfaces; a band of small teeth on palatines and anterior limbs of ectopterygoids; similar teeth on entire ventral surface of vomer; a large, oval patch of densely set, minute teeth on each mesopterygoid. Upper limb of 1st gill arch with 2-4 well developed gill rakers restricted to its posterior V* to Vi\ the rest of the limb covered with an anterior large and a posterior small dentigerous plate. Base of dorsal fin equal in length to or longer than that of anal fin. Base of adipose fin over middle or posterior half of base of anal fin. Scales large, cycloid, deciduous. Pseudobranchia well developed. Swimbladder present. Luminous organs present, arranged in a single series along the periphery of the tongue, and in a midventral and several bilateral series on trunk. Size. Members of this genus grow to a size of about 300 mm. Range. Close to land masses in tropical and subtropical waters of all three major oceans. Absent or rare in the eastern parts of the Pacific and Atlantic Oceans. Species. The genus contains three species: N. macrolepidotus, N. microchip and N. porosus. The first two occur in the North Atlantic, whereas the recently described N. porosus is, so far, known only from off central and southern Japan. Neoscopelus macrolepidotus Johnson 1863 Figure 3 Study Material. USNM 159894, 07°46'N, 54°36'W, 400 fms, 40' shrimp trawl, 5 (123-152); USNM 186285, 07°34'N, 54°49'W, 225 fms, 40' shrimp trawl, 4 (64-75); USNM 188055, 14°18'N, 81°44'W, 2 (178-223); USNM 47736, 21°08/30//N, 157°49'W, 3 (140-149); USNM 125979, off Hawaii, 4 (112166); USNM 148869, 35°06'N, 138°40'E, 197 fms, 2 (158-159); USNM 149555, 33°24'50"N, 135°38' 40"E, 253 fms, 4 (101-138).

Distinctive Characters. In the Atlantic Ocean this species is distinguished from N. microchir by its shorter LO series, lower num-

Fishes of the Western North Atlantic

7

FIGURE 3. Neoscopelus macrolepidotus, young, 101 mm, from Japan.

her of gill rakers, higher numbers of pectoraland anal-fin rays, and longer base of the anal fin in relation to that of the dorsal fin. For characters differentiating Pacific populations of the two species see under Geographic Variation. Description. The following description is based on 11 western North Atlantic and Caribbean specimens, 64—223 mm, and 7 specimens, 112-166 mm, from Hawaiian waters. Measurements are from 14 of the above individuals, ranging from 112 to 223 mm. Fin rays: dorsal 12-13; anal 12 (11-13); pectoral 18-19. Gill rakers: 2 (3 in a single specimen from Hawaii) + 1 + 8 (7 in two individuals from off Surinam, and 9 in a single specimen from Hawaii), total 11 (10-12). Photophores: LO 12-14. Vertebrae: 30-31, five X-rayed specimens. Measurements in percent of SL. Mean values are followed by ranges in parentheses. Length of head: 34.3 (33.0-36.0). Depth of body: at origin of dorsal fin 24.0 (22.5-25.5). Posterior end of base of dorsal fin to: anterior end of base of adipose fin 22.4 (21.024.2).

Tip of snout to: upper end of base of pectoral fin 35.3 (34.2-37.0); base of outermost ray of pelvic fin 46.7 (44.5-48.0); origin of dorsal fin 45.7 (44.2-48.0); origin of anal fin 73.2 (71.4—76.0); anterior end of base of adipose fin 79.4 (77.7-82.3). Head. Dorsal profile of head straight or somewhat concave. Mouth large, oblique, with lower jaw slightly projecting beyond upper; upper jaw extending about to vertical through posterior margin of orbit, its length 1.8-2 in hi and 5.3-6 in SL. Eye large, its diameter 2.3-2.7 in length of upper jaw, 4.55 in hi, and 13-14.4 in SL. Fins. Origin of dorsal fin usually a little in advance of base of pelvic fin. Length of base of anal fin 1-1.3 in that of base of dorsal fin. Pectoral fins long, extending to vertical through posterior margin of anus. Base of adipose fin directly over or a little behind middle of base of anal fin. Luminous Organs. LO not reaching vertical through origin of anal fin. Vc series often turning upward and continuing posteriorly at level of preceding LO; in such cases caution should be exercised so as not to confuse the organs of the two series. 7 (8) Is. Color. According to Matsubara (1943),

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Memoir 1, fart 7—Sears Foundation for Marine Research

"color in life dark red on sides of head and body; belly silvery white with bluish reflection; pupil light green, translucent, sclerotic silvery white; fins uniformly pink." In alcohol, depending on original condition of animals and method as well as length of preservation, head, except operculum, and trunk light brown with operculum, back and ventral photophore regions dark brown; or head, including operculum, and ventral half of body silvery iridescent. Size. The largest specimen in the collections studied was a 223-mm female from off Nicaragua with very large, thick-walled ovaries containing small, loosely packed eggs. The ovaries of a 152-mm long female from off Surinam were densely packed with eggs that appeared to be ripe or nearly so. A specimen reported by Maul (1951) from Madeira measured 250 mm. Range. The great morphological similarity of the species in the genus and the very limited circulation of Matsubara's (1943) work on N. microchir have resulted in the assignment by previous workers of most of the Atlantic material to N. macrolepidotus. The confusion can be resolved only after a careful re-examination and correct identification of all the material reported so far. We know at present that both N. macrolepidotus and N. microchir occur in the North Atlantic, where their ranges seem to overlap, and that N. microchir is as common as (if not commoner than) its congener. Except for the holotype and the specimen reported by Maul (1951) from off Madeira, there are no confirmed records of N. macrolepidotus from the eastern North Atlantic. In the western part of the ocean, the species has been taken off Surinam, and in the western Caribbean Sea off Nicaragua. Specimens from the northern Gulf of Mexico and the Florida Straits (Bullis and Thompson, 1965) may prove to belong to N. microchir. Captures in the South Atlantic include one specimen at 38°38'S, 50°48'W, and two at

30°03'S, 47°44'W, off southern Brazil. All three specimens were taken by bottom trawl at depths of 500 and 800 m (G. Krefft, personal communication). Elsewhere, N. macrolepidotus is found in Hawaiian waters, off the coast of southern Japan, and in the waters of the Great Australian Bight. Capture data indicate that N. macrolepidotus occurs over continental and island slopes, not far from the bottom and at depths between approximately 300 and 800 m. Morphological features, such as well-ossified skeleton, firm musculature, well-developed swimbladder, and countershaded coloration (silvery iridescent ventral parts, dark red or brown backs) attest to a benthopelagic existence in relatively shallow to moderately deep waters. There are no indications that the species migrates vertically. Geographic Variation. Japanese specimens have a higher number of gill rakers [14 (13)] than specimens from Atlantic and Hawaiian waters [11 (10-12)]. Further, the distance between the posterior end of the base of the dorsal fin and the anterior end of the base of the adipose fin is somewhat shorter [20.9 (20.3-21.4) percent of SL] in Japanese than in Atlantic and Hawaiian specimens [22.4 (21.0-24.2) percent of SL]. Synonyms and References: Neoscopelus macrolepidotus Johnson, 1863: 44, PL 7 (Orig. descr., off Madeira; holotype BMNH No. 1862.10.3.3); Gilbert, 1913: 69 (records from Suruga Bay, compar. with AtL specim.); McCulloch, 1914: 90, PI. 17 (record from Great Australian Bight, char.); Matsubara, 1943: 56, Fig. 12 (descr. of specim. from Japan; compar. with N. microchir); Maul, 1951: 56, Fig. 13 (records from off Madeira; compar. with N. microchir); Nielsen, 1973: 170 (synon., ref.). Neoscopelus alcocks Jordan and Starks, 1904: 580, PL 2, Figs. 1, 2 (Orig. descr., Suruga Bay, 173-260 fms; holotype USNM 51477). Neoscopelus bruuni Whitley 1931: 312 [proposed new name for N. macrolepidotus reported by McCulloch (1914) from Great Australian Bight, 129°28'E].

Fishes of the Western North Atlantic

9

FIGURE 4. Neoscopelus microcbir, young, 77 mm, from off Jamaica.

Neoscopelus microchir Matsubara 1943 Figure 4 Study Material. USNM: 108273, 18°39'N, 67°17' W, 300 fms, 2 (147-159); 187897, 17°40'N, 77°55' W, 4 (77-102); 188056, 16°58'N, 87°53'W, 14 (88124); 188297, 23°59'N, 79°43'W, 350 fms, 10' beam trawl, 30 (37-130); 135420, 13°46'45"N 121°35'08" E, 190 fms, 25 (81-118); 135840, 09°20'30"N, 123° 23'45"E, 310 fms, 1 (128); 135841, 06°03'15"N, 120°35'30"E, 318 fms, 1 (131); 135843, 12°52'N, 121°48'30"E, 281 fms, 1 (105); 135844, 12°25'35"N, 121°31'35"E, 234 fms, 2 (139-141); 135845, 13°47' 20"N, 120°43'30"E, 180 fms, 2 (107-119); 135846, OS°54'48"N, 120°44'24"E, 193 fms, 1 (89); 135847, 08°35'30"N, 124°36'E, 200 fms, 1 (124); 135848, 20°37'N, 115°43'E, 208 fms, 5 (70-126); 135849, 00°07'N, 127°28'E, 5 (110-146); 135850, 10°33'30" N, 122°26'E, 137 fms, 1 (61); 135852, 10°09'15"N, 123°52'E, 162 fms, 1 (88); 135854, 16°38'N, 119° 57'18"E, 186 fms, one damaged specimen; 135855, 12° 54'40"N, 123°20'30"E, 209 fms, 10 (35-103); 135856, 12°51'30"N, 123°26'15"E, 226 fms, 1 (125); 135857, 13°49'40"N, 121°40'15"E, 83 (?) fms, 2 (149-152); 135858, 00°07'30"N, 127°29'E, 265 fms, 7 (113145); 196650, Japan: Owashi, 1 (ca. 127).

Distinctive Characters. In the Atlantic Ocean, N. microchir is distinguished from N. macrolepidotus by its longer LO series that extends over the base of the anal fin, by its higher gill-raker counts, lower numbers of pectoral- and anal-fin rays, and shorter base

of the anal fin in relation to that of the dorsal fin. For characters differentiating western North Pacific populations see under Geographic Variation. Description. The following description is based on 16 western North Atlantic and Caribbean specimens, 59-159 mm. Finrays: dorsal 13 (12); anal 11 (10-12); pectoral 16-17. Gill rakers: 3 (4 in one specimen ) + 1 + 10 (11 in 3 specimens), total 14 (If in two specimens, 16 in one). Photophores: LO 20-22. Vertebrae: 30-31, six X-rayed specimens. Measurements in percent of SL. Mean values are followed by ranges in parentheses. Length of head: 33.5 (32.5-35.0). Depth of body: at origin of dorsal fin 23.6 (22.3-25.5). Posterior end of base of dorsal fin to: anterior end of base of adipose fin 20.1 (18.221.5). Tip of snout to: upper end of base of pectoral fin 34. J (33.4-35.4); base of outermost ray of pelvic fin 45.5 (43.5-47.5); origin of dorsal fin 43.9 (42.2-4J.6); origin of anal fin 747 (72.1-76.6); anterior end of base of adipose fin 80.2 (78.0-82.3).

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Memoir 1, Part 7—Sears Foundation for Marine Research

Head. Dorsal profile of head straight or a little concave. Mouth large, oblique, with lower jaw slightly projecting beyond upper; upper jaw extending to or somewhat behind vertical through posterior margin of orbit, its length 1.8-2 in hi, and 5.2-6 in SL. Eye large, its diameter 2.1-2.6 in length of upper jaw, 3.9-^.3 in hi, and 11.6-13 in SL. Fins. Origin of dorsal fin directly over or a little in advance of base of pelvic fin. Length of base of anal fin 1.5-1.7 in that of base of dorsal fin. Pectoral fins long, reaching anus in young individuals (smaller than about 120 mm), somewhat shorter in larger specimens. Base of adipose fin over posterior half of base of anal fin. Luminous Organs. Posteriormost 1-2 LO behind vertical through end of base of anal fin. 9 (8) Is. Color. According to Matsubara (1943), "color in life dark red or blood-red on sides of head and body, but paler below; belly silvery white, with bluish reflection. Pupil translucent light green; sclerotic silvery white. Fins uniformly pink." In alcohol, depending on original condition of animals and method as well as length of preservation, head, except operculum, and trunk light brown with operculum, back and ventral photophore regions dark brown; or head, including operculum, and ventral half of body silvery iridescent. Size. The largest specimens in the collections examined measured 159 mm (western North Atlantic) and 175 nun (western North Pacific). Matsubara (1943) reported a 259mm individual from "off Heta," and Maul (1951) a 305-mm specimen from off Madeira. A number of gravid females, ranging in size from 120 mm to 175 mm, were found among the material from the western tropical Pacific. Range. N. microchir has been collected in waters around the Virgin Islands, in the western Caribbean off Jamaica and Honduras, and in the Straits of Florida. The species is most likely present in the Gulf of Mexico.

Maul's (1951) specimen from Madeira is the only confirmed record from the eastern North Atlantic. Neoscopelus microchir appears to be rather common in western tropical Pacific waters, the waters around the Philippine Islands, the northern China Sea, and off southern Japan. Collections reported from the Andaman and Arabian Seas (Alcock, 1899), east coast of Africa (Brauer, 1906), Indo-West Pacific, and off northeastern New Zealand (Brauer, 1906; Weber and DeBeaufort, 1913) under the name N. macrolepidotus should be reexamined, for although the figures in those reports are those of N. microchir, the accompanying data suggest that both species were represented in the collections. Like its congener, N. microchir is a benthopelagic fish found over continental and island slopes at depths mainly between 250 and 700 m. Available data fail to reveal whether or not this species migrates vertically. Geographic Variation. Listed below are differences in meristic and morphometric characters between the Atlantic and western North Pacific (in brackets) populations of N. microchir. Anal-fin rays 11 (10-12), [12 (11)]; pectoral-fin rays 16-17, [15-16]; gill rakers 3 (4) + 1 + 10 (11), total 14 (15-16) [4 (3) + 1 + 12 (11-13), total 17 (16-18)]; LO 20-22 [23-25]; posterior end of base of dorsal fin to anterior end of base of adipose fin 20.1 (18.2-21.5) percent of SL, [22.8 (21.224.5)]; diameter of eye: in SL 12.1 (11.613.0), [13.4 (12.2-14.6)], in hi 4.0 (3.94.3), [4.5 (4.0-4.9)]; length of base of anal fin in that of base of dorsal fin 1.6 (1.5-1.7), [1.3 (1.2-1.5)]. Moreover, in western Pacific specimens the pectoral fins are 1-2 eye diameters shorter than those in Atlantic specimens. Reference: Neoscopelus microchir Matsubara, 1943: 59, Fig. 13 (Orig. descr., "off Heta"; holotype No. 6582, 146 mm SL, Repository ?); Maul, 1951: 56, Fig. 14 (records from of? Madeira; compar. with N. macrolepidotus); Nielsen, 1973: 170 (ref.).

Fishes of the Western North Atlantic

11

FIGURE 5. A, Neoscopelus porosus; B, lateral series of luminous organs (LO) in N. porosus. After Arai (1969).

Neoscopelus porosus Arai 1969 Figure 5 I have not seen representatives of this form. According to Arai (1969), it differs from its two congeners in having 36-40 photophores in its LO series which is subdivided into four subseries, LOi through LO4. Reference: Neoscopelus porosus Arai, 1969: 465, Figs. 1-3, PL 1, Fig. 3 (Orig. descr., off Heta, Suruga Bay, central Japan; holotype: National Science Museum, Tokyo, P.7629).

LITERATURE CITED ALCOCK, A. 1890. Natural history notes from H.M. Indian Marine Survey Steamer "Investigator," Commander R. F. Hoskyn, R. N., commanding. No. 18. On the bathybial fishes of the Arabian Sea, obtained during the season 1889-90. The Annals and Magazine of Natural History, Ser. 6, 6: 295311. . 1899. A descriptive catalogue of Indian deepsea fishes in the Indian Museum, collected by the Royal Indian Marine Survey Ship "Investigator." Calcutta. 211 pp. ARAI, R. 1969. A new iniomous fish of the genus Neoscopelus from Suruga Bay, Japan. Bulletin of the National Science Museum, Tokyo, 12: 465470. BERRY, F. H., AND H. C. PERKINS.

1966. Survey of

pelagic fishes of the California Current area. Fishery Bulletin, 65 (3): 625-682. BOLIN, R. L. 1939. A review of the myctophid fishes of the Pacific coast of the United States and of Lower California. Stanford Ichthyological Bulletin, 1 (4): 1-156. BRAUER, A. 1906. Die Tiefsee-Fische. I. Systematischer Teil. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition auf dem Dampfer "Valdivia" 1898-1899, 15, 1. 432 pp. BULLIS, H. R., JR., AND J. R. THOMPSON. 1965. Collections by the exploratory fishing vessels "Oregon," "Silver Bay," "Combat," and "Pelican" made during 1956-1960 in the southwestern North Atlantic. United States Fish and Wildlife Serivce, Special Scientific Report—Fisheries No. 510. 130 pp. BUSSING, W. A. 1965. Studies of the midwater fishes of the Peru-Chile Trench. Antarctic Research Series, 5: 185-227. BUTLER, J. L., AND E. H. AHLSTROM. 1976. Review of the deep-sea fish genus Scopelengys (Neoscopelidae) with a description of a new species, Sropelengys clarkei, from the central Pacific. Fishery Bulletin, 74 (1): 142-150. DEVANY, T. 1969. Ecologic interpretation of distribution of the lanternfishes (Myctophidae) in the straits of Florida. Ph.D. Thesis, University of Miami, Florida. FOWLER, H. W. 1925. New taxonomic names of west African marine fishes. American Museum Novitates, (162): 1-5.

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Memoir 1, Part 7—Sears Foundation for Marine Research

FRASER-BRUNNER, A. 1949. A classification of the fishes of the family Myctophidae. Proceedings of the Zoological Society of London, 118: 1019-1106. CARMAN, S. 1899. Reports on an exploration off the west coasts of Mexico, Central and South America, and off the Galapagos Islands, in charge of Alexander Agassiz, by the U. S. Fish Commission Steamer "Albatross," during 1891, Lieut. Commander Z. L. Tanner, U.S.N., commanding. XXVI. The fishes. Memoirs of the Museum of Comparative Zoology, Harvard College, 24: 1^31. GILBERT, C. H. 1913. The lantern-fishes of Japan. Memoirs of the Carnegie Museum, 6 (2) : 67-107. JOHNSON, J. Y. 1863. Descriptions of five new species of fishes obtained at Madeira. Proceedings of the Zoological Society of London, 33 (5): 36-47. JORDAN, D. S., AND £. C. STARRS. 1904. List of fishes dredged by the steamer "Albatross" off the coast of Japan in the summer of 1900, with descriptions of new species and a review of the Japanese Macrouridae. Bulletin of the United States Fish Commission, 22 (for 1902): 577-628. KOTTHAUS, A. 1967. Fische des Indischen Ozeans. Ergebnisse der ichthyologischen Untersuchungen wahrend der Expedition des Forschungsschiffes "Meteor" in den Indischen Ozean, Oktober 1964 bis Mai 1965. "Meteor" Forschungsergebnisse, ReiheD, Heft 1: 1-84. MARSHALL, N. B. 1955. Alepisauroid fishes. "Discovery" Reports, 27: 303-336. . 1960. Swimbladder structure of deep-sea fishes in relation to their systematics and biology. "Discovery" Reports, 31: 1-122. MATSUBARA, K. 1943. Ichthyological annotations from the depth of the Sea of Japan. III. A review of the scopelid fish, referable to the genus Neoscopelus. The Journal of the Sigenkagaku Kenkyusyo, J (1): 55-63. MAUL, G. E. 1951. Nota sobre as duas especies do genero Neoscopelus. Boletim do Museo Municipal do Funchal, Madeira, (5): 56-63. McCuLLOCH, A. R. 1914. Report on some fishes obtained by the F. I. S. "Endeavour" on the coasts of Queensland, New South Wales, Victoria, Tasmania, South and Southwestern Australia. Biological Results of the Fishing Experiments carried

on by the F. I. S. "Endeavour," 1909-14. Fisheries, 2: 77-165. MEAD, G. W. 1963. Observations on fishes caught over the anoxic waters of the Cariaco Trench, Venezuela. Deep-Sea Research, 10: 251-257. MILLER, R. R. 1947. A new genus and species of deep-sea fish of the family Myctophidae from the Philippine Islands. Proceedings of the United States National Museum, 97 (3211): 81-90. MOSER, H. G., AND E. H. AHLSTROM. 1970. Development of lanternfishes (family Myctophidae) in the California Current. Part I. Species with narrow-eyed larvae. Bulletin of the Los Angeles County Museum of Natural History, Science (7). 145 pp. NELLEN, W. 1973. Fischlarven des Indischen Ozeans. Ergebnisse der Fischbrutuntersuchungen wahrend der ersten Expedition des Forschungsschiffes "Meteor" in den Indischer Ozean und den Persischen Golf, Oktober 1964 bis April 1965. "Meteor" Forschungsergebnisse, Reihe D, (14). NIELSEN, J. 1973. Neoscopelidae. In Check-list of the fishes of the north-eastern Atlantic and of the Mediterranean (Clofnam). J. C. Hureau and Th. Monod (Ed.), 1: 170. UNESCO. PARR, A. E. 1928. Deepsea fishes of the order Iniomi from the waters around the Bahama and Bermuda Islands, with annotated keys to the Sudidae, Myctophidae, Scopelarchidae, Evermannellidae, Omosudidae, Cetomimidae and Rondeletiidae of the world. Bulletin of the Bingham Oceanographic Collection, 3 (3): 1-192 (Myctophidae, 47-156). REGAN, C. T. 1911. The anatomy and classification of the teleostean fishes of the order Iniomi. The Annals and Magazine of Natural History, Ser. 8, 7: 120-133. SMITH, J. L. B. 1949. The sea fishes of southern Africa. Fifth Edition, 1965. Central News Agency, Ltd., South Africa. 580 pp. WEBER, M., AND L. F. DEBEAUFORT. 1913. The fishes of the Indo-Australian Archipelago. Malacopterygii, Myctophoidea, Ostariophysi: I Siluroidea. 2. 404 pp. WHITLEY, G. P. 1931. New names for Australian fishes. Australian Zoologist, 6; 310—334.

Family Myctophidae

BASIL G. NAFPAKTITIS Department of Biological Sciences and Allan Hancock foundation University of Southern California Los Angeles, California

R I C H A R D H. BACKUS, JAMES E. CRADDOCK, R I C H A R D L. H A E D R I C H , and B R U C E H. ROBISON*t Woods Hole Oceanographic Institution Woods Hole, Massachusetts

and

CHARLES KARNELLA Smithsonian Institution Washington, D. C.

tions, generic and species accounts, and some accounts of Extra-Atlantic Occurrence (the last identified by the letter N in parentheses at the end of the account).

Authorship. Backus, Craddock, Haedrich, and Kobison prepared the distribution maps. Backus and Craddock prepared the introductory account on North Atlantic Genera and Species, the accounts of the Atlantic Distribution of species, and some of the accounts of Extra-Atlantic Occurrence (the last identified by the letters BC in parentheses at the end of the account). Karnella and Craddock prepared the accounts of the Vertical Distribution of species. Nafpaktitis prepared all other parts, including most of the introductory sec-

Acknowledgments (Nafpaktitis). This study received support through grants GB 1)389 and DEB76-00120 from the National Science foundation. Gratefully acknowledged are also a Fulbright-Hays grant and a grant from the Johannes Schmidt foundation for Oceanographic Research which made possible the study of the extensive, worldwide Danish DANA Collections. I thank the National Bank of Denmark for kindly providing full housing facilities during my 4-month stay in Denmark, and E. Bertelsen, Jjrgen Nielsen, and Niels Christensen of the Zoological Museum, University of Copenhagen, for their great help and warm hospitality.

* Robison now at University of California, Santa Barbara, California. t Contribution No. 3769 from the Woods Hole Oceanographic Institution.

13

14

Memoir 1, Part 7—Sears foundation for Marine Research

1 wish to express my deepest appreciation to Richard H. Backus, James E. Craddock, Richard L Haedrich, and David L. Shores, WHO1, for making available to me large amounts of material from the vast midwater collections of that institution, and for sharing with me valuable data and information. 1 also thank the following for kindly supplying specimens and data: Robert H. Gibbs, Jr., Victor G. Springer, and Charles Karnella, USNM; Richard B. Roe, Daniel M. Cohen, National Marine Fisheries Service; Myvanwy M. Dick, MCZ; Gerhard Krefft, 1SH; W. B. Scott, ROM; Jakob Gjosaeter, Institute of Marine Research, Bergen; Charles L. Brownell, Institut des Peches Maritimes du Maroc, Casablanca; Richard H. Rosenblatt, S1O. 1 am grateful to Brent Davy, University of Southern California, for his help in counting and measuring specimens, and to Mary Nafpaktitis for typing and retyping the manuscript. Acknowledgments (Backus, Craddock, Haedrich, and Robison). The work at WHO1 has been supported by the National Science foundation from 1961 to the present through grant DES 74-23209 and its predecessors. The Office of Naval Research recently has helped forward the work by means of Contract N00014-74CO262, NR 083-004. We are grateful to shipmates too numerous to mention for the witting hand that they gave us at sea; we wish especially to acknowledge the help of Captains Herbert L. Babbitt, Charles A Davis, Michael Palmieri, Jr., and Emerson H. Miller. Charles Karnella, Barbara Jones Cormack, Wayne N. Witzell, Stephanie Fofonoff Witzell, Denise Franklin Backus, and David L. Shores, particularly the last, identified large amounts of material. Others who have worked especially closely with us in the laboratory and at sea are Richard J. Beamish, Sneed B. Collard, Michael H. Horn, Martha M. Howbert, Andrew E. Jahn, David C. Judkins, Jane M. Peterson, Stanley E. Poole, Virginia Scarlett, Harry R. Tyler, Jr., and Asa S. Wing. L. V. Worthington, Eli /. Katz, William G, Metcalf, and Bruce A. Warren have discussed North Atlantic circulation with us many times. Roger A. Goldsmith and Mary M. Hunt helped with computer programming and Woollcott K. Smith advised on statistical matters. Gerhard Krefft, 1SH, allowed us the use of data from OVERFLOW 1973 and has been helpful to us in many ways. We also thank past and present colleagues of the MCZ: Karel Liem, Myvanwy M. Dick, Robert Schocknecht, and especially Giles W. Mead. G. D. Grice, G. R. Harbison, A. E. Jahn, T. J. Lawson, Jr., L. P. Madin, and L. V. Worthington have read parts or all of the manuscript and made useful suggestions.

We have had informative talks with all of the foregoing, but also with Julian Badcock, E. Bertelsen, Francis G. Carey, Daniel M. Cohen, Peter Foxton, Robert H. Gibbs, Jr., E. M. Hulburt, Frank J. Mather, III, N. B. Marshall, Rudolf S. Scheltema, William E. Schevill, John M. Teal, and Peter H. Wiebe. Acknowledgments (Karnella). My work has been part of the Ocean Acre program, which was supported by contracts from the Navy Underwater Systems Center, New London, Connecticut. Recently, the work has been supported in part by the Office of Naval Research and by the Smithsonian Research Foundation. 1 wish to thank the many people associated with the Ocean Acre program, both at sea and ashore. Special thanks are due to Robert C. Kleckner, Joel F. Janosky, and, particularly, Michael J. Keene and William H. Howell for sorting and initially identifying much of this material collected during the program; to Richard H. Goodyear and Dante Piacesi for designing and writing the computer programs used to analyze vertical distribution patterns; and to Robert H. Gibbs, Jr. for making the material available to me and for his help in all phases of this study.

General Characters. Deep-sea pelagic fishes with compressed body and head. Eyes well developed, large, lateral (dorsolateral in Hierops). Mouth large, terminal (subterminal in Loweina, Gonichtbys, and Centrobranchus); jaws extending to or far beyond vertical through posterior margin of orbit. Adipose fin present. Origin of anal fin under or close behind base of dorsal fin. Ventral fin rays 8, except in Notolychnus which has 6 and G0»ichthys which may have 7. A rudimentary spine at base of first dorsal, first anal, uppermost pectoral, and outermost ventral fin ray. Principal caudal fin rays 10 dorsal and 9 ventral. Discrete, round or kidney-shaped photophores in distinct groups on trunk and head of all species but one (Taaningichthys paurolychnus). Much smaller, secondary photophores on trunk and head in some species, best developed in Scopelopsis. Luminous organs of various shapes and sizes present on head, caudal peduncle, or on both. Scales cycloid (ctenoid in four species of Myctophum), firm in forms found in relatively shallow depths, loose and easily lost in deeper-dwelling species. Dentition. Premaxillaries and dentaries

Fishes of the Western North Atlantic with bands of closely-set teeth, the inner ones of which may be enlarged. In some species of Diaphus the posterior premaxillary and dentary teeth are broad-based and strongly hooked forward. Similar teeth are found on either side of the premaxillary and dentary symphysis in species of Taaningichthys. The most specialized dentition is found in Diogenichthys. In addition to a number of forwardhooked teeth on the posterior parts of both jaws, there is a single series of flattened, lanceolate premaxillary teeth most of which bear a minute spine on each edge at the widest point. The teeth in the outer series on the dentary are closely set, flattened, and wider than high. Palatines with a long, narrow band of closely-set small teeth or with one or two rows of distinctly enlarged, widely spaced ones. Each mesopterygoid with a patch of teeth. The size of the patch varies in different species and the teeth may be closely set and small or widely spaced and enlarged. In most species there is a cluster of minute teeth on each side of the vomer. In most myctophids the 3rd pharyngobranchials are the largest of the four pairs in the series (Paxton, 1972: 26; Rosen, 1973: 454) and bear enlarged, strong teeth. In Gonichthys these teeth are modified into rounded protuberances and in Centrobranchus into rectangular, ridged plates arranged in closely-set rows. The modified pharyngeal dentition is apparently used for crushing the shells of pelagic gastropods on which these slender-tailed myctophids feed (Hartmann and Weikert, 1970 in Paxton, 1972: 26; also personal observations) . Skeletal Characters. Six circumorbital bones, the third, or jugal, being the largest. A subocular shelf extends medially from the third, fourth and usually the fifth circumorbital (Rosen and Patterson, 1969: 379; Paxton, 1972: 10). The maxillary, which is toothless and completely excluded from the gape by the premaxillary, is greatly expanded pos-

15

teriorly in Protomyctophum, Electrona, Benthosema, Diogenichthys, and Hygophum, less so or not at all in the other genera. A small, L-shaped supramaxillary is present in Lampanyctodes, Gymnoscopelus, Lampichthys, NotoscopeluSy and Scopelopsis (Paxton, 1972: 14). Branchiostegal rays 7-11, but there may be as few as 6 (Moser and Ahlstrom, 1970: 9, Table 5) and as many as 12 (McAllister, 1968: 93). The posterodorsal opercular margin is markedly serrate in species of Myctophum, weakly so or smooth in the rest of the genera. Well-developed gill rakers are present in all genera except Centrobranchus. There are 4 proximal radials in the pectoral fins, but sometimes there may be only 3 due to fusion (Paxton, 1972: 30). Vertebrae range in number from 28 in Notolychnus to 45 in Gymnoscopelus (Moser and Ahlstrom, 1970: 9, Table 5; Paxton, 1972: 33, Table 8). Three (2) epurals, 7 (1-7) hypurals, the numbers depending on the degree of fusion. Five to 14 dorsal and 5-15 ventral procurrent caudal fin rays; these may be flexible or stiff. The stiff elements are considered to be rays by Paxton (1972: 36) and spines by Rosen and Patterson (1969: 454) and Rosen (1973: 452). Luminous Organs and Sexual Dimorphism. Myctophids have a variety of luminous organs, hence their common name "lanternfishes." However, the most characteristic type of luminous organ found in all but one (Taaningichthys paurolychnus) of the numerous species of the family is the photophore. Lanternfishes may have anywhere between 50 and 80 of these photophores studding the ventral halves of their trunks and heads. Photophores are highly specialized, complex organs, richly vascularized, those on the head receiving nerve supply from branches of the nervus facialis, those on the body from branches of the spinal nerves (Ray, 1950). Each body photophore consists of a scale embedded in the dermis and modified into a shallow cup that provides mechanical support to the delicate tissues in it (Fig. 1). Lining the

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Memoir 1, Part 7—Sears Foundation for Marine Research

DR

FIGURE 2. Schematic stereo-diagram of a body photophore of Stenobrachius leucopsarus. The overlying scale lens, the reflector layers associated with the scale lens, and some vascular tissue have been omitted to reveal the interior of the photophore. Abbreviations: B, blood; CT, connective tissue; DN, dorsal nerve; LC, lining cell; PC, photocyte; PP, primary pigment backing; PR, primary reflector backing; SC, scale cup; VN, ventral nerve. From O'Day (1972).

FIGURE 1. Schematic diagram of a median transverse section of a body photophore of Stenobrachius leucopsarus. Abbreviations: B, blood; CT, connective tissue; DC, dense connective tissue; DN, dorsal nerve; DR, dorsal reflector; PC, photocytes; PP, primary pigment backing; PR, primary reflector backing; SC, scale cup; SLcal, scale lens (calcified layer); SLcol, scale lens (collagenous layer); SP, secondary pigment backing; SR, secondary reflector backing; VR, ventral reflector. From O'Day (1972).

convex surface of the scale cup is a reflector layer which is in turn backed by a layer of dark pigment. Inside the scale cup, connective tissue provides support for the blood vessels, nerves, and the extremely delicate photogenic tissue. O'Day (1972) described the photogenic tissue in the body photophores of Stenobrachius leucopsarus as consisting of "a stack of very thin cells, flattened in a plane parallel with the overlying scale lens" (Fig. 2). The scale that overlies the scale cup and its contents is modified into a lens. Its central portion is very thick, generally biconvex, without growth rings and transparent (O'Day, 1972). Work so far has shown that the bluish light emitted by myctophid photophores is the result of a chemical reaction which involves the oxidation of a substrate (luciferin) by molecular oxygen in the presence of an enzyme

Fishes of the Western North Atlantic (luciferase). The spectral range of the light produced by the photophores of Myctophum punctatum was found by Nicol (1960) to be from about 410 to 600 nanometers, with maximal emission at about 470 nanometers. This, as pointed out by Nicol (1969), lies in about the region of maximal absorption of the visual pigments in the eyes of this and other deep-sea fishes (around 480 nanometers). The grouping of the photophores is remarkably consistent within the family, but the number and arrangement of photophores in each group are usually species specific; hence their importance in taxonomic studies. This species specificity has often led to the assumption that these organs play an important role in intraspecific recognition. Further, it has been hypothesized that, since most of the photophores are located on the ventral and ventrolateral aspects of the bodies of Ianternfishes and other deep-sea midwater fishes, their function is to emit a sustained, low-intensity light which would tend to conceal the silhouettes of these fishes when viewed from below by potential predators against the dim downwelling light. These and other hypotheses concerning the possible functions of luminous organs in deep-sea fishes have been reviewed by Nicol (1969). Besides the typical photophores described above, some species belonging to different genera (e.g., Bolinichthys, Lampanyctus, Scopelopsis) also have minute "supernumerary" or "secondary" or "unspecialized" photophores. These may be well developed in some regions of the body, head and median fins and poorly developed or lacking in others. In Lampanyctus pusillus, L. alatus, and L. australis, for instance, secondary photophores develop on the head and the entire body where they are found arranged in the definite pattern of one photophore per scale. In Scopelopsis multipunctatus these photophores are so well developed as to mask the presence of the typical primary photophores, which are reduced in size. In their recent description

17

of a number of developmental stages of this interesting myctophid, Moser and Ahlstrom (1972) have shown that the first photophores to appear are some of the typical, primary ones. The secondary photophores begin developing during transformation stages (about 17 mm) and soon attain the adult pattern of one photophore at the posterior margin of each scale pocket. In adults the two types of photophores may be differentiated not by virtue of any difference in size, but by the fact that only the primary ones are overlain by a modified scale (scale lens). In addition to photophores (the term "photophore" is restricted to the discrete, complex, round or kidney-shaped luminous organs described above), myctophids have other kinds of luminous organs. One kind includes the supracaudal and infracaudal luminous glands found on the dorsal and ventral surfaces of the caudal peduncle, respectively. These vary in size and in gross structure. They may be small and simple, large and undivided, or complex, consisting of a series of separate or overlapping luminous scale-like structures. In some genera both supra- and infracaudal glands are found in both sexes without any indication of sexual dimorphism (e.g., Lampanyctus). In other genera the males have a supracaudal and the females an infracaudal gland (e.g., Myctophum). In a few species only males have a supracaudal gland, females have none (e.g., Notoscopelus). Finally, if both sexes of a particular species have a supracaudal only, that in males is larger and better developed (e.g., Notolychnus). These glands are entirely missing in the genus Diaphus. The assumption has been made that the caudal glands, also known as "stern chasers," serve as defensive mechanisms against predators. To quote Bolin (1961: 37): The usual explanation of the function of these sternchasers is that they serve as deflective marks. I have on several occasions observed their momentary flash in freshly captured Lampanyctus [= Steno-

18

Memoir I, Part 7—Sears Foundation for Marine Research

brachius] leucopsarus. The light is of a beautiful blue color and of such intensity that one is at once reminded of an electric spark. There can be no doubt that it is bright enough not only to attract, but to command, attention. It is assumed that when a lantern fish senses the presence and the impending attack of a predator it flashes its sternchaser to focus the attention of the aggressor on the extreme posterior portion of the body. By the time the attack can be launched the light has been extinguished, and a flick of the tail has sent the myctophid into the surrounding dark waters, while the predator's thrust is spent on the spot where the lantern fish was an instant before.

All myctophids also have one or more pairs of luminous organs on the head around the orbit. These organs are best developed in the genus Diaphus, in some members of which they are very large and massive, occupying most or all of the snout area. In a number of species these organs are sexually dimorphic, being larger and better defined in males than in females. Finally, several species in different genera have scalelike luminous structures and amorphous patches of luminous tissue at the bases of the procurrent caudal rays (Lepidophanes, Ceratoscopelusy Notoscopelus, Gymnoscopelus), at the base of the adipose fin (some species of Lampanyctus), above the base of the pectoral fin (most species of Diaphus), at the bases of the dorsal, anal, and ventral fins (Lepidophanes, Bolinichthys, Ceratoscopelus, Hintonia), on top of the head (Bolinichthys, one species of Ceratoscopelus), and on various other parts of the body (Bolinichthys, Ceratoscopelus, Notoscopelus, Gymnoscopelus, Hintonia, and Scopelopsis). Swimbladder. The myctophid swimbladder is of the euphysoclistous type in which the gas-resorbing part is clearly separate from the gas-secreting glandular part. Marshall (1960) described the myctophid swimbladder as having the oval (gas-resorbing part) at its anterior end, with three unipolar retia mirabilia entering at the front of the bladder and carrying blood to a three-lobed gas gland. Differences between myctophid and stomiatoid

swimbladder structures led Marshall to conclude that the myctophids could not have been derived from an isospondylous stock like the gonostomatids as proposed by FraserBrunner (1949). Not all adult lanternfishes have a swimbladder, however. Marshall (1960) found that the adult specimens of four of the 26 species he studied lacked this organ. These were: Gonichthys cocco, Centrobranchus nigroocellatus, Diaphus coeruleus, and Gymnoscopelus braueri. Furthermore, it has been found that in some species the swimbladder regresses with age (Marshall, 1960; Butler and Pearcy, 1972; Kleckner and Gibbs, 1972), in others it becomes partially or wholly invested by oil-filled or fatty tissue (Ray, 1950; Capen, 1967; Zahuranec and Pugh, 1971; Butler and Pearcy, 1972), and in still others it is partially or almost entirely filled with a "cottony tissue" (Capen, 1967). But, Butler and Pearcy (1972) found that, in the juveniles of all the species in which adults had regressed or fatinvested swimbladders, this organ was a thinwalled, gas-filled structure characteristic of the family. Marshall (1960) has pointed out that although replacement of gas by fat is an inadequate substitution as far as buoyancy is concerned, this replacement "can have but little effect on the 'credit side' of the 'buoyance balance sheet'." This may very well be true, especially in the presence of such compensatory adaptations for buoyancy as reduced ossification, reduced muscle-tissue density, and the presence of body lipids, generally found to be higher in fishes lacking gas-filled swimbladders (Butler and Pearcy, 1972). Accumulation by myctophids of body lipids in the form of wax esters may serve the functions of providing a stable buoyancy fraction and a long-term energy reserve (Butler and Pearcy, 1972). Vertical Distribution and Migrations. Although the overwhelming majority of collections have been made with open nets of various types, repetitive sampling in the same

Fishes of the Western North Atlantic general area, at various depths, and at various times during both day and night has significantly contributed to our knowledge of the vertical distribution of many myctophids. This knowledge has been enhanced and refined considerably by the few studies of discrete-depth samples taken with openingclosing gear (e.g., Pearcy and Laurs, 1966; Badcock, 1970; Badcock and Merrett, 1976; Ebeling et al., 1971; Gibbs and Roper, 1971; Gibbs et al., 1971; Pugh, 1973; Baird et al., 1974; Frost and McCrone, 1974). Peak abundances of most myctophids during the day have been found to occur at depths between 300 and 1200 m, with infrequent captures above and much below this range. Recently obtained evidence supports Marshall's (1960: 109) remarks that "conditions of life at the bottom are favourable enough to attract detachments of active pelagic organisms, such as ... lantern fishes/' During one of the dives of the deep submersible vehicle ALVIN off the coast of New England, James Craddock of the Woods Hole Oceanographic Institution (personal communication) observed large Lamp any ctus macdonaldi swimming very near the bottom. Specimens of Lampadena luminosa have been found in the stomachs of white hake (Merluccius albidus) taken in the Gulf of Mexico (personal data), while large specimens of Diaphus adenomus, D. watasei, and D. coeruleus have consistently been taken with nets fishing on or very near the bottom on continental shelves and slopes (Nafpaktitis, 1974; and unpublished data). During the night vertical distributions change greatly. The vast majority of lanternfishes migrate from their day-time depths to the surface mixed layer. While many spend the night at depths between about 30 and 100 m, depending on the depth and strength of the thermocline that usually marks the lower limit of the mixed layer, a good number of species enter the uppermost 10 m. Several of the latter are commonly dipnetted at the sur-

19

face or taken with neuston nets. Kawaguchi et al. (1972) showed that in the tropical and subtropical Pacific and Indian Oceans the myctophids most commonly collected at the surface at night included Myctophum spinosum, M. nitidulum, M. obtusirostre, and M. asperum. These were followed in abundance by species of Symbolophorus, Centrobranchus, Hygophum, and Gonichthys, in that order. In the eastern North Pacific Tarletonbeania crenularis is commonly dipnetted under night lights (Pearcy, 1964). While these are the species most regularly captured at the surface after sunset, a number of other, less extensively migrating myctophids have from time to time been dipnetted. These sporadic appearances at the surface of more restricted migrators may be due to short-range, hydrological and biological conditions, such as breaking down of the thermocline in temperate latitudes, local, seasonal currents and eddies, upwellings, etc. (Nafpaktitis, 1968: 37; Nakamura, 1970). As noted, most myctophids migrate, many for several hundred meters. However, adults of deeper-dwelling forms, such as some Lampanyctusy Lampadena, Notoscopelus, Gymnoscopelus, and Taaningichthys migrate much less extensively or not at all. It should be pointed out here that, whatever the daytime depths of occurrence of different lanternfish species may be, critical analyses of collections taken with opening-closing nets indicate intraspecific patterns of vertical distribution that seem to be similar among the carefully studied species. Evidently, juveniles occupy the shallower reaches of the bathymetric range of any given species. Furthermore, juveniles tend to reach shallower depths in their upward migrations than do their conspecific adults. This tendency may be due to functional differences in the swimbladders between juveniles and adults. Finally, regardless of the daytime depth of occurrence of adults and juveniles, larvae of most myctophid species are found

20

Memoir I, Part 7—Sears Foundation for Marine Research

in the upper mixed layer, between the surface and approximately 12 5 m (Ahlstrom, 1959). Contrary to earlier beliefs, not all of the individuals of any particular, vertically migrating lanternfish population move up every night. Evidence of this has been obtained from studies of discrete-depth samples in relation to biological sound scattering (Gibbs and Roper, 1971) and from observations during dives of deep submersible vehicles (Barham, 1971). The results of field studies and laboratory experiments suggest that light exerts an important control on vertical migrations of oceanic animals (Kampa and Boden, 1954, 1956; Marshall, 1954: 180; Clarke and Denton, 1962). It is conceivable, as Clarke and Backus (1956) have suggested, that the upward migration is initiated primarily by changes in light intensity. Specifically, once the stimulus has been received from a sufficient reduction in light, the animals swim toward the surface even though this means moving into higher light intensities. If this is so, then it may be assumed that the individuals remaining at midday depths while the rest of the population moves upward at dusk are in a physiologically refractory condition; that is, their nervous system becomes temporarily non-responsive to changes in illumination. Migratory disposition may depend on such factors as recency of last meal and reproductive state. Capture of some of Barham's (1971) "lethargic" fishes and examination of their gonads and stomach contents may prove rewarding. Very likely light initiates and probably controls the descent in early morning hours. As for species living in depths below the limits of light penetration, it is quite possible that their generally limited migrations are triggered by substantial increases in bioluminescence from shallower forms during their twilight climb. It has long been assumed that midwater oceanic animals move from their midday depths to the upper, productive layers in order to feed. With his appreciation of the

energy demands and of the physiological constraints placed upon vertical migrators, Marshall (1960: 87) observed that, "the time and effort given each day to vertical migrations by countless oceanic animals is one of the most striking features of their biology.... Considering the fishes, there can be little doubt that their daily climb towards the surface is a feeding migration." However, that this is indeed so remains to be shown. The few published and unpublished studies on the feeding chronology of some myctophids and other vertically migrating midwater fishes are mostly inconclusive (Anderson, 1967;Paxton, 1967a, 1967b; Collard, 1970; Cailliet, 1972). True, investigations of this nature have been hampered by a number of difficulties. These include: prevention of captured fishes from feeding or ejecting their stomach contents while in the net; lack of objective methods for determining the degree to which stomach contents have been digested; limited availability of reliable, discrete-depth sampling gear; and, most important, lack of knowledge regarding rates of digestion in myctophids and other vertically migrating midwater fishes. Several hypotheses have been put forth regarding the adaptive value of vertical migrations. These have been briefly reviewed by McLaren (1963). Although these hypotheses are based on studies of zooplankton, some may be found applicable to nekton as well. Of interest is McLaren's (1963) own hypothesis, according to which animals that feed in warm surface waters and "rest" in deeper, cooler waters gain an energy bonus which may be put into fecundity. Whatever the adaptive aspects of vertical migrations may prove to be, the fact remains that at night the myriads of vertical migrators find themselves in a trophically richer environment which they obviously exploit. Upon their return to their respective midday depths they are preyed upon by predators largely confined to those depths. The latter, in turn, serve as food for still larger animals, and so

Fishes of the Western North Atlantic on. The importance therefore of vertical migrations in the transfer of energy from the upper productive zone to deeper, trophically poorer ones is obvious. food. Myctophids feed primarily on copepods, euphausiids, and ostracods, but they will eat practically any small-size zooplankter that is available to them at any particular time and place, including fish eggs and fish larvae. They will even eat juveniles of their own and other midwater-fish species. This tendency to devour whatever item in their diverse food repertory happens to be seasonally or locally most abundant, reflects their rather non-discriminatory, opportunistic feeding habits (Collard, 1970; Cailliet, 1972), although Merrett and Roe (1974) and Baird et al. (1975) have shown some degree of selectivity among certain lanternfishes. Diversity and Range. Ever since Rafinesque described the first lanternfish (Myctophum punctatum) in 1810, descriptions of "species" have proliferated enormously. To date, more than 340 myctophids have been described (recent compilation by J. R. Paxton, personal communication). These have been assigned to some JO genera. According to current estimates, approximately 240 species in 30 genera are generally recognized. Bolin (unpublished manuscript) once remarked: "The lantern fishes... are so common that a plankton net of fair size and straining capacity, drawn at a depth of 200 meters or more anywhere in the oceans of the world is almost certain to capture specimens/' Moser and Ahlstrom (1974) have found that larvae of this most speciose and widespread family of midwater fishes make up about 50% of all larvae taken in open-ocean plankton tows. A survey in the northeastern Pacific off British Columbia, Washington, and Oregon (Waldron, 1972) revealed that myctophid larvae ranked second in abundance (31.6%), after scorpaenid larvae (39.5%). Lanternfish range from arctic to antarctic waters and from the very surface at night to

21

depths exceeding 2,000 m. They have been taken predominantly in open oceanic waters but they also occur over continental slopes and even continental and island shelves. A number of species have been observed from deep submersible vehicles and/or collected very near the bottom. As mentioned earlier, however, within this enormous vertical range, careful studies and increased utilization of discrete-depth collecting gear have revealed interspecific as well as intraspecific patterns of vertical distribution that are subject to some modification depending upon latitude, season, and local hydrological conditions. In general, the geographic ranges of myctophids seem to correlate quite well with definable types of water and pelagic regions as delimited by physical boundaries (see the separate chapter by Backus et al. on Atlantic Mesopelagic Zoogeography). Although some species in the southern hemisphere have an almost circumglobal distribution, the widespread occurrences reported for others may be due to the existence of expatriate populations in waters far beyond the normal ranges of the species involved. For instance, representatives of tropical and subtropical species and species with ranges in the eastern North Atlantic are often taken in the Slope Water off the northeastern U.S. coast and Canada. These expatriates, some of which may occur in large, dense populations (Hersey and Backus, 1954; Nafpaktitis, 1968; Backus et al., 1968), are mostly large adults. No larvae have ever been found among expatriate populations, which evidently lose their ability to reproduce (O'Day and Nafpaktitis, 1967; Zurbrigg and Scott, 1972). The phenomenon of expatriation appears to be more widespread than has been thought. It should be looked for and expected wherever ocean currents flow through different water masses and pelagic regions. Commercial Value. Although abundant and widespread, myctophids are only now beginning to draw attention as an exploitable source of animal protein. Lanternfish, mainly

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Memoir I, Part 7—Sears Foundation for Marine Research

Lampanyctodes hectoris, have accounted for 0.30-10.47% (1,134-42,760 metric tons) of the total fish catch landed by South African pelagic fishing boats operating in the cold water off the west coast of South Africa during the years 1969-1973 (Centurier-Harris, 1974). Approximately 15 tons of another species, Diaphus dumerflii, were taken in a single haul at a depth of 260-265 m off Uruguay (WALTHER HERWIG Sta. 208/1966; Institut fur Seefischerei, Hamburg; Gerhard Krefft, personal communication). Biochemical studies in the Soviet Union have indicated that the southern-hemisphere myctophid, Gymnoscopelus nicholsi, is suitable for human consumption (Dubrovskaya and Makarov, 1969). Numerous studies have shown that myctophids are preyed upon by a variety of fishes and other vertebrates, many of which are of high commercial value. These include: spring and coho salmon (Shimada, 1948), sockeye salmon (Manzer, 1968), Atlantic cod (Popova, 1963; Kashintsev, 1963), redfish (Kashintsev, 1963), hake (HaUiday and Scott, 1969; also personal observations), rockfish and jack mackerel (Fitch, 1951), albacore (McHugh, 1952), yellowfin and skipjack tunas (Alverson, 1963), albacore and bluefin tuna (Pinkas et al., 1971), swordfish (Scott and Tibbo, 1968), fur seals (Mead and Taylor, 1953). Furthermore, Fitch and Brownell (1968) found that more than 89% of a total of 18,164 fish otoliths recovered from the stomachs of seven cetacean species belonged to at least 19 species of lanternfishes. Impressed with the "apparent dependency of the smaller cetaceans on mesopelagic fishes, especially myctophids," Fitch and Brownell (1968) concluded that "If the day ever arrives that man finds it economically feasible to harvest fishes from the scattering layers [often composed predominantly of myctophids], uncontrolled exploitation could have a disastrous effect on our dolphin, porpoise, and whale populations/'

Thus, myctophids emerge as a vital link in the complex oceanic food web. Systematic*. On the basis of osteological and adult external morphological characters (mainly number and arrangement of photo phores and other luminous organs) Paxton (1968, 1972) established two subfamilies within the family Myctophidae: the Myctophinae and the Lampanyctinae. He further allotted the genera within each subfamily to a number of tribes each representing a major evolutionary line. Paxton's scheme may be summarized as follows: Subfamily MYCTOPHINAE Tribe Myctophini, with seven genera in three apparent evolutionary groups: (a) Protomyctophum and Electrona, (b) Diogenichthys and Benthosema, and (c) Hygophum, Myctophum, and Symbolophorus. Metelectrona Wisner (1963) was considered a synonym of Electrona. Tribe Gonichthyini, with two pairs of closely related genera: (a) Lawetna and Tarletonbeania, and (b) Gonichthys and Centrobranchus. Subfamily LAMPANYCTINAE Tribe Lampanyctini, with eight genera representing three definite lines: (a) Lampadena and TaaningichthySy (b) Bolinichtbys, Lepidophanes, and Ceratoscopelus, and (c) StenobrachiuSj Lampanyctus, and Triphoturus. Had specimens of Dorsadena Coleman and Nafpaktitis 1972 been available to Paxton at the time of his study, he would probably have placed this genus in the same group with Lampadena and Taaningichthys. Parvilux Hubbs and Wisner 1964 was considered a synonym of Lampanyctus. Tribe Diaphini, with two genera: Lobianchia and Diaphus. Tribe Gymnoscopelini, with six genera: LampanyctodeSy Gymnoscopelus, Notoscope-

Fishes of the Western North Atlantic lus, Lampicbtbys, Scopelopsis, and Hintonia. Paxton considered this to be a specialized group. Interestingly, all genera but Gymnoscopelus and Notoscopelus are monotypic and all but Notoscopelus are restricted to the southern hemisphere. Tribe Notolychnini, with a single monotypic genus: Notolycbnus valdiviae. The position and relationships within the Myctophidae of this enigmatic lanternfish have been argued at length by Bolin (1946), FraserBrunner (1949), Paxton (1968, 1972), and Moser and Ahlstrom (1974). Besides its unique specializations, this ubiquitous, diminutive form shares some characters with the Myctophinae and others with the Lampanyctinae. Its unique features prompted Paxton to erect a separate tribe which he chose to include in the subfamily Lampanyctinae. There is a remarkable agreement between Paxton's scheme of subfamilial relationships within the family Myctophidae and that arrived at by Moser and Ahlstrom on the basis of their extensive studies of myctophid larvae (Moser and Ahlstrom, 1970, 1972, 1974). Points of disagreement include Paxton's subdivision of the genera in the subfamily Myctophinae into two tribes. Moser and Ahlstrom (1970, 1974) found no larval characters that could justify such a subdivision. They also suggested the resurrection of Metelectrona as a valid genus. In the view of Moser and Ahlstrom (1974), the tribe Lampanyctini includes the genera Lampanyctus, Tripboturus, Stenobracbius, and Parvilux whose validity, they suggested, should be reconsidered in light of the distinctness of its larvae. Removal by these authors of the genera Lampadena, Taaningichthys, Bolinicbtbys, Lepidopbanes, and Ceratoscopelus from the tribe Lampanyctini and their placement in the tribe Gymnoscopelini were prompted by the discovery of larval characters shared by these genera and those originally assigned to the Gymnoscopelini by Paxton. Finally, regarding the status of Notolycb-

23

nus valdiviae, Moser and Ahlstrom (1974) characteristically remarked: "The larval characters are of little help in elucidating the affinities of this species within the Myctophidae and, when added to the list of unique adult characters, only magnify the problem. It would seem to make just as much sense to establish a separate subfamily for Notolycbnus as to place it in a monotypic tribe in the subfamily Lampanyctinae." Briefly, the two subfamilies of the family Myctophidae may be defined as follows (slightly modified from Paxton, 1972: 51): Subfamily Myctophinae. Two Prc (one in Tarletonbeania only), neither above lateral line; secondary photophores absent; larvae with narrowed elliptical eyes; dorsal and ventral extrascapulars separate or only ventral element present; posteromedial shelf on cleithrum absent. Subfamily Lampanyctinae. More than two Prc (except for Notolycbnus which has two, with one of them well above lateral line); secondary photophores present or absent; larvae with rounded eyes (except for Notolycbnus larvae which have eyes of irregular shape); dorsal and ventral extrascapulars fused into one element, or extrascapulars not ossified; posteromedial shelf on cleithrum present (absent in Notolychnus). North Atlantic Genera and Species. Eightytwo species of myctophids have been recorded from the North Atlantic. These belong to 20 genera. The two largest genera in the North Atlantic are Diaphus (23 species) and Lampanyctus (13 species). Only one myctophid genus, Lepidopbanes (with two species), is restricted to the Atlantic. It is virtually certain that the species Bentbosema glaciale, Ceratoscopelus maderensis, Hygophum benoiti, Lampadena pontifex, Lampanyctus crocodilus, Myctophum punctatum, Notoscopelus bolini, and Notoscopelus elongatus are restricted to the North Atlantic. Diaphus minax, D. rafinesquii, and D. roei

Memoir 1, Part 7—Sears foundation for Marine Research

24

Sopracaida!

S«o Cs

Art

_PM»_ ^ JL

no \

]|I

{

:!6

Si

FIGURE 3. General distribution of luminous organs (Br and Op omitted) and their abbreviated terminology in the family Myctophidae.

have not been reported outside the North Atlantic, but the genus Diapbus has not been studied completely enough on a global basis to make this certain. If Protomyctophum arcticum is held to be distinct from the very similar P. subparallelum and P. thompsoni (as we hold here), then it should be added. Finally, Symbolophorus veranyi may be restricted to the North Atlantic, but its relationship to S. hoops and other species occurring outside the North Atlantic is not clear. Additionally, the S. veranyi of the Mauritanian Upwelling may prove to be a distinct species. Thus, the list of North Atlantic endemic myctophids surely includes eight species and possibly as many as 14. In addition to the 8-14 myctophid species restricted to the North Atlantic alone, there are 12 species found in both North and South Atlantic, but not yet known with certainty from anywhere else. Preeminent are the two species in the Atlantic genus Lepidophanes. Both L. gaussi, a bipolar subtropical species, and L. guentheri, a tropical species, are abundant, especially the latter. To these can be added Diaphus holti, D. subtilis, D. taaningi, D. vanhoeffeni9 Gonichthys cocco, Hygophum macrochir, H. taaningi, Lampanyctus cuprariuSy L. isaacsi, and Myctophum affine. Some

of these, especially those in Diaphus, may yet prove to be extra-Atlantic inhabitants. All in all, those North Atlantic myctophids that are not found outside the North and South Atlantic may number as many as 26.

TERMINOLOGY AND METHODS Fish Characters. The identification of myctophids strongly depends on the number and position of the various luminous organs on the head and body. The general distribution of these organs is shown in Fig. 3. Their names and abbreviations are as follows: Dn—dorsonasal; Vn—ventronasal; So—suborbital; Ant —antorbital, a small triangular or oval-shaped organ situated between the Dn and the anterodorsal margin of the orbit (present in some species of Diaphus); Suo—supraorbital; Br— branchiostegal; Op—opercular; Ce—cervical; PO—thoracic; PVO—subpectoral; PLO—suprapectoral; VO—ventral; VLO—supra ventral; SAO—supra-anal; AOa—anterior anal; AOp—posterior anal; Pol—posterolateral; Prc —precaudal. Luminous organs on the dorsal and ventral aspects of the caudal peduncle are always referred to as supracaudal and infracaudal luminous glands, respectively. A single luminous organ below the Dn, re-

Fishes of the Western North Atlantic gardless of its size and position along the anterior, anteroventral or ventral orbital margin, is always called Vn. In the case of two luminous organs below the Dn, the anterior one is the Vn and the posterior the So. With few exceptions, lanternfish scales, including lateral-line ones, are deciduous and very few specimens retain them following capture and preservation. Therefore, counts of the horseshoe-like lateral-line organs are here presented instead of counts of lateral-line scales. Distribution Maps. The distribution maps were drawn by CalComp Plotter. The projection is the Mollweide equal-area one. The x's mark the position of tows that did not catch the species in question in spite of the fact that the tows were at the right depth for doing so (based on a conservative interpretation of the vertical distribution of hauls producing the positive data). The radius of the black dots is proportional to catch rate. The same catch rate classes were used for all maps. The catch rate classes were chosen to be as sensitive as possible to changes in abundance in all species, both abundant and rare. All tows (day, night, and twilight) were used in making the maps in spite of the fact that a unit of effort by day often or usually caught less than a unit of effort by night. For some species a few records (marked by triangles not having any quantitative meaning) have been added from the literature. This has been done only when it has been reasonably certain that the records were based upon correct identifications and when using them would give a more correct impression of a species' distribution. The sources of these records are given in the figure captions of the distribution maps of the relevant species. Records from the "Ocean Acre" program off Bermuda (Gibbs et al., 1971) also have been added. Descriptions of Atlantic Distributions. The Atlantic Ocean ranges of individual species are described in terms of the zoogeographic system of mesopelagic regions and provinces

25

described in the separate chapter by Backus et al. on Atlantic Mesopelagic Zoogeography. Particular reference is made to those regions and provinces in which the species is most abundant. In this connection, the term "ranking" is used as a modifier of species. When it is said that a species is a ranking species in a certain region, it is meant that the species is one of the several most abundant myctophid species whose numbers together make up at least 80% of the total number of myctophid specimens caught in that region. By the ranking species the most abundant myctophid species is indicated. In the Atlantic Subarctic Region there is only one ranking myctophid, Benthosema glacial e^ it makes up well over 80% of all myctophid specimens caught in that region. In the Atlantic Tropical Region, on the other hand, where diversity and evenness are much higher, 12 species are required to comprise 80% of the total number of myctophid specimens. Here, the ranking species, Lepidophanes guentheri, makes up only 17% of the total number, while the twelfth ranking species, Lampanyctus nobilis, makes up 2.2% of the total number of myctophid specimens in that region. The ranking species in each of the Atlantic faunal regions are given in the chapter on Atlantic Mesopelagic Zoogeography, Table V. Vertical Distributions. The accounts of vertical distribution are based on the relatively numerous and widespread WHOI collections, which were made with open nets, and on four sets of discrete-depth data from nets employing opening-closing devices and covering the water column by day and by night down to 1,500 or 2,000 m. The vertical distribution of the fishing effort for the WHOI collections is shown in Backus et al., this volume, Table II. The vertical series of Badcock (1970) from off Fuerteventura, Canary Islands, using a cod-end catch-dividing bucket, and those of Badcock and Merrett (1976) from 30°N, 23°W, about 400 n. mi. WNW of the Ca-

26

Memoir 1, Part 7—Sears Foundation for Marine Research

naries, in which the entire net was opened and closed, are combined and referred to as "near the Canary Islands." There was little to suggest that the two sets should be considered separately, although the two localities are somewhat different physically. The "Ocean Acre" collections (Gibbs et al., 1971; Karnella, unpublished data) made with a cod-end closing sampler, include the only seasonal data among the discrete-depth sets. These collections are referred to in the accounts as coming from "near Bermuda." The Canaries and Bermuda localities lie in subtropic seas. The fourth set of closing-net data comprises vertical series from five loca-

tions in the temperate Eastern and Western Mediterranean Seas (Goodyear et al., 1972). Subtropical waters are generally relatively transparent, and because ambient-light level affects the daytime depths of occurrence of mesopelagic animals (Clarke and Backus, 1964; Kampa, 1971), the data from near Bermuda and the Canary Islands may represent near maximum depth occurrences. In more productive and less transparent waters, as are typical of tropical and temperate regions, generally shallower depths of occurrence can be expected. The WHOI data include a wide range of conditions.

Key to the North Atlantic and Mediterranean Genera la. Three photophores (VLO, SAO3 and Pol) very close to dorsal contour of body; 2 Prc; Prc2 well above horizontal septum (I). Notolycbnus Fraser-Brunner 1949, p. 91

Ib. No photophores close to dorsal contour of body; 2 or more Prc; Prc2 never above horizontal septum or lateral line 2a. PLO from less than its diameter above to well below level of upper end of base of pectoral fin 2b. PLO more than its diameter above level of upper end of base of pectoral fin ... 3a. PLO well below level of upper end of base of pectoral fin; AO not distinctly divided into AOa and AOp; Pol not differentiated; mouth terminal, snout not protruding; caudal peduncle not markedly slender, its least depth less than 2. J times in its length'. 3b. PLO at or slightly above level of upper end of base of pectoral fin; AO divided into AOa and AOp; Pol well differentiated; mouth subterminal, snout more or less protruding; caudal peduncle markedly slender, its least depth 2.J times or more in its length 4a. PLO in front of and, often, slightly higher than PVOl5 PLO, PVOi and PVO2 on a somewhat angulated line (IIA). Protomyctophum Fraser-Brunner 1949, p.

2 j 7 4

j 29

Fishes of the Western North Atlantic

4b. PLO over PVOi; PLO, PVOi and PVO2 forming a triangle (IIB). Electrona Goode and Bean 1896, p. 5 a. Gill rakers absent. Centrobranchus Fowler 1904, p. 5b. Gill rakers present . ( 6a. Origin of anal fin about under middle of base of dorsal fin; none or only one AOp over base of anal fin; least depth of caudal peduncle about 2.5 times in its length. Loweina Fowler 1925, p. 6b. Origin of anal fin on or slightly in front of vertical through end of base of dorsal fin; 5-7 AOp over base of anal fin; least depth of caudal peduncle 3.5 times or more in its length. Gonichthys Gistel 1850, p. 7a. PVO2 at or below level of upper end of base of pectoral fin (IIIA)

27

33 89 6 81 86 8

7b. PVO2 well above level of upper end of base of pectoral fin (IIIB); 2, sometimes 3, Pol horizontally arranged; numerous stiff, spine-like procurrent caudal fin rays; patches of luminous tissue on trunk and at bases of procurrent caudal fin rays. Notoscopelus Giinther 1864, p. 247 8a. Two Prc 9 8b. More than 2 Prc 13 9a. PVO arranged horizontally or nearly so, with PVOi not more than its diameter below level of PVO2; VO2 more or less elevated 10 9b. PVO on an inclined line, with PVOi more than its own diameter below level of PVO2; VO level 11 lOa. Prc2 much higher than Prci, lying twice its own diameter or less below lateral line; small, simple teeth on premaxillaries and dentaries. Benthosema Goode and Bean 1896, p. 49 lOb. Prc2 slightly higher than Prci; premaxillary teeth flattened, lanceolate, many with minute denticle on each edge at widest point; outer anterior teeth on dentary closeset and flattened, posterior ones broad-based and sharply hooked forward. Diogenicbtbys Bolin 1939, p. 56 lla. Two Pol. Hygopbum (Taning) Bolin 1939, p. 35 lib. One Pol 12 12a. SAO strongly angulated; SAOi in advance of, seldom directly over VO3. Symbolopborus Bolin and Wisner 1959, p. 75

28

Memoir ly Part 7—Sears foundation for Marine Research

12b. SAO on a straight or slightly angular line; SAd behind VO8. Myctophum Rafinesque 1810, p. 59 13a First PO and two PVO on a straight, ascending line; first 3 VO on a straight, ascending line; males with supracaudal, females with infracaudal luminous glands or caudal 14 glands absent; 4 Prc • * * " 13b. First PO and two PVO not on a straight line; first 3 VO not on a straight, ascending line; both sexes with supracaudal and infracaudal luminous glands; 3-* Prc . . . 15 14a. More than one pair of luminous organs on head; caudal luminous glands absent; usually a luminous scale at PLO (IV). Diaphus Eigenmann and Eigenmann 1890, p. 102

14b. Only one pair (Dn) of luminous organs on head; supracaudal (males) and infracaudal (females) luminous glands well developed; no luminous scale at PLO. Lobianchia Gatti 1903, p. 94 15a. Caudal luminous glands large, undivided, bordered by black pigment; 3 Prc or none (VA) 16

15b. Caudal luminous glands consisting of a series of overlapping scale-like structures not bordered by black pigment (VB); 3—4 Prc 17 16a. Origin of dorsal fin directly over or somewhat in front of base of ventral fin; photophores well developed; 3 SAO; lateral line well developed; no large crescent of whitish tissue on posterior half of iris (except for L. chavesi which has one on dorsal half of iris). Lampadena Goode and Bean 1896, p. 171 16b. Origin of dorsal fin behind base of ventral fin; photophores present or absent; if present, poorly developed; one SAO; lateral line very poorly developed or absent; a large crescent of whitish tissue on posterior half of iris (best seen in preserved specimens). Taaningichthys Bolin 1959, p. 186 17a. PO4 not elevated; luminous scalelike structures midventrally between bases of ventral fins or between bases of ventral fins and anus; 4 Prc. Ceratoscopelus Giinther 1864, p. 241 17b. PO4 highly elevated; no luminous scalelike structures midventrally between bases of ventral fins or between bases of ventral fins and anus; 3-4 Prc 18

Fishes of the Western North Atlantic 18a. Four VO; SAO strongly angulated, a line through SAOi and SAO2 not intersecting VO series; luminous tissue other than photophores restricted to caudal glands and, sometimes, base of adipose fin; 4 Prc; SAO3, Pol2 and PLO at or below lateral line. Lampanyctus Bonaparte 1840, p. 18b. Five VO; SAO weakly angulated, a line through SAOi and SAO2 intersecting VO series; patches of luminous tissue at bases of median and paired fins; 3-4 Prc; SAO3, Pol2 and, often, PLO just above lateral line 19a. Four Prc; no crescent of whitish tissue on posterior half of iris; jaws long, extending one or more times the diameter of eye behind vertical through posterior margin of orbit. Lepidophanes Fraser-Brunner 1949, p. 19b. Three Prc; a crescent of whitish tissue on posterior half of iris; jaws short, extending one-half the diameter of eye or less behind vertical through posterior margin of orbit. Bolinichthys Paxton, 1972, p. Genus Protomyctophum Fraser-Brunner 1949 Protomyctophum Fraser-Brunner, 1949: 1045 (introduced as a subgenus of Electron*; type-species Myctophum tenisoni Norman 1930, by original designation) ; Bolin, 1959: 5 (proposed full generic status) ; Andriashev, 1962: 224 (definition of genus Protomyctophum, with two subgenera: Protomyctophum and Hierops); Paxton, 1972: 42 (definition, including osteological characteristics, of Protomyctophum and subgenera Protomyctophum and Hierops).

Characters. Mouth moderately large, extending to or somewhat beyond vertical through posterior margin of orbit; maxillary greatly expanded posteriorly, truncate. Base of anal fin longer than that of dorsal fin. Lateral line, if present, very weakly developed. Dn, if present, minute; Vn present, small; PLO below base of pectoral fin, in front of and, often, slightly higher than PVd, the three organs (PLO and two PVO) in a straight or somewhat angulated line; J PO, level; 4 VO, level; 3 SAO in a straight or weakly angulated line; no Pol; AO in a continous series; 2 Prc, level or very nearly so; supracaudal and infracaudal luminous glands present. Subgenus Protomyctophum Fraser-Brunner 1949 Protomyctophum Fraser-Brunner, 1949: 1045 (typespecies Myctophum tenisoni Norman 1930, by original designation); Andriashev, 1962: 226 (definition); Paxton, 1972: 42 (definition).

29

193 19 226 231

Characters. Interorbital space wider than posterior, expanded portion of maxillary. Eyes normal in position, pupil and lens not displaced dorsally. Origin of anal fin about under end of base of dorsal fin. Range. Antarctic and temperate waters of the southern hemisphere. Species. Five species have been described: P. anderssoni, P. andriashevi, P. bolini, P. normani, and P. tenisoni. None occurs in the North Atlantic. Subgenus Hierops Fraser-Brunner 1949 Hierops Fraser-Brunner, 1949: 1046 (type-species Scopelus arcticus Liitken 1892, by original designation); Bolin, 1959: 4 (accorded full generic status; definition); Andriashev, 1962: 224, 234 (maintained subgeneric status; definition); Paxton, 1972: 42 (definition of subgenus).

Characters. Interorbital space usually narrower than posterior, expanded portion of maxillary. Eyes with pupils and lenses displaced dorsally. Origin of anal fin well in advance of end of base of dorsal fin. Range. North Atlantic and Pacific Oceans; subtropical and temperate waters of the southern hemisphere. Species. The following seven species have been described: H. arcticum, H. beckeri, H. chilensis, H. crockeri, H. parallelum, H. subparallelum, and H. thompsoni. Of these, only H. arcticum occurs in the North Atlantic.

30

Memoir 1, Part 7—Sears Foundation for Marine Research

FIGURE 4. Protomyctophum arcticum: male, 32 mm; A, infracaudal luminous gland of female, 34 mm.

Protomyctophum arcticum (Liitken) 1892 Figures 4, 5 Study Material. One hundred and sixty-one western North Atlantic specimens, 16—43.5 mm; in LACM.

Distinctive Characters. The continuous AO, the PLO-PVO configuration, and the "semi-telescopic" eyes will separate this species from all other North Atlantic myctophids. For characters distinguishing P. (H.) arcticum from the North Pacific P. (H.) thompsoni and the southern hemisphere P. (H.) subparallelum see under Remarks. Description. Fin rays: dorsal 12 (11-13); anal 22-23 (21-24); pectoral 16-17 (15). Gill rakers: 4-5 + 1 + 14^15, total 19-21. Photophores: AO 15-16, in a continuous series. Head. Length of head 3-3.5 in SL. Mouth oblique with lower jaw slightly protruding; maxillary greatly expanded posteriorly, truncate, extending below premaxillary; length of upper jaw 1.3-1.5 in hi and 4.2-4.8 in SL. Eyes approaching each other dorsally; interorbital space much narrower than expanded

portion of maxillary; diameter of eye 1.7-1.9 in length of upper jaw, about 2.5 in hi and 7-8 in SL. Fins. Origin of dorsal fin well behind base of ventral fin. Origin of anal fin about under middle of base of dorsal fin. Pectoral fins just about reaching 1st SAO. Ventral fins extending to origin of anal fin. Base of adipose fin well in advance of end of base of anal fin. Luminous Organs. Dn and Vn present, very small, on anterodorsal and anteroventral margin of orbit, respectively. PLO less than one organ diameter in front of and slightly higher than PVOi which is behind PO2; PVO2 at lower end of base of pectoral fin. VLO about 3 times its diameter above base of ventral fin. SAO in a straight line or slightly angulated; SAOi usually a little behind VO3; SAO2 over origin of anal fin; SAO3 about over 1st AO. AO evenly spaced, level. Prc2 slightly higher than, and 1-1.5 times its own diameter behind Prci. Sexual Dimorphism. Adult males with a single, undivided supracaudal luminous gland surrounded by black tissue and with the bulk of the luminous tissue concentrated in the pos-

Fishes of the Western North Atlantic terior one-third of the gland. The supracaudal gland first appears in individuals about 21 mm long. In young females, 25-26 mm long, a single patch of luminous tissue appears inf racaudally. Soon a second patch develops anterior to the first one. In specimens about 32 mm long, the two patches coalesce to form a single structure. Size. Sexual maturity is reached at a size of about 32 mm. The species grows to about 45 nun. Development. Tining (1918) illustrated and briefly discussed a number of larval stages of this species from the eastern North Atlantic. Remarks. P. (H.) arcticum is very similar to the North Pacific P. (H.) thampsoni (Chapman) 1944, from which it differs primarily in having the two Prc "separated from each other by a space equal to or slightly greater than an organ diameter/' whereas in P. (H.) thompsoni the Prc are "very close, almost overlapping, the space between them much smaller than an organ diameter" (Bolin, 1959). In 1932, Tining described a lanternfish from "east of New Zealand, Southern Island," which he considered to be subspecifically distinct from P. (H.) arcticum (Tining, 1932). Tuning's southern form, Myctophum arcticum subparallelum was subsequently recorded as a subspecies of Electrona (Hierops) arctica by Fraser-Brunner (1949). Bolin (1959) pointed out that while P. (H.) arcticum and P. (H.) subparallelum are very closely related they represent good species. Andriashev (1962) expressed some doubts as to the specific distinctiveness of the two forms, but did not draw any conclusions since he had no material of P. (H.) arcticum for direct comparison. The same author added (footnote) that, according to V. E. Bekker, "P. arcticum is well distinguished from P. subparallelum by the structure of the supracaudal gland in males" (Andriashev, 1962: 237). I have examined and directly compared a large number of the North Atlantic P. (H.) arcticum with nu-

31

merous P. (H.) subparallelum collected by the USNS ELTANIN in the southern oceans. The two fishes are remarkably similar. The supracaudal glands in males of both forms show no marked differences. Of all the characters counted and measured, the following ones show the greatest differences [averages are given in percent of SL and are based on 40 P. (H.) arcticum, 21-*3.5 mm, and 22 P. (H.) subparallelum, 19.5-34 mm, in parentheses] : distance from tip of snout to origin of dorsal fin: 53 (57); distance from origin of dorsal fin to posterior end of hypurals: 53 (49). Furthermore, although very similar in morphology, the otoliths of the two forms differ markedly in relative length. Those of P. (H.) arcticum are less than 8 percent of SL (two pairs measured), whereas those of P. (H.) subparallelum measure more than 9 percent of SL (three pairs measured). P. (H.) arcticum grows to a size of about 45 mm, whereas P. (H.) subparallelum does not seem to grow larger than about 35 mm. Finally, P. (H.) arcticum is limited to the North Atlantic where it occurs between approximately 40° and 70°N. On the other hand, P. (H.) subparallelum is almost circumglobally distributed in the southern hemisphere between approximately 35° and 60°S. On the basis of the above differences I choose to follow Bolin (1959) in maintaining the specific distinctiveness of the two forms. Atlantic Distribution. Protomyctophum arcticum (Fig. 5) is a subpolar-temperate species. It was much more abundant in WHOI subarctic collections than in temperate ones. The species has been recorded from north of 70°N on the coast of West Greenland and probably occurs everywhere in the subarctic Atlantic. P. arcticum does not occur in the Mediterranean Sea nor in the Mediterranean Outflow and southern part of the AzoresBritain Province. P. arcticum is restricted to the North At-

32

Memoir 1, Part 7—Sears Foundation for Marine Research

FIGURE 5. Protomyctophum arcticum, a subpolar-temperate species. Distribution, based on the WHOI collections. Additional records are from Jensen (1948) and Zahuranec and Pugh (1971).

lantic, but a companion species, P. subparallelum, is widely distributed in temperate waters of the southern hemisphere, almost circumglobally (McGinnis, 1974). Furthermore, there exists in the North Pacific another very similar species, P. thompsoni (see Remarks) . Vertical Distribution. In WHOI collections, P. arcticum occurred by night between 90 and 325 m and by day between 250 and 850m. Maximum catch rates were at 250 and 350 m by night and day, respectively.

Synonyms and References: Scopelus arcticus Liitken 1891 [1892]: 207 (orig. descr. off West Greenland; five syntypes: ZMUC 81, 87, 89, 93, 97; fide Krefft and Bekker, 1973); Liitken, 1892: 249, Fig. 6 (char.). Myctophum arcticum. Taning, 1918: 151, Fig. 48 (brief discussion of larval stages); Taning, 1931 (illus. of larva and adult, diag., distr.). Electron* (Hierops) arc tic a. Fraser-Brunner, 1949: 1047, fig. (in key). Hierops arctic a. Bolin, 1959: 5 (synon., char., key, distr., desig. of lectotype: ZMUC 81, from Sukkertoppen, Greenland); Halliday and Scott, 1969: 2695 (records from Canadian Atlantic).

fishes of the Western North Atlantic

33

FIGURE 6. Electrona risso: male, 50.5 mm.

Protomyctophum (Hierops) arcticum. Andriashev, 1962: 237 [compar. of P. (H.) arcticum with P. (H.) subparallelum]; Nafpaktitis, 1973: 5 [compar. of P. (H.) arcticum with P. (H.) subparallelum]. Protomyctophum arcticum. Bekker, 1967b: 90 (records, depths of occur.); Krefft and Bekker, 1973: 196 (synon., ref., distr.).

Genus Electrona Goode and Bean 1896 Electrona Goode and Bean, 1896: 91 (type-species Scopelus risso Cocco 1829, by original designation); Bolin, 1939: 97 (description includes Protomyctophum and Hierops); Fraser-Bninner, 1949: 1045 (subdivision of genus into subgenera Electrona, Protomyctophum, Hierops, and Elampa); Bolin, 1959: 5 (accorded Hierops full generic status and suggested equal status for Protomyctophum; definition of genus Electrona); Paxton, 1972: 42 (osteological characteristics; synonyms Elampa Fraser-Bninner 1949, Elampa Jena Whitley 1953, and Metelectrona Wisner 1963). Elampa Fraser-Brunner, 1949: 1048 (as subgenus of genus Electrona: type-species Scopelus subasper Giinther 1864, by original designation). Elampadena Whitley, 1953: 135 [type-species Scopelus subasper Gunther 1864, by original designation; replacement name for Elampa Fraser-Bninner 1949, not preoccupied by Elampus Spinola 1806, Hymenoptera (J. R. Paxton, personal communication)]. Metelectrona Wisner, 1963: 24 [type-species Metelec-

trona ahlstromi Wisner 1963, by original designation (= Electrona ventralis Bekker 1963)].

Characters. Mouth moderately large, extending to or somewhat beyond vertical through posterior margin of eye; maxillary greatly expanded posteriorly. Eyes not converging dorsally. Base of anal fin longer than that of dorsal fin. Lateral line present, well developed. Dn and Vn present, small; PLO below level of upper end of base of pectoral fin and forming a triangle with two PVO; 5 PO, level; 4 VO, level or VO2 distinctly raised; SAO weakly to strongly angulate; AO in a continuous or somewhat interrupted series with, in the latter case, one or two more or less distinctly raised photophores (incipient Pol?); 2 Prc, level or very nearly so; supracaudal and infracaudal luminous glands present. Size. Members of the genus may grow to about 110 mm. Range. In antarctic and subantarctic waters. One species, E. risso, occurs in warmer waters of both the northern and southern hemisphere. Species. Six species are currently recognized. These are: E. antarctica, E. carlsbergi, E. pan-

34

Memoir 1, Part 7—Sears Foundation for Marine Research

FIGURE 7. Electrona risso, an eastern species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Blache and Stauch (1964), Geistdoerfer et al. (1971), Goodyear et al. (1972), G. Krefft (in litt.), Norman (1930), Parin et al. (1974), and Taning (1918).

cirastra, E. risso, E. subaspera, and £. ventralis. Of these, only £. risso occurs in the North Atlantic. Electrona risso (Cocco) 1829 Figures 6, 7 Study Material. A single specimen, approximately 75 mm (head badly damaged), taken by the WHOI vessel ATLANTIS II cruise 20, Sta. SUN 1216, 1°12'N, 44°39'W, 11-12 April 1966, 2050-0005 hrs, surface; in LACM.

Distinctive Characters. The deep body (body depth about 3 times in SL), large, deep head (nearly as deep as it is long), large, heavyrimmed, horizontally subdivided photophores, and the low number of AO easily differentiate £. risso from all the rest of its congeners. Description. Because of its poor condition the specimen can not be measured accurately. However, its meristic characters are as follows (ranges in parentheses are from Bolin, 1959),

Fishes of the Western North Atlantic Fin rays: dorsal 13 (13-14); anal 19 (1819); pectoral 15 (13-16). Gill rakers: 9 (8-9) + 1 + 19 (17-20). Photophores: AO 11 (10-13). Size. The species seems to grow to a size of about 80 mm. Development. Tining (1918) described and illustrated a number of larval stages of this species from the Mediterranean Sea. The development of E. risso was recently described in great detail by Moser and Ahlstrom (1970) on the basis of material from the California Current. Atlantic Distribution. Electrona risso (Fig. 7) is one of the two eastern myctophids. Like the other, Diaphus holti, E. risso is limited, except for occasional specimens, to the eastern side of the Atlantic and, there, mostly to the provinces of the temperate, tropical, and Mauritanian Upwelling regions. Extra-Atlantic Occurrence. Widely scattered Southern Ocean records between 30°S and the Subtropical Convergence have been summarized by McGinnis (1974). They come from off Chile, New Zealand and Australia, and from mid-South Pacific near the Convergence. In the North Pacific the larvae have been recorded off California and Baja California west to the longitude of Hawaii (Moser and Ahlstrom, 1970). Hartmann and Clarke (1975) found a single specimen at 3°30'N, 145 °W in mid-tropical Pacific. Nafpaktitis and Nafpaktitis (1969) and Kotthaus (1972b) recorded a few specimens of E. risso from the western Indian Ocean. (BC) Vertical Distribution. Electrona risso was taken in small numbers by opening-closing devices in the Mediterranean Sea at 200 m (one specimen) and 700-750 m by day and at 150-200 m and 400-700 m at night. Nighttime specimens taken at 150-200 m were 9-31 mm, those at 400-500 m, 40-45 mm, and those at 700 m, 8-10 mm. In the WHOI collections, E. risso occurred between 225 and 750 m by day and at 90-375

35

m and 450-550 m at night, with maximum concentrations at 200 m and 500 m. Synonyms and References: Scopelns risso Cocco, 1829: 144 (orig. descr. from Messina, fide Krefft and Bekker, 1973). Myctophum rissoi. Taning, 1918: 28, Fig, 9 (descr. of larval stages, adult char.; distr. in Mediterranean; reprod.); Norman, 1930: 320 (records from east. South Atlantic). Myctophum risso salubris Whitley, 1933: 62 (orig. descr. Tasman Sea; type AMS-E5701, fide Krefft and Bekker, 1973). Electrona (Electrona) rissoi. Fraser-Brunner, 1949: 1048, fig. (in key). Electrona rissoi. Bolin, 1959: 5 (synon., char., distr.); Bekker, 1967: 92 (records from east, and west, equat. Atlantic); Nafpaktitis and Nafpaktitis, 1969: 10, Fig. 8 (record from South Indian Ocean, 41°07' S, 60°08'E); Craddock and Mead, 1970: 3.27 (records from southeast. Pacific, approx. 30-34°S, 8293°W); Moser and Ahlstrom, 1970: 35, 123, Figs. 8, 9, 40 (descr. of larval stages from Calif. Current; distr. of larvae in east. North Pacific); Bini, 1971: 185, illus. (morphol., distr. in Mediterranean); Kotthaus, 1972b: 13 (record from west, equat. Indian Ocean; photo of otol.); Hulley, 1972a: 220 (record from southeast. Atlantic, 23°25'S, 11°39/E; char.); Hulley, 1972b: 240 (record from southeast. Atlantic, 31°38'S, 8°21.5'E; char.); Krefft and Bekker, 1973: 181 (synon., distr.).

Genus Hygophum Bolin 1939 Hygophum. Taning, 1932: 133 (invalid introduction of subgeneric name Hygophum). Hygophum Bolin, 1939: 113 (first valid designation of Hygophum as subgenus of Myctophum; typespecies Scopelus hygomii Liitken 1892); FraserBrunner, 1949: 1049 (elevation to full generic rank; diagnosis and description); Bolin, 1959: 6 (brief historical account of introduction and establishment of genus Hygophum; Bekker, 1965: 62103 (rev. of genus Hygophum); systematics and distribution).

Characters. Maxillary broadly expanded posteriorly. Base of pectoral fin high, its upper end about equidistant from dorsal and ventral margins of trunk. Base of anal fin longer than that of dorsal fin. Vn somewhat larger and better defined than Dn; Suo present; 5 PO, level; 4 VO, level; SAO angular;

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Memoir I, Part 7—Sears foundation for Marine Research

2 Pol; AOa-AOp interspace well in advance of end of base of anal fin; 2 Prc, second elevated; supracaudal and infracaudal glands present. Size. Small myctophids, not exceeding 70 mm in length. Range. Members of the genus have been reported mainly from the middle latitudes of all three major oceans. Of the five species that occur in the North Atlantic, two, H.

benoiti and H. hygomii, are common in the Mediterranean Sea. One species, H. hanseni, is restricted to the southern hemisphere. Species. The genus currently includes nine species. These are: H. atratum, H. benoiti, H. bruuni, H. hanseni, H. hygomii, H. macrochir, H. proximum, H. reinhardtii, and H. taaningi. Of these, five (H. benoiti, H. hygomii, H. macrochir, H. reinhardtii, and H. taaningi) occur in the North Atlantic.

Key to the North Atlantic Species of Hygophum la. Last AOa, Poll and Pol2 on a straight line or, at most, Poll slightly in advance of, but in contact with, a straight line through anterior margins of last AOa and Pol2, always behind vertical through center of last AOa 2 Ib. Last AOa, Poll and Pol2 not on a straight line; Poll distinctly in advance of a straight line through anterior margins of last AOa and Pol2, on or in front of vertical through center of last AOa 3 2a. Prc2 low in position; Prci-Prc2 interspace equal to, or smaller than, distance between Prc2 and lateral line; distance between posterior end of base of dorsal fin and Prc2 smaller than distance between tip of snout and base of ventral fins. benoiti (Cocco) 1838, p. 36 2b. Prc2 high in position; Prci-Prc2 interspace much greater than distance between Prc2 and lateral line; distance between posterior end of base of dorsal fin and Prc2 greater than distance between tip of snout and base of ventral fins. reinhardtii (Liitken) 1892, p. 39 3a. VLO in contact with, or less than its diameter below lateral line; SAOi in front of, rarely on, vertical through center of VO2. hygomii (Liitken) 1892, p. 42 3b. VLO midway between base of ventral fin and lateral line, or somewhat higher; SAOi well behind VO2 4 4a. SAOi in front of vertical through center of VO3; VO4, SAO2 and SAOS on a straight line; pectoral fins extending beyond AOai; gill rakers 5 (4) + 1 + 14 (13-15), total 19-20; supracaudal luminous gland of 5-7, usually 6, distinct scalelike structures. macrochir (Giinther) 1864, p. 44 4b. SAOi behind, rarely on, vertical through center of VO3; a straight line through SAO2 and SAO8 passing behind VO4; pectoral fins not reaching AOai; gill rakers 4 + 1 + 12 (11-13), total 17 (16-18); supracaudal luminous gland with no distinct scalelike structures. taaningi Bekker 1965, p. 47 Hygophum benoiti (Cocco) 1838 Figures 8, 9

in the key will separate this species from its North Atlantic congeners.

Study Material. Over 500 North Atlantic specimens, 11-52 mm; in WHOI and LACM.

Description. Fin rays: dorsal 12-14; anal 19-21; pectoral 13-15.

Distinctive Characters. Characters included

Fishes of the Western North Atlantic

37

FIGURE 8. Hygopbum benoiti: male, 52 mm; A, infracaudal luminous gland of female, 42 mm.

Gill rakers: 4 (J) + 1 + 13-14, total 1819 (20). Photophores: AO 6 (5-7) + 6 (5-7), total 12 (11-13). Lateral-line organs: 36-37. Head. Length of head 3-3.5 in SL. Mouth oblique, lower jaw slightly protruding; length of upper jaw about 1.5 in hi and 4.5-5 in SL. Eye large, its diameter about 1.5 in length of upper jaw, 2-2.5 in hi and 7-8 in SL. Opercular margin distinctly angular and, in adult individuals, lightly serrate posterodorsally. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin somewhat in advance of vertical through end of base of dorsal fin. Pectoral fins long, extending to about SAO2. Ventral fins reaching anus in juveniles, shorter in adult individuals. Base of adipose fin in advance of vertical through end of base of anal fin. Luminous Organs. PLO about 1.5 times its diameter anterodorsad to upper end of base of pectoral fin. PVOi somewhat behind PO2 and on a straight line connecting POi and PVO2 which is on or slightly in advance of vertical through center of PO3 and at lower end of base of pectoral fin. VLO midway between base of ventral fin and lateral line, or slightly higher. SAOi in advance of VO3 and below

a straight line connecting VLO and SAO2; VO4, SAO2 and SAO3 in a straight line; SAO3 in contact with lateral line. AOai usually somewhat depressed. Last AOa and two Pol in a straight line; sometimes Poll, which is distinctly nearer to last AOa than to Pol2, may be slightly in advance of straight line connecting Pol2 and last AOa; Pol2 slightly in advance of base of adipose fin and in contact with lateral line. Two or 3 AOp over base of anal fin. Prc2 well below lateral line. Sexual Dimorphism. Males have a single, undivided supracaudal luminous gland framed with black tissue. In mature North Atlantic specimens this gland occupies from % to % of the distance between the base of the adipose fin and the procurrent caudal fin rays. The same gland is markedly longer in mature specimens from the Mediterranean (Bekker, 1965). Females have an infracaudal luminous gland which may or may not be distinctly subdivided into 3—4 components. Occasionally, mature females with well-developed infracaudal glands may also have small, poorly developed supracaudal glands. Caudal glands appear in 17-20-mm-long males and in 24— 25-mm-long females (Tuning, 1918: 47). Size. A number of gravid females found in the collections examined ranged in size

38

Memoir 1, Part 7—Sears foundation for Marine Research

FIGURE 9. Hygophum benoiti, a temperate-semisubtropical species. Distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and Timing (1918).

from 40 to 50 mm. Members of this species do not appear to grow much larger than 55 mm. Development. Tining (1918) described a series of postlarvae, 5-11 mm, from the Mediterranean Sea. He found that metamorphosis takes place at sizes between 10 and 12.5 mm. Atlantic Distribution. Hygophum benoiti (Fig. 9) is a temperate-semisubtropical species. It is common also in the Mauritanian Upwelling. It is a ranking myctophid in the latter place, where it is found mostly in the

northern province. It is common also in the northern Gulf of Mexico. The species is noticeably more abundant in the Western Mediterranean Sea than in the Eastern. Our data suggest that this is a species that flourishes along regional (oceanographic) boundaries. H. benoiti is not known from outside the North Atlantic. Vertical Distribution. Opening-closing devices captured H. benoiti by day at 5001,050 m near Bermuda, with most between 500 and 850 m, at 250-1,000 m in the Medi-

Fishes of the Western North Atlantic

39

FIGURE 10. Hygophum reinhardtii: female, 42 mm; A, supracaudal luminous gland of male, 44 mm.

terranean Sea, with most between 700 and 1,000 m, and in small numbers near the Canaries at 700-92 5 m. At night, it was taken at 20-1,000 m near Bermuda, where maximum abundance was in the upper 50 m in January-February and at 6 5 0-700 m in June and August-September; in the Mediterranean, it was taken at 12-400 m and 7001,000 m, with maximum abundance below 700 m. Partial migrants and non-migrants, other than post-larvae, were juveniles. In the WHOI collections, H. benoiti occurred between 225 and 8JO m by day, with maximum numbers at 475-850 m, and between the surface and 225 m at night, with maximum catch between the surface and 60 m. By far, the largest surface collections of H. benoiti were made in the western Mediterranean near the Strait of Gibraltar. Synonyms and References: Scopelus benoisti Cocco, 1838: 12, PL 2, Fig. 4 (orig. descr.). Myctophum benoiti. Taning, 1918: 45, Figs. 15, 16 (descr., develop., reprod., distr. in Mediterranean); Taning, 1928: 57 (in key); Taning, 1932 (illus., diag., distr., reprod.). Hygophum benoiti. Fraser-Brunner, 1949: 1049, fig. (in key); Bolin, 1959: 8 (synon., brief descr., distr.);

Bekker, 1965: 65, Figs. 1, 2 (synon., descr., distr.); Backus et al., 1970: 194 (distr.); Bini, 1971: 195, illus. (morphol., biol., distr.); Goodyear et al., 1972: 157 (horiz. and vert, distr., growth and reprod. in Mediterranean); Rotthaus, 1972a: 12 (records from east. North Atlantic, char., photo of otol.); Krefft and Bekker, 1973: 183 (synon, ref., distr.).

Hygophum reinhardtii (Lutken) 1892 Figures 10, 11 Study Material. Thirty-one North Atlantic specimens, 12—46 mm; in ZMUC and LACM.

Distinctive Characters. The distance from the end of the base of the dorsal fin to the Prc2 in relation to the distance from the tip of the snout to the base of the ventral fin (the former is longer than the latter in H. reinhardtii and equal to or shorter than the latter in the rest of the North Atlantic species of this genus) is a helpful diagnostic character when comparing adult specimens. Specifically H. reinhardtii is distinguished from H. benoiti by its higher Prc2; from H. hygomii by the position of its VLO, SAOi and Poli; from H. macrochir by the position of its Poll, and the higher number of its anal fin rays and AO photophores; and from H. taaningi by the position of its Poh and SAOi, and the higher

40

Memoir 1, Part 7—Sears Foundation for Marine Research

number of its anal fin rays and AO photophores. Description. fin rays: dorsal 13-14; anal 22-24; pectoral 13-15. GUI rakers: 4-5 + 1 + 12-14, total 17-20. Photophores: AO 7 (6-8) + 7 (6-9), total 14 (13-15). Lateral-line organs: 39-40. Head. Length of head 3.5-4 in SL. Mouth oblique with lower jaw slightly protruding; length of upper jaw 1.5 in hi and 5.3-6 in SL. Eye large, its diameter about 1.5 in length of upper jaw, 2-2.2 in hi and 7-8 in SL. Operculum almost evenly rounded throughout its posterior margin. Fins. Origin of dorsal fin somewhat behind base of ventral fin. Origin of anal fin under end of base of dorsal fin. Pectoral fins long, extending to about 1st AOa. Ventral fins not reaching anus. Base of adipose fin well in advance of vertical through end of base of anal fin. Luminous Organs. PLO in advance of base of pectoral fin and usually nearer to it than to lateral line. PVOi directly over, slightly in front of or behind PO2, on or a little in advance of straight line connecting PVO2 and POi; PVO2 directly over or somewhat in advance of PO3 and at lower end of base of pectoral fin. VLO midway between base of ventral fin and lateral line. SAOi somewhat behind VO2 and below a straight line connecting SAO2 with VLO; SAO2 on or slightly in advance of straight line connecting SAO8 with VO4; SAO8 on or a little behind vertical through origin of anal fin and in contact with lateral line. AOaa usually somewhat depressed; AOai-AOa2 interspace often enlarged. Two Pol and last AOa in a straight line or very nearly so; Pol2 in advance of base of adipose fin and in contact with lateral line. Four, rarely 3, AOp over base of anal fin. Prc2 immediately below lateral line. Sexual Dimorphism. Males with supracaudal and females with infracaudal luminous

glands. The supracaudal gland which, in mature individuals, occupies % to 34, sometimes even more, of the distance between the adipose fin and the procurrent caudal fin rays, appears as a series of 4—6 distinct scalelike structures. These soon lose their distinctiveness and the gland appears as an undivided, long structure. The infracaudal gland consists of a series of 3—4 oval patches of luminous tissue in varying degrees of fusion with each other. The glands appear in males and females about 21 and 24 mm in length, respectively. Size. It seems that, in the North Atlantic, H. reinhardtii attains sexual maturity at a size between 40 and 45 mm, and the species does not grow much larger than 50 mm. Development. A detailed description of several larval stages of this species from the California Current has been presented by Moser and Ahlstrom (1970). They found that east Pacific H. reinhardtii larvae metamorphose at sizes between 15 and 16.4 mm. Atlantic Distribution. Hygophum reinhardtii (Fig. 11) is a questionably bipolar subtropical species. The alternative is that the species is a tropical-subtropical one; additional collecting in the tropics and South Atlantic subtropics should settle the point. In WHOI collections H. reinhardtii is most abundant in the eastern subtropics. It is common in the Gulf of Mexico, absent from the Mauritanian Upwelling. Extra-Atlantic Occurrence. H. reinhardtii is found in the eastern and western North Pacific Ocean between approximately 20° and 39°N, but in the central North Pacific it has not been taken to the north of about 23 °N (Bekker, 1965). This, together with captures in the South Pacific between about 25° and 35°S, suggest that H. reinhardtii has a bipolar distribution in the Pacific Ocean (Bekker, 1965). H. reinhardtii has not been reported from the Indian Ocean. (N) Vertical Distribution. Opening-closing devices took H. reinhardtii in small numbers by

Fishes of the Western North Atlantic

41

FIGURE 11. Hygophum reinhardtii, a questionably subtropical species. Atlantic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et al. (1971).

day from between 600-700 m to 850 m both near Bermuda and the Canaries; one individual was taken at 1,050-1,100 m near Bermuda. The species was taken at night from the surface to 200-250 m in both areas. Non-migrating juveniles were taken at night at 600900 m near the Canaries and at 550-600 m near Bermuda. In the WHOI collections, H. reinhardtii occurred from 475 to 850 m by day and from the surface to about 175 m at night with two maxima, at the very surface and at 100 m.

Synonyms and References: Scopelus reinhardtii Liitken, 1892: 257, Fig. 16 (orig. descr., lectotype desig. by Gilbert, 1908; 34°22'N, IS^O'W; ZMUC 24). Myctophum braueri Gilbert, 1905: 598, PL 70, orig. descr. erroneously named M. lutkeni in Fig. 1 (south of Oahu, Hawaii, surface tow; USNM 51527). Myctophum reinhardti. Gilbert, 1908: 219 (M. braueri placed in synon. of M. reinhardti); Taning, 1928: 57 (in key); Parr, 1929: 12 (exam, of type of M. braueri, and confirm, of its synon. with M. reinhardti). Myctophum (Hygophum) reinhardtii. Bolin, 1939: 113, Fig. 12 (descr.).

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Memoir 1, Part 7—Sears foundation for Marine Research

FIGURE 12. Hygophum hygomii: female, 57 mm; A, supracaudal luminous gland of male, 53 mm. Hygophum reinhardti. Fraser-B runner, 1949: 1050, fig., partim (in key); Bolin, 1959: 7 (synon., brief descr., distr.); Bekker, 1965: 89, Fig. 9 (synon., descr., distr.); Bekker, 1967b: 93 (horiz. and vert, distr. in Atlantic and Pacific Oceans); Moser and Ahlstrom, 1970: 66, Figs. 19, 20 (devel., distr. of larvae and young in east. North Pacific); Kotthaus, 1972a: 12 (record from eastern North Atlantic, char., photo of otol.); Krefft and Bekker, 1973: 184 (synon., ref., distr.).

Hygophum hygomii (Liitken) 1892 Figures 12, 13 Study Material. One hundred and ten North Atlantic specimens, 15-60 mm; in LACM and ZMUC.

Distinctive Characters. This species is readily distinguished from all of its congeners by the highly elevated position of its VLO. Description. Fin rays: dorsal 14 (13-15); anal 21 (2022); pectoral 1J-16. Gill rakers: J + 1 + 14 (13-1 J ) , total 20 (19-21). Photophores: AO 7 (6-8) + 6 (5-7), total 13 (12-14). Lateral-line organs: 38-39. Head. Head length 3.5 in SL. Mouth

oblique, lower jaw slightly protruding; length of upper jaw 1.5 in hi and about 5 in SL. Eye large, its diameter 1.5 in length of upper jaw, 2.2-2.4 in hi and 7.5-8 in SL. Posterodorsal margin of operculum weakly serrate. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin about under end of base of dorsal fin. Pectoral fins long, extending to 1st AOa. Ventral fins barely reaching anus. Base of adipose fin in advance of vertical through end of base of anal fin. Luminous Organs. PLO in advance of, and about twice its own diameter from upper end of base of pectoral fin. PVOi behind PO2, on a line connecting POi with PVO2 which is somewhat behind PO3 and at lower end of base of pectoral fin. VLO immediately below lateral line. SAOi in advance of VO2 and below a line connecting PVO2 with SAO2; SAO2 in advance of line connecting SAO3 with VO4; SAO3 behind origin of anal fin and in contact with lateral line. First AOa distinctly depressed, the series forming a gentle arc. Poll at least twice its own diameter in advance of a line connecting centers of Pol2 and last AOa; Pol2 well behind last AOa, slightly in advance of base of adipose fin and

Fishes of the Western North Atlantic

43

FIGURE 13. Hygophum hygomii, a bipolar temperate-semisubtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971), Krefft (1974), and Taning (1918).

in contact with lateral line. Two AOp over base of anal fin. Prc2 about % its own diameter below lateral line. Sexual Dimorphism. Males with a single, small, saddle-shaped supracaudal luminous gland immediately in front of procurrent caudal rays. It appears in individuals 32-34 mm long. Females with 1-2 equally small, lanceolate infracaudal patches of luminous tissue that begin developing in fish 43-45 mm long. Size. This species apparently attains sexual

maturity at a relatively large size. None of the largest (5 5-60 mm) females examined had ripe ovaries. Development. Taning (1918) has described several stages in the development of H. hygomii on the basis of material primarily from the Mediterranean. Metamorphosis appears to take place at sizes between 13 and 14.5 mm. Atlantic Distribution. Hygophum hygomii (Fig. 13), like its congener Hygophum benoiti (Fig. 9), is a temperate-semisubtropical

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Memoir 1, Part 7—Sears foundation for Marine Research

species. The Atlantic ranges of the two species are much alike with the principal exceptions that H. hygomii is bipolar and appears to be missing from the Mauritanian Upwelling. Other lesser differences in distribution are evident in comparing the range maps for the two. The species often occur together in collections although one generally greatly preponderates. Krefft (1974) caught H. bygomii continuously from about the latitude of Lisbon (ca. 37°N) to the Cape Verdes, but presumably at a lesser catch rate in the southern part. Extra-Atlantic Occurrence. H. hygomii is known from the Indian Ocean between about 23 °S and 35°S (Nafpaktitis and Nafpaktitis, 1969) and from the Pacific Ocean off Chile and Peru (Craddock and Mead, 1970; Wisner, 1976) between about 18°S and 34°S and off "northern New Zealand" (Bolin, 1959). Thus, it appears that H. hygomii may be circumglobal in the southern hemisphere, but live in the northern hemisphere only in the Atlantic. (BC) Vertical 'Distribution. Opening-closing devices took H. hygomii by day at 5 00-8 JO m near Bermuda, at 400-700 m near the Canaries, and at 600-7JO m in the Mediterranean. Maximum abundance was at JO0-600 m near both Bermuda and the Canaries; a few individuals were also taken at 1,000-1,J JO m near Bermuda. At night, H. hygomii was caught from the surface to 1,0JO m near Bermuda, with maximum concentration at 501JO m, at 10-100 m and JOO-600 m near the Canaries, with maximum abundance at 1025 m, and from the surface to 23 J m in the Mediterranean. Only postlarvae and juveniles less than 20 mm were taken below 200 m at night near Bermuda and only early juveniles at JOO-600 m near the Canaries. In the WHOI collections, H. hygomii occurred between 42J and 7JO m during the day and from the surface to 12 J m at night, with concentrations both at the very surface and at 7J m. Surface captures were mostly

in the temperate provinces and along the temperate-subtropical boundaries; no specimens were collected at the surface in the Gulf of Mexico and few in the subtropics. Synonyms and References: Scopelus hygomii Liitken, 1892: 256, Fig. 15 (orig. descr.; lectotype desig. by Bolin, 1959: 38°N, 22°20'W; ZMUC 41). Myctophum remiger Goode and Bean, 1896: 74, PL 22, Fig. 84 (orig. descr., from eight spec.: USNM 43792, 40°34/18"N, 64°09'W; surface). Myctophum hygomi. Taning, 1918: 51, Figs. 17, 18 (descr., develop., reprod., distr. in Mediterranean); Taning, 1928: 57 (in key); Parr, 1928: 76 (synon., records from west. North Atlantic). Hygophum hygomi. Fraser-Brunner, 1949: 1050, fig. (in key); Bolin, 1959: 6 (synon., brief descr., distr., desig. of lectotype); Bekker, 1965: 68, Fig. 3 (synon., descr., distr.); Bekker, 1967b: 92 (horiz. and vert, distr.); Halliday and Scott, 1969: 2695 (records from Canadian Atlantic); Nafpaktitis and Nafpaktitis, 1969: 19, Fig. 19 (descr., distr. in west. South Indian Ocean); Craddock and Mead, 1970: 3.28 (records from southeast. Pacific); Bini, 1971: 193, illus. (morphol., biol., distr.); Goodyear et al., 1972: 154 (horiz. and vert, distr., growth and reprod, in Mediterranean); Hulley, 1972a: 221 (records from off southeast coast of S Africa); Kotthaus, 1972a: 12 (records from east. North Atlantic, char., photo of otoL); Krefft and Bekker, 1973: 183 (synon., ref., distr.).

Hygophum macrochir (Giinther) 1864 Figures 14, If Study Material. One hundred and nineteen specimens, 12-59 mm, including the lectotype, from across the tropical North Atlantic and the Caribbean; in ZMUC, LACM, and BMNH.

Distinctive Characters. This species may be confused with H. taaningi. The characters in the key should be used in conjunction with the features included under Description and also with the observations under Geographic Variation in mind. Description. Fin rays: dorsal 13 (12-14); anal 19 (1820); pectoral 14 (13-15). Gill rakers: 5 + 1 + 14 (13-15), total 20 (19-21).

Fishes of the Western North Atlantic

45

FIGURE 14. Hygophum macrocbir: lectotype (BMNH 1947.12.16.1), male, S3 mm; A, infracaudal luminous gland of female, 58 mm.

Photophores: AO 4-6 + 5-7, total 10-12. Lateral-line organs: 37. Head. Head length 3.2-3.5 in SL. Mouth oblique, lower jaw slightly protruding; length of upper jaw 1.6-1.7 in hi and 5.2-5.7 in SL. Eye large, its diameter 1.5 in length of upper jaw, 2.3-2.5 in hi and 7.5-8.5 in SL. Posterior opercular margin broadly convex with a slight, bluntly angular protrusion just below PLO; posterodorsal opercular margin angular and, in specimens 35 mm and larger, weakly but distinctly serrate. Fins. Origin of dorsal fin slightly behind base of ventral fin. Origin of anal fin about under end of base of dorsal fin. Pectoral fins long, extending to about midway between SAO2 and Poll* Ventral fins not reaching anus. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PLO in advance of base of pectoral fin and nearer to it than to lateral line. PVOi slightly behind PCfe; PVOfe directly over or slightly in advance of PO3 and at lower end of base of pectoral fin. VLO midway between base of ventral fin and lateral line or slightly higher. SAOi in advance of VO3 and from less than to slightly more

than its own diameter below a straight line tangent to ventral margins of VLO and SAO2 (see under Geographic Variation); VO4, SAO2 and SAO3 on a straight line; SAO3 about over origin of anal fin and in contact with lateral line. AOa evenly spaced and level, or AOai slightly depressed. Poll in front of, rarely directly over, last AOa; Pol2 somewhat in advance of base of adipose fin and in contact with lateral line. Anterior 3-4, rarely 2, AOp over base of anal fin. Prc2 in contact with lateral line. Sexual Dimorphism. Adult males with a supracaudal luminous gland consisting of a series of 5-7, more or less distinct, scalelike structures occupying almost the entire dorsal surface of the caudal peduncle. The gland is distinct in 28-30-mm individuals. In adult females the infracaudal gland consists of 2-3 (seldom one) patches of luminous tissue that may be separate or fused. It appears in individuals about 37 mm long. Size. The species does not seem to grow much larger than 60 mm. Several gravid females were found in the collections examined; they ranged in size between 45 and 55 mm. Geographic Variation. Specimens from the

46

Memoir I, Part 7—Sears Foundation for Marine Research 100 90

60

70

60

50

UO

30

20

10

0

-10 -20 -30 -HO

60

FIGURE 15. Hygophum macrochir, i tropical species. Distribution, based on the WHOI collections. The southern hemisphere records are based on determinations in which it was impossible to distinguish H. macrocbir from H. taaningi.

eastern, central, and western tropical Atlantic show variation in a number of characters. The "typical" H. macrochir was apparently described from the eastern tropical Atlantic. Members of the eastern population have the VLO midway between the base of the ventral fin and the lateral line; the SAd is about midway between VLO and SAO2 and less than its diameter below a straight line tangent to the ventral margins of the VLO and SAO2. In specimens from the central tropical and

Caribbean waters the VLO may be slightly nearer to the lateral line than to the base of the ventral fin; the SAOi is distinctly nearer to the SAO2 than to VLO and about its diameter below a straight line tangent to the ventral margins of the VLO and the SAO2. Furthermore, the eye seems to be larger in specimens from the east (7.5-8 times in SL) than in those from central and western waters (8-8.5 times in SL). Finally, in an eastwest direction the average number of AOa

Fishes of the Western North Atlantic tends to increase, whereas that of AOp tends to decrease. Of 60 AOa counts obtained from 32 eastern specimens 70% were 5 and 30% 4, whereas of 65 AOa counts obtained from 33 central and western specimens 83% were 5 and 17% 6. In the eastern specimens 2% of the AOp counts were 5, 61.5% 6, and 36.5% 7, whereas in the central and western specimens 17% were 5, 80% 6, and 3% 7. It is because of the above variations which, in the western North Atlantic, approach those found in H. taaningi, that the two species have been confused in the past. Atlantic Distribution. Hygophum macrochir (Fig. 15) is a tropical species more abundant in the east than in the west. It is a ranking species in the Atlantic Tropical Region and in the Mauritanian Upwelling, where it is virtually restricted to the southern province. (The southern hemisphere records on the map for this species are based on determinations in which it was impossible to distinguish H. macrochir from H. taaningi.) In the North Atlantic the range of H. macrochir is complementary to that of H. taaningi, the two meeting more or less at the tropical-subtropical boundary. Both appear to occur in the Caribbean Sea, where H. macrochir is the more abundant. H. macrochir is restricted to the Atlantic Ocean. (BC) Vertical Distribution. In the WHOI collections, H. macrochir occurred from 27 5 to 750 m during the day and from the surface to about 125 m at night with two maxima, at the surface and at 50 m (compare with H. taaningi). Synonyms and References: Scopelus macrochir Giinther, 1864: 408 (orig. descr.; lectotype desig. by Bolin, 1959: BMNH 1947.12. 16.1). Hygophum macrochir. Fraser-Bmnner, 1949: 1050, fig. (in key); Bolin, 1959: 7 (desig. of lectotype; descr. based on data from both H. macrochir and the then undescribed H. taaningi); Bekker, 1965: 73, Fig. 4 (synon., descr., distr.); Bekker, 1967b: 93 (horiz. distr., depth of capture).

47

Hygophum taaningi Bekker 1965 Figures 16, 17 Study Material. Two hundred and twenty-three specimens, 11—46 mm, from across the North Atlantic, the Caribbean Sea, and the Gulf of Mexico; in ZMUC and LACM.

Distinctive Characters. This species is very similar to H. macrochir. In the western North Atlantic the similarity between the two forms is even more striking, and the characters in the key should be used with constant reference to the descriptions of the two species. Description. Fin rays: dorsal 13-14; anal 19-20; pectoral 13-14. Gill rakers: 4 + 1 + 12 (11-13), total 17 (16-18). Photophores: AO 5 (4-6) + 5 (4-6), total 10 (9-11). Lateral-line organs: 37. Head. Head length 3.2-3.4 in SL. Mouth oblique, lower jaw slightly protruding; length of upper jaw 1.5 in hi and 4.8-5.2 in SL. Eye large, its diameter 1.5 in length of upper jaw, 2-2.4 in hi and 6.7-7.8 in SL. Posterior opercular margin forming a slight angular protrusion just below PLO; posterodorsal opercular margin angular and, in specimens 3 5 mm and larger, distinctly serrate. Fins. Origin of dorsal fin directly over or slightly behind base of ventral fin. Origin of anal fin slightly in advance of vertical through end of base of dorsal fin. Pectoral fins long, extending to about SAO2. Ventral fins extending to anus in young fish (25 nun and smaller), not reaching anus in larger individuals. Base of adipose fin well in advance of end of base of anal fin. Luminous Organs. PLO in advance of base of pectoral fin and midway between it and lateral line or a little lower. PVOi behind, rarely directly over, PO2; PVO2 at lower end of base of pectoral fin and in advance of PO3. VLO slightly nearer to lateral line than to base of ventral fin. SAOi behind, sometimes di-

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Memoir I, Part 7—Sears Foundation for Marine Research

FIGURE 16. Hygophum taaningi: male, 43 mm; A, infracaudal luminous gland of female, 42 mm.

rectly over, VO3 and at least its own diameter below a straight line tangent to ventral margins of VLO and SAO2; a straight line through centers of SAO3 and SAO2 passing behind VO*; SAO8 behind vertical through origin of anal fin and in contact with lateral line. AOa evenly spaced and in line. Poll directly over or slightly in advance of last AOa; Pol2 slightly in advance of base of adipose fin and in contact with lateral line. Anterior 3, rarely 2, AOp over base of anal fin. Prc2 in contact with lateral line. Sexual Dimorphism. Adult males with a massive supracaudal luminous gland occupying 34 to % of the dorsal surface of the caudal peduncle. The gland appears in males about 23 mm long and is well developed in individuals 28-30 mm long. In adult females the infracaudal gland usually consists of 2-3 small, elongate patches of luminous tissue that may be distinct or coalesced to varying degrees; they appear in fishes about 23 mm long (Bekker, 1965). Size. Available data indicate that this species does not grow larger than 50 mm. Sexual maturity is attained at a size of about 40 mm.

Atlantic Distribution. Hygophum taaningi (Fig. 17) is a subtropical questionably bipolar species. The doubt stems from the fact that, while the North Atlantic population of H. taaningi clearly is distributed subtropically, we are not able to distinguish southern hemisphere taaningi from its closest relative, the tropical H. macrochir; (southern hemisphere specimens of the macrochir-taaningi complex have been plotted on the map for macrochir and are omitted from the map for taaningi). In the North Atlantic H. taaningi is most abundant in the southern subtropics. The ranges of taaningi and macrochir are more or less complementary, the first being subtropical, the second tropical. Additionally, taaningi is absent from the Mauritanian Upwelling, where macrochir is abundant in the southern province. H. taaningi is not known from outside the Atlantic. Vertical Distribution. Opening-closing devices caught H. taaningi in very low numbers near Bermuda by day at 950-1,000 m and at night at 20-200 m and 650-1,250 m. At night, most fish were taken at 20-100 m; those at 650-1,250 m were all juveniles.

Fishes of the Western North Atlantic

49

FIGURE 17. Hygophum taaningi, a subtropical species. Distribution, based on the WHOI collections. Southern hemisphere specimens of macrocbir-taaningi have been plotted on the map for macrochir (Figure 15) and are omitted here. The additional record is from Gibbs et al. (1971).

In the WHOI collections, H. taaningi occurred at night from near the surface to about 250 m, with maximum concentration at 100 m (compare with H. macrochir); by day, it occurred between 475 and about 1,000 m.

Genus Benthosema Goode and Bean 1896

References:

Benthosema Goode and Bean, 1896: 75 [type-species Benthosema mulleri (=Scopelus glacialis Reinhardt 1837), by original designation]; Bolin, 1939: 116 (subgenus of Myctophum, characters); FraserBrunner, 1949: 1051 (characters); Bolin, 1959: 9 (characters); Pazton, 1972: 42 (osteological characters).

Hygophum taaningi Bekker, 1965: 76, Fig. 5 (orig. descr.; 22°47'N, 63°40/W; holotype, Zool. Inst. AN USSR 37538); Bekker, 1967b: 93 (horiz. distr., depths of capture).

Characters. Mouth moderate in size; jaws extending somewhat beyond vertical through posterior margin of orbit; maxillary expanded

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Memoir 1, Part 7—Sears Foundation for Marine Research

FIGURE 18. Benthosema glaciale: young female, 54 mm; A, supracaudal luminous gland of male, 64 mm.

posteriorly. Base of anal fin longer than that of dorsal fin. Dn and, especially, Vn very small and poorly defined; PVO horizontal or nearly so, not in line with Pd; 5 PO, the fifth sometimes displaced dorsolaterally; 4 VO, the second from slightly raised to highly and abruptly elevated; SAO weakly to strongly angular; one Pol; 2 Prc, the second elevated; supracaudal and infracaudal glands present in males and females, respectively, except in B. fibulatum in which both sexes have supracaudal and infracaudal glands, those in mature males being much better developed than those in mature females.

Size. Small myctophids, seldom exceeding 70 mm in length. Range. With the exception of Benthosema glaciale, which appears to be restricted to the North Atlantic, the Mediterranean and, evidently, the Arctic waters (see Bolin, 1959: 10), members of the genus have been collected in tropical and subtropical waters of all three major oceans. Species. Five species are here recognized. These are: B. glaciale, B. subarbitale, B. fibulatum, B. pterotum, and B. panamense. Only the first two occur in the North Atlantic.

Key to the North Atlantic Species of Benthosema la. Suborbital photophore absent; VO2 well behind VOi and little but distinctly raised; SAO on a straight or nearly straight, gently ascending line; Prc2 1-2 times its own diameter below lateral line. glaciale (Reinhardt) 1837, p. 50 Ib. Suborbital photophore present; VO2 highly elevated, almost directly over VO^ SAO angular; Prc2 at lateral line. suborbitale (Gilbert) 1913, p. 53 Benthosema glaciale (Reinhardt) 1837 Figures 18, 19 Study Material. Over 600 North Atlantic specimens, 14-70 mm; in LACM, ZMUC, and WHOL

Distinctive Characters. Characters in the key will readily differentiate this species from its North Atlantic congener B. suborbitale.

Description. Fin rays: dorsal 13 (12-14); anal 18 (1719); pectoral 12 (11-13). Gill rakers: 4 (5) + 1 + 11 (10-12), total 16 (15-18). Photophores: AO 6 (7) + 7 (6-8), total 13 (12-14).

Fishes of the Western North Atlantic

51

FIGURE 19. Benthosema glaciate, a subpolar-temperate species. Distribution, based on the WHOI collections. Additional records are from Bolin (1959), Geistdoerfer et al. (1971), Gibbs et al. (1971), Gjosaeter (1973) and records summarized therein, and Jensen (1948).

Lateral-line organs: 36-37. Head. Length of head 3.5 in SL. Mouth oblique; maxillary expanded posteriorly; length of upper jaw 1.5 in hi and 5 in SL. Eye large, its diameter 1.6-2 in length of upper jaw, 2.4-2.7 in hi and 8.5-9.5 in SL. Operculum abruptly tapering to a point behind PLO. Fins. Origin of dorsal fin well behind base of ventral fin. Origin of anal fin on or somewhat in advance of vertical through middle

of base of dorsal fin. Pectoral fins extending to a point between SAOi and SAO2. Ventral fins reaching anus. Base of adipose fin directly over or a little behind end of base of anal fin. Luminous Organs. PLO well in advance of base of pectoral fin and nearer to it than to lateral line. PVOi about midway between, and very nearly in line with, PO2 and PLO; PVO2 a little higher than PVOi and at lower end of base of pectoral fin. VLO in advance of base of ventral fin and midway between it

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Memoir 1, Part 7—Sears Foundation for Marine Research

and lateral line or a little lower. VO2 distinctly raised above level of adjacent organs of same series. SAO in a straight, or nearly straight, ascending line; SAOi on or somewhat behind vertical through center of second, raised VO2; SAO2 in advance of VO4; SAO3 behind first AOa and its own diameter or less below lateral line. AOa evenly spaced and level. Pol in advance of base of adipose fin and immediately below lateral line. First AOp usually over base of anal fin. Prc2 1-2 times its own diameter below lateral line. Sexual Dimorphism. Males with a small (about % the length of caudal peduncle) undivided supracaudal luminous gland framed by black tissue. Females with, usually, 2 very (small, roundish patches of luminous tissue infracaudally. The glands first appear in individuals about 25 mm long. Occasional specimens may have both supracaudal and infracaudal glands, but the supracaudal is better developed in males and the infracaudal in females. Size. North Atlantic B. glaciate reach sexual maturity at a size between 50 and 60 mm. Mediterranean members of this species seem to mature "... at a length of abt. 30 mm (excl. caudal) or more" (Tuning, 1918: 44). This fish grows to about 70 mm in the North Atlantic and to about 45 mm in the Mediterranean. Maximum recorded size is 103 mm (Gjosaeter, 1973). Development. Larvae of B. glaciate were first described by Holt (1898) on the basis of North Atlantic material. Tuning (1918) described a series of larval stages, 5-11 mm, and individuals in the metamorphosis stage, 10-11.5 mm, mainly from the Mediterranean and the Sea of Marmora. He observed that in the Atlantic, "metamorphosis takes place at a somewhat greater length than in the Mediterranean." Otherwise, his descriptions agreed with those of Holt. Atlantic Distribution. Benthosema glaciale (Fig. 19) is a subpolar-temperate species and probably the most abundant of North At-

lantic myctophids. It is the ranking myctophid in the Atlantic Subarctic and North Atlantic Temperate Regions. It completely dominated the WHOI Subarctic Region collections, where in 20 shallow (< 200 m) nighttime collections (26.1 collecting hours) it comprised over 96% of all myctophid specimens taken. In nighttime collections at all depths in the Subarctic Region the average catch rate was 754 specimens per hour. The species was an important constituent in collections from all temperate provinces except the Eastern Mediterranean Sea. Here, it was moderately abundant in the Tyrrhenian Sea, but occurred but little east of Sicily. The species was especially abundant in the Alboran Sea, the western extremity of the Mediterranean; here, the average catch rate in six shallow (< 200 m) nighttime collections was over 1,100 specimens per hour. These Mediterranean observations agree with those of Tining (1918), who reported the species also from the Adriatic and the Sea of Marmora. B. glaciale is of common occurrence also in both provinces of the Mauritanian Upwelling Region. Our map suggests that this population is isolated from that to the north, but information from Johannes Kinzer and Julian Badcock (personal communications) shows that the species lives in a very narrow zone just off the continental shelf continuously from Gibraltar to the Mauritanian Upwelling. Otherwise, the range of B. glaciale ends more or less abruptly at the temperatesubtropical boundary where that of its congener B. suborbitale begins. Jensen (1948) reported specimens from as far north as 70°N off West Greenland and Johnsen (1922) specimens from off Spitzbergen near 80°N, 10°E. Such northern records suggest that B. glaciale lives everywhere in the subarctic. The only arctic record of which we know comes from between Jan Mayen and East Greenland at 72°10'N, 14° 30'W (Day, 1886). [Jensen's (1948) record from 69° 50^, 61°36^ is probably only

fishes of the Western North Atlantic nominally arctic as it comes from just across Dunbar's (1951) arctic-subarctic boundary in southern Baffin Bay.] Although Walters (1955) said that Wilimovsky saw B. glaciate at Pt. Barrow, and Wilimovsky (1954) listed it among Alaskan fishes, this was evidently based on a waif or waifs, for there are no indications that the species lives regularly anywhere in the Polar Sea. Johnsen (1945), who has studied this fish in the northeasternmost part of its range, says that it occurs "in areas where the warm and salt water from the Atlantic prevails." With the exception of the Alaska record mentioned, B. glaciate is known from nowhere outside the North Atlantic. Vertical Distribution. Opening-closing devices took B. glaciate in the Mediterranean Sea by day at 375-800 m with maximum abundance at 500 m, and at night at 12-200 m and 600-800 m with maximum abundance at 50-70 m. Non-migrants included all developmental stages. Near Bermuda where it is uncommon, B. glaciate was found at 7501,200 m at all times of the day. In the WHOI collections, B. glaciate occurred between 275 and 850 m by day, and from near the surface to about 225 m at night, with maximum catch at 25 and 75m. Synonyms and References: Scopelus glacialis Reinhardt, 1837: 33 (orig. descr.; off Greenland; holotype, ZMUC 62, fide Krefft and Bekker, 1973). Myctophum glaciate. Taning, 1918: 31, Figs. 11-14 (descr., develop., reprod., distr. in Mediterranean); Taning, 1928: 56 (in key); Taning, 1931, figs, (diag., distr., reprod.); Andriashev, 1954: 129, Fig. 62 (synon., descr., distr., biol.). Myctophum glaciate vn. thori Taning, 1918: 33 (name proposed for Mediterranean and Sea of Marmora populations); Nafpaktitis, 1973: 8, fig. 5 (descr. and discussion). Benthosema glaciate. Goode and Bean, 1896: 76, Pi. 22, Fig. 85 (descr., coll. data); Fraser-Brunner, 1949: 1051, fig. (in key); Bolin, 1959: 9 (key, synon., brief descr., distr.); Bekker, 1967b: 94 (horiz. and vert, distr.); Halliday, 1970: 105 (growth and vert, distr. in northwest. Atlantic);

53

Bini, 1971: 187, illus. (morphol., biol., distr.); Goodyear et al., 1972: 163 (horiz. and vert, distr., growth and reprod. in Mediterranean); Krefft and Bekker, 1973: 172 (synon., ref., distr.).

Benthosema suborbitale (Gilbert) 1913 Figures 20, 21 Study Material. Over 3 50 North Atlantic specimens, 10-32 mm; in LACM and WHOI.

Distinctive Characters. Characters in the key will separate this species from its North Atlantic congener B. glaciate. Description. Fin rays: dorsal 12-13 (11-14); anal 17 (16); pectoral 13-14 (12). Gill rakers: 3 + 1 + 10 (9-11), total 14 (13-H). Photophores: AO 6 + 5 (4-6), total 11 (10-12). Lateral-line organs: about 34, those anterior to SAOs weakly developed. Head. Length of head 3 in SL. Mouth oblique, terminal; maxillary expanded posteriorly; length of upper jaw 1.5 in hi and 5 in SL. Eye large, its diameter 1.5-1.8 in length of upper jaw, 2.5-3 in hi and 8-8.5 in SL. Operculum abruptly tapering to a point above base of pectoral fin. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin under posterior half of base of dorsal fin. Pectoral fins long, extending to 1st or 2nd AOa. Ventral fins reaching anus. Base of adipose fin somewhat in advance of end of base of anal fin. Luminous Organs. A photophore near posteroventral margin of orbit. PLO well in advance of base of pectoral fin and nearer to it than to lateral line. PVOi over PO2; PVO2 somewhat higher than PVOi, at lower end of base of pectoral fin. VLO in advance of base of ventral fin and 2-2.5 times its own diameter below lateral line. VO2 highly elevated, on or slightly behind vertical through VOiSAO angular; SAOi on or somewhat behind vertical through center of VO3; SAO2 behind VO4; SAO3 about over 1st AOa and at lateral

54

Memoir I, Part 7—Sears Foundation for Marine Research

FIGURE 20. Benthosema suborbitale: female, 30 mm; A, supracaudal luminous gland of male, 29 mm.

line. AOa in line, or AOai slightly depressed. Pol under or slightly in advance of base of adipose fin and in contact with lateral line. First AOp over base of anal fin. Prc2 well behind Prci and at midlateral line. Sexual Dimorphism. Males with supracaudal and females with infracaudal luminous glands. The glands are distinct in both sexes in specimens about 19 mm long. The caudal gland develops as one unit in males, whereas in females it first appears as two midventral patches of luminous tissue which later coalesce to form a single patch with only a slight indication of its previous two-component condition. Size. B. suborbitale is a small fish; the largest specimen found in the collections examined measured 38 nun. The species apparently reaches sexual maturity at a size between 24 and 26 mm, and fully gravid females 26 to 28 mm long are quite common. Atlantic Distribution. Eenthosema suborbitale (Fig. 21) is a tropical-subtropical species whose range more or less complements that of its congener B. glaciate. For the most part, the temperate-subtropical boundary is the northern limit of the first, the southern

limit of the second. Both species occur in the Slope Water and in the Mauritanian Upwelling, but B. glaciale is the more abundant in both places; although a single collection from either place can contain both species, generally one species greatly preponderates. This myctophid is a ranking one in our collections from the Atlantic Tropical and North Atlantic Subtropical Regions and Gulf of Mexico. B. suborbitale was noticeably more abundant in the eastern tropics and subtropics than in the western parts of those regions. Indeed, the species was absent from collections from the western part of the South Atlantic Subtropical Region. Extra-Atlantic Occurrence. B. suborbitale occurs in both Indian and Pacific Oceans. The Indian Ocean distribution is similar to the Atlantic one in that the species has been reported from both tropics and subtropics (Nafpaktitis and Nafpaktitis, 1969; Kotthaus, 1972b). In the Pacific, however, records appear to be mostly or wholly subtropical ones (near Hawaii, Clarke, 1973; off Japan, Gilbert, 1913; subtropical eastern Pacific, Wisner, 1976 and Berry and Perkins, 1966; Bekker, 1967a; McGinnis, 1974). Hartmann

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FIGURE 21. Benthosema suborbitale, a tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and Parin et al. (1974).

and Clarke (1975) called attention to the absence of the species in collections made between 12°N and 3°30'S at 145°W. (BC) Vertical Distribution. Opening-closing devices collected B. suborbitale by day at 500700 m near Bermuda, with maximum abundance at 550-650 m, and at 400-650 m near the Canary Islands, with maximum abundance at 500-600 m. It was taken at night at 10100 m (to 250 m off Fuerteventura), with maximum abundance at 10-50 m in both regions. Recently transformed juveniles and transforming postlarvae were taken at night

at 700-800 m near Bermuda and at 600-700 m near the Canaries. In the WHOI collections, B. suborbitale occurred between 375 and 750 m by day and from near the surface to about 125 m at night, with maximum abundance at 50 m. Synonyms and References: Myctophum suborbitale Gilbert, 1913: 82 (orig. descr.; Suruga Bay, Japan, between surface and 300 fms; holotype, USNM 74473). Myctophum simile Taning, 1928: 56 (orig. descr.; in key). Myctophum imitator Parr, 1928: 60 (a new name

56

Memoir I, Part 7—Sears Foundation for Marine Research

for M. suborbitole Gilbert, 1913, since Diapkus suborbitale Weber and deBeaufort, 1913, had priority, the two genera not being separated by all authors at the time); Parr, 1929: 6, Fig. 3 (compar. with M. suborbitale Gilbert 1913). Benthosema suborbitale. Fraser-Bninner, 1949: 1051, fig. (in key); Bolin, 1959: 10 (key, synon., brief descr., distr.); Bekker, 1967b: 95 (horiz. and vert, distr.); Nafpaktitis and Nafpaktitis, 1969: 11, Fig. 9 (records from Indian Ocean; size, brief descr. of caudal lum. glands); Kotthaus, 1972a: 11 (records from east. North Atlantic, char., photo of otol.); Kotthaus, 1972b: 14, photo 261 (records from Indian Ocean; char.); Hulley, 1972a: 220 (records from off west coast of S Africa); Krefft and Bekker, 1973: 173 (synon., ref., distr.). Benthosema simile. Nafpaktitis, 1973: 10, Fig. 6 (descr., desig. of lectotype: 31°47'N, 41°4l'W, 600 m.w.o.; ZMUC P2329235).

Genus Diogenichtbys Bolin 1939 Diogenichthys Bolin, 1939: 119 (type-species Myctopbum laternatum Carman 1899, by original designation); Fraser-Bninner, 1949: 1053 (characters); Bolin, 1959: 11 (characters); Pazton, 1972: 42 (osteological characters).

Characters. Mouth small; jaws extending to

or a little beyond vertical through posterior margin of orbit; maxillary expanded posteriorly; premaxillary teeth flattened, lanceolate, many with minute denticle on each edge at widest point, and some posterior ones bent forward; outer anterior teeth on dentary close-set and flattened, posterior ones broadbased and sharply hooked forward. Base of anal fin longer than that of dorsal fin. Lateral line weakly developed. Dn present, sexually dimorphic, especially in D. laternatus and D. panurgus; Vn absent; PVO almost horizontally arranged; 5 PO, level; 4 VO, the second elevated; one Pol; 2 Prc, in an almost horizontal line; males with large supracaudal and females with much smaller infracaudal luminous glands. Size. Diminutive lanternfish hardly exceeding a size of 30 mm. Range. Mainly in tropical and subtropical waters of all three major oceans. Species. The genus contains three species: D. atlanticus, D. laternatus, and D. panurgus. Of these, only D. atlanticus has so far been shown to occur in the North Atlantic.

Key to the Species of Diogenichthys la. Prci-Prc2 interspace wide, more than one-half the space between last AOp and SAOi in advance of, seldom directly over, VO4; a highly developed sexually dimorphic Dn absent in adult males. atlanticus (Tining) 1928, p. 56 Ib. Prci-Prc2 interspace narrow, one-half the space between last AOp and Prc^ or less; SAOi directly over or slightly behind VOi; a highly developed sexually dimorphic Dn present in adult males 2 2a. Length of upper jaw less than 2 times in hi and less than 6 times in SL; gill rakers 3 + 1 + 9-10, total 13-14. laternatus (Carman) 1899 Eastern tropical and subtropical Pacific Ocean

2b. Length of upper jaw 2 or more times in hi and 6 or more times in SL; gill rakers 2 + 1 + 8-9, total 11-12. panurgus Bolin 1946 Tropical Indian, southeastern Atlantic, and southwestern tropical Pacific Oceans.

Diogenichthys atlanticus (Tining) 1928 Figures 22, 23 Study Material. More than 300 specimens, 11-24 mm, from across the North Atlantic, the Caribbean Sea, and the Gulf of Mexico; in LACM.

Distinctive Characters. The unique dentition, the elevated VO2, the single Pol, the nearly horizontally arranged Prc, and the low numbers of AOp and gill rakers will readily separate this diminutive form from all other North Atlantic myctophids.

Fishes of the Western North Atlantic

57

FIGURE 22. Diogenichthys atlantirus: lectotype (ZMUC P2329229), female, 20 mm; A, supracaudal luminous gland of male, 22 mm; B, premazillary teeth.

Description. Fin rays: dorsal 11-12; anal 15-16; pectoral 12-13. Gill raktrs: 2 + 1+9-11, total 12-14. Photophores: AO 6 (5-7) + 3 (2-^t), total 9 (8-10). Head. Length of head 3.2-3.5 in SL. Mouth small, jaws extending to or very slightly beyond vertical through posterior margin of orbit; length of upper jaw 1.8-2 in hi and 6-7 in SL. Eye large, its diameter 1.2-1.5 in length of upper jaw, 2.4—2.8 in hi and 8—9 in SL. Upper half of posterior opercular margin convex, lower half straight or slightly concave. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fins long, extending to about SAO2. Ventral fins reaching anus. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PLO in advance of base of pectoral fin and midway between it and lateral line or a little higher. PVOi well in front of and at or slightly below level of PVO2 which is at lower end of base of pectoral fin.

VLO midway between base of ventral fin and lateral line or somewhat higher. VO3, SAOi and SAO2 in a straight line usually passing in front of SAO8 which is over base of anal fin and at lateral line. AOa evenly spaced and level. Pol under or slightly behind base of adipose fin and at lateral line. First AOp sometimes over end of base of anal fin. Prc2 slightly higher than Prci, the two organs separated by a distance nearly equal to that between last AOp and Prci. Sexual Dimorphism. Dn noticeably larger and better developed in males than in females. Also, adult males with a large, undivided supracaudal luminous gland occupying % to 34 of dorsal aspect of caudal peduncle and first appearing in young fish about 15 nun long. Females with a small infracaudal gland consisting of 2-4 tiny, coalesced patches, discernible in fishes about 16 mm long. Size. Sexual maturity is reached at a size of about 20 mm. The largest specimen found in the collections examined measured 29 mm. Development. Tining (1918) illustrated and briefly described a series of developmental

Memoir l,Part 7—Sears Foundation for Marine Research

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"(J

»V6"""-feo'""'-bo

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FIGURE 23. Diogenichthys atlanticvs, a tropical-subtropical species. Atbntic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et aL (1971).

stages of this species under the name Myctophum laternatum Carman 1899. In their recent, detailed study of myctophid larvae, Moser and Ahlstrom (1970) agreed with Tining regarding the distinctiveness of the larvae of D. atlanticus which, alone among myctophid larvae, have a barbel on the lower jaw. This barbel first develops in larvae about J mm long and persists until metamorphosis which occurs at a size between 14 and 1J mm. Atlantic Distribution. Diogenichthys atlanticus (Fig. 23) is a common but unevenly

distributed tropical-subtropical species. It is a ranking myctophid in the Tropical Atlantic Region and in the North and South Atlantic Subtropical Regions. The species occurs also in the Mauritanian Upwelling and in the Gulf of Mexico. In addition, there are significant numbers of the species in those parts of the North Atlantic Temperate Region that are adjacent to the subtropics. On the other hand, the species is almost wanting in some parts of the Southern Sargasso Sea, North African Subtropical Sea, Lesser Antillean Province, Carib-

Fishes of the Western North Atlantic bean Sea, and South Atlantic Subtropical Region. Extra-Atlantic Occurrence. Nafpaktitis and Nafpaktitis (1969) reported D. atlanticus from the western Indian Ocean between about 22°S and 45°S, D. panurgus Bolin between about 4°N and 18 °N, and no Diogenichthys in between. Bradbury et al. (1971) reported D. panurgus from the Indian Ocean between about 7°N and 3°S. In the Pacific D. atlanticus seems to be widely but unevenly distributed. Hartmann and Clarke (1975) found it to be common in equatorial waters at 145 °W. Clarke (1973) found it rare off Hawaii (at about 21°N). Wisner (1976) reported it from widely separated localities in the eastern Pacific between about 35°N and 35°S, where its range is interrupted in the eastern tropical Pacific by D. laternatus (Carman). (BC) Vertical Distribution. Opening-closing devices caught D. atlanticus by day at 450-1,250 m (mostly 500-850 m) near Bermuda, with maximum abundance at 600-650 m, and at 400-930 m near the Canary Islands, with maximum abundance at 500-600 m. At night, the species was taken near Bermuda at 18-1,050 m, with maximum abundance at 50-100 m, and near the Canaries at 10-100 m and 500-700 m. Partial migrants and non-migrants taken near Bermuda accounted for more than half of the population in January-February and June and more than one-third in AugustSeptember; they were most abundant at 750900 m and, other than postlarvae, consisted mostly of juveniles, but included a few subadults. Near the Canaries, non-migrants were all juveniles. Full migrants in both regions included most sizes. In the WHOI collections, D. atlanticus occurred mostly bet wen 425 and 850 m by day and mostly between 40 and 125 m at night. Synonyms and References: Myctophum laternatum. Taning, 1918: HO, Fig. 46 (brief descr. of larval series from North Atlantic).

59

Myctophum laternatum atlanticum Taning, 1928: 56 (orig. descr.; in key; subspecific name introduced for North Atlantic form); Taning, 1931 (illus. of larva and adult, diag., distr.). Diogenichthys scofieldi Bolin, 1939: 122, Fig. 16 (orig. descr.; off Cortez Banks, 31°33'N, 119°57'W, 050 m depth; holotype CAS (SU) 33657). Diogenichthys atlanticus. Fraser-Brunner, 1949: 1054, fig. (elev. to species; in key); Bolin, 1959: 11 (synon., char., distr.); Bussing, 1965: 202 (records from off Chile); Bekker, 1967b: 95 (records from Atlantic Ocean, depths of capture); Nafpaktitis and Nafpaktitis, 1969: 13, Figs. 12-13 (records from Indian Ocean, char.); Craddock and Mead, 1970: 3.27 (records from southeast. Pacific); Moser and Ahlstrom, 1970: 40, 123, Figs. 10-11, 41-43 (descr. of larvae, distr. in east. Pacific); Kotthaus, 1972a: 11 (records from east. North Atlantic, char., photo of otol.); Hulley, 1972a: 220 (records from southwest. Indian and southeast. Atlantic Oceans; char.); Clarke, 1973: 406, 408 (occur, off Hawaii); Krefft and Bekker, 1973: 181 (synon., ref., distr.); Nafpaktitis, 1973: 12, Fig. 8 (desig. and descr. of lectotype: 20°00'N, 21°55'W, 220 m.w.o.; ZMUC P2329229).

Genus Myctophum Rafinesque 1810 Myctophum Rafinesque, 1810: 56 (type-species Myctophum punctatum Rafinesque 1810, by monotypy); Fraser-Brunner, 1949: 1054 [definition, two subgenera: Scopelus (=Symbolophorus) and Myctophum]; Bolin, 1959: 13 (characters); Paxton, 1972: 43 (osteological characters). Scopelus Cuvier, 1817: 169 [type-species Scopelus humbold ft (Risso) 1810 = Myctophum punctatum Rafinesque 1810, by subsequent designation of Goode and Bean, 1896: 70]. Dasyscopelus Giinther, 1864: 405, 411 [type-species Scopelus as per (Richardson) 1845, by subsequent designation of Goode and Bean, 1896: 91]. Ctenoscopelus Fraser-Brunner, 1949: 1059 (typespecies Scopelus phengodes Liitken 1892: 2 5 3 ) .

Characters. Maxillary from slightly to markedly expanded posteriorly. Small teeth in bands on premaxillaries, dentaries and palatines; similar teeth in a large patch on each mesopterygoid; vomerine teeth present or absent. Base of anal fin longer than that of dorsal fin. Lateral line well developed. Dn small and often ill-defined; Vn somewhat larger; 5 PO, level; 4 VO, level; SAO in a straight

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Memoir 1, Part 7—Sears Foundation for Marine Research

or somewhat curved line with SAOi always behind VO3; one Pol; 2 Prc. Adult males and females of all species but M. selenops with supracaudal and infracaudal luminous glands, respectively; in M. selenops both sexes with a supracaudal gland. Size. The members of this genus attain maximum sizes of between 60 and 105 mm. Range. Low and middle latitudes of all three major oceans.

Species. The genus contains 13 recognized species: M. affine, M. asperum, M. aurolaternatum, M. brachy gnathum, M. fissunovi, M. imperceptum, M. nitidulum, M. obtusirostre, M. orientaley M. phengodes, M. punctatum, M. selenops, and M. spinosum. Of these, six occur in the North Atlantic. These are: M. affine, M. asperum, M. nitidulum, M. obtusirostre, M. punctatum, and M. selenops.

Key to the North Atlantic Species of Myctophum la. Ib. 2a. 2b. 3a. 3b. 4a.

AOp 7 or more, 3-4 over base of anal fin. punctatum Rafinesque 1810, p. 60 AOp 7 or fewer, 1 or none over base of anal fin 2 Gill rakers 14-16; SAO in a distinctly curved line. asperum Richardson 1845, p. 68 Gill rakers 18 or more; SAO in a straight or very nearly straight line 3 Gill rakers 18-22; AO 12-15; pectoral fin rays 13-14 4 Gill rakers 22-25; AO 9-12; pectoral fin rays 16-18 5 Posterodorsal opercular margin sharply angular; scales cycloid. nitidulum Garman 1899, p. 65 4b. Posterodorsal opercular margin evenly rounded; scales ctenoid. affine (Liitken) 1892, p. 62 5a. Body deep; head nearly as deep at it is long; upper posterior opercular margin smooth; scales strongly ctenoid. "* selenops Tining 1928, p. 72 5b. Body slender; head considerably longer than deep; upper posterior opercular margin obtusirostre Tining 1928, p. 70 serrate; scales cycloid. Myctophum punctatum Rafinesque 1810 Figures 24, 25 Study Material. About 250 North Atlantic specimens, 19-104 mm; in ZMUC, LACM, and WHOI.

Distinctive Characters. In addition to the characters in the key, the high number of gill rakers distinguishes M. punctatum from all of its North Atlantic congeners except M. obtusirostre and M. selenops. From the latter two species it can readily be separated on the basis of the higher number of its AOp (710 versus 3-5) and the lower number of pectoral fin rays (13-14 versus 16-18). Description. Fin rays: dorsal 13-14; anal 20-21 (22); pectoral 13-14. Gill rakers: 7 (6-8) + 1 + 17 (16-18), total 25 (24-27).

Pbotopbores: AO 8 (7-9) + 8-9 (7-10), total 16-17 (14-18). Lateral-line organs: 43—44. Head. Head length 3.3-3.6 in SL. Mouth somewhat oblique; length of upper jaw 1.5 in hi and 5-5.5 in SL. Eye large, its diameter 1.5-1.7 in length of upper jaw, 2.4—2.6 in hi and 8-9 in SL. Opercular margin almost evenly rounded posteriorly and posteroventrally, slightly concave posterodorsally. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin under end of base of dorsal fin. Pectoral fins extending to vertical through VOa. Ventral fins reaching anus. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PLO in advance of base of pectoral fin and usually somewhat nearer to it than to lateral line, sometimes midway

Fishes of the Western North Atlantic

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FIGURE 24. Myctopbum punctatum: male, 51 mm; A, supracaudal luminous gland of male, 50 mm; B, infracaudal luminous gland of female, 53 mm.

between the two. PVd over PO2; PVO2 at lower end of base of pectoral fin and in advance of PO8. VLO midway between base of ventral fin and lateral line. SAO and VO8 in a straight line or very nearly so; SAOi slightly in advance of vertical through center of VO4; SAO3 about over origin of anal fin and in contact with lateral line. First and, often, 2nd AOa somewhat depressed. Pol in advance of base of adipose fin and immediately below lateral line. Anterior 3-4 AOp over base of anal fin. Prc2 slightly higher than, and its diameter or less behind Prci. Sexual Dimorphism. Adult males with a supracaudal luminous gland consisting of 2-4 overlapping, scalelike structures framed by a narrow band of darkly pigmented tissue. The gland begins developing in males about 3 5 mm long. Adult females with an infracaudal gland consisting of 4— J, occasionally 3, heartshaped, more or less overlapping patches of luminous tissue. Several females examined had, in addition to the well-developed infracaudal gland, one or two small supracaudal patches of luminous tissue immediately in front of the procurrent caudal rays. The infracaudal gland appears in females 38-40 mm long.

Size. The largest specimen examined measured 104 mm. Several gravid females were found ranging in size between 50 and 63 mm. Development. Larvae of this species have been described by T&ning (1918) on the basis of material mainly from the Mediterranean Sea. He found that metamorphosis takes place at sizes between 17.5 and 19.5 mm. Atlantic Distribution. Myctophum punctatum (Fig. 25) is a subpolar-temperate species commonly taken both in midwater trawls and at the surface at night in neuston nets. In addition to the Atlantic Subarctic and North Atlantic Temperate Regions, the species occurs in the Mauritanian Upwelling. M. punctatum is not known from outside the North Atlantic. Vertical Distribution. Most specimens of this species have been taken at the surface at night. Opening-closing devices caught M. punctatum in the Mediterranean Sea by day at 100-1 JO m and at 700-1,000 m; maximum abundance was between 700 and 800 m. At night, specimens were from between the surface and 200 m and from 700-800 m. In the WHOI collections M. punctatum occurred at the surface at night throughout

Memoir 1, Part 7—Sears Foundation for Marine Research

62

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FIGURE 25. Myctophum punctatum, a subpolar-temperate species. Distribution, based on the WHOI neuston collections. Additional records are from Badcock (1970), Gibbs et al. (1971), Krefft (1974), Lourie (1969), Taning (1918), and WHOI midwater trawl data.

its range and, in smaller numbers, throughout the upper 125 m. By day, it was caught between 225 and 750 m. References: Myctophum punctatum Rafinesque, 1810: 56 (orig. descr.; west. Mediterranean); Taning, 1918: 57, Figs. 19-20 (descr., develop., reprod., distr. in Mediterranean); Taning, 1928: 53 (in key); Taning, 1932 (illus., diag., distr., reprod.); FraserBrunner, 1949: 1056, fig. (in key); Bolin, 1959: 13 (synon., brief descr., distr.); Bekker, 1967b: 97 (horiz. distr., depths of capture); Halliday and

Scott, 1969: 2696 (records from Canadian Atlantic); Bini, 1971: 169, illus. (morphol., reprod., distr.); Goodyear et al., 1972: 168 (horiz. and vert, distr., growth and reprod. in Mediterranean); Krefft and Bekker, 1973: 171 (synon., ref., distr.).

Myctophum affine (Liitken) 1892 Figures 26, 27 Study Material. Over 300 North Atlantic specimens, 14-60 mm; in LACM and ZMUC.

Distinctive Characters. The kind of scala-

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FIGURE 26. Myctophum affinei female, 49 mm; A, supracaudal luminous gland of male, 57 mm; B, infracaudal luminous gland of female, 58 mm.

tion (ctenoid) and the shape of the posterodorsal opercular margin (rounded) will separate this species from M. nitidulum. The first character (scalation) is helpful in identifying individuals larger than about 30 mm; the second character (shape of operculum) is useful in differentiating individuals of all sizes. Description. Fin rays: dorsal 12-13; anal 18-20; pectoral 13-14. Gill rakers: 5-6 + 1 + 12-15, total 18-22. Photophores: AO 8-9 (7) + 5 (4-6), total 13-14 (12-15). Lateral-line organs: 41-42. Scales: ctenoid. Head. Head length 3.4^3.8 in SL. Mouth oblique; length of upper jaw 1.5-1.7 in hi and 5.5-6 in SL. Eye large, its diameter 1.51.7 in length of upper jaw, 2.4-2.6 in hi and 8.5-9.5 in SL. Posterior opercular margin forming a very obtuse, blunt angle; posterodorsal margin rounded and smooth. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin on or slightly behind vertical through end of base of dorsal

fin. Pectoral fins extending to vertical through VO2. Ventral fin not reaching anus. Base of adipose fin well in advance of end of base of anal fin. Luminous Organs. PLO in advance of base of pectoral fin and midway between it and lateral line or a little lower. PVOi directly over or slightly in advance of PO2; PVO2 at lower end of base of pectoral fin and in advance of POa. VLO midway between base of ventral fin and lateral line. SAO and VO8 in a straight line or very nearly so; SAOi directly over or slightly in advance of VO4; SAOs about over origin of anal fin and % of its diameter or less below lateral line. AOa level or AOai and, sometimes, AOa2 distinctly depressed. Pol over last AOa, under base of adipose fin and % of its diameter or less below lateral line. First AOp usually over end of base of anal fin. Prc2 slightly higher than, and about its own diameter behind Prci. Sexual Dimorphism. Adult males with a supracaudal luminous gland consisting of a series of 7-8 overlapping, scalelike structures occupying nearly the entire dorsal surface of the caudal peduncle. The gland begins de-

Memoir ly Part 7—Sears Foundation for Marine Research

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FIGURE 27. Myctophum affine, a tropical species. Distribution, based on the WHOI neuston collections. Additional records are from Gibbs et al. (1971) and WHOI midwater trawl data.

veloping in individuals about 25 mm long. Adult females with an infracaudal gland consisting of 3-4 oval or lanceolate patches of luminous tissue in contact with each other or slightly overlapping. The gland appears in young females 28-30 mm long. Size. Large ovaries and eggs were found in several females ranging in size between 46 and 5 8 mm. This fish is seldom caught much larger than 60 mm; the largest WHOI specimen is reported to be 79 mm (Craddock, personal communication).

Atlantic Distribution. Myctophum affine (Fig. 27) is a tropical species best represented by its distribution at the surface at night from neuston tows. It is abundant in the eastern Atlantic in the tropical Guinean Province and in the Mauri tanian Up welling; in the western Atlantic it is common in the Gulf of Mexico, Caribbean Sea, and Slope Water; it is relatively scarce, however, between these two areas of abundance, that is, in the Amazonian and Lesser Antillean Provinces. Just as M. affine appears to be waifed north to the Slope

Fishes of the Western North Atlantic

65

FIGURE 28. Myctopbum nitidulum: young female, 40 mm; A, supracaudal luminous gland of male, 65 mm; B, infracaudal luminous gland of female, 68 mm.

Water by the Gulf Stream, so it seems to be carried south to the Argentine Basin by the Brazil Current. M. affine is not known to occur outside the Atlantic Ocean, although the name has often been used mistakenly for M. nitidulum and perhaps other species. Vertical Distribution. In WHOI collections M. affine occurred at the surface at night throughout its range and, in much smaller numbers, in the upper 275 m. By day, it occurred between 300 and 650 m. Synonym and References: Scopelus affinis Liitken, 1892: 252, Fig. 10 (orig. descr.). Myctopbum affine. Gibbs, 1957: 230 (char, distinguishing M. affine from M. nitidulum\ distr. in west. North Atlantic); Bolin, 1959: 15, Fig. 3 (char., desig. of kctotype: 8°44'N, 21°W; ZMUC 16).

Myctophum nitidulum Garman 1899 Figures 28, 29 Study Material. Two hundred and seventy North Atlantic specimens, 15-74 mm; in LACM.

Distinctive Characters. This species is distinguished from the most similar to it, M. affine, by its sharply angular posterodorsal opercular margin (rounded in M. affine), its cycloid scales (ctenoid in M. affine) and a number of minor morphological differences mentioned below. Description. Fin rays: dorsal 13-14; anal 19-20; pectoral 13-14. GUI rakers: 5-6 + 1 + 13-14 (12-15), total 19-20 (18-22). Photophores: AO 9 (8-10) + 5 (4-6), total 14 (13-15). Lateral-line organs: 39-40. Scales: cycloid. Head. Head length 3.4-3.6 in SL. Mouth oblique; length of upper jaw 1.5-1.6 in hi and 5-5.5 in SL. Eye large, its diameter 1.61.8 in length of upper jaw, 2.5-2.8 in hi and 8.8-9.8 in SL. Lower % of posterior opercular margin convex, upper % nearly straight; posterodorsal margin sharply angular and, in specimens 50 mm and larger, distinctly serrate.

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Memoir 1, Part 7—Sears Foundation for Marine Research

Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin on or slightly in front of vertical through end of base of dorsal fin. Pectoral fin extending about to vertical through VO2. Ventral fins barely reaching anus. Base of adipose fin well in advance of end of base of anal fin. Luminous Organs. PLO 1-1.5 times its own diameter anterodorsad to upper end of base of pectoral fin. PVOi directly over or slightly behind PO2; PVO2 at lower end of base of pectoral fin and somewhat in advance of PO3. VLO midway between base of ventral fin and lateral line. SAO in a straight line passing behind VO3; SAOi slightly behind, seldom directly over, VO4; SAO3 on or a little behind vertical through origin of anal fin and about % of its diameter below lateral line. AOa level or AOai slightly depressed. Pol over last AOa, under base of adipose fin and about l/2 of its diameter below lateral line. First AOp usually over end of base of anal fin. Prc2 slightly higher than, and about its own diameter behind Prci. Sexual Dimorphism. Adult males with a supracaudal luminous gland consisting of 6-7 overlapping, scalelike structures occupying, when fully developed, % of the dorsal surface of the caudal peduncle. The gland begins developing in young males about 35 mm long. Adult females with a series of 3-5 slightly overlapping, oval-shaped, infracaudal patches of luminous tissue that appear in individuals about 48 mm long. Size. All gravid females found in the collections examined were larger than 5 5 mm. The species is seldom taken larger than about 80 mm; the largest WHOI specimen is 99 mm (Craddock, personal communication). Development. The larval development of this species has been described by Moser and Ahlstrom (1970) on the basis of material from the California Current. Metamorphosis takes place at a size between 11.7 and 14.7 mill. Remarks. Pacific M. nitidulum is indis-

tinguishable in terms of external morphology from Atlantic and Indian Ocean individuals. However, tropical and eastern Pacific populations tend to have a somewhat higher number of gill rakers (20-24 as compared to 1822). Furthermore, John E. Fitch, of the California Department of Fish and Game Marine Laboratory, has found distinct differences in otolith morphology between the Atlantic and eastern North Pacific populations (personal communication). A careful study of M. nitidulum from the two oceans would, therefore, be very worthwhile. Atlantic Distribution. Myctophum nitidulum (Fig. 29) is a tropical-subtropical species not well sampled by midwater trawls. It is most often taken at the surface at night by neuston nets. The most productive WHOI collections of the species came from the eastern tropics and subtropics (Guinean Province and Southern North African Subtropical Sea). It is uncommon in the tropics and subtropics of the eastern South Atlantic. Extra-Atlantic Occurrence. Myctophum nitidulum was originally described from northeast of Hawaii. It has subsequently been reported from the Indian Ocean between approximately 7°N and 24°S (Nafpaktitis and Nafpaktitis, 1969; Bradbury et al., 1971; Kotthaus, 1972b). The species has been collected in the tropical and subtropical Pacific Ocean between about 32°N and 31°S (Sarenas, 1954; Bussing, 1965; Craddock and Mead, 1970; Moser and Ahlstrom, 1970; Kawaguchi and Aioi, 1972; Clarke, 1973; Hartmann and Clarke, 1975; and numerous unpublished data, especially from the eastern Pacific). The northernmost occurrences off Japan at approximately 40 °N (Kawaguchi and Aioi, 1972) are probably due to the effect of the Kuroshio Current. (N) Vertical Distribution. The vast majority of specimens of M. nitidulum were taken at the surface at night. Opening-closing devices caught it near Bermuda at 600-8 50 m by day

Fishes of the Western North Atlantic 7°

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FIGURE 29. Myctophum nitidulum, a tropical-subtropical species. Atlantic Ocean distribution, based on WHOI neuston collections. Additional records are from Gibbs et al. (1971) and WHOI midwater trawl data.

and to 200 m, with an occasional fish between 400 and 950 m, by night; individuals below the surface at night were all smaller than 30 mm. Daytime WHOI collections took it between 475 and 850m. Synonyms and References: Myctophum nitidulum Carman, 1899: 266, Pi. 56, Fig. 3 (orig. descr., 27°50'N, 145°45'30"W; holotype, MCZ 28493); Gibbs, 1957: 230 (char, distinguishing M. nitidulum from M. affine; distr. in west. North Atlantic); Bolin, 1959: 14, Fig. 2 (descr., relat. with M. affine); Bussing, 1965: 202 (records from Peru-Chile Trench; char.); Nafpak-

titis and Nafpaktitis, 1969: 21, Fig. 22 (records from west. Indian Ocean; descr.); Craddock and Mead, 1970: 3.30 (record from southeast. Pacific); Moser and Ahlstrom, 1970: 80, Figs. 24-25 (devel., distr. of larvae and young in east. North Pacific); Kawaguchi and Aioi, 1972: 166, Figs. 3—4 (records from west, and trop. Pacific; descr.); Kotthaus, 1972b: 23, Photo 267 (records from west. Indian Ocean; char.); Krefft and Bekker, 1973: 172 (synon., ref.). Myctophum margaritatum Gilbert, 1905: 596, Pi. 68, Fig. 2 (orig. descr., "off the south coast of Molokai," Hawaii, surface; USNM 51536); Sarenas, 1954: 395, Fig. 5 (descr.; distr. in the Philippines).

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FIGURE 30. Myctophum asperum: young female, 41 mm; A, supracaudal luminous gland of male, 71 mm; B, infracaudal luminous gland of female, 78 mm.

Myctophum asperum Richardson 1845 Figures 30, 31 Study Material. Eighty-nine North Atlantic specimens, 15-77 mm; in LACM and ZMUC

Distinctive Characters. The low number of gill rakers, angular SAO and ctenoid scalation (distinct in 19-mm-long juveniles) readily differentiate this species from the rest of its North Atlantic congeners. Description. Fin rays: dorsal 13 (12-14); anal 17-18; pectoral 14-15. Gill rakers: 4 (5) + 1 + 10 (9-11), total 15 (14-16). Photophores: AO 7 (6-8) + 6 (5-7), total 13 (12-14). Lateral-line organs: 39 (38).

Scales: ctenoid. Head. Head length 3.5-3.8 in SL. Mouth somewhat oblique; length of upper jaw 1.61.8 in hi and 6-6.5 in SL. Eye large, its diameter 1.4—1.6 in length of upper jaw, 2.4—2.6 in hi and 8.8-10 in SL. Posterior opercular margin forming a very obtuse, blunt angle about at level of PVO2; posterodorsal margin slightly angular and smooth. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin behind end of base of dorsal fin. Pectoral fins extending about to a point midway between VLO and SAOi. Ventral fins barely reaching VO4. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PLO in advance of base of pectoral fin and midway between it and

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FIGURE 31. Myctophum tspervm, a tropical species. Atlantic Ocean distribution, based on WHOI neuston collections. Additional records are based on WHOI midwater trawl data.

lateral line or a little lower. PVOi directly over or slightly behind PO2; PVO2 at lower end of base of pectoral fin and directly over or slightly in advance of PO8. VLO midway between base of ventral fin and lateral line or a little lower. SAO forming an obtuse angle; SAOX in front of VO4; SAO2 and SAO8 in line with VO4; SAOS on or slightly in advance of vertical through origin of anal fin and immediately below lateral line. AOai usually somewhat depressed. Pol about over last AOa, in advance of base of adipose fin and

immediately below lateral line. AOpi usually over base of anal fin. Prc2 about 1.5 times its diameter posterodorsad to Prci9 approximately midway between bases of ventral procurrent caudal rays and lateral line. Sexual Dimorphism. Adult males with a supracaudal luminous gland consisting of 5-6 overlapping, scalelike structures occupying, when fully developed, 80 to 85 percent of the dorsal surface of the caudal peduncle. The gland begins developing in young males about 32 mm long. Females with 2 (1-3) heart-

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Memoir 1, Part 7—Sears Foundation for Marine Research

FIGURE 32. Myctophum obtusirostrei lectotype (ZMUC P2329232), male, 85 mm; A, supracaudal luminous gland of same; B, infracaudal luminous gland of female, 75 mm.

shaped, slightly overlapping patches of luminous tissue infracaudally. Occasionally, females have, in addition to the infracaudal gland, a small patch of luminous tissue supracaudally. The infracaudal gland appears in individuals 48-52 mm long. Size. Five gravid females from the eastern Caribbean Sea measured 70-77 mm. Although the largest North Atlantic specimens examined were 77 nun long, the species apparently grows to sizes over 85 mm. Atlantic Distribution. Myctophum asperum (Fig. 31), an abundant myctophid caught more often at the surface at night by neuston nets than by midwater trawls, conforms closely to the tropical pattern. In WHOI collections it was most numerous in the Amazonian and Guinean Provinces. Extra-Atlantic Occurrence. Myctophum asperum has been reported from the equatorial Indian Ocean (Nafpaktitis and Nafpaktitis, 1969; Bradbury et al., 1971; and Kawaguchi et al., 1972) and from the equatorial Pacific (Ahlstrom, 1972; Kawaguchi et al., 1972; and Hartmann and Clarke, 1975), where its latitudinal range appears to be greater in the west than in the east. Clarke (1973) did not

report the species from subtropical Hawaii. Wisner (1976) warned that there appear to be two asperum-Vke species in the Pacific, neither of which may be asperum. (BC) Vertical Distribution. In the WHOI collections M. asperum occurred at the surface at night throughout its range and, in much smaller numbers, in the upper 125 m. By day, it was collected between 425 and 750 m. Synonym and References: Myctophum asperum Richardson, 1845: 41, PI. 27, Figs. 13-15 orig. descr.; Taring, 1928: 54 (in key); Fraser-Bmnner, 1949: 1058, fig., partim (in key); Nafpaktitis and Nafpaktitis, 1969: 24, Fig. 24 (records from west. Indian Ocean; compar. with M. spinosum); Wisner, 1970 ( 2 ) : 362 (compar. with M. spinosum; desig. of lectotype: larger specimen fromBMNH 1855. 9.19.1929-30); Rawaguchi and Aioi, 1972: 170, Figs. 9, 10 (records from west, trop. and northwest. Pacific; descr.). Dasyscopelus as per. Gilbert, 1913: 73 (records from off Japan; descr.; compar. with M. spinosum).

Myctophum obtusirostre Tining 1928 Figures 32, 33 Study Material. Fifty-five North Atlantic specimens, 15-85 mm; in LACM, ZMUC, and WHOI.

Fishes of the Western North Atlantic Distinctive Characters. This species can be differentiated from its North Atlantic congeners on the basis of the following combination of characters: gill rakers 22-25, AO 912, pectoral fin rays 16-18, posterodorsal opercular margin serrate (specimens larger than about 30 mm), scales cycloid (feebly ctenoid scales may be present in the thoracic and abdominal regions of specimens larger than about 50 mm). Description. Fin rays: dorsal 13 (12); anal 18 (17-19); pectoral 16-18. Gill rakers: 6-7 + 1 + 15-17, total 22-25. Photophores: AO7 (6-8) +4 (3-5), total 11 (9-12). Lateral-line organs: 37-39. Scales: cycloid. Head. Head length 3.4-3.6 in SL. Mouth oblique; maxillary markedly expanded posteriorly, the expanded portion extending medially and below premaxillary; length of upper jaw 1.6-1.8 in hi and 5.5-6 in SL. Eye large, its diameter 1.5 in length of upper jaw, 2.4-2.6 in hi and 8.4-8.8 in SL. Posterior opercular margin forming an obtuse, blunt angle about at level of PVO2; posterodorsal margin serrate in specimens larger than about 30 mm. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin on or slightly behind vertical through end of base of dorsal fin. Pectoral fins extending to a point about midway between VLO and SAO2. Ventral fins reaching VO4 in specimens smaller than about 50 mm, a little shorter in larger individuals. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PLO anterior to base of pectoral fin and at least twice nearer to it than to lateral line. PVOi behind PO2; PVO2 at lower end of base of pectoral fin, directly over, slightly in front of or behind PO3. VLO midway between base of ventral fin and lateral line. SAO in a somewhat curved line; SAOi slightly in advance of VO4; SAO3 usually on

71

or behind vertical through origin of anal fin and immediately below lateral line. First AOa often a little depressed. Pol over last AOa, under or slightly in advance of base of adipose fin and immediately below lateral line. First AOp over base of anal fin. Prc2 about its own diameter posterodorsad to Prci. Sexual Dimorphism. Adult males with a supracaudal luminous gland consisting of a series of one small followed by 3—4 markedly larger, overlapping scalelike structures occupying 70-75 percent of the dorsal surface of the caudal peduncle. The gland begins developing in young males about 35 mm long. Adult females with 2-3 lanceolate patches of luminous tissue infracaudally. These appear in individuals larger than 50 mm. Size. Females seem to reach sexual maturity at sizes over 75 mm, males at somewhat smaller sizes. The species grows to about 90 mm. Atlantic Distribution. Myctophum obtusirostre (Fig. 33), taken commonly at the surface at night in neuston nets, is a species of the tropical pattern most abundant in the Amazonian and Lesser Antillean Provinces, Caribbean Sea, and Straits of Florida—the western tropical provinces. The species is uncommon or missing in the eastern tropics (Guinean Province) and Mauritanian Upwelling. Extra-Atlantic Occurrence. Myctophum obtusirostre has been reported from the Indian Ocean between approximately 7°N and 12°S (Nafpaktitis and Nafpaktitis, 1969—erroneously under M. brachygnathum\ Kawaguchi and Aioi, 1972). The species has also been collected in tropical waters of the western North and central South Pacific (Kawaguchi and Aioi, 1972) near Hawaii (Clarke, 1973), and at the equator and 3°30'N on the meridian 145°W (Hartmann and Clarke, 1975). Available data indicate that it occurs east to about 105°W. (N) Vertical Distribution. WHOI collections caught M. obtusirostre at night at the surface

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ijnuniif |IMMIII Mniimiiii in?n 1 1 iTTfimi 11 20 10 0 -10 -20 -

FIGURE 33. Myctophum obtusirostre, a tropical species. Atlantic Ocean distribution, based on the WHOI neuston collections. Additional records are from WHOI midwater trawl data.

throughout its range and, in much smaller numbers, in the upper 125 m. By day, it occurred between 325 and 750 m. Synonyms and References: Myctophum pristilepis obtusirostre Taning, 1928: 53 (orig. descr.; in key). Myctophum obtusirostris. Fraser-Bninner, 1949: 1058, fig. (in key); Bekker, 1967b: 97 (records from North Atlantic). Myctophum brachygnat hum. Sarenas, 1954: 399, Fig. 6 (Philippine records; descr.); Nafpaktitis and Nafpaktitis, 1969: 25, Fig. 27 (records from west. trop. Indian Ocean).

Myctophum obtusirostrum. Kawaguchi and Aioi, 1972: 172, Figs. 11, 12 (records from cent, and west. trop. Pacific and east. trop. Indian Oceans; char.); Nafpaktitis, 1973: 13, Fig. 9 (descr.; compar. with M. brachygnathum; desig. of lectotype: 17°54/N, 64° 54'W, 5,000 m.w.o.; ZMUC P2329232); Clarke, 1973: 410 (depths of capture off Hawaii).

Myctophum selenops Tdning 1928 Figures 34, 35 Study Material. Ninety-six North Atlantic specimens, 11-72 mm; in LACM.

fishes of the Western North Atlantic

73

FIGURE 34. Myctophum selenops: lectotype (ZMUC P2329234), male, 53 mm; A, supracaudal luminous gland of same.

Distinctive Characters. Characters in the key readily separate this species from its North Atlantic congeners. Description. Fin rays: dorsal 13 (12-14); anal 17-18; pectoral 16-18. Gill rakers: 7 (6) + 1 +15 (14-16), total 23 (22-24). Photophores: AO 7 (6) + 3 (4), total 10 (11). Lateral-line organs: 37 (36-38). Scales: ctenoid. Head. Head depth nearly equal to hi; hi 3.2-3.4 in SL. Mouth oblique; maxillary markedly expanded posteriorly, the expanded portion extending medially and below premaxillary; length of upper jaw 1.4—1.5 in hi and 4.5-5 in SL. Eye large, its diameter 1.4— 1.6 in length of upper jaw, 2.2-2.4 in hi and 7-7.5 in SL. Posterior opercular margin convex, except in front of base of pectoral fin where it is slightly concave; posterodorsal margin rounded and smooth. Fins. Origin of dorsal fin about over base

of ventral fin. Origin of anal fin under end of base of dorsal fin. Pectoral fins extending to SAO2. Ventral fins reaching anus in young individuals, extending to VO4 in adult specimens. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PLO distinctly smaller than rest of body photophores and about twice its own diameter anterodorsad to upper end of base of pectoral fin. PVOi directly over or slightly behind PO2; PVO2 at lower end of base of pectoral fin, directly over or a little in advance of PO3« VLO distinctly nearer to base of ventral fin than to lateral line. SAO in a straight or nearly straight line; SAOi slightly behind VO4; SAO3 over base of anal fin and about % of its own diameter below lateral line. AOa level and less than one organ diameter apart from each other. Pol directly over or a little behind last AOa, under or slightly in advance of base of adipose fin and its own diameter or less below lateral line. AOp very closely set, often in contact with each other; AOpi usually over base of

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FIGURE 35. Myctopbum selenops, a tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et al. (1971).

anal fin. Prc2 somewhat higher than, and less than its own diameter behind Prci. Sexual Dimorphism. Both males and females with a supracaudal luminous gland. In adult males the gland consists of 5-6 overlapping scalelike structures extending over the entire length of the caudal peduncle or nearly so. In adult females it consists of 4 similar but smaller structures occupying a little more than % of the length of the caudal peduncle. The gland appears in young fe-

males 34-36 mm long and in males about 30 mm long. Size. Three gravid females found in the collections examined measured 59-71 mm. The species does not seem to grow much larger than 75 mm. Remarks. Comparison of M. selenops with type material of M. selenoides Wisner from the central tropical Pacific revealed no significant differences. Therefore, M. selenoides is here placed in the synonymy of M. selenops.

Fishes of the Western North Atlantic Atlantic Distribution. Myctophum selenops (Fig. 35) is an uncommon myctophid apparently distributed according to the tropicalsubtropical pattern. Our largest collections come from the Caribbean Sea. Extra-Atlantic Occurrence. Myctophum selenops is known from a few scattered records from the Indian Ocean (Kotthaus, 1972b), the Southeast Asian seas and western North Pacific (Bekker, 1967a), from near Hawaii (Wisner, 1971; Clarke, 1973), and from about 3°30'N, 145°W (Hartmann and Clarke, 1975). These records suggest a tropical-subtropical range. (N) Vertical Distribution. A few captures of M. selenops with opening-closing devices were made near Bermuda at 300-350 m by day and at 100 m by night. In the WHOI collections, M. selenops occurred from 40 to 22 5 m at night and between 225 and about 450 m by day. This is the only species of Myctophum in the Atlantic that does not regularly come to the surface at night. Synonym and References: Myctophum selenops Taning, 1928: 54 (orig. descr.; in key); Fraser-Bninner, 1949: 1059, fig. (in key); Kotthaus, 1972b: 25, Photo 269 (record from Indian Ocean; merist., morphom.); Nafpaktitis, 1973: 14, Fig. 11 (desig. and descr. of lectotype: 23°13'N, 82°21'W, 600 m.w.o.; ZMUC P2329234); Krefft and Bekker, 1973: 172 (synon., ref., distr.). Myctophum selenoides Wisner, 1971 ( 1 ) : 43, Fig. 3 (orig. descr. about 8 miles W of Keahole Point, western side of the Island of Hawaii, 0-1,150 m; holotype SIO 60-251); Clarke, 1973: 410 (occur, and capture depths near Hawaii).

Genus Symbolophorus Bolin and Wisner 1959 Symbolophorus Bolin and Wisner, 1959: 11 (type-species Myctophum californieme Eigenmann and Eigenmann 1889, by original designation); Paxton, 1972: 43 (definition, osteological characters). Scopelus (not of Cuvier 1817 = Myctophum Rafinesque 1810). Fraser-Bninner, 1949: 1054 (subgenus of Myctophum).

75

Characters. Maxillary moderately expanded posteriorly. Base of anal fin longer than that of dorsal fin. Dn very small and often poorly defined; Vn larger, usually clearly defined; 5 PO, the fifth somewhat displaced dorsolaterally; 4 VO, level; SAO very strongly angulated, with SAOi in advance of VO3; one Pol; 2 Prc. Adult males and females usually with supracaudal and infracaudal luminous glands, respectively; females of at least one form with both supracaudal and infracaudal glands. Size. Members of this genus attain sizes of over 150 mm. Range. In all three major oceans, between 50°N (Atlantic Ocean) and 50°S (Pacific Ocean). Species. Studies recently completed and others currently in progress indicate the existence in the World Ocean of several undescribed species of Symbolophorus. Seven nominal species have been described, but not all of these may be valid. The inadequate original descriptions of some of the latter and the remarkable similarity of the members of this genus to each other have contributed to much of the existing taxonomic confusion. The need, therefore, for a thorough revision of this group of lanternfish can not be overemphasized. Available data suggest that the members of the genus may be assigned to one or the other of two groups, depending on the presence or absence of distinctly enlarged palatine teeth (i.e., S. boops-veranyi complex versus S. evermanni-californiensis complex, respectively). The seven described species are: S. barnardi, S. boops, S. californiensis, S. evermanni, S. hookeri, S. rufinus, and S. veranyi. Of these, two (S. rufinus and S. veranyi) are found in the North Atlantic. A third form has been taken off the northwestern coast of Africa, between approximately 10°N and 25°N. It belongs to the S. boops-veranyi complex and is very similar to S. humboldti barnardi (Taning) 1932, in that, among other features, fe-

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Memoir I, Part 7—Sears Foundation for Marine Research

FIGURE 36. Symbolophorus veranyi: young, 62 mm; A, supracaudal luminous gland of male, 105 mm; B, infracaudal luminous gland of female, 104 mm.

males have both a supracaudal and an infracaudal luminous gland. However, since S. hum bold ti barnardi may itself prove to be the female of either S. hoops (Richardson) 1845 or S. hookeri (Whitley) 1953, naming of the northwestern African form will have to wait until the taxonomy of the above mentioned species is clarified. Symbolophorus veranyi (Moreau) 1888 Figures 36, 37 Study Material. One hundred and eighty-six specimens, 21-113 mm, from across the North Atlantic and from the Mediterranean Sea; in ZMUC, MCZ, and LACM.

Distinctive Characters. This species is readily differentiated from S. rufinus by the following characters: (1) SAOi directly over or in advance of VO2 and midway between VLO and SAO2 instead of behind VO2 and nearer to SAO2 than to VLO; (2) a straight line connecting SAO2 with SAO3 passing in front of instead of through VO4; (3) AOa series forming an arch instead of being straight; (4) Pol well in advance of base of adipose fin instead of under it; (5) pectoral fin extending beyond SAOi instead of not

reaching it; and (6) palatines with a series of enlarged, conical teeth (specimens larger than about 3 5 mm) instead of a band of uniformly minute ones. Description.

Fin rays: dorsal 13-14 (12); anal 22 (21-

23); pectoral 12-13.

Gill rakers: 5 (6) + 1 + 13-14 (12), total 19-20 (18-21). Photophores: AO 7-9 + 7-9, total 15-16.

Lateral-line organs: 41-42. Head. Head length 3.5-3.8 in SL. Mouth somewhat oblique; length of upper jaw 1.51.7 in hi and 5-6 in SL; a narrow band of minute teeth on palatines of specimens smaller than about 25 mm; in specimens larger than about 30 mm a series of markedly enlarged palatine teeth, some fixed and some medially depressible; a patch of small teeth (increasing in number with size of fish) on each side of vomer. Eye moderately large, its diameter 1.8-2 in length of upper jaw, 2.8-3 in hi and 9.8-11.8 in SL. Posterior opercular margin rounded, except at a level between PLO and base of pectoral fin where it forms a short, obtuse angle. Fins. Origin of dorsal fin over or slightly

Fishes of the Western North Atlantic lUJiyiliiuiuiflui

u,

M,,

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FIGURE 37. Symbolophorus veranyi, a temperate species. Distribution, based on the WHOI neuston collections. Additional records are from Gibbs et al. (1971) and WHOI midwater trawl data.

behind base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fins extending beyond SAO2 in juveniles, reaching a point about midway between SAOi and SAO2 in adults. Ventral fins not reaching anus. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PLO nearer to base of pectoral fin than to lateral line. PVOi directly over or slightly in advance of PO2; PVO2 at lower end of base of pectoral fin and in advance of POs. VLO in front of base

of ventral fin and midway between it and lateral line or slightly lower. SAOi slightly in advance of, sometimes directly over, VO2 and on or just below a straight line connecting VLO with SAO2; SAO2 in front of a straight line connecting SAOg with VO4; SAO3 in advance of origin of anal fin and less than its own diameter below lateral line. First and, to some degree, 2nd AOa depressed, the series forming a pronounced arch. Pol well in advance of base of adipose fin and its own diameter or less below lateral line. An-

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Memoir l> Part 7—Sears foundation for Marine Research

terior 3-4 AOp over base of anal fin. Prc2 about 1.5 times its own diameter posterodorsad to Prci. Sexual Dimorphism. Adult males with a supracaudal luminous gland consisting of 1-2 small coalescent patches immediately in front of procurrent caudal rays. The gland appears in individuals about 52 mm long. Adult females with 2-3 slightly overlapping patches of luminous tissue infracaudally, distinct in specimens about 58 mm long. Size. Gravid females found in the collections examined measured 101-112 mm. However, in the Mediterranean sexual maturity may be attained at a smaller size. The species apparently grows to a size of at least 120 mm. Development. Developmental stages of this fish have been described in detail by MazzareUi (1912) and Taning (1918) primarily on the basis of material from the Mediterranean where the species apparently spawns (Taning, 1918). Atlantic Distribution. Symbolophorus veranyi (Fig. 37) is a temperate species, taken more often at the surface at night in neuston nets than in midwater trawls. WHOI collections in the eastern North Atlantic were larger on the average than western ones. The Mauritanian UpweUing specimens shown on our map apparently represent the undescribed species referred to above. Extra-Atlantic Occurrence. Symbolophorus veranyi belongs to a relatively unstudied group of species including S. boops. At present, nothing can be said of its possible extraAtlantic occurrence. A species in the WHOI South Atlantic material that we tentatively called S. boops occurred in the southeasternmost part of the Guinean Province and south of there in the Benguela Current. (BC) Vertical Distribution. At night, S. veranyi is most abundant at the surface; however, it was also taken with opening-closing devices in small numbers at 20 m and at 800 m near Bermuda and between 12 and 150 m in the Mediterranean. By day, it was taken in small

numbers between 700 and 800 m in the Mediterranean. WHOI collections, at night, caught S. veranyi at the surface throughout its range, and, to a much lesser extent, throughout the upper 90 m. By day, the few specimens were from 550 to 750 m. Synonyms and References: Scopelus veranyi Moreau, 1888: 108 (orig. descr.; off Nice, fide Bolin, 1959, and Kretft and Bekker, 1973). Myctophum humboldti. Taning, 1918: 63, Figs. 21, 22 (descr., develop., reprod., distr. in Mediterranean); Taning, 1932 (illus., diag., distr., reprod.). Symbolophorus veranyi. Bolin, 1959: 12 (synon., brief descr., compar. with S. rufinusy distr.); Bini, 1971: 197, illus. (morphol, reprod., distr.); Goodyear et al., 1972: 172 (vert, distr., growth and reprod, in Mediterranean); Kretft and Bekker, 1973: 197 (synon., ref., distr.).

Symbolophorus rufinus (Taning) 1928 Figures 38, 39 Study Material. Fifteen specimens, 22—87 mm, from across the North Atlantic and the Gulf of Mexico; in LACM and ZMUC.

Distinctive Characters. SAd behind VO2 and nearer to SAO2 than to VLO; VO4, SAO2 and SAO3 in line; AOa in a straight line; Pol under base of adipose fin; pectoral fin not reaching SAd; palatines with a band of uniformly minute teeth. Description. Fin rays: dorsal If (14-16); anal 20-21; pectoral 15 (14-16). Gill rakers: 5-6 + 1 + 14-15, total 20-22. Photophores: AO 8 (7-9) + J-6, total 1314. Lateral-line organs: 41 (40). Head. Head length 3.3-3.5 in SL. Mouth oblique; length of upper jaw 1.4—1.6 in hi and 4.7-J.3 in SL; a narrow band of minute teeth on palatines and a small patch of similar teeth on each side of vomer. Eye large, its diameter 1.8 in length of upper jaw, 2.6-2.8 in hi and 8.5-9.5 in SL. Posterior opercular margin rounded, except at a level between

Fishes of the Western North Atlantic

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o o o o o QOQO o

FIGURE 38. Symbolophorus rufinus: female, 63 mm; A, supracaudal luminous gland of male, 65 mm; B, infracaudal luminous gland of female, 87 mm.

PLO and base of pectoral fin where it forms a short, obtuse angle. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin on or just behind vertical through end of base of dorsal fin. Pectoral fins not reaching SAOi. Ventral fins reaching anus. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PLO midway between base of pectoral fin and lateral line or slightly lower. PVOi usually a little in advance of, but may be on or slightly behind vertical through PO2; PVO2 at lower end of base of pectoral fin and in front of POa- VLO over base of ventral fin and midway between it and lateral line. SAO forming an obtuse angle; SAOi somewhat in advance of VO3, below a straight line connecting SAO2 with VLO and nearer to former than to latter; SAO2 in a straight line with VO* and SAO3; SAOa on or just in front of vertical through origin of anal fin and immediately below lateral line. AOa evenly spaced and level. Pol about under base of adipose fin and immediately below lateral line. Anterior 1-2 AOp over base of anal fin. Prc2 1-2 times its own diameter posterodorsad to

Sexual Dimorphism. Adult males with a supracaudal series of 5-6 discrete, semicircular patches of luminous tissue occupying 70 percent or more of the length of the caudal peduncle. Adult females with 3-4 non-overlapping, oval-shaped patches of luminous tissue inf racaudally. Size. The largest specimen in the collections examined was an 87-mm-long gravid female. Another two females, 70 and 75 mm long, had large ovaries and eggs. Atlantic Distribution. Symbolophorus rufinus (Fig. 39) is an uncommon species taken in both midwater trawls and at the surface at night in neuston nets. It appears to be distributed either according to the tropical-subtropical pattern or the tropical-semisubtropical pattern. The largest WHOI collections came from the Amazonian Province. The species is rare in the Mauritanian Upwelling, the Caribbean Sea, and the Gulf of Mexico. Extra-Atlantic Occurrence. S. rufinus has been recorded from the western Indian Ocean off Africa between 2°N and 4°S (Kotthaus, 1972b) and in 60° to 65°E between about 5°N and 10°S (Nafpaktitis and Nafpaktitis, 1969). (BC)

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FIGURE 39. Symbolophorus rufinus9 a tropical-subtropical or tropical-semisubtropical species. Atlantic Ocean distribution, based on the WHOI neuston collections. Additional records are from Parin et al. (1974) and WHO! midwater trawl data.

Vertical Distribution. Near Bermuda, S. rufinus was collected in small numbers with opening-closing devices at 750-850 m by day, and at the surface, at 150-200 m, and at 850900 m at night. In the WHOI collections, S. rufinus occurred at night both at the surface and throughout the upper 125 m in about equal numbers. By day, individuals were from between 42 5 and 850 m.

Synonyms and References: Myctophum rufinum Taning, 1928: 54 (orig. descr.; in key). Myctophum (Scopelus) rufinum. Fraser-Brunner, 1949: 1055, fig. (in key). Symbohphorus rufinus. Bolin, 1959: 13 (compar. with S. veranyi); Nafpaktitis and Nafpaktitis, 1969: 29, Fig. 32 (descr., records from west. Indian Ocean; compar. with S. evermanni); Rotthaus, 1972b: 26, photos of specim. (271) and otol. 2 (10) (records from west. Indian Ocean; merist., morphom.); Nafpaktitis, 1973: 16, Fig. 13 (descr.; desig. of

Fishes of the Western North Atlantic

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FIGURE 40. Lowcina rarai male, 39 mm.

lectotype: 15°JOTM, P2330210).

26°32'W,

surface;

ZMUC

Genus Loweina Fowler 1925 L&weina Fowler, 1925: 2 [proposed as a subgenus of the genus Scopelus; type-species Scopelus (Rhinoscopelus) rarus Lutken 1892, by original designation]; Fraser-Brunner, 1949: 1060 (elevation to full generic rank; characters); Bekker, 1964: 17 (description); Paxton, 1972: 43 (definition, osteological characters).

Characters. Mouth subterminal, moderately large; jaws extending somewhat less than diameter of eye behind vertical through posterior margin of orbit; bands of small teeth on premaxillaries, dentaries and mesopterygoids; a few similar teeth on each side of vomer; palatine teeth distinctly enlarged, widely but regularly spaced, in single series. Origin of dorsal fin well behind base of ventral fin; base of anal fin longer than that of dorsal fin, its origin about under middle of base of dorsal fin. Caudal peduncle rather short and slender, its least depth about 2.5 times in its length. Lateral line weakly developed. Dn and Vn present, at anterodorsal and anteroventral orbital margin, respectively. PLO in front of and at or slightly below level of upper end of base of pectoral fin; 5-6 PO, level, in a 2 + 2 + 1, 4+1 or 2 + 3 + 1 arrangement; VLO

nearer to base of ventral fin than to lateral line; 2-4 (5) VO with Vd of each side very near to, or in contact with each other, the pair situated close and posteromesad to bases of ventral fins; 2-3 SAO; one Pol; 2 Prc; no infracaudal glands; an undivided supracaudal gland in adult males only. Size. Small myctophids, not growing larger than about 5 5 mm. Range. Chiefly in tropical and subtropical waters of all three major oceans. Members of the genus have repeatedly been taken in the surface at night. Species. Inadequate original descriptions and paucity of material have caused much difficulty in the study of this genus which needs to be carefully reviewed. Of the four described species two, L. rara (Lutken) and L. interrupta (Tining), occur in the North Atlantic. L. terminata Bekker 1964 is known only from the North Pacific between 20° and 35°N, and L. laurae Wisner 1971 (most probably a synonym of L. rara) from the eastern Pacific between 30°N and 30°S. Lmveina rara (Lutken) 1892 Figures 40, 41 Study Material. Twenty-three specimens, 21—44 mm, from the North Atlantic and eastern South Atlantic; in ZMUC and LACM.

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FIGURE 41. Loweina rara, a tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Badcock (1970), Bekker (1964), Gibbs et al. (1971), Rotthaus (1972a), and W. Rrueger (in litt.).

Distinctive Characters. The position of the PVOi which is behind the PO2, the higher number of VO (4, occasionally 5), and the lower number of SAO (2) readily distinguish this species from its North Atlantic congener, L. interrupta. Description. fin rays: dorsal 11-13; anal 15-16; pectoral 11 (10-12).

Gill rakers: 2+ 1 + 6 (5). Photophores: PO 5; VO 4 ( 5 ) ; SAO 2;

AO 6-7 (5) + 6-7 (5), total 12-13 (1114). Fins. Pectoral fins not reaching bases of ventral fins. Ventral fins extending about to VO8. Base of adipose fin over end of base of anal fin. Luminous Organs. PVOi behind vertical through center of PO2. PO commonly in a 2 + 2 + 1 arrangement. Four, occasionally 5, VO. Two SAO, in line with last VO; upper SAO usually over origin of anal fin and about

Fishes of the Western North Atlantic twice its diameter below lateral line. AOaiAOa2 interspace often markedly enlarged. Pol somewhat in advance of base of adipose fin and about twice its diameter below lateral line. First AOp often over end of base of anal fin. Prc about one organ diameter apart from each other. Sexual Dimorphism. Males with a supracaudal gland occupying 50-80 percent of length of caudal peduncle and appearing soon after metamorphosis. Size. Members of this species do not seem to grow much larger than 45 mm. Two nearly ripe females found in the collections examined measured 28 and 32 mm, respectively. Development. A series of larval stages of L. rara from the California Current has recently been described by Moser and Ahlstrom (1970). They found that larvae of this species are among the largest of myctophid larvae at metamorphosis, attaining a length of 21 mm. [Moser and Ahlstrom's material has been considered as being L. laurae by Wisner (1971), but L. laurae is probably a synonym of L. rara.] Atlantic Distribution. Loweina rara (Fig. 41), although not so rare as its congener L. interrupta, is very uncommon. Scattered WHOI records and those from the literature attributable to this species come mainly from the northern subtropics, but also from the eastern tropics, and suggest a tropical-subtropical pattern. Extra-Atlantic Occurrence. Loweina rara is widely distributed in the Pacific and Indian Oceans. According to Moser and Ahlstrom (1970) it is found "in the California Current, the central water masses of the north and south Pacific, and throughout the tropical eastern Pacific"; some or all Pacific records would be referable to L. laurae Wisner, if that species proved to be valid. Bekker (1964) gave records spanning the Indian Ocean between about 10°S and 22°S. (N) Vertical Distribution. Near Bermuda, opening-closing devices caught L. rara at 800-

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1,050 m during the day and at 50-350 m at night. WHOI collections caught it from the surface (a single specimen) to 175 m at night and from 550 m to deeper than 1,000 m during the day. In the Indian and Pacific oceans, L. rara has been taken at the surface at night with lighted neuston nets (Bekker, 1964) and by dip net and lights (Wisner, 1971). This, plus the almost complete absence in unlighted neuston nets, strongly suggests its occurrence in the upper few m, but not at the very surface. Synonyms and References: Scopelus (Rhinoscopelus) rarus Liitken, 1892: 246, Fig. 4 erroneous (orig. descr. North Atlantic; two syntypes: ZMUC 223, 224, fide Krefft and Bekker, 1973). Evidently, Liitken did not specifically differentiate the two forms, rara and that which was later to be described by Taning as interrupt a. Consequently, what Liitken partly described and fully figured under the name Scopelus (Rhinoscopelus) rarus happened to be L. interrupt a (Taning) 1928. Rhinoscopelus rarus. Goode and Bean, 1896: 91 (remarks on char, as shown in Liitken's (1892) erron. Fig. 4). Myctophum (Myctophum) rarum forma integer Brauer, 1904: 390 (orig. descr. in key); Brauer, 1906: 205, Fig. 125, partim (records from east. North Atlantic, descr.). Myctophum rarum. Taning, 1928: 55 (in key); Taning, 1932, fig. (char., distr.). Loweina rara. Fraser-Brunner, 1949: 1060, fig. (in key); Bekker, 1964: 22, Fig. 5 (descr., distr. in Indian and Pacific Oceans); Moser and Ahlstrom, 1970: 87, Figs. 26-28, 50-51 (descr. of larvae from Calif. Current, distr. in east. Pacific); Kotthaus, 1972a: 12 (record from east. North Atlantic, char., photo of otol.); Krefft and Bekker, 1973: 193 (synon., ref.); Wisner, 1976: 78-79 (descr., desig. of lectotype ZMUC 223).

Loweina interrupta (Tining) 1928 Figures 42, 43 Study Material. Eleven specimens, 21.5-38.5 mm, as follows: lectotype, ZMUC 18 (38.5 mm), 37°40'S, 12°00'E; paralectotypes ZMUC 225 (approx. 35 mm), 34°50'S, 04°30'W and ZMUC P2329228 (28 mm), 35°53'N, 07°26'W. 1 (24 mm), DANA Sta. 4198 II,

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FIGURE 42. Loweina interrupt*: paralectotype (ZMUC P2329228), male, 28 mm.

44°28'N, 25°53'W; in ZMUC 1(25.5 mm), ATLANTIS II, Cr. 13, Sta. RHB 1036,42°20'N, 29°09'W; 3 (21.526 mm), CHAIN Cr. 105, Sta. RHB 2532, 44°07'N, 30°36'W; 1 (27 mm), ATLANTIS II Cr. 60, Sta. RHB 2225, 35°50'S, 02°32'W; 1 (30.5 mm) ATLANTIS II Cr. 60, Sta. RHB 2258, 30°49'S, 06°39'E; 1 (31 mm), ANTON BRUUNCr. 3, label no. 7127, 40°53'S, 60°01'E; in LACM.

Distinctive Characters. The position of the PVOi which is in front of the vertical through the center of the PO2, the lower number of VO (2), and the higher number of SAO (3) distinguish this species from L. rara. Description. Pin rays: dorsal 11-12; anal 15-16; pectoral 11-12. Gill rakers: 3 + 1 + 8-9 (7-10), total 1213 (11-14). Photophores: PO 5 (6); VO 2; SAO 3; AO 6-7 (5-8) + 5-7, total 11-14 (10-15). Fins. Pectoral fins extending to VLO in young fish, somewhat shorter in adult specimens. Ventral fins not reaching posterior VO. Base of adipose fin over end of base of anal fin. Luminous Organs. PVOi in advance of vertical through center of PO2. PO commonly in a 4 + 1 arrangement. Two VO, anterior pair immediately posteromesad to inner ends of bases of ventral fins and very close to midventral line; posterior pair in

front of anus. SAO in a straight or slightly angular line; SAO8 directly over or somewhat behind origin of anal fin and about its own diameter below lateral line. AOai-AOa2 interspace sometimes distinctly enlarged. Pol usually a little in front of base of adipose fin. First AOp often over end of base of anal fin. Prc one organ diameter or less apart from each other. Sexual Dimorphism. Males with a supracaudal gland occupying from 70 percent (young individuals) to very nearly the entire length of caudal peduncle (adult fish). In a 21.5-mm-long specimen the gland was already well developed. Size. The lectotype (38.5 mm) was the largest specimen examined. Judging from the development of the gonads, this species does not seem to grow much larger than its congener, L. rara. Atlantic Distribution. Loweina interrupta (Fig. 43) is a rare species of which only 11 Atlantic specimens are known to us. Judging from this inadequate material the species is a bipolar temperate or bipolar temperate-semisubtropical one. Extra-Atlantic Occurrence. Nafpaktitis and Nafpaktitis (1969) reported an Indian Ocean specimen from about 40°S, 60°E. This and records given by McGinnis (1974) sug-

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gest that L. interrupta is distributed circumglobally in the southern hemisphere. (BC) Vertical Distribution. A single individual was taken with an opening-closing device at 800 m at night near Bermuda. The WHOI specimens were all taken at night between 60 and 175 m. Synonyms and References: Scopelus (Rhinoscopelus) rams. Liitken, 1892: 246, partim, Fig. 4; Fowler, 1925: 2 (erected subgenus Loweina to include this species, thus indicating a

greater than specific distinction between it and the rest of the then known slendertailed myctophids). Myctophum (Myctophum) rarum. Brauer, 1906: 204, Fig. 123 (descr.). Myctophum interruptum Taning, 1928: 55 (orig. descr.; in key; lectotype 37°40/S, 12°00/E, ZMUC 18, desig. by R. L. Wisner); Norman, 1930: 324 (records from east. South Atlantic). Loweina interrupta. Fraser-Bninner, 1949: 1060, fig. (in key); Nafpaktitis and Nafpaktitis, 1969: 31, Fig. 34 (record from west. South Indian Ocean, char.); Nafpaktitis, 1973: 17, Fig. 14 (descr. based on syntypes, ZMUC 18 and P23 29228); Krefft and Bekker, 1973: 193 (synon., ref.); Wisner 1976: 71-81 (descr., desig. of lectotype ZMUC 18).

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Genus Gonichthys Gistel 1850 Gonichthys Gistel, 1850: 71 [type-species Alysia Ioncat a Lowe 1839 (= Scopelus cocco Cocco 1829), by monotypy]; Fraser-Brunner, 1949: 1061 (definition); Bolin, 1959: 16 (characters, key to species); Bekker, 1964: 28 (definition); Pazton, 1972: 44 (definition, osteological characters). Alysia Lowe, 1839: 87 (type-species Alysia loricate Lowe 1839 = Scolepus cocco Cocco 1829, by monotypy), preoccupied by Alysia Latreille 1804 (Hymenoptera), fide Bolin, 1959. Rhinoscopelus Liitken, 1892: 232, 242 (type-species Scopelus cocco Cocco 1829, by original designation).

Characters. Snout projecting. Mouth subterminal; small teeth on premaxillaries, dentaries, each side of vomer and on mesopterygoids; a narrow band of similar teeth on each palatine; teeth of third pharyngobranchials modified into rounded protuberances. Gill rakers well developed. Origin of dorsal fin well behind base of ventral fin; base of anal fin much longer than that of dorsal fin. Ventral fins with 8, very rarely 7, rays. Caudal peduncle markedly slender, its least depth more than 3.5 times in its length. Lateral line developed to varying degree. Dn and Vn present, at anterodorsal and anteroventral orbital margin, respectively. PLO about at level of upper end of base of pectoral fin; PVOi well below and in front of PVO2, the two organs in a straight line with second PO or nearly so; 5 PO, level; 4 VO, level; one Pol, well in front of base of adipose fin; AOaAOp interspace well in advance of end of base of anal fin; 2 Prc, level; males with a supracaudal series of separate or slightly overlapping luminous structures bordered by black pigment; females with a series of non-overlapping luminous patches inf racaudally. Size. Small myctophids not growing larger than about 60 mm. Range. Tropical and subtropical waters of all three major oceans. Species. Of the four described species (see Remarks below) only one, G. cocco, occurs in the North Atlantic. This species is also found in the Mediterranean Sea.

Remarks. The specific composition of the genus is by no means clear. The four forms described so far [G. cocco (Cocco) 1829, G. tenuiculus (Carman) 1899, G. barnesi Whitley 1943, and G. venetus Bekker 1964] are very similar to each other with many of the proposed adult morphological characters overlapping to a degree that identifications cannot always be made with reasonable certainty. Future studies of larvae and otoliths are necessary before the taxonomic relationships of the described forms are better understood. Gonichthys cocco (Cocco) 1829 Figures 44, 45 Study Material. Eight hundred and thirty-two specimens, 17-52 mm, from the North and South Atlantic, Gulf of Mexico, and Mediterranean Sea; in LACM.

Distinctive Characters. The presence of gill rakers will immediately separate this species from Centrobranchus nigroocellatus, which lacks these structures. It differs from the species of Loweina in having 5-7 AOp photophores over the anal-fin base, the anal-fin origin at or only slightly in front of the end of the dorsal-fin base, and a more slender caudal peduncle (its least depth 3.5 times or more in its length). Description. Fin rays: dorsal 11-12; anal 20-22 (23); pectoral 13-15; ventral 8 (occasionally 7). Gill rakers: 3 (4) + 1 + 5-6, total 9-10 (11). Photophores: AO 5-6 (4-8) + 11-13 (1014), total 16-19 (20). Lateral-line organs: 26-30. Fins. Origin of anal fin on or slightly in advance of vertical through end of base of dorsal fin. Pectoral fin extending beyond base of ventral fin, to a point nearer to SAOi than to VLO. Ventral fins reaching VO3. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PVOi on or slightly in advance of straight line connecting PVO2 with

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FIGURE 44. Gonichthys cocco: male, 50 mm; A, infracaudal luminous gland of female, 52 mm.

PO2. VLO about twice nearer to base of ventral fin than to lateral line. SAO forming an obtuse angle; a straight line through SAO2 and SAOi passing well in front of base of ventral fin; position of SAOi varying from slightly in front of to a little behind VO2; SAO3 on or slightly in advance of vertical through origin of anal fin and its own diameter or less below lateral line. AOa evenly spaced or AOa2-AOa8 interspace somewhat enlarged. Pol slightly behind last AOa and its diameter or less below lateral line. Five to 7 AOp over base of anal fin, the series sometimes continuous with AOa (position of Pol defining end of AOa and beginning of AOp). Prc about one organ diameter apart from each other, sometimes continuous with AOp. Sexual Dimorphism. Adult males with a supracaudal series of 6-7 (rarely 5 or 8) welldefined, rounded luminous organs bordered by black pigment, first appearing in individuals about 24 mm long. Adult females with an infracaudal series of 5 (4—6) separate, oval patches first appearing in young fish about 31 mm long. Size. The largest specimen in the collections examined measured 60 mm. Sexual maturity apparently is reached at a size of about 3 8 mm. Development. Tining (1918) described and illustrated a series of larval stages on the

basis of material from the eastern Mediterranean basin. In the absence of metamorphosis stages, Tining referred his larval specimens to G. cocco "with some degree of certainty." There is hardly any doubt that the larvae described by Tining belong to G. cocco, for no other slendertailed myctophid has been reported from the Mediterranean. Further, his larvae, with the exception of some differences in pigmentation, look morphologically very similar to those of G. tenuiculus described by Moser and Ahlstrom (1970) from the California Current. Atlantic Distribution. Gonichthys cocco (Fig. 45) is a questionably tropical-subtropical species. The most striking features of its distribution are its absence from the Caribbean Sea and adjacent Lesser Antillean Province and its presence in the eastern Mediterranean Sea; these are exceptional for tropical-subtropical species. The range of G. cocco resembles that of the tropical-subtropical species Diogenichthys atlanticus (Fig. 23) more than any other myctophid, although D, atlanticus is not a regular inhabitant of the Mediterranean Sea. Within its range, G. cocco is the most abundant of those mesopelagic fishes that come up to the very sea surface at night (neuston species).

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Extra-Atlantic Occurrence. G. cocco is not known with certainty from outside the Atlantic Ocean. Bolin (1959) and Wisner (1976) call attention to cocco-like specimens in the northeastern South Pacific, but they are probably better considered at present as belonging to a separate species, G. venetus Bekker 1964. (BC) Vertical Distribution. The vast majority of specimens of G. cocco were collected at the Surface at night,

Opening-closing devices by day took a few specimens at 500-1,000 m near Bermuda and at 500-675 m in the Mediterranean. At night, specimens were taken at 33-200 m and at 750-900 m near Bermuda and at 80-135 m in the Mediterranean. Only juveniles were taken deeper than 750 m day or night near Bermuda. In the WHOI collections, G. cocco occurred between 425 and about 1,000 m during the day, with maximum catch at 425-

Fishes of the Western North Atlantic 650 m, and from the surface to about 175m at night. Synonyms and References: Scopelus cocco Cocco, 1829: 143 (orig. descr.; Messina; no type material). Alysia loricata Lowe, 1839: 87 (orig. descr.; Madeira; no type material). Myctophum hians Richardson, 1845: 41, Pi. 27, Figs. 19-21 (orig. descr.; no locality; syntypes BMNH 1847.12.31.1-2). Scopelus (Rhinoscopelus) coccoi. Liitken, 1892: 243, partim, Fig. 2 (descr. based on material that included the southern form G. barnesi). Myctophum coccoi. Taning, 1918: 67, Figs. 23-24 (descr. of larval and adult char., distr. in Mediterranean); Taning, 1928: 55 (in key); Taning, 1932, figs, (diag., distr.). Gonichthys cocco. Fraser-Brunner, 1949: 1061, fig. (synon., taxon. remarks). Gonichthys coccoi. Bblin, 1959: 16 (key, synon., char., distr.); Bini, 1971: 175, illus. (char., distr.); Goodyear et al., 1972: 176 (abund., growth, depth of capture); Krefft and Bekker, 1973: 182 (synon., refer.).

Genus Centrobranchus Fowler 1904 Centrobranchus Fowler, 1904: 754 (type-species Centfobranchus choerocephalus Fowler 1904, by original designation); Fraser-Brunner, 1949: 1061 (definition); Bolin, 1959: 17 (characters); Bekker, 1964: 46 (definition); Pazton, 1972: 44 (definition, osteological characters).

Characters. Snout pointed and protruding. Mouth subterminal; small teeth in narrow bands on premaxillaries and dentaries; patches of small, blunt teeth on each side of vomer and on mesopterygoids; somewhat enlarged, sharp teeth in a single or double series on palatines; third pharyngobranchials with series of ridged plates fanning ventrolaterally. Gill rakers absent; gill arches with a few, widely set, low protuberances bearing spinelike structures. Origin of dorsal fin well behind base of ventral fin; base of anal fin much longer than that of dorsal fin. Ventral fins with 8 rays. Caudal peduncle markedly slender, its least depth 3.5 or more times in its length. Lateral-line organs very poorly de-

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veloped. Dn and Vn present, at anterodorsal and anteroventral orbital margin, respectively. PLO about at level of upper end of base of pectoral fin; PVOi below and in front of PVO2, the two organs in a straight line with PO2 or nearly so; 5 PO, level; 4 VO, level; SAO in a straight line or nearly so; one Pol, well in front of base of adipose fin; AOaAOp interspace well in advance of end of base of anal fin; 2 Prc, level; males with a supracaudal series of separate or slightly overlapping luminous organs bordered by black pigment; females with a series of separate, round or oval luminous structures infracaudally. Size. Small myctophids attaining a size of about 65 mm. Range. Tropical and subtropical waters of all three major oceans. Species. According to the most recent review (Bekker, 1964), the genus includes four species: C. nigroocellatus (Giinther) 1873, C. andreae (Liitken) 1892, C. brevirostris Bekker 1964, and C. choerocephalus Fowler 1904. The latter two forms are very similar to C. nigroocellatus and careful comparative studies of larval and otolith morphology are needed before their specific distinction is firmly established. In spite of records presented by Liitken (1892: 245), I have not been able to confirm the presence of C. andreae in the North Atlantic. C. nigroocellatus seems to be the only member of the genus occurring in this ocean. Centrobranchus nigroocellatus (Giinther) 1873 Figures 46, 47 Study Material. Three hundred and seventeen specimens, 12—48 mm, from the North and South Atlantic, the Caribbean Sea, and the Gulf of Mexico; in LACM.

Distinctive Character. The absence of gill rakers readily separates this species from Gonichthys cocco.

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FIGURE 46. Centrobranchus nigroocellatus: male, 38 mm; A, infracaudal luminous gland of female, 45 mm.

Description. fin rays: dorsal 10-11; anal 17-18 (1619); pectoral 13-15. Photophores: AO 4-6 + 8-10 (11), total 13-15 (12-16). Fins. Origin of anal fin on or slightly behind vertical through end of base of dorsal fin. Pectoral fins extending to or somewhat beyond VLO. Ventral fins reaching VO3. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. PVd on a straight line with PVO2 and PO2 or very nearly so. VLO at level of PVO2 or a little lower. SAO in a straight line or SAO2 slightly behind line through SAOi and SAO3; SAOi over or in front of VO3; SAO3 in advance of, sometimes on, vertical through origin of anal fin. AOa evenly spaced or AOa2-AOa3 interspace somewhat enlarged. Pol over last AOa. Three to 4 AOp over base of anal fin. Prc2 its diameter or less behind Prci. Sexual Dimorphism. Adult males with a supracaudal series of 5-6 (rarely 4 or 7) welldefined, rounded luminous organs bordered by black pigment, first appearing in individuals about 19 mm long. Adult females with a series of 4—5 (rarely 3 or 6) non-overlapping, oval patches of luminous tissue in-

fracaudally; these begin developing in individuals about 23 mm long. Size. This species does not seem to grow much larger than 50 mm. Sexual maturity apparently is reached at a size of about 34 mm. Atlantic Distribution. Centrobranchus nigroocellatus (Fig. 47), whose distribution is best represented by neuston net captures at the surface at night, is a questionably tropicalsubtropical species. (The more questionable alternative would be to consider the species a bipolar subtropical one.) The species was rare in WHOI collections from the eastern South Atlantic. Extra-Atlantic Occurrence. Nafpaktitis and Nafpaktitis (1969) recorded C. nigroocellatus from the western Indian Ocean between 6°S and 26°S. It occurs off Chile (Craddock and Mead, 1970) and off New Zealand (Bekker, 1964), but apparently is absent from the equatorial and North Pacific (Bekker, 1964). (BC) Vertical Distribution. The vast majority of C. nigroocellatus were collected at the surface at night. Opening-closing devices took the species near Bermuda at 500-800 m by day and at 100-200 m at night. By day, WHOI speci-

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FIGURE 47. Centrobranchus nigroocellatus, a questionably tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI neuston collections. Additional records are from Gibbs et al. (1971) and WHOI midwater trawls.

mens were from 375-650 m, most from about 500 m. Synonyms and References: Scopelus nigroocellatus Giinther, 1873: 267 (orig. descr.; "South Atlantic"; holotype, BMNH 1873. 8.1.40), fide Krefft and Bekker, 1973. Myc top hum nigro-ocellatum. Taning, 1928: 55 (in key); Taning, 1932, fig. (diag., distr.). Centrobranchus nigro-ocellatus. Fraser-Brunner, 1949: 1062 (in key); Bekker, 1964: 57, Fig. 24 (descr., distr.; records from Indian Ocean and a single record from west. South Pacific, 29°52'S, 172°00'E).

Centrobranchus nigroocellatus. Bolin, 1959: 17 (char., distr.); Nafpaktitis and Nafpaktitis, 1969: 32, Fig. 36 (records from west. South Indian Ocean, char.); Craddock and Mead, 1970: 3.26 (records from east. South Pacific, 30°-34°S, 89°-93°W); Kotthaus, 1972a: 12 (single record from east. North Atlantic, char., photo of otol.); Krefft and Bekker, 1973: 174 (synon., ref.).

Genus Notolychnus Fraser-Brunner 1949 Vestula Bolin, 1946: 144 (type-species Myctophum valdiviae Brauer 1904, by original designation), preoccupied by Vestula Stal 1865, Hemiptera.

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FIGURE 48. Notolychnus valdiviae i male, 19 mm.

Notolychnus Fraser-Brunner, 1949: 1077 (replacement name for Vestula Bolin, 1946); Bolin, 1959: 23 (characters); Paxton, 1972: 45 (osteological characters) .

Characters. Mouth large, extending far beyond orbit; maxillary abruptly expanded posteriorly. Dorsal and anal fins extensively overlapping. Adipose fin far behind end of base of anal fin. Lateral line absent. Dn present; Vn absent; 5 PO, PO3 and especially PO4 highly elevated; 4 VO, first elevated; 2 Pol; 2 Prc; VLO, SAO3, Pol2, and Prc2 high above horizontal septum; a supracaudal luminous gland present in both sexes, larger in males than in females; infracaudal luminous glands absent. Size. Diminutive, not exceeding a size of about 25 mm. Range. In all three oceans; mainly in tropical and subtropical waters, but extending to temperate latitudes. Species. The genus contains a single species, Notolychnus valdiviae. Notolychnus valdiviae (Brauer) 1904 Figures 48, 49 Study Material. Over 460 North Atlantic specimens, 9-22 mm; in LACM.

Distinctive Characters. This species is readily distinguishable from all other myctophids by the very high position of the VLO,

SAO3, and PoU. However, most often the skin and the shallow photophores are rubbed off. In this case the peculiar, dome-shaped protuberance on top of the head, the low number of ventral fin rays (6), the low number of gill rakers (10-11), and the early development of the supracaudal gland are all useful in the identification of this diminutive form. Description. fin rays: dorsal 11 (10-12); anal 13 (1214); pectoral 12-13; ventral 6. GUI rakers: 2 + 1 + 7-8. Photophores: PO 5; VO 4; AO 4 + 4 (3); Pol 2; Prc 2. Head. Mouth large, about 5 times in SL; maxillary abruptly expanded at its posterior end. Eye larger in males (0.40-0.45 of length of upper jaw) than in females (0.30-0.35 of length of upper jaw). Frontal bones forming a small, median, transparent dome into which the pineal organ extends. Operculum very thin, its posterior margin rounded. Fins. Origin of dorsal fin well behind base of ventral fin. Origin of anal fin on or somewhat in advance of vertical through middle of base of dorsal fin. Pectoral fins extending about to vertical through VO2. Ventral fins barely reaching anus. Base of adipose fin far behind end of base of anal fin. Luminous Organs. A small but distinct Dn. PLO well in advance of base of pectoral fin and in contact with, or less than its own

Fishes of the Western North Atlantic diameter below, horizontal septum. PVOi well below and in advance of PVO2 which is in front of lower half of base of pectoral fin. Pd, PO2, and PO5 nearly equidistant and in line; PO3 elevated, at level of PVOi or somewhat higher; PO4 very high, about its own diameter below horizontal septum. VLO about twice its diameter below origin of dorsal fin. Vd elevated, directly over or somewhat in advance of VO2. SAO more or less angulated; SAOi usually a little behind VO4; SAO2 over base of anal fin and its own diameter or less below horizontal septum; SAO3 very near to end of base of dorsal fin. AO widely spaced; last AOa behind base of anal fin. Position of Poll variable but nearer to horizontal septum than to ventral margin of caudal peduncle; Pol2 1-2 times its diameter below base of adipose fin. Prc2 directly over Prci, the two organs equidistant from horizontal septum. Both sexes with a single, undivided supracaudal luminous gland which is distinctly larger and more massive in adult males than it is in adult females; the gland first appears in young males about 11 nun long. Size. Sexual maturity is reached at a size of about 19 mm and members of this monotypic genus do not seem to grow larger than 2 5 mm. Development. Tining (1918) illustrated a number of developmental stages of this myctophid. In his brief, general discussion accompanying the illustrations, Tining remarked that the larva of this species "is extremely characteristic" and that "there is no possibility of confusion with the postlarvae of any other known species, if only from the fact that at a length of abt. 5 mm it is already as far developed as other [myctophid] postlarvae of twice or three times that length." Metamorphosis apparently occurs at a size of about 8.5 mm. Moser and Ahlstrom (1974) also emphasized the uniqueness of the larva of this species. Atlantic Distribution. Notolychnus valdiviae (Fig. 49) is an abundant little species

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distributed according to the tropical-subtropical pattern. Beyond the tropics and subtropics, it is numerous in the Mauritanian Upwelling and in the Gulf of Mexico. There are lesser, but significant numbers, in those parts of the temperate provinces that are adjacent to the subtropics. N. valdiviae is a ranking myctophid in the Gulf of Mexico, the Mauritanian Upwelling, and in the Atlantic Tropical and North and South Atlantic Subtropical Regions, that is, in all Atlantic regions except the North Atlantic Temperate and Atlantic Subarctic Regions. The principal exception that we have noted to N. valdiviae's general abundance in warm waters is that WHOI collections from near the equator and in the northwestern part of the South Atlantic Subtropical Region are noticeably smaller than others from the tropics and subtropics. Extra-Atlantic Occurrence. N. valdiviae is widely distributed in the tropics and subtropics of the Indian and Pacific Oceans. Some of these records have been summarized by Bolin (1959) and McGinnis (1974). (BC) Vertical Distribution. By day, openingclosing devices took N. valdiviae near Bermuda at 450-8 JO m, with maximum concentration at 450-600 m, and near the Canaries at 400-700 m, with maximum abundance at 400-500 m. At night, it was caught from 25 to 700-800 m in both areas, but captures were not made at all intermediate depths; maximum abundance near Bermuda was at 33-100 m. Non-migrants and partial migrants were most abundant in winter near Bermuda. In the WHOI collections, N. valdiviae occurred between 375 and 650 m by day, and mostly between 40 and 125 m at night. Evidence for non-migration was inconclusive. Synonyms and References: Myctophum (Myctophum) valdiviae Brauer, 1904: 398, Fig. 6 [prig, descr.; no locality; twelve presumable syntypes: ZMHU 17586 (2), 17587 (2), 17588 (4), 17589 (4), fide Krefft and Bekker,

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FIGURE 49. Notolychnus valdiviae, a tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et al. (1971).

1973]; Taning, 1918: 151, Fig. 47 (brief discus, of larval and adult char.); Taning, 1928: 57 (in key); Taning, 1931 (illus. of larva and adult, diag., distr.). Vestula valdiviae. Bolin, 1946: 146, Fig. 4 (descr., Indian Ocean). Notolychnus valdiviae. Fraser-Bninner, 1949: 1077, fig. (in descr. of genus); Bolin, 1959: 23 (synon., char., distr.); Bekker, 1967b: 108 (records from Atlantic Ocean, distr., depth of occur.); Legand, 1967: 47-98 (biol. cycl., season, changes in distr. in southeast. Indian Ocean); Nafpaktitis and Nafpaktitis, 1969: 33, Figs. 37-38 (records from Indian Ocean, char.); Craddock and Mead, 1970:

3.30 (record from southeast. Pacific, 30°57/S, 89°13/ W); Kotthaus, 1972b: 28 (records from west. trop. Indian Ocean; merist., morphom.; photo of specim. and otol); Hulley, 1972a: 222 (records from off Cape Agulhas, 38°09'S, 19°50/E, and from southwest. Indian Ocean); Clarke, 1973: 406, 414, Fig. 5 (season, abund., vert, distr. off Hawaii); Rrefft and Bekker, 1973: 193 (synon., ref., distr.).

Genus Lobiancbia Gatti 1903 Lobianchia Gatti, 1903: 28 (type-species, Nycthophus gemellarii Cocco 1838, by monotypy); Bolin, 1959:

Fishes of the Western North Atlantic 18, Fig. 4 (resurrection of genus, characters); Nafpaktitis, 1968: 11 (diagnosis); Paxton, 1972: 49 (definition, osteological characters). Hyperphotops Fraser-Brunner, 1949: 1066 (subgenus of genus Diaphus-y type-species Nycthophus gemellarii Cocco 1838, by original designation).

Characters. Mouth large, moderately oblique; jaws extending one or more times the diameter of the eye behind vertical through posterior margin of orbit; maxillary slightly expanded posteriorly; small, needlelike teeth in bands on premaxillaries, dentaries and palatines; similar teeth on mesopterygoids; a few minute teeth on each side of vomer. Base of dorsal fin slightly longer than that of anal fin. Lateral line well developed. A small, inconspicuous Dn; no Vn; no streak or band of darkly pigmented tissue along anterior and anteroventral margin of orbit; PVO in line with Pd or nearly so; 5 PO, the 4th elevated; 5 VO, the first 3 progressively elevated, forming a straight, ascending line; 1st AOa not

elevated; one Pol, often continuous with AOa; 4 Prc; supracaudal and infracaudal luminous glands in adult males and females, respectively; no other luminous tissue on head and body. Size. Small fishes, normally attaining a size of about 60 mm, but apparent expatriates reaching 100 mm. Range. Tropical and temperate waters of all three major oceans. Species. As here understood, the genus contains two species: L. dofleini and L. gemellarii. The Pacific form urolampa (Gilbert and Cramer) 1897 is sufficiently distinct from both Lobianchia and Diaphus to deserve a generic status of its own (paper in preparation). Both, L. dofleini and L. gemellarii are found in the North Atlantic and in the Mediterranean Sea. No material has been examined for the present study. The species descriptions are based on the work of Nafpaktitis (1968).

Key to the North Atlantic Species of Lobianchia la. Distance between Pol and base of 2.5 times as great as that between vexity directed posteroventrally; tween Prc4 and Prc3 equal to or, (I).

anal fin or ventral contour of caudal peduncle 2 to Pol and lateral line; SAO forming a gentle arc, conPrc4 greatly displaced posterodorsally; distance beusually, greater than that between Prci and Prc3 dofleini (Zugmayer) 1911, p. 96

SAO

Ib. Pol midway between lateral line and base of anal fin or lower; SAO on a straight or slightly curved line, convexity directed an ter odor sally; Prc evenly spaced, sometimes Prc4 somewhat displaced posteriorly, but distance between Prc4 and Prc3 always smaller than that between Prci and Prc3 (II). gemellarii (Cocco) 1838, p. 99

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SAO

Lobianchia dofleini (Zugmayer) 1911 Figures 50-52 Distinctive Characters. Characters in the key will separate this species from its congener, L. gemellarii. Description. Fin rays: dorsal 16 (15-17); anal 14 (1315); pectoral 11-12 (13). Gill rakers: 5-6 + 1 + 12-14 (15), total 18-21 (22). Photophores: AO 5 (4^6) + 5 (4^6), total 10 (9-11, rarely 12). Lateral-line organs: 36 (34-36). Head. Length of head 3-3.5 in SL. Mouth large, moderately oblique; length of upper jaw 1.2 to 1.3 in hi. Eye moderately large (generally larger in males than in females), its diameter 2.7 to 3.7 in length of upper jaw and 3.5 to 4.7 in hi. Operculum tapering posteriorly to a blunt lobe.

FIGUKE 50. Lobiancbia doflrini:

male, 27 mm.

Fins. Origin of dorsal fin somewhat in advance of base of ventral fin. Origin of anal fin on or slightly in advance of vertical through end of base of dorsal fin. Pectoral fins short, extending to somewhere between PO4 and POB. Base of adipose fin over end of base of anal fin. Luminous Organs. PLO about twice as near to base of pectoral fin as to lateral line. VLO midway between base of ventral fin and lateral line or slightly lower. Three SAO (occasionally 2 or 4), on a more or less curved line, convexity directed posteroventrally; SAOi above and slightly posterior to VOB; SAO2 over origin of anal fin; SAOa somewhat in advance of AOai9 the distance between the latter two organs being almost twice as long as that between SAO3 and lateral line. First 3-4 AOa on a straight line, last AOa raised. Pol nearer to lateral line

Fishes of the Western North Atlantic

FIGURE 51. Caudal luminous glands. Lobiancbia dofleini: A, infracaudal of female, 33 mm; B, supracaudal of male, 33 mm. Lobiancbia gemellarii: C, infracaudal of female, 43 mm; D, supracaudal of male, 48 mm.

than to base of anal fin, directly over or slightly in advance of end of base of anal fin in western North Atlantic populations; usually somewhat behind base of anal fin in eastern North Atlantic and Mediterranean populations. AOp behind base of anal fin and level. First three Prc forming a gentle arc; Prc4 displaced far behind Prc3. Sexual Dimorphism. A supracaudal gland first appears in males about 19 mm long in the form of black pigment concentration. The gland is usually well developed in 23- to 24-mm males and fully developed in fishes 26 to 28 mm long. When fully developed, the gland consists of a series of 7-8 main scalelike structures flanked by smaller, triangular ones (Fig. 5IB). An infracaudal gland first appears in females about 22 mm long in the form of minute, whitish patches of luminous tissue. Fully grown in specimens about 30 mm long, the gland consists of a series of 3 overlapping scalelike structures flanked by 2 pairs of smaller ones (Fig. HA).

97

Size. A small myctophid. In the North Atlantic and Mediterranean it grows to about 36 mm, but occasional individuals may be as large as 45-50 mm. Development. Tuning (1918) has described and illustrated a series of postlarvae 5.5 to 11.5 mm in length from the Mediterranean. He found that metamorphosis takes place at sizes between 10.5 and 13 mm. Geographic Variation. A number of morphometric differences have been found between eastern and western North Atlantic populations. The most marked of these differences involve head and body depth. Specimens from the eastern North Atlantic and the western Mediterranean have a significantly deeper head and body than specimens from the western North Atlantic. Furthermore, males from the western North Atlantic tend to have 8 main luminous scales in their supracaudal gland, whereas 7 is the predominant number in males of the eastern populations. Atlantic Distribution. Lobianchia dofleini (Fig. 52) is an abundant bipolar temper atesemisubtropical species. We call it "bipolar" because it has in each hemisphere a widespread population only narrowly connected to the other across the tropics in the extreme east. Thus, L. dofleini is an interesting intermediate between species that are strictly bipolar, that is, strictly separate, and those whose northern and southern hemisphere populations are broadly connected across the tropics from east to west. With the exception of this narrow eastern connection the range of L. dofleini is similar to that of the other bipolar temperate-semisubtropical species, especially Lampanyctus pusillus, but also, though to a lesser extent, Hygophum hygomii and Diaphus metopoclampus. The Atlantic range of L. dofleini should be compared with that of its congener L. gemellarii. The last, regarded as a tropical-subtropical species, is missing or nearly so from the eastern tropics (Guinean Province), Mauritanian Upwelling, and Mediterranean Sea, all of which are places

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FIGURE 52. Lobianchia dofleini, a bipolar temperate-semisubtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Geistdoerfer et al. (1971), Gibbs et al. (1971), and Taning (1918).

where L. dofleini is abundant. L. dofleini is a ranking myctophid in the Mauritanian Upwelling and in the North Atlantic Temperate and Subtropical Regions. Extra-Atlantic Occurrence. From the records given and summarized by McGinnis (1974) it is apparent that L. dofleini is circumglobally distributed in the southern hemisphere in the neighborhood of the Subtropical Convergence; however, the species is not known from the northern hemisphere outside the Atlantic. (BC)

Vertical Distribution. By day, openingclosing devices took L. dofleini from 300-400 m to 600-700 m near Bermuda, near the Canary Islands, and in the Mediterranean Sea; maximum abundance was at 500-600 m near Bermuda and about 400-500 m near the Canaries and in the Mediterranean. The species was taken at night from 20 to 200 m near Bermuda and near the Canaries and from 20 to 400 m in the Mediterranean; maximum abundance was between 50 and 150 m in each region. The species was stratified, with size

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FIGURE 53. Lobianchia gemellarii: male, 47.5 mm.

increasing with depth both night and day in each region. In the WHOI collections, L. dofleini, most of which were collected in temperate provinces, occurred somewhat shallower by day than at Bermuda, maximum abundance being at about 400 m. At night, maximum abundance was at 50 m. Synonyms and References: Myctophum (Lampanyctus) dofleini Zugmayer, 1911: 3 (orig. descr.; Mediterranean; seven syntypes at the MOM, fide Krefft and Bekker, 1973). Myctophum (Diaphus) dofleini. Taning, 1918: 76, Figs. 29, 31 (descr. of larv. and adult char., reprod., distr. in Mediterranean). Diaphus dofleini. Parr, 1928: 124 (discus, of char.); Taning, 1928: 58 (in key); Taning, 1933, figs, (diag., distr.). Diaphus (Hyperphotops) dofleini. Fraser-Bninner, 1949: 1066, fig. not of dofleini (in key). Lobianchia dofleini. Bolin, 1959: 19, Fig. 4 (synon., char., distr.); Bekker, 1967b: 98 (records from North and South Atlantic, depths of capture); Nafpaktitis, 1968: 12, Figs. 3—8 (key, descr., distr., geog. var., North Atlantic); Craddock and Mead, 1970: 3.30 (records from southeast. Pacific); Bini, 1971: 191, illus. (morphol, biol, distr.); Kotthaus, 1972a: 12 (records from east. North Atlantic, char., photo of otol.); Hulley, 1972a: 226 (records from off west coast of S. Africa); Goodyear et al., 1972:

178 horiz. and vert, distr., growth, reprod. in Mediterranean); Kretft and Bekker, 1973: 192 (synon., ref.).

Lobianchia gemellarii (Cocco) 1838 Figures 51, 53-55 Distinctive Characters. Characters in the key will separate this species from its congener, L. dofleini. Description. Fin rays: dorsal 17 (18); anal 14 (13-15); pectoral 11-12. Gill rakers: 4-6 + 1 + 10-14, total 15-21. Photophores: AO 5 (6) + 6. Lateral-line organs: 36-37. Head. Length of head 3-3.4 in SL. Mouth large, its cleft moderately oblique; length of upper jaw 1.2 to 1.3 in hi and extending 1.3 to 1.5 times the diameter of eye behind vertical through posterior margin of orbit. Eye of moderate size, its diameter 3 to 4.3 in length of upper jaw and 4 to 5.3 in hi. Operculum tapering posteriorly to a blunt point. Fins. Origin of dorsal fin somewhat in advance of base of ventral fin. Origin of anal fin in advance of vertical through end of base of dorsal fin. Pectoral fins short, extending

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FIGURE 54. Lobianchia gemellarii: variation in the pattern of arrangement of the last AOa, Pol and first AOp. The arrow points at the Pol.

to PO4. Base of adipose fin directly over, or slightly in advance of end of base of anal fin. Luminous Organs. PLO about 2.5 times nearer to base of pectoral fin than to lateral line. VLO nearer to base of ventral fin than to lateral line. SAO in a straight or, usually, slightly curved line, convexity directed anterodorsally; SAOi above and behind VOB; SAO2 over origin of anal fin; SAO8 somewhat in advance of AOai, the distance between the latter two organs being less than 1.5 times as long as that between SAO3 and lateral line. First 3-4 AOa in a straight line; AOa6 and, when present, AOae raised and forming various patterns with Pol and AOpi (Fig. 54). Pol in advance of end of base of anal fin and midway between it and lateral line or lower. AOpi in line with, or elevated above rest of organs of same series, behind end of base of anal fin or, rarely, directly over it. Prc evenly spaced or, sometimes, Prc3-Prc4 interspace distinctly enlarged but always smaller than distance between Prci and Prc3.

Sexual Dimorphism. Adult males with a supracaudal gland consisting of a series of 6 large, well-defined scalelike structures flanked by 5 pairs of smaller, triangular ones (Fig. 5ID). The character appears in young males at a size of about 26 mm in the form of dark pigment concentration along the middorsal aspect of the caudal peduncle. In males about 40 mm long the luminous scales are clearly defined and from then on the supracaudal gland changes only in size. The infracaudal gland first appears in females 30-32 mm long and consists of 2 main small, heart-shaped structures flanked by 2 pairs of smaller, roughly triangular ones. In females about 40 mm long the infracaudal gland is very well developed, growing only in size from then on (Fig. 51C). It should be pointed out here that in expatriate L. gemellarii the caudal luminous glands either do not develop at all, or their development is arrested at an early stage. Size. The species attains maturity at sizes between 40 and 45 mm. It does not exceed 60 mm. However, outside the spawning area, one occasionally finds individuals of abnormally large size. A number of specimens, caught in the Slope Water off New England, ranged in size between 85 and 100 mm. These animals lacked any traces of caudal glands and their sex could hardly be determined by gross examination of the gonads. Development. Tining (1918) described and illustrated a series of larval stages 5 to 10 mm in length, and a 14-mm specimen at the stage of metamorphosis. Geographic Variation. With the exception of gill-raker counts and AO-Pol patterns of arrangement, populations of L. gemellarii from various parts of the North Atlantic show very little, if any, variation in meristic and other characters. However, the differences in the number of gill rakers among populations from different latitudes are remarkable. Starting from low latitudes to approximately 22°N, the prevalent configuration is 5 + 1

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FIGURE 55. Lobiancbia gemellarii, a tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et al. (1971).

+ 11-12, total 17-18 gill rakers. The predominant counts between about 22° and 28°N, especially in the eastern part of the ocean, are 4 + 1 + 10-11, total 15-16. In latitudes higher than 32°N one finds a mixture of 17-18 and 20-21. Higher than about 3 J°N and up to the northernmost limits of the species range the counts are almost exclusively 20-21 (6 + 1 + 13-14). These data suggest a possible correlation between gill-raker counts and temperature distribution in the North Atlantic.

Regarding the variation in the AO-Pol arrangement, I have been able to find no correlation between it and any of the factors considered. Atlantic Distribution. Lobianchia gemellarii (Fig. 55) is a tropical-subtropical species much less abundant in WHOI collections than its congener L. dofleini. L. gemellarii occurs in the Gulf of Mexico as abundantly as it does in the tropics and subtropics and is found also in significant numbers in collections from the western temperate provinces (Slope Water

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and Northern Gyre). L. gemellarii and L. dofleini have more or less complementary distributions, but this is masked to some extent by the fundamental difference in the abundance of the two. The two species overlap in the northern subtropics and adjacent temperate regions, where L. dofleini is by far the more abundant. In most of the southern subtropics, in the western tropics, and in the Gulf of Mexico, L. gemellarii occurs to the exclusion of L. dofleini. On the other hand, L. dofleini is found in the eastern tropics and Mauritanian Upwelling to the exclusion of gemellarii. A small population of gemellarii is found in the Eastern Mediterranean Sea; it and the questionably tropical-subtropical Gonichthys cocco are the only species of non"northern" patterns to live there. Extra-Atlantic Occurrence. Lobianchia gemellarii is common in the Indian Ocean west of about 75 °E between 2°N and 25 °S. No records exist from the eastern part. The species also has been collected in the South China Sea to about 15°N and in the western North Pacific from Japan eastward to 170°E between approximately 12°N and 32°N (Gilbert, 1913; Kulikova, 1961). It seems to be quite common between New Caledonia and New Zealand, and there are several records from off Sydney, Australia. In the eastern Pacific it has been reported from off Chile between 30°S and 34°S (Craddock and Mead, 1970), and there are apparently several records from between 110°W and 85°W from 40 °S northward to about 5°N. Finally, the species has been collected in the eastern and central North Pacific between about 20° and 30°N. (N) Vertical Distribution. By day, openingclosing devices caught L. gemellarii at 400800 m near Bermuda and at 300-650 m near the Canary Islands, with maximum abundance between 450 and 500 m in both regions. At night, it was taken in both areas between 25 and 300 m and, in smaller numbers, at daytime depths. Individuals larger than 40 mm

did not migrate into the upper 150-200 m in either region. In the WHOI collections, L. gemellarii occurred at 325-550 m by day and at 40-175 m at night. Synonyms and References: Nycthophus gemellarii Cocco, 1838: 186 (orig. descr.; Messina). Scopelus (Nyctophus) gemellarii. Liitken, 1892: 260 (char.). Diaphus nipponensis Gilbert, 1913: 86 (orig. descr.; 30°34'N, 129°22'E, 300 fms; holotype, USNM 74467); Parr, 1928: 116 (in key); Parr, 1929: 31 (brief ref. and fig.)Myctophum (Diaphus) gemellarii. Taning, 1918: 73, Figs. 27, 28 (descr. of larv. stages, reprod., distr. in Mediterranean). Diaphus gemellarii. Taning, 1928: 58 (in key). Diaphus gemellari. Parr, 1928: 123, Figs. 21, 22 (synon., records, char.). Diaphus (Hyperphotops) nipponensis. Fraser-Brunner, 1949: 1066, fig. (in key). Diaphus (Hyperphotops) gemellari. Fraser-Brunner, 1949: 1066, fig. (in key). Lobianchia gemellari. Bolin, 1959: 19 (brief compar. to L. dofleini); Bekker, 1967b: 98 (records from North and South Atlantic); Nafpaktitis, 1968: 18, Figs. 9-12 (key, descr., distr., geog. var., North Atlantic) ; Craddock and Mead, 1970: 3.30 (records from southeast. Pacific); Bini, 1971: 189, illus. (morphol., biol., distr.); Kotthaus, 1972a: 12 (records from east. North Atlantic, char., photo of otol.); Clarke, 1973: 406, 411 (vert, distr., off Hawaii); Krefft and Bekker, 1973: 191 (synon., ref.).

Genus Diaphus Eigenmann and Eigenmann 1890 Diaphus Eigenmann and Eigenmann, 1890: 3 (typespecies Diaphus theta Eigenmann and Eigenmann 1890, by original designation); Fraser-Brunner, 1949: 1063 [characters; subdivided into subgenera Hyperphotops (= Lobianchia), Panthophos, Lamprossa, and Diaphus]; Bolin, 1959: 20, partim (characters); Nafpaktitis, 1968: 22 (diagnosis); Pazton, 1972: 48—49 (osteological characters, definition). Aethoprora Goode and Bean, 1896: 86 [type-species Scopelus metopoclampus (Cocco) 1829, by subsequent designation of Jordan, 1963 (1920): 467]; Bolin, 1959: 22, partim (characters).

Fishes of the Western North Atlantic Collettia Goode and Bean, 1896: 88 [type-species Myctophnm rafinesquii (Cocco) 1838, by original designation] . Lamprossa Jordan and Hubbs, 1925: 156 (type-species Diaphus anteorbitalis Gilbert 1913, by original designation) . Pantophos Jordan and Hubbs, 1925: 156 (type-species Diaphus glandulifer Gilbert 1913, by original designation) . Cavelampus Whitley, 1933: 62 (type-species Aethoprora perspicillata Ogilby 1898, by original designation) .

Characters. Mouth medium-sized to large; jaws extending from less than half to more than one eye diameter behind vertical through posterior margin of orbit; maxillary not or slightly expanded posteriorly; premaxillaries and dentaries with densely set, small, villiform or needlelike teeth, the inner ones generally enlarged, simple or broad-based and strongly hooked; a long, narrow band of small teeth on each palatine and a patch of similar teeth on each mesopterygoid; vomer with a few minute teeth or toothless. A well-developed pterotic spine often present. Base of dorsal fin from slightly shorter to longer than that of anal fin. Lateral line well developed. With very few exceptions, more than one pair of,

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in most cases sexually dimorphic luminous organs on head; a streak or band of darkly pigmented tissue along much of anterior half of orbital margin; PVO in line with PCX or very nearly so; 5 PO, the 4th abruptly and highly elevated; 5 VO, the first 3 progressively elevated, forming a straight, or nearly straight, ascending line; with very few exceptions, AOai elevated; one Pol, sometimes continuous with AOa; 4 Prc; supracaudal and infracaudal glands absent; with very few exceptions, a luminous scale at PLO. Size. Small to medium-sized myctophids, very few species exceeding 200 mm. Range. Tropical, subtropical, and temperate waters of all three major oceans. Species. As here understood, the genus contains some 60 species, with at least 10 additional Pacific and Indian Ocean forms awaiting description. Twenty-three species occur in the North Atlantic. The following species descriptions are basically from Nafpaktitis (1968, 1974). Where additional material has been examined it is so indicated in the Study Material under the particular species involved.

Key to the North Atlantic Species of Diaphus Some diagrams appear below with the sex of the fish indicated. For the other sex, see Sexual Dimorphism under the appropriate species description. la. So always present, on ventral orbital margin, completely separated from Vn or connected with latter by a strand of dark tissue of varied breadth (I); inner series of teeth on posterior part of premaxillary always with broad bases and strongly recurved (IA); vomer naked or with very few, scattered minute teeth

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Ib. So absent, inner series of teeth on posterior part of premaxillary of various sizes, sometimes distinctly recurved; vomer with a small, round or oval patch of teeth on each side 8 2a. Dn very small, inconspicuous, directed laterally, shallowly embedded and almost completely fused with much larger, upward spreading Vn; a narrow band of dark tissue extending along ventral border of eye connects the Vn with the small So, the latter located somewhat behind vertical through center of lens; diameter of eye more than 2 times in length of upper jaw; upper jaw extending about one time the diameter of eye behind vertical through posterior border of orbit (II). vanhoeffeniftrzuer 1906, p. If 3

2b. Dn well defined, round, equal in size to or somewhat smaller than nasal rosette, directed forward and set in deep, cup-shaped recess above nasal apparatus; Vn on ventral orbital margin, completely and widely separated from Dn; diameter of eye 2 times in length of upper jaw or less; upper jaw extending about one-half the diameter of eye behind vertical through posterior margin of orbit 3 3a. So behind vertical through posterior margin of pupil; Vn very long, longer than horizontal diameter of pupil, occupying the anteroventral and most of ventral orbital margin; no luminous scale at PLO (III). bracbycepbalus Tining 1928, p. 167

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3b. So in advance of vertical through posterior margin of pupil; Vn elongate but shorter than horizontal diameter of pupil, or small, rounded, about equal in size to So; a luminous scale at PLO, this sometimes poorly defined or rubbed off . . . . 4 4a. Vn and So about equal in size, roundish or oval, small, one-third to one-half the size of a general body photophore and widely separated from each other; body photophores placed low, very large in size and separated by narrow spaces, those between the AO equal to about one-half the diameter of a photophore; AOai not raised; a very large luminous scale at PLO (IV). anderseni Tining 1932, p. 169

Vn

4b. Vn elongate, much larger than roundish or oval So, the two organs close to each other, sometimes confluent; body photophores of moderate size, those of AO series separated by spaces greater than one-half the diameter of a photophore 5 5a. AOp 5 or more, usually 6, continuous or nearly so with Prc; distance between Prci and Prcs larger than AOp-Prc interspace; gill rakers 6 (7) + 1 + 13-14, total 2022 (V). subtilis Nafpaktitis 1968, p. 164

5b. AOp 5 or less, usually 4, well separated from Prc; distance between Prci and Prcs equal to or usually smaller than AOp-Prc interspace 6 6a. AOa 6, seldom 5 or 7; AOai abruptly elevated, its ventral margin above a line through dorsal margins of next two organs of same series; SAO on a straight or very slightly angular line; a large luminous scale at PLO; gill rakers 7-8 + 1 + 1416, total 22-24 (25) (VI). rafinesquii (Cocco) 1838, p. 156

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6b. AOa 5, seldom 6; AOai in a straight line with next two organs of same series or raised forming with next two or three organs of this series a gentle curve; SAO on a straight or distinctly angular line; a small luminous scale at PLO, this often poorly defined or rubbed off; gill rakers 15-20 7 7a. Distance between PLO and lateral line 1.5 times as great as that between PLO and upper end of base of pectoral fin or less; SAO forming a distinctly angular line; SAOB 1-1.5 times its own diameter below lateral line; Pol about its own diameter below lateral line; depth of caudal peduncle more than 8 times in SL; posterodorsal opercular margin angular; gill rakers 4-5 + 1 + 11 (10-12), total 16-17 (rarely 15 or 18) (VII). woJ/wTining 1928, p. 159

7b. Distance between PLO and lateral line 2-2.5 times as great as that between PLO and upper end of base of pectoral fin; SAO in a straight or slightly angular line; SAO8 2-2.5 times its own diameter below lateral line; Pol about twice its own diameter below lateral line; depth of caudal peduncle 8 times in SL or less; posterodorsal opercular margin evenly rounded; gill rakers 5-6 + 1 + 12-13 (11), total 18-20 (VIII). hdti Tining 1918, p. 161

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8 a. Dn small, thin, rather poorly defined (usually larger and better defined in adult males), shallowly embedded and directed laterally; Vn equally small, completely separated from Dn, located at ventral orbital margin, or somewhat larger and located at anteroventral aspect of orbit and connected with Dn by a narrow streak of luminous tissue in between eye and nasal apparatus 9 8b. Dn well defined, in more or less deep recess above nasal apparatus and directed forward; Vn restricted to anteroventral or ventral aspect of orbit, or spreading along anterior orbital margin, often reaching the Dn 11 9a. A small, round or oval Vn, half the size of a general body photophore, completely separated from Dn, located at the ventral orbital margin on or slightly in advance of vertical through anterior margin of pupil; PLO in advance of vertical through upper end of base of pectoral fin and very high, 1-2 times its own diameter below lateral line; SAO angular; SAO3 and Pol at lateral line; AOai not elevated (IX). dumer&n (Bleeker) 1856, p. 113

IX

9b. Vn at anteroventral aspect of orbit, somewhat larger than Dn and connected with it by a thin streak of luminous tissue extending between eye and nasal apparatus; PLO behind vertical through upper end of base of pectoral fin; SAO series not or slightly 10 angular; AOai abruptly elevated, well above next 2-3 organs of same series . . . lOa. PLO nearer to lateral line than to base of pectoral fin; VLO midway between lateral line and base of ventral fin; SAO3 and Pol in contact with lateral line; first AOp entirely behind end of base of anal fin; gill rakers 7 (rarely 6 or 8) + 1 + 13-14 (rarely 12 or 15), total 21-22 (rarely 20 or 23) (X). garmani Gilbert 1906, p. 116

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lOb. PLO nearer to base of pectoral fin than to lateral line; VLO nearer to lateral line than to base of ventral fin; SAO8 and Pol 1-1.5 times their diameters below lateral line; first AOp over base of anal fin; gillrakers4 + 1 + 9 (8), total 14 (13) (XI). problematicus Parr 1928, p. 119

n. MgJl

XI 11 a. Dn smaller than nasal rosette; Vn extending upward to or beyond level of Dn or restricted below nostril but connected with Dn by a strand of dark tissue extending along anterior orbital margin 12 lib. Dn equal in size to or larger than nasal rosette, round or rectangular, often reaching medial ethmoid crest; Vn also very large, spreading along entire area in front of eye, coming in contact with Dn, its ventral portion extending at least a short distance along ventral orbital margin; an Ant may or may not be present - . . * 17 12a. Vn extending dorsally between eye and nasal apparatus, reaching Dn 13 12b. Vn not spreading dorsally beyond lower margin of nasal apparatus 14 13 a. Vn not extending along ventral orbital margin, its posterior end barely reaching vertical through anterior margin of pupil; elongate luminous organ along dorsal margin of orbit absent; anterior end of supraorbital frontal ridge produced into a forward directed spine—often broken in preserved specimens; PLO nearer to base of pectoral fin than to lateral line; SAOs and Pol in contact with lateral line (XII). splendidus (Brauer) 1904, p. 123

spin*

13b. Vn extending along ventral orbital margin, its posterior end on or behind vertical through center of lens; a luminous organ extending along entire or nearly entire dorsal orbital margin; anterior end of supraorbital frontal ridge not produced into

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109

a spine; PLO midway between base of pectoral fin and lateral line or somewhat higher; SAO3 and Pol not in contact with lateral line (XIII). adenomus Gilbert 1905, p. 121

XIII 14a. SAOi above level of VO5; upper jaw extending less than one time the diameter of eye behind vertical through posterior margin of orbit; ventral fins about reaching origin of anal fin 15 14b. SAOi on same level with VO5; upper jaw extending more than one time the diameter of eye behind vertical through posterior margin of orbit; ventral fins extending beyond origin of anal fin 16 15a. Body photophores of moderate size, those of AOp series separated by spaces larger than one-half the diameter of a photophore; VLO midway between lateral line and base of ventral fin or somewhat higher; gill rakers 6-7 + 1 + 13-14, total 20-22 (XIV). taaningi Norman 1930, p. 126

15b. Body photophores large, those of AOp series separated by spaces equal to one-half the diameter of a photophore or less; VLO nearer to base of ventral fin than to lateral line; gill rakers 5 + 1 + 12 (XV). berteheni Nafpaktitis 1966, p. 128

16a. Vn very long, extending along most of ventral border of eye, its dorsal margin with small, round, bud-like projections; dorsal and anal fins overlapping (XVI). luetkeni (Brauer) 1904, p. 131

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9

Vn

XVI 16b. Vn roundish or oval, located on ventral orbital margin, about under center of pupil; dorsal and anal fins not overlapping (XVII). termophilus Tining 1928, p. 133

17a. Ant absent 17b. Ant present 18a. D. 13-15; A. 13-14; eye diameter 3 times or less in hi and 2 times or less in length of upper jaw; body photophores of average size 18b. D. 17; A. 17-18; eye diameter 3.5 times or more in hi and 2.5 or more in length of upper jaw; body photophores noticeably small (XVIII). lucidus (Goode and Bean) 1896, p.

18 20 19 138

XVIII

19a. Head as deep as it is long or very nearly so; upper jaw extending 0.5 the diameter of eye or less behind vertical through posterior margin of orbit; Dn round, about equal in size to nasal rosette (XIX). minax Nafpaktitis 1968, p. 136

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XIX 19b. Head considerably longer than it is deep; upper jaw extending more than 0.5 the diameter of eye behind vertical through posterior margin of orbit; Dn roughly rectangular, much larger than nasal rosette (XX). roei Nafpaktitis 1974, p. 149 PLO

20a. Ventral portion of Vn not reaching vertical through anterior margin of pupil; head much longer than it is deep; body photophores of average size 21 20b. Vn extending along ventral orbital margin to somewhat behind vertical through center of pupil; head nearly as deep as it is long; body photophores noticeably small (XXI). metopoclampus (Cocco) 1829, p. 150

Ant,

21a. Dn hardly extending higher than level of dorsal margin of eye; PLO midway between lateral line and base of pectoral fin or higher; SAO3 and Pol in contact with, or less than their diameter below lateral line 22

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21b. Dn extending higher than level of dorsal margin of eye; PLO nearer to pectoral base than to lateral line; SAO3 and Pol 1.5-3 times their diameter below lateral line; gill rakers 6-7+1 + 13 (14), total 20-21 (22) (XXII). effulgent (Goode and Bean) 1896, p. 146

Ant.

22a. Vn not spreading behind nasal apparatus; diameter of eye less than 10% of SL; lower jaw with inner series of markedly large, widely but more or less regularly spaced teeth (Fig. 83A); gill rakers 5 (6) + 1 + 11-12, total 17-18 (19) (XXIII). fragilis Taning 1928, p. 140

22b. Vn spreading behind nasal apparatus, reaching the medial ethmoid crest; diameter of eye more than 10% of SL; no markedly enlarged teeth on lower jaw; gill rakers 9-10 + 1 + 16-17 (18), total 26-28 (29) (XXIV). perspicittatus (Ogilby) 1898, p. 143

Ant

XXIV

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FIGURE 56. Diaphus dumeriliii female, 61.5 mm.

Diaphus dumerilii (Bleeker) 1856 Figures 56-58 Distinctive Characters. This species can readily be distinguished from its congeners by (a) the size, structure, and position of its Vn; (b) the high positions of PLO, SAO3, and Pol; and (c) the position of the 1st AOa which is in line with the following organs of the same series—an uncommon arrangement in the genus. Description. Fin rays: dorsal 14 (15); anal 15 (14); pectoral 12 (11). Gill rakers: 6-8 (rarely 5 or 9) + 1 + 13-17 (rarely 18), total 20-26 (rarely 19 or 27). Photophores: AO 6-8 + 5-6 (4, rarely 7), total 11-13 (rarely 10 or 14). Lateral-line organs: 37 (36-38). Head. Length of head 30-33.5 percent of SL. Mouth large, its cleft oblique; length of upper jaw 1.3-1.5 in hi and extending 0.71 time the diameter of eye behind vertical through posterior margin of orbit. Eye large, its diameter 2.3-2.6 in length of upper jaw and 3.2-3.7 in hi. Operculum tapering posteriorly to a sharp point. fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin behind base of

dorsal fin. Pectoral fin extending to base of ventral fin. Base of adipose fin on or slightly in advance of vertical through end of base of anal fin. Luminous Organs. Females with a small, irregularly shaped, laterally directed Dn; same organ much larger in males. A small, round or oval Vn, % the size of a general body photophore, situated on the 1st circumorbital bone, on or slightly in advance of vertical through anterior margin of pupil (because of its size and position, the Vn is sometimes difficult to find without removing the skin between the ventral border of the orbit and the upper jaw). PLO 1-2 times its diameter below lateral line. VLO midway between base of ventral fin and lateral line. SAO angular; SAOi, SAO2, and VO6 evenly spaced and forming a straight, steeply ascending line; SAO3 directly over or slightly in advance of SAO2 and at lateral line. AOa evenly spaced and in line, except for the last organ in the series which is often somewhat raised. Pol behind last AOa and at lateral line. AOp behind (occasionally AOpi directly over) end of base of anal fin, evenly spaced and in line. Prc forming a gentle curve; Prca-Prc4 interspace often 1.5-2 times as wide as those between first 3 organs of same

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FIGURE 57. Diaphus dumeriliii sexually dimorphic Dn of male, 56 mm.

series; Prc4 about twice its own diameter below midlateral line. A small luminous scale at PLO. Sexual Dimorphism. This is reflected in the shape and, especially, size of the Dn. This organ in females has already been described. In mature males it is a large structure, about the size of the nasal rosette, massive, occupying the entire space between the nasal apparatus, the anterodorsal border of the orbit, and the supraorbital frontal ridge, often pushing the latter upward. It grows downward in between the nasal apparatus and the anterior border of the orbit reaching, at the peak of its development, somewhat below the ventral margin of the nasal rosette. A thick band of dark tissue extends from the anterodorsal margin of the orbit to the Vn. Sexually dimorphic growth of the Dn becomes noticeable in males at a size of about 34 mm. Development of Headlights. In 12-15mm-long individuals the Dn is a tiny spot, distinguished by the dark pigment around it rather than by the luminous tissue itself. Fortunately, however, the Vn is clearly distinct in fishes immediately after metamorphosis (8 to 9 mm). Size. This fish attains sexual maturity at about 52 mm in the Caribbean Sea and adjacent waters, but in the Gulf of Guinea it does so at a size of about 44 mm. The largest specimen examined measured 86 mm.

Geographic Variation. D. dumerilii apparently spawns in two distinct areas. One is in the waters around the Lesser Antilles and the other in the Gulf of Guinea. Distinct differences in the number of gill rakers exist between the eastern and western populations. A difference is also found in the relative size at which the two populations become sexually mature, members of the eastern population maturing at a smaller size (females with ripe eggs measure 40 to 42 mm) than those of the western population (no females smaller than about 52 mm have been found with ripe eggs). Gill-raker counts from five areas within the range of the species in the Atlantic Ocean are as follows: Gulf of Guinea, south of the equator, 24-27; Gulf of Guinea, north of the equator, 20-25; central equatorial Atlantic, 20-23; eastern Caribbean and Lesser Antilles, 19-21; western North Atlantic, north of 30°N, 23-26. Available data indicate that north of the equator, but still in the Gulf of Guinea, the western and eastern populations come in contact and interbreed. Specimens from that area show an intermediate condition in gillraker counts. Fishes with intermediate counts are found across the equatorial Atlantic. Atlantic Distribution. Diaphus dumerilii (Fig. 58) is a common tropical species. It is a ranking myctophid in the Atlantic Tropical Region and probably the most abundant myctophid in the Caribbean Sea. It is common in the Mauritanian Upwelling. From the Caribbean Sea it appears to be carried north in considerable numbers by the Gulf Stream to end up in the Slope Water, the northwestern Sargasso Sea, and even to some extent in the Northern Gyre. The southern hemisphere analog of this phenomenon appears to exist in the western South Atlantic; here a significant population of D. dumerilii lives in the Argentine Basin, whence it may be carried by the south-flowing Brazil Current, Extra-Atlantic Occurrence. The extra-

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FIGURE 58. Diaphus dumerilii, a tropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971), Nafpaktitis (1968), Parin et aL (1974), and unpublished ALBATROSS IV data.

Atlantic range of D. dumerilii is not at all understood. The type locality is in the Celebes Sea (off Manado at about 1°N, 125°E), but there have been no further certain extraAtlantic records so far as we are aware. Fowler (1928) reported it from near Hawaii and Beebe and Vander Pyl (1944) from west of Mexico, but Wisner (1976) questions these. (BC) Vertical Distribution. In the WHOI collections, D. dumerilii occurred between 22 5

and 7 JO m by day, with maximum abundance at 450-500 m, and between the surface and about 125 m at night with maximum abundance at JO m. Opening-closing devices fished near Bermuda took one specimen at 600 m during the day and three specimens at 50 m at night. Synonyms and References: Scopelus dumerilii Bleeker, 1856: 66 (orig. descr.; off Manado, Celebes; two syntypes, RMNH 6931, fide Krefft and Bekker, 1973).

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FIGURE 59. Diaphus garmani: female, 42.5 mm. Myctophum nocturnum Poey, 1861: 426 (orig. descr.; off Cuba; lectotype MCZ 6871, desig. by Gilbert 1906). Ltmpanyctus lacerta Goode and Bean, 1896: 81, Pi. 24, Fig. 89 (orig. descr.; descr. based on three specim., USNM 43778, from 28°38'30"N, 85°52'30"W). Diaphus nocturnus. Gilbert, 1906: 255, Pi. 1 (desig. of lectotype; comp. with Lampanyctus lacerta Goode and Bean and synon. of latter; descr.). Diapbus dumerili nocturnus. Taring, 1928: 58 (in key). Diapbus (Pantbopbos) dumerili. Fraser-Brunner, 1949: 1068, fig. (in key). Diaphus dumerili. Parr, 1928: 126, Fig. 23 (synon., char.); Bekker, 1967b: 99 (horiz. and vert, distr.); Nafpaktitis, 1968: 30, Figs. 13-16 (key, descr., distr., geog. var.); Kretft and Bekker, 1973: 177 (synon., ref., distr.).

Diaphus garmani Gilbert 1906 Figures 59-61 Distinctive Characters. Characters in the key will separate this species from D. problematicus. Description. Fin rays: dorsal 15 (14-16); anal 16 (1517); pectoral 12 (11). GUI rakers: 7 (6-8) + 1 + 13-14 (rarely 12 or 15), total 21-22 (rarely 20 or 23). Photophores: AO7 (6-8) + 5 (4-6, rarely 7), total 12 (11-13, rarely 14).

Lateral-line organs: 38-39. Head. Length of head 27.5-30.5 percent of SL. Mouth large, its cleft oblique; length of upper jaw 1.3-1,4 in hi and extending about one time the diameter of eye behind vertical through posterior margin of orbit. Eye rather large, its diameter 2.4—3.2 in length of upper jaw and 3.3-4.3 in hi. Operculum tapering to a point just under PLO. fins. Origin of dorsal fin approximately over base of ventral fin. Origin of anal fin behind end of base of dorsal fin. Pectoral fins reaching base of ventral fin. Base of adipose fin directly over or slightly in advance of end of base of anal fin. Luminous Organs. A tiny, round organ dorsolaterally to Dn. Dn directed anterolaterally, rather small and ill defined in females, much larger and sharply demarcated in males, located dorsolaterally to and in contact with nasal apparatus, tapering as it extends ventrally until it meets and overlaps with the dorsal, attenuated extension of the Vn, the distinctness of the two organs often being obscured. Vn distinctly larger than Dn in mature females, but equal in size to, or smaller than, Dn in males of comparable sizes; posterior tip of Vn not reaching vertical through anterior margin of pupil. PLO nearer to lateral line than to base of pectoral fin.

Fishes of the Western North Atlantic VLO midway between base of ventral fin and lateral line. SAO on a straight or slightly angular line, with distance between SAO2 and SAO3 1.5-2 times as large as that between SAd and SAO2; SAO3 on or somewhat in advance of vertical through origin of anal fin and at lateral line. AOai abruptly elevated, often directly above AOa2; AOa2 through AOa4 or AOa5 level, with AOa2AOa3 interspace usually enlarged; AOa6 or, if present, AOa7 elevated. Pol in contact with lateral line. AOp immediately behind end of base of anal fin, evenly spaced and level. First 3 Prc evenly spaced, forming a gentle curve; Prc4 separated from Prca by a space twice as large as those between first 3 Prc, and about 1.5 times its own diameter below lateral line. A luminous scale at PLO. Sexual Dimorphism. Differences in size and shape of the Dn between the two sexes are already shown in fishes 26-27 mm long, and specimens 30 mm or larger can usually be sexed easily on the basis of the morphology of this organ. Development of Headlights. Before attaining their definitive size and shape, the luminous organs of the head go through several stages of development which, briefly, are as follows: individuals 11-11.5 mm long show the round, darkly pigmented structure at the anterior ends of the supraorbital frontal ridges, with the Dn in the form of a tiny patch of luminous tissue ventromesad to it. At 14.5-15 mm a longitudinal trace of luminous tissue appears immediately below the Dn and between the nasal organ and the orbit (Fig. 60S). This trace grows downward, and in fishes 16.5-17.5 mm long it meets and overlaps with another narrow strip of luminous tissue from the general area where the Vn is soon to appear. The Vn becomes distinct in juveniles 18.5-19.5 mm long. From then on the whole system grows in size. Size. This fish reaches sexual maturity at a size of about 40 mm and grows to about 60 mm.

117

FIGURE 60. Diaphus garmani: A, sexually dimorphic Dn of male, 42 mm. B, young, 15 mm.

Atlantic Distribution. Diaphus garmani (Fig. 61) is a tropical species restricted to the western Atlantic provinces. WHOI records come almost entirely from the Amazonian Province and from the Caribbean Sea, but it seems that the species must occur in the intervening Lesser Antillean Province to a greater extent than existing records suggest. Nafpaktitis (1968) recorded specimens from the Straits of Florida. Extra-Atlantic Occurrence. Outside of the Atlantic Diaphus garmani can be confused with D. signatus (Gilbert) and an as yet undescribed form. Confirmed Indian Ocean records indicate that the species is found mainly in the western part of the ocean along and close to the east coast of Africa from about 5°N to 10°S, around the Comoros Islands, and along the west coast of Madagascar to about 25°S. The only east Indian Ocean record is from near 5°N, 85°E. The species has been taken in Southeast Asian seas and the western tropical Pacific,

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FIGURE 61. Diapkus garmani, a tropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from R. Baird (in litt.) and Nafpaktitis (1968).

It has been reported from about 2°N, 157° W (Nakamura, 1970) and from 12°N and 7° 30^ along the meridian 145°W (Hartmann and Clarke, 1975). Unconfirmed data suggest that it occurs eastward to about 105°W. (N) Vertical Distribution. In the WHOI collections, D. garmani occurred between 325 and 750 m by day, with most specimens from about 400 m, and between 40 and 125 m at night, with maximum abundance at 100 m. Nafpaktitis (1968) called D. garmani

"pseudopelagic" due to its capture in shallow waters near Caribbean Islands and in the Tongue of the Ocean in the Bahamas (Parr, 1928). Likewise, Nakamura (1970) recorded huge shoals at the surface in 15 to 20 m of water at Christmas Island. However, WHOI data show that the species is not restricted to such situations. Synonyms and References: Diaphus garmani Gilbert, 1906: 258, Pi. 2 (orig. descr.; off Cuba; holotype, MCZ 29070); Parr, 1928, 145, Fig. 33 (records, char.); Taning, 1928: 60 (in

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FIGURE 62. Diaphus problematicus: young, 42.5 mm.

key); Bekker, 1967b: 106 (horiz. and vert, distr.); Nafpaktitis, 1968: 35, Figs. 17-19 (key, descr., distr.). Diaphus (Lamprossa) garmani. Fraser-Brunner, 1949: 1070, fig. (in key).

Diaphus problematicus Parr 1928 Figures 62, 63 Study Material. Thirty-two specimens, 33—85 mm, taken by the NMFS vessel OREGON in the southeastern and southwestern Caribbean, and in the central and northern Gulf of Mexico; in LACM.

Distinctive Characters. Characters in the key will distinguish D. problematicus from D. garmani. It differs from D. splendidus primarily in the lower number of its gill rakers, its lack of supraorbital spine, and the lower position of its VLO and SAOs. Description. fin rays: dorsal 16 (17); anal 17 (16-18); pectoral 11-12. GM rakers: 4 + 1 + 9 (8). Photophores: AO 6 (7) + 5 (4-6), total 11 (10-12). Lateral-line organs: 37-38. Head. Length of head 26.5-30.5 percent of SL. Mouth large, oblique; length of upper jaw 1.3-1.4 in hi and extending 1.2-1.5 times the diameter of eye behind vertical through posterior margin of orbit. Eye of moderate size, its diameter 2.7-3.5 in length of upper jaw and 3.8-4.4 in hi. Operculum tapering

posteriorly to a sharp point somewhat above PLO. Fins. Origin of dorsal fin slightly in advance of base of ventral fin. Origin of anal fin in advance of vertical through end of base of dorsal fin. Pectoral fin not reaching base of ventral fin. Base of adipose fin well in advance of end of base of anal fin. Luminous Organs. A very small, round structure immediately dorsomesad to the Dn which is roughly heart-shaped, small (larger in males) and shallowly embedded in the surrounding translucent tissue. Vn 2-3 times larger than the Dn, roughly triangular, located at the anteroventral margin of the orbit, its posterior tip not reaching a vertical through the anterior margin of the pupil. A streak of luminous tissue connects Dn with Vn. PLO nearer to base of pectoral fin than to lateral line. VLO nearer to lateral line than to base of ventral fin. SAO in a straight or nearly straight, steeply ascending line; SAOi posterodorsad to VO5, about over anus; SAO2 on or slightly in advance of vertical through origin of anal fin; SAO3 over base of anal fin and 1-1.5 times its own diameter below lateral line. AOai elevated high above and somewhat in advance of AOa2; AOa2 through AOa5 evenly spaced and in a straight or gently curved line; AOafl elevated. Pol under base of adipose fin and 1-1.5 times its own diameter below lateral line. AOp

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FIGURE 63. Diaphus problematic™, a tropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and Parin et al. (1974).

evenly spaced and level; AOpi over base of anal fin. First 3 Prc evenly spaced, forming a gentle arc; Prc3-Prc4 interspace enlarged; Prc4 1-1.5 times its own diameter below lateral line. A luminous scale at PLO. Sexual Dimorphism. Differences in the luminous organs of the head between the two sexes are hardly noticeable in specimens smaller than about 55 nun. Direct comparison of individuals 65 mm and larger will show that the Dn and especially the Vn in

males are larger and more massive than those in females. Development of Headlights. The luminous organs of the head in this species and in D. garmani undergo very similar changes in their development, the only differences being the relative sizes of the two fishes at which the Vn first appears, and at which the definitive pattern and shape of these organs are attained. In D. problematic™ the Vn first appears in individuals 25-26 mm long, and the

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FIGURE 64. Diaphus adenomus: young, 96 mm.

whole system attains the adult pattern in fishes 30-32 mm long. Size. This myctophid grows to a size of about 90 mm, becoming sexually mature at sizes between 68 and 74 mm. Atlantic Distribution. Diaphus problematicus (Fig. 63) is an uncommon tropical species most abundant in the Caribbean Sea, much less so in the eastern tropics. It is absent from the Mauritanian Upwelling. Extra-Atlantic Occurrence. Diaphus problematicus occurs in equatorial waters of the eastern Indian Ocean between 6°N and 8°S. In the western part of that ocean it has been taken between the equator and 10°S and in the Mozambique Channel to about 25°S. Elsewhere the species has been reported from Z^O'N and 3°30'N on the meridian 145°W (Hartmann and Clarke, 1975) and is known to occur in the Southeast Asian seas and the western tropical Pacific. (N) Vertical Distribution. In the WHOI collections, D. problematicus occurred between 375 and 750 m by day, with maximum concentration at about 500 m, and between 40 and 225 m at night, with maximum abundance at 100 m. Three specimens of D. problematicus were captured with opening-closing devices near

Bermuda, one at 600-650 m by day and two at 100-250 m at night. Synonyms and References: Diaphus problematicus Parr, 1928: 143, Fig. 32 (orig. descr.; 24°29'N, 77°29/W; holotype, BOG 2195); Nafpaktitis, 1968: 38, Figs. 20, 21 (key, descr., distr.). Diaphus (Lamprossa) problematicus. Fraser-Brunner, 1949: 1069, fig. (in key). Diaphus weberi Taning, 1932: 138, Fig. 10 (orig. descr.; 7°22'N, 121°16'E; holotype, ZMUC P2329219); Nafpaktitis, 1973: 20, Fig. 18 (descr. of holotype). Diaphus (Lamprossa) weberi. Fraser-Bninner, 1949: 1070, fig. (in key).

Diaphus adenomus Gilbert 1905 Figures 64, 65 Distinctive Characters. The luminous organs on the head, particularly the long one along the dorsal margin of the orbit will distinguish this fish from any other North Atlantic Diaphus. Description. Fin rays: dorsal 15 (14); anal 15 (16); pectoral 12 (11). Gill rakers: 5 + 1 + 11. Photophores: AO 6 (7) + 5 (4-6), total 11 (rarely 12).

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FIGURE 65. Diapkus aJenomus, a pseudoceanic species. Atlantic Ocean distribution, based on records from Nafpaktitis (1974).

Lateral-line organs: 37. Head. Length of head 28.5-33.5 percent of SL. Mouth large, oblique; length of upper jaw 1.3-1.4 in hi and extending 1-1.3 times the diameter of eye behind vertical through posterior margin of orbit. Eye large, its diameter 2.4-3 in length of upper jaw and 3.24 in hi. Operculum tapering posteriorly to a point at or slightly below PLO. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fins short, extending to,

or somewhat beyond PO4. Base of adipose fin somewhat in advance of vertical through end of base of anal fin. Luminous Organs. A small, shallow Dn. Vn extending along ventral and anterior border of orbit to level of Dn. A luminous organ, similar in form to Vn, between eye and supraorbital frontal ridge. This organ and the Vn are framed by black tissue and extend posteriorly to about vertical through center of lens in specimens up to approximately 95 mm long, and to vertical through posterior

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FIGURE 66. Diaphus splendidus: female, 53.5 mm.

margin of lens in larger individuals. PLO midway between base of pectoral fin and lateral line or somewhat higher. VLO midway between base of ventral fin and lateral line or somewhat higher. SAO in a straight or very nearly straight, subvertical line; SAOi well above and behind last VO; SAO3 in advance of vertical through origin of anal fin and about its own diameter below lateral line. AOai highly elevated, the series forming a trough continuous posteriorly with Pol which is 1.5-2 times its own diameter below lateral line. AOp evenly spaced, level, with AOpi behind, seldom over, end of base of anal fin. Prc evenly spaced, forming a gentle curve; Prc4 3-4 times its diameter below lateral line. A vertically elongate luminous scale at PLO. Size. A large myctophid, attaining a size of over 180 mm. Atlantic Distribution. Diaphus adenomus (Fig. 65), a pseudoceanic (land-associated) species, is known from six near-shore localities in the Atlantic: a single collection off Casablanca, three collections in the Caribbean, and two collections off the Bahamas (Nafpaktitis, 1974). Extra-Atlantic Occurrence. Diaphus adenomus is known from the Pacific Ocean off Hawaii (Gilbert, 1905; Clarke, 1973) and off Japan (Gilbert, 1913). (BC) Vertical Distribution. Clarke (1973)

thought D. adenomus to be epibenthic, occurring mostly near the bottom at depths from 180 m at night to 500-600 m by day, although specimens were taken in midwater. All Atlantic Ocean specimens were collected by bottom trawls (Nafpaktitis, 1974). Synonyms and References: Diaphus adenomus Gilbert, 1905: 592, Pi. 68, Fig. 1 (orig. descr.; Kaiwi Channel between Oahu and Molokai, 335-350 fms; holotype, USNM 5 1 5 8 8 ) ; Parr, 1929: 41 (descr. of holotype; compar. with D. anteorbitalis Gilbert 1913); Clarke, 1973: 406, 414 (depth of occur, off Hawaii); Nafpaktitis, 1974: 1, Fig. 1 (descr., distr. in North Atlantic). Diaphus anteorbitalis Gilbert, 1913: 92, Pi. 12, Fig. 1 (orig. descr.; off Shiwo Misako, 33°24'50"N, 135° 38'40"E, 253 fms; holotype, USNM 74471); Parr, 1929: 41 (char, of holotype). Diaphus (Lamprossa) anteorbitalis. Fraser-Brunner, 1949: 1073, fig. (in key).

Diaphus splendidus (Brauer) Figures 66-68

1904

Distinctive Characters. D. splendidus can readily be distinguished from D. problematicus by (a) its supraorbital spine; (b) size, structure and, especially, position and orientation of its Dn—this organ is bulkier, set in a deep recess and directed forward in D. splendidus^ whereas in D. problematicus the same organ is smaller, shallower, and directed

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laterally; (c) its high VLO, SAO3, and Pol; (d) its large triangular luminous scale at PLO, which is quite prominent in very young stages (14-15 mm); and (e) its higher number of gill rakers. Description. Fin rays: dorsal 15 (14); anal 16 (15-17); pectoral 12 (11). GUI rakers: 5 (6) + 1 + 12 (11-13), total 18 (17-19, rarely 20). Photophores: AO 6 (7) + 6 (5, rarely 7), total 12 (11, rarely 13). Lateral-line organs: 38 (37-39). Head. Length of head 28-31 percent of SL. Mouth large, its cleft oblique; length of upper jaw 1.3-1.4 in hi and extending 1.21.5 times the diameter of eye behind vertical through posterior margin of orbit. Eye of moderate size, its diameter 2.8-3.4 in length of upper jaw and 3.7-4.5 in hi. Anterior ends of frontal supraorbital ridges produced into forward directed spines. Operculum tapering posteriorly to a sharp point located very near to PLO. Fins. Origin of dorsal fin directly over or slightly in advance of base of ventral fin. Origin of anal fin on or slightly behind vertical through end of base of dorsal fin. Pectoral fin not quite reaching base of ventral fin. Base of adipose fin over end of base of anal fin. Luminous Organs. A tiny, roundish organ immediately ventromesad to supraorbital spine, difficult to discern in adult individuals. Dn well developed, round, directed forward, set in a rather deep recess immediately posterodorsad to nasal apparatus. Vn well developed, roughly triangular, its main bulk situated at the anteroventral aspect of the eye, extending dorsally between eye and nasal apparatus in the form of a strand of luminous tissue, reaching Dn in mature females, larger and more massive in mature males; posterior tip of Vn barely reaching vertical through anterior margin of pupil. PLO nearer to base of pectoral fin than to lateral line. VLO much

FIGURE 67. Diaphus spltndidus: A, sexually dimorphic Vn of male, 66 mm; B, young, 16 mm.

closer to lateral line than to base of ventral fin. SAO usually somewhat angular, with SAO2 a little in advance of straight line through SAOi and SAO8; SAOi and SAO2 in line with VO5; SAOa about over origin of anal fin and in contact with lateral line. AOai more or less abruptly elevated; AOa2 through AOa5 usually in a straight line; AOae elevated. Pol in contact with lateral line. AOp evenly spaced and level, with AOpi usually over base of anal fin. Prc forming a wide arc, with interspaces becoming progressively wider; Prc4 0.5-1 time its own diameter below midlateral line. A large, triangular luminous scale at PLO. Sexual Dimorphism. In males the Vn expands as it grows dorsally, filling the entire space between the anterodorsal margin of the orbit and the supraorbital spine. The organ begins to show signs of sexual dimorphism in males 38-40 mm long. In 4 5-mm individuals it has attained its full shape and size and the two sexes can easily be differentiated. Development of Headlights. In its early growth stages, D. splendidus has only two

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FIGURE 68. Diapbus splendidus, a tropical-semisubtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from J. Badcock (in litt.) and Gibbs et al. (1971).

luminous organs on the head, namely a Dn in its recess and a tiny roundish structure under the tip of the supraorbital spine (Fig. 67B). The Vn first appears in fish about 25 mm long as a very thin streak of luminous tissue at the anteroventral aspect of the orbit. This streak soon takes up a roughly triangular shape, with the dorsal angle of the triangle growing upward between the orbit and the nasal apparatus, until it reaches the level of the Dn and stops in females or proceeds further up in males.

Size. This myctophid grows to about 90 mm. It becomes sexually mature at sizes between 50 and 55 mm. Atlantic Distribution. Diapbus splendidus (Fig. 68) is a tropical-semisubtropical species most abundant in the Caribbean Sea and other western parts of the tropics. It is uncommon in the eastern tropics (Guinean Province). Extra-Atlantic Occurrence. Diapbus splendidus is common across the Indian Ocean between 7°N and 23 °S in the west and between about 5°N and 12°S in the east. In the west-

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FIGURE 69. Diaphus taaningi: female, 58 mm.

ern part of the ocean it is sympatric with a very similar undescribed form. The species is also common in the Southeast Asian seas and the western tropical Pacific. Further, it has been reported from 7° 30'N and 3°30'N on the meridian 145°W (Hartmann and Clarke, 1975), and a single record comes from the South Pacific at 11° GO'S, 172°37'W. (N) Vertical Distribution. Opening-closing devices caught D. splendidus in small numbers near Bermuda by day at JO0-6JO m and by night at J 0-2 JO m. In the WHOI collections, mostly from the tropics, D. splendidus occurred between 37J and 7 JO m by day, with maximum abundance at 4JO-JOO m, and between 40 and 22J m at night, with maximum abundance at 100 m. Synonyms and References: Myctophum (Nyctophus) splendidum Brauer, 1904: 392, 399, Fig. 7 (orig. descr.; "Im Atlantischen und Indischen Ozean auf verschiedenen Stationen;"). Diaphus splendidus. Parr, 1928: 123 (in key); Taning, 1928: 60 (in key); Bekker, 1967b: 106 (horiz. and vert, distr.); Nafpaktitis, 1968: 42, Figs. 2224 (key, descr., distr.). Diaphus steadi Fowler, 1934: 310, Fig. 65 (orig. descr.; 02°56'S, 118°47'30"E; holotype, USNM 93164).

Diaphus scapulofulgens Fowler, 1934: 316, Fig. 71 (orig. descr.; OS°3S'S, 122°20'E; holotype, USNM 93155). Diaphus (Lamprossa) splendidus. Fraser-Brunner, 1949: 1070, fig. (in key).

Diaphus taaningi Norman 1930 Figures 69, 70 Study Material. One hundred and forty specimens, 16-66 mm, taken by the NMFS vessel OREGON in the northern Gulf of Mexico and the Straits of Florida; in LACM.

Distinctive Characters. Characters in the key will differentiate D. taaningi from D. bertelseni. Additional differences between the two forms are to be found in the proportional dimensions presented here and under D. bertelseni. Description. Proportional dimensions are in percent of SL and based on eight specimens, 44 to 59 mm. Initial values are arithmetic means; values in parentheses represent the range of variation. Body: greatest depth 24.0 (23.2-24.9). Head: depth 23.6 (22.9-24.7). Upper jaw: length 20.2 (19.9-20.9). Distance from tip of snout to: base of pectoral fin 27.8 (27.0-29.2); base of ventral

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FIGURE 70. Diaphus taaningi, a pseudoceanic species. Distribution, based on the WHOI collections. Additional records are from Nafpaktitis (1968) and unpublished ALBATROSS IV data.

fin 42.3 (41.3-43.5); origin of anal fin 63.0 (62.1-63.9). Fin rays: dorsal 14; anal 14 (15); pectoral

11.

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10-11 (9).

Lateral-line organs: 3 6 ( 3 5 ) . Head. Length of head 28.5-30.5 percent of SL. Mouth moderately large, oblique; length of upper jaw 1.4—1.5 in hi and extend-

ing 0.5-0.6 of eye diameter behind vertical through posterior margin of orbit. Eye large, its diameter 1.9-2 in length of upper jaw and 2.7-3 in hi. Operculum tapering posteriorly to a sharp point at or somewhat above PLO. Fins. Origin of dorsal fin directly over or slightly behind base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin extending to base of ventral fin. Base of adipose fin slightly in advance of vertical through end of base of anal fin. Luminous Organs. A rather small, round,

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forward directed Dn, half the size of nasal rosette, set in a cup-shaped recess above nasal apparatus. Vn elongate, at least 4 times as large as Dn, immediately posteroventrad to nasal apparatus, occupying the anteroventral border of orbit, extending posteriorly to or somewhat beyond vertical through anterior margin of pupil. PLO nearer to base of pectoral fin than to lateral line. VLO midway between base of ventral fin and lateral line or slightly higher. SAO usually in a straight, steeply ascending line; SAOi posterodorsad to VO6; SAO3 over origin of anal fin and 1.52 times its own diameter below lateral line. First and, to a lesser degree, last AOa elevated. Pol 1.5-2 times its diameter below lateral line. AOp evenly spaced, level; occasionally AOpi over end of base of anal fin. Prc forming a gentle curve; Prc4 about 3 times its own diameter below lateral line. A roundish luminous scale at PLO. Sexual Dimorphism. In adult males the Vn is enlarged, reaching down almost to the upper jaw (Pugh, 1973). Development of Headlights. At a size of about 19 mm D. taaningi shows a distinct Dn embedded in the pale tissue of the snout and a clearly visible Vn in its future, adult position. Dark tissue completely surrounds the Dn, extends downward between olfactory organ and anterior border of eye and reaches the Vn, investing all but the ventral margin of this organ. Size. In the northern Gulf of Mexico this species seems to become sexually mature at a size of about JO mm. On the basis of southeastern Caribbean material, Pugh (1973) indicated that sexual maturity apparently is attained at a size of approximately 40 mm, "at which size secondary sexual dimorphism of the ventronasal photophore (Vn) is prominent." This fish grows to about 70 mm. Atlantic Distribution. Diaphus taaningi (Fig. 70) is a pseudoceanic (land-associated) species. In the eastern Atlantic it is known from the Gulf of Guinea to the Mauritanian

Upwelling and in the western Atlantic from the Caribbean Sea, Gulf of Mexico, and Slope Water. Diaphus taaningi is not known from outside the Atlantic Ocean. Vertical Distribution. In the WHOI collections, D. taaningi occurred by day between 32 5 and 47 5 m and at night between 40 and 250 m, with maximum abundance at 100 m. In the atypical Cariaco Trench, which is anoxic below 400 m and high in free hydrogen sulfide below 375 m, D. taaningi occurred at about 250 m by day and in the upper 50 m at night (Baird et al., 1974). Synonyms and References: Diaphus taaningi Norman, 1930: 332, Fig. 30 (orig. descr.; 00°36'S, 8°28'E); Nafpaktitis, 1968: 45, Figs. 25, 26 (key, descr., distr.); Pugh, 1973: 362, Fig. 1 (occur, over Cariaco Trench, Venezuela; char.); Baird et al., 1974 (ecology in Cariaco Trench); Baird et al., 1975 (diet, feeding chronology in Cariaco Trench). Diaphus (Panthophos) taaningi, Fraser-Brunner, 1949: 1069, fig. (in key).

Diaphus bertelseni Nafpaktitis 1966 Figures 71, 72 Study Material. Four specimens: 1 (21), WHOI vessel CHAIN, Sta. RHB 1263, 12°58'N, 73°34'W; 2 (34-35), NMFS vessel OREGON, Sta. 2191, 25°11/N, 89°50'W; and 1 (80), NMFS vessel SILVER BAY, Sta. 2583, 32°11'N, 77°24'W; in LACM.

Distinctive Characters. Characters in the key will differentiate D. bertelseni from D. taaningi. Additional differences between the two forms are to be found in the proportional dimensions presented below and under D. taaningi. Description. Proportional dimensions are in percent of SL and based on 5 specimens, 21-80 mm. Initial values are arithmetic means; values in parentheses represent the range of variation. Body: greatest depth 27.3 (26.1-28.6). Head: depth 26.6 (2J.9-27.6).

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FIGURE 71. Diapbus bertelseni: male, 80 nun.

Upper jaw: length 23.8 (23.1-24.5). Distance from tip of snout to: base of pectoral fin 33.8 (32.5-34.7); base of ventral fin 50.0 (48.4-52.4); origin of anal fin 69.1 (67.2-71.4). Fin rays: dorsal 14—15; anal 15; pectoral 11. Gill rakers: 5 + 1 + 12. Photophores: AO 6 + 4. Lateral-line organs: 35 (34). Head. Length of head 33-35 percent of SL. Mouth moderately large, somewhat oblique; length of upper jaw 1.4—1.5 in hi and extending 0.6-0.9 times the diameter of eye behind vertical through posterior margin of orbit. Eye rather large, its diameter 2.1-2.5 in length of upper jaw and 3-3.6 in hi. Operculum abruptly tapering to a point above PLO. fins. Origin of dorsal fin somewhat in advance of base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin not reaching base of ventral fin. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. Dn % to % the size of nasal rosette, round, forward directed, in cupshaped recess. Vn elongate, between nasal apparatus and anteroventral border of orbit, barely reaching vertical through anterior mar-

gin of pupil posteriorly. Body photophores large and very close to each other. PLO much nearer to base of pectoral fin than to lateral line. VLO nearer to base of ventral fin than to lateral line. SAO in a straight line or nearly so; SAOi posterodorsad to VO6; SAOs over origin of anal fin and 3-3.5 times its own diameter below lateral line. AOa usually forming a curve, sometimes continuous with Pol which is about 3 times its own diameter below lateral line. AOp level and less than % the diameter of a photophore apart from each other (in contact with each other in individuals less than about 40 mm); AOpi over or immediately behind end of base of anal fin. Prc forming a slightly curved line, with spaces between them becoming progressively wider; Prc4 2.5-3 times its own diameter below lateral line. A large, triangular luminous scale at PLO. Development of Headlights. At a size of about 9 mm, D. bertelseni already show a prominent, spherical or lentil-shaped Dn which is only a little smaller than the nasal rosette. The Vn appears in individuals about 20 nun long in the form of an elongate, thin patch of luminous tissue, attenuated dorsally into a streak extending upwards along the

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FIGURE 72. Diaphus bertelseni, a questionably tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from R. Baird (in litt.), Gibbs et aL (1971), and Nafpaktitis (1968).

anterior margin of the orbit until it reaches the Dn. A little later, however, the thin streak between Vn and Dn disappears and the two organs remain widely separated. Size. The largest specimen found in the collections examined was an 80-mm-long male. The size at which this species reaches sexual maturity is unknown. Atlantic Distribution. Diaphus bertelseni (Fig. 72) is a rare species questionably tropical-subtropical. The few WHOI records come

almost entirely from western Atlantic provinces as do the few DANA ones (Nafpaktitis, 1968). Extra-Atlantic Occurrence. Clarke (1973) reported this species from near Oahu. (N) Vertical Distribution. All WHOI specimens of D. bertelseni were collected at night between 60 and 17 J m. The DANA, however, took three Atlantic specimens between 200 and 300 m during the day (600 m.w.o.) (Nafpaktitis, 1968).

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FIGURE 73. Diaphus luetkeni: female, 48 mm.

References: Diaphus bertelseni Nafpaktitis, 1966: 405, Figs. 2-5 (orig. descr.; 00°15'S, 18°35'W; holotype, MCZ 43121); Nafpaktitis, 1968: 48, Figs. 27, 28, 52 (key, descr., distr.); Clarke, 1973: 406, 411 (depth of occur., off Hawaii); Krefft and Bekker, 1973: 176 (ref., distr.).

Diaphus luetkeni (Brauer) 1904 Figures 73-75 Distinctive Characters. Characters in the key will differentiate D. luetkeni from any of its North Atlantic congeners. Description. Fin rays: dorsal 16 (15-17); anal 15 (1416); pectoral 11. Gill rakers: 6-7 + 1 + 13-14 (15), total 20-22 (23). Photophores: AO 6 (5-7) + 4-5 (6), total 10-11 (12). Lateral-line organs: 36 (35). Head. Length of head 31.5-34 percent of SL. Mouth very large, oblique; length of upper jaw 1.2-1.4 in hi and extending 1.21.5 times the diameter of eye behind vertical through posterior margin of orbit. Eye of moderate size, its diameter 2.9-3.6 in length of upper jaw and 3.8-4.5 in hi. Operculum

evenly and gradually tapering to a point usually posterodorsad to PLO. Fins. Origin of dorsal fin directly over or slightly behind base of ventral fin. Origin of anal fin well in advance of end of base of dorsal fin. Pectoral fin short, extending to or a little beyond PO4. Ventral fins long, extending beyond origin of anal fin. Base of adipose fin about over base of anal fin. Luminous Organs. A lentil-shaped Dn, about % the size of nasal rosette, directed forward, in a recess immediately dorsad to nasal apparatus. Vn long, extending along nearly entire ventral border of orbit, terminating behind vertical through posterior margin of pupil, its dorsal border with 3-5 small, round projections, appearing as if budding off from main body of organ and protruding into iris. PLO nearer to base of pectoral fin than to lateral line. VLO somewhat nearer to lateral line than to base of ventral fin. SAO in a straight or nearly straight, subvertical line; SAOi at same level with VO6, sometimes slightly higher; SAO3 on or a little in advance of vertical through origin of anal fin and about its own diameter below lateral line. First AOa elevated; last AOa usually somewhat raised. Pol about its own diameter below lateral line. AOp evenly spaced and level;

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FIGURE 74. Diapbus luetkeni: sexually dimorphic Vn of male, 56 mm.

AOpi usually over end of base of anal fin. Prc forming a gentle curve with first 3 organs evenly spaced; Prc8-Prc4 interspace distinctly enlarged; Prc4 about 1.5 times its own diameter below lateral line. A small luminous scale at PLO. Sexual Dimorphism. This is reflected in the shape and, especially, size of the Vn. In adult females the Vn is a rather narrow band of luminous tissue, uniformly wide throughout its length, and beginning anteriorly well below and behind the nasal apparatus. The same organ in adult males is wide, much more so anteriorly than posteriorly, reaching the nasal apparatus with which it is in broad contact (Fig. 74). In 30-mm-long males the Vn is already larger than that in females of comparable size, and 3 5-nun-long specimens can be sexed without difficulty. Development of Headlights. At a size of 10-11 mm, D. luetkeni show a well-developed, round Dn, equal in size to, or larger than, the nasal rosette. A prominent strand of dark tissue frames the Dn dorsally and laterally, continues downward along the anterior, anteroventral and ventral borders of the orbit until it reaches a point somewhere between the center and the posterior margin of the pupil. At its posterior end the dark strand has already formed one or even two small folds

protruding into the iris. With growth, more of these folds are formed in a forward direction, and as new folds are being formed the older, posterior ones usually grow into welldefined round structures consisting of a patch of luminous tissue framed by dark tissue. By then the fish is about 18 mm and a long, narrow streak of luminous tissue appears underlying the round structures. Size. Judging from the degree of development of the gonads, D. luetkeni attains sexual maturity at sizes between 42 and 45 mm. It does not seem to grow much larger than about 60 mmAtlantic Distribution. Diaphus luetkeni (Fig. 75) is a tropical species and a ranking myctophid in the Atlantic Tropical Region. It reaches its greatest abundance in the east (Guinean Province) and diminishes in abundance westward through the Amazonian and Lesser Antillean Provinces and Caribbean Sea. Although most tropical species are much more abundant in the Caribbean Sea than in the Gulf of Mexico, the reverse seems to be true of D. luetkeni. Extra-Atlantic Occurrence. Diaphus luetkeni is one of the commonest myctophids in the tropical Indian Ocean. It has been collected across the entire ocean from Zanzibar to Sumatra between 10°N and 12°S. In the west its range extends into the Mozambique Channel and south in the Agulhas Current to about 36°S. The species is also common in the Southeast Asian seas and the western tropical Pacific. It has been reported from the central tropical Pacific (Hartmann and Clarke, 1975) and available data indicate that it occurs eastward to about 105°W. (N) Vertical Distribution. In the WHOI collections, D. luetkeni occurred between 375 m and 750 m by day and between 40 and 325 m at night, with maximum abundance at 50-100 m. A single specimen was taken by an openingclosing device at 90 m by night near Bermuda.

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FIGURE 75. Diaphus luetkeni, a tropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Badcock (1970), Gibbs et al. (1971), and Nafpaktitis (1968).

Synonyms and References: Myctophum (Nyctopbus) liitkcni Brauer, 1904: 393, 400 (orig. descr.; "Auf mehreren Stationen im Indischen Ozean"). Diaphus liitktni. Parr, 1928: 118 (in key); Taring, 1928: 59 (in key); Norman, 1930: 333 (records from east, equat. Atlantic); Bekker, 1967b: 99 (tazon. discus., records from Atlantic Ocean, vert, distr.); Nafpaktitis, 1968: 51, Figs. 29-31 (key, descr., distr.). Diaphus (Diaphus) lutkeni. Fraser-Brunner, 1949: 1076, fig. (in key). Diaphus liitktni pacificus Kulikova, 1961: 24, Fig. 16

(orig. descr.; subspec. based on male D. liitkcni\ Pacific Ocean).

Diaphus termophilus Tuning 1928 Figures 76, 77 Distinctive Characters. Characters in the key will separate D. termophilus from D. luetkeni. Description. Fin ray si dorsal 14 (13); anal I f ; pectoral 11 (12).

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FIGURE 76. Diaphus termophilus: male, 46 mm.

Gill raksrs: 8 (7-9) + 1 + 15 (14-16), total 23-25 (26). Photophores: AO 6 (5) + 4-5, total 1011. Lateral-line organs: 36 (35). Head. Length of head 32-34 percent of SL. Mouth very large, oblique; length of upper jaw 1.2-1.3 in hi and extending 1.1-1.2 times the diameter of eye behind vertical through posterior margin of orbit. Eye rather large, its diameter 2.6-2.9 in length of upper jaw and 3.1-3.6 in hi. Operculum evenly tapering to a point at or a little above PLO. Fins. Origin of dorsal fin somewhat behind base of ventral fin. Origin of anal fin on or slightly behind vertical through end of base of dorsal fin. Pectoral fin almost reaching base of ventral fin. Ventral fins long, reaching origin of anal fin in juveniles, extending about to AOai in adult individuals. Base of adipose fin about over end of base of anal fin. Luminous Organs. A small, lentil-shaped, forward-directed Dn, about % the size of a body photophore, set in a shallow recess under anterior edge of supraorbital frontal ridge. Vn much larger than Dn, roughly elliptical in shape, on ventral border of orbit about under center of lens. A narrow strand of dark tissue extending between Dn and Vn along border of orbit, with 2 or 3 minute,

roundish, apparently luminous organs embedded in, or closely associated with it. PLO nearer to base of pectoral fin than to lateral line. VLO midway between base of ventral fin and lateral line or slightly higher. SAO on a straight or nearly straight, subvertical line; SAOi close behind and usually at same level with VO6; SAO3 on or slightly in advance of vertical through origin of anal fin and 2-2.5 times its own diameter below lateral line. AOa forming an arc. Pol about 1.5 times its diameter below lateral line. AOp entirely behind base of anal fin, evenly spaced and level. Prc forming an arc, with Prc8Prc4 interspace somewhat enlarged; Prc4 about twice its own diameter below lateral line. A small luminous scale at PLO. Sexual Dimorphism. This is reflected in the size of the Vn which is much thicker and about 3 times as large in adult males as it is in females of comparable size. Development of Headlights. At a size of approximately 12 mm, D. termophilus has a relatively large, spherical Dn about one-half the size of the nasal rosette, surrounded by dark tissue and characteristically bulging forward. Also, in fishes of this size the Vn has already appeared on the ventral margin of the orbit, thus providing an excellent diagnostic feature.

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FIGURE 77. Diaphus termophilus, a questionably tropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et aL (1971) and Krefft and Bekker (1973).

Size. This fish grows to about 75 mm. Atlantic Distribution. Diaphus termophilus (Fig. 77) fits no distribution pattern very well, but is tentatively classed as tropical. Our specimens come mainly from three tropical provinces, Caribbean Sea, Lesser Antillean Province, and Straits of Florida, yet are lacking from the other tropical provinces, the Amazonian and Guinean ones. In addition, there are significant numbers of D. termophilus from the southern part of the Southern North African Subtropical Sea.

Extra-Atlantic Occurrence. Diaphus termophilus does not seem to occur in the Indian Ocean, where it is replaced by a very closely related undescribed form. The species is found in the Southeast Asian seas and the western tropical Pacific between New Caledonia and New Zealand and in the Tasman Sea to about 34°S. (N) Vertical Distribution. In the WHOI collections, D. termophilus occurred by day between 325 and 850 m, with maximum abundance at 400-500 m, and at night between

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FIGURE 78. Diaphus minax: holotype (MCZ 44952), female, 45.5 mm.

40 and 225 m, with maximum abundance at 100 m. Opening-closing devices caught one specimen at night near Bermuda at 230 m and one at 290 m near sunrise. Synonyms and References: Diaphus termophilus Taning, 1928: 59 (orig. descr.; in key); Bekker, 1967b: 99 (records from North Atlantic); Nafpaktitis, 1968: 54, Figs. 32, 33 (key, descr., distr. in North Atlantic); Nafpaktitis, 1973: 26, Fig. 24 (desig. and descr. of lectotype: 14°38' N, 61°16'W, 1,000 m.w.o.; ZMUC P2329218); KrefFt and Bekker, 1973: 180 (synon., ref., distr.). Diaphus bypolucens Parr, 1928: 130, Fig. 24 (orig. descr.; 23°58'N, 77°26/W, 7,000 f.w.o.; holotype, BOC 2197). Diaphus (P ant hop ho s) termophilus. Fraser-Brunner, 1949: 1068, fig. (in key; places D. hypolucens Parr 1928 in synon. of D. termophilus).

Diaphus minax Nafpaktitis 1968 Figures 78, 79 Study Material. Ten specimens: 4 (34-39) and 5 (42-53), taken by the WHOI vessel CHAIN at 13° OO'N, 73°26'W (Sta. RHB 1262) and at 13°07'N, 78°23'W (Sta. RHB 1274), respectively; 1 (66.5) taken by the NMFS vessel OREGON at 18°26^N, 67° 10.5'W (Sta. 2654); in LACM.

Distinctive Characters. D. minax is readily distinguishable from D. hertelseni and D. taaningi by its larger Dn and, especially, Vn, and from D. lucidus by its smaller Dn, shorter and deeper head, lower VLO, SAO8 and Pol, and lower numbers of dorsal and anal fin rays. Description. Fin rays: dorsal 14 (13); anal 14 (13); pectoral 11. Gill rakers: 6 (J) + 1 + 12-13 (11-14), total 19-20 (18-21). Photophores: AO 6 (J) + 5 (4), total 11 (10). Lateral-line organs: 35-36. Head. Head almost as deep as it is long, its length 28.5-30.5 percent of SL. Mouth short; length of upper jaw 1.4-1.6 in hi and extending 0.3-0.4 times the diameter of eye behind vertical through posterior margin of orbit. Eye large, its diameter 1.6-1.9 in length of upper jaw and 2.6-2.8 in hi. Operculum ending posteriorly in a sharp point at or slightly above PLO. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin behind base of

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FIGURE 79. Diapkus minax, a questionably pseudoceanic species. Distribution, based on WHOI collections and records from R. Baird (in litt.), Nafpaktitis (1968), and unpublished ANTON BRUUN data.

dorsal fin. Pectoral fin extending to base of ventral fin. Base of adipose fin in advance of vertical through end of base of anal fin. Luminous Organs. A round, forward directed Dn, about equal in size to nasal rosette, set in a recess above nasal apparatus. Vn large, beginning immediately under Dn and extending along anterior and anteroventral orbital margin, terminating in advance of vertical through anterior margin of pupil. PLO midway between base of pectoral fin and lateral line or a little lower. VLO midway between

base of ventral fin and lateral line. SAO in a straight line or very nearly so; SAd close behind and above VO6; SAO3 about over origin of anal fin and 1-2 times its own diameter below lateral line. AOai highly and abruptly elevated; last 3 AOa forming an ascending arc sometimes continuous with Pol which is 1-1.5 times its own diameter below lateral line. AOp evenly spaced and level; AOpi behind, seldom over, end of base of anal fin. Prc forming a slightly curved, ascending line, with Prc4 2-3 times its own

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^pn FIGURE 80. Diaphus lucidus: female, 60 mm; A, front view of head of specimen, 66.5 mm.

diameter below lateral line. A large, rounded luminous scale at PLO. Size. The largest specimen known measures 66.5 mm. Atlantic Distribution. Diaphus minax (Fig. 79) is known from but nine collections in the Caribbean Sea, the eastern Gulf of Mexico (R. C Baird, University of South Florida, personal communication), and the Straits of Florida. Although 14 of the 16 known specimens were collected in midwater trawls, it is possible that D. minax is pseudoceanic (land-associated) in the sense of Krefft (1974). D. minax has not been reported from outside the North Atlantic. Vertical Distribution. In the WHOI collections, all specimens of D. minax were taken at night between 60 and 12 J m. Reference: Diaphus minax Nafpaktitis, 1968: 57, Fig. 34 (orig. descr.; 26°34.5'N, 79°04.5'W; holotype, MCZ 44952).

Diaphus lucidus (Goode and Bean) 1896 Figures 80, 81 Study Material. Thirty specimens, 21-93 mm, taken by the NMFS vessel OREGON in the southwestern Caribbean and the northern Gulf of Mexico; in LACM.

Distinctive Characters. This species is distinguished from D. minax by its larger Dn, higher position of its VLO and higher numbers of its dorsal and anal fin rays. Its large Dn and lack of Ant and enlarged teeth on the dentary separate it from D. fragilis. Description. Fin rays: dorsal 17; anal 17-18; pectoral 11 (12). GUI rakers: 5 (6) + 1 + 11 (10-12); total 17(16-19). Photophores: AO 7-8 + 4-5 (6), total 12 (13). Lateral-line organs: 38-39. Head. Length of head 27.5-30.5 percent of SL. Mouth moderately large, oblique; length of upper jaw 1.3-1.4 in hi and extending 0.9-1.2 times the diameter of eye

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FIGURE 81. Diapkus lucidus, a tropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Badcock (1970, and unpublished), Gibbs et al. (1971), Rotthaus (1972a), and Nafpaktitis (1968).

behind vertical through posterior margin of orbit. Eye of moderate size, its diameter 2.63.2 in length of upper jaw and 3.7-4.4 in hi. Operculum with a weakly serrate lobe posterodorsally, tapering posteriorly to a point below PLO. Fins. Origin of dorsal fin directly over or slightly in advance of base of ventral fin. Origin of anal fin in advance of vertical through end of base of dorsal fin. Pectoral fin not reaching base of ventral fin. Base of

adipose fin somewhat in advance of vertical through end of base of anal fin. Luminous Organs. Dn round, very large, almost % the diameter of eye, its dorsal half above anterior edge of supraorbital frontal ridge and, in adult individuals, reaching median ethmoid crest. Vn long and narrow, not spreading behind nasal apparatus, extending along anterior and anteroventral border of orbit, its posterior end not reaching vertical through anterior margin of pupil. Dn and

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Vn in contact with each other immediately dorsolaterally to nasal apparatus. Body photophores small, distinctly smaller than average Diapbus photophores. PLO midway between base of pectoral fin and lateral line or slightly higher. Distance between VLO and base of ventral fin about 3 times as great as that between VLO and lateral line. SAO in a straight or nearly straight, subvertical line; SAOi well behind and somewhat higher than VO6; SAO3 on or slightly behind vertical through origin of anal fin, in contact with or its own diameter below lateral line. AOai elevated well above and somewhat in front of AOa2; rest of organs of same series in a straight or slightly curved line. Pol in contact with or less than its own diameter below lateral line. AOp evenly spaced; AOpi sometimes over end of base of anal fin. Prc forming a curved, ascending line, with Prc8-Prc4 interspace often enlarged; Prc4 1.5-3 times its diameter below lateral line. A luminous scale at PLO. Development of Headlights. Specimens 2 526 mm long, have a round, well-defined Dn, about equal in size to the nasal rosette. Furthermore, the Vn, in the form of a thin streak, can be found mesad to the well-developed, broad band of dark tissue which extends along the entire anterior border of the orbit. Size. This lanternfish attains a size of over 115 mm. It reaches sexual maturity at sizes between 90 and 100 mm. Atlantic Distribution. Diaphus lucidus (Fig. 81) is a tropical species nowhere common, but reaching its greatest abundance in the Caribbean Sea. It occurs in the Gulf of Mexico, and Gulf Stream waifs are not uncommon. It does not occur in the Mauritanian Upwelling and is generally absent off west Africa. Extra-Atlantic Occurrence. Diaphus lucidus has been taken in equatorial waters across the Indian Ocean. However, west of about 70°E the range expands, mainly southward. The species is not uncommon in the

Mozambique Channel, and specimens have been collected southeast of Cape Agulhas at about 36°S, 23°E. Elsewhere, D. lucidus occurs in the Southeast Asian seas and the southwestern tropical Pacific. It has also been reported from near 3°30'N, 145°W (Hartmann and Clarke, 1975) and available data indicate that it occurs east to at least 120°W. (N) Vertical Distribution. In the WHOI collections, D. lucidus occurred between 425 and 750 m by day and between 40 and 550 m at night, with maximum concentration at 100 m. Larger subadults and adults were in the deeper parts of the range both day and night. Two specimens were taken with an opening-closing device at 175 m by night near Bermuda. Synonyms and References: Aethoprora lucida Goode and Bean, 1896: 87, PL 27, Fig. 102 (orig. descr.; 19°45'N, 75°04'W; holotype, USNM 44084). Diaphus lucidus. Taning, 1928: 61 (in key); Parr, 1928: 141, Fig. 31 (char.); Parr, 1929: 44 (exam, of type); Bekker, 1967b: 107 (records from South Atlantic); Nafpaktitis, 1968: 59, Figs. 35-37 (key, descr., distr. in North Atlantic); Kotthaus, 1972a: 12 (record from east. North Atlantic, char., photo of otolith); Krefft and Bekker, 1973: 178 (synon., ref.). Diaphus monodi Fowler, 1934: 306, Fig. 62 (orig. descr.; Tanon Strait, east coast of Negros, Philip., 295 fms; holotype, USNM 92315). Diapbus reidi Fowler, 1934: 309, Fig. 64 (orig. descr.; 13°35'30"N, 121°48'E, 181 fms; holotype, USNM 93154). Diaphus (Lamprossa) lucidus. Fraser-Brunner, 1949: 1071, fig. (in key).

Diaphus fragilis Tining 1928 Figures 82-84 Distinctive Characters. Characters in the key will separate D. fragilis from D. perspicttlatus. Description. Fin rays: dorsal 17-18 (19); anal 17-18; pectoral 12 (11-13).

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FIGURE 82. Diaphus fragilis: female, Jl.S mm.

Gill rakers: 5 (6) + 1 + 11-12, total 1718 (19). Photophores: AO 6 (7) + 5 (4-6), total 11 (12). Lateral-line organs: 36-37. Head. Length of head 28-32.5 percent of SL. Mouth large, oblique; length of upper jaw 1.3-1.5 in hi and extending 0.7-1 time the diameter of eye behind vertical through posterior margin of orbit; dentary with inner series of enlarged, sharp, forward-bent teeth. Eye rather large, its diameter 2.3-2.9 in length of upper jaw and 3.2-4 in hi. Operculum evenly tapering posteriorly to a point located about midway between PLO and base of pectoral fin. Fins. Origin of dorsal fin usually slightly in advance of base of ventral fin. Origin of anal fin on or somewhat in advance of vertical through end of base of dorsal fin. Pectoral fin not reaching base of ventral fin. Base of adipose fin in advance of vertical through end of base of anal fin. Luminous Organs. A rather large, forwarddirected Dn, equal in size to or somewhat larger than nasal rosette. Vn superficially continuous with Dn, extending along anterior and anteroventral border of orbit, ending posteriorly well in advance of vertical

through anterior margin of pupil. A roughly triangular Ant dorsolaterally to and in contact with Dn. PLO nearer to lateral line than to base of pectoral fin. VLO midway between base of ventral fin and lateral line, or slightly

FIGURE 83. Diaphus fragilis: A, enlarged teeth on lower jaw; B, young, 19 mm.

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FIGURE 84. Diapbus fragilis, a tropical species. Atlantic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et al. (1971).

higher. SAO in a straight or very nearly straight, subvertical line; SAOi above and behind VO5; SAO3 directly over or slightly in advance of origin of anal fin and immediately below lateral line. AOai abruptly and highly elevated above and slightly in front of AOa2; last AOa also elevated. Pol somewhat in advance of base of adipose fin and immediately below lateral line. AOpi usually in front of, sometimes on or behind, vertical through end of base of anal fin. Prc forming a gentle arc, with interspaces becoming pro-

gressively larger; Prc4 about twice its own diameter below lateral line. A roundish luminous scale at PLO. Sexual Dimorphism. This is reflected primarily in the size of the Ant, which is conspicuously larger and more sharply delineated in adult males than in females of comparable sizes. Development of Headlights. In 19-mmlong specimens both the Dn and Vn are rather well-developed and quite clearly suggest the adult pattern of these two organs (Fig. 83B).

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FIGURE 85. Diaphus perspicillatus: female, 52 mm.

The Ant appears in fishes about 32 mm long and is clearly distinct in individuals about 37 mm long. Size. This fish grows to a size of about 90 mm. Sexual maturity is attained at sizes between 65 and 70 mm. Atlantic Distribution. Diaphus fragilis (Fig. 84) conforms closely to the tropical pattern. It is missing from the Mauritanian Upwelling and, indeed, may live nowhere close to the continental slope of west Africa. The species is of little importance in the Gulf of Mexico. It is waifed to some extent by the Gulf Stream. Extra-Atlantic Occurrence. Diaphus fragilis is quite common in equatorial Indian Ocean waters from about 55°E to 106°E between 8°N and 12 °S. Over most of its range it co-occurs with its close relative D. thiollierei Fowler. However, with the exception of a single record from near the Comoros Islands, D. fragilis, unlike D. thiollierei, has not been taken west of about 55°E. In the eastern Indian Ocean and the western IndoMalay region the two forms become difficult to differentiate from each other. D. fragilis has also been collected in the western tropical Pacific (Nafpaktitis, unpublished) , and has been reported from near Ha-

waii (Clarke, 1973), and from 12°N to 3° 30'S along the meridian 145 °W (Hartmann and Clarke, 1975). It would certainly be interesting to re-examine the central Pacific material for possible D. thiollierei. (N) Vertical Distribution. In the WHOI collections, D. fragilis occurred between 375 and 750 m by day and between 40 and 125 m at night, with maximum abundance at 75 m. Opening-closing devices captured a few specimens at night in the upper 150 m near the Canary Islands. Synonyms and References: Diaphus fragilis Tailing, 1928: 61 (orig. descr.; in key); Bekker, 1967b: 107 (record from equat. Atlantic); Nafpaktitis, 1968: 63, Figs. 38-40 (key, descr., distr.) ; Nafpaktitis, 1973: 23, Fig. 21 (desig. and descr. of lectotype: 12°11/N, 3S°49'W, 1,000 m.w.o.; ZMUC P2329202); Clarke, 1973: 406, 412 (depth of occur., seasonal abund., off Hawaii).

Diaphus perspicillatus (Ogilby) 1898 Figures 85-87 Distinctive Characters. Characters in the key will differentiate D. perspicillatus from D. fragilis and D. effulgens. Description. Fin rays: dorsal 16-17 (15); anal (16); pectoral 11-12.

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FIGURE 86. Diaphus perspicillatus: A, front view of head of male, 53 mm. B, young, 17 mm.

Gill rakers: 9-10 + 1 + 16-17 (18), total 26-28 (29).

Photophores: AO 6 (5-7) + 5 (4-6), total 11 (10-12). Lateral-line organs: 3 7 ( 3 6-3 8). Head. Length of head 31-35 percent of SL. Mouth moderately large; length of upper jaw 1.4-1.5 in hi and extending 0.6-0.8 of the diameter of eye behind vertical through posterior margin of orbit. Eye large, its diameter 1.9-2.3 in length of upper jaw and 2.8-3.3 in hi. Operculum rounded and feebly serrate (in adults) dorsally, tapering to a point posteriorly. Fins. Origin of dorsal fin in advance of base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin not quite reaching base of ventral fin. Base of adipose fin over end of base of anal fin. Luminous Organs. Dn large, thick, directed forward and roughly rectangular in shape, its dorso- and ventromedial corners in contact with median ethmoid crest (Fig. 86A). Vn equally large and massive, extending behind olfactory organ to ethmoid crest, in contact with Dn and continuing along anteroventral border of orbit, terminating in advance of vertical through anterior margin of pupil. A well-developed Ant in contact with Dn. PLO midway between base of pectoral fin and lateral line or somewhat higher. VLO distinctly nearer to base of ventral fin than

to lateral line. SAO on a straight or nearly straight, subvertical line; SAOi behind and a little higher than VO5; SAO3 on or slightly in advance of vertical through origin of anal fin and in contact with lateral line. AOai elevated above and somewhat in advance of AOa2; last AOa also elevated. Pol in contact with, or less than its own diameter below lateral line. AOpi behind, seldom over, end of base of anal fin. Prc forming a gentle arc, with Prc4 1.5-2.5 times its own diameter below lateral line. A luminous scale at PLO. Sexual Dimorphism. In adult males the Ant is larger and more sharply delineated than in females of comparable sizes. Development of Headlights. Specimens 1213 mm long show a relatively large Dn and a strand of dark tissue extending along the entire anterior and anteroventral border of the orbit. In individuals about 17 mm long a thin streak of luminous tissue can be found running parallel and anteromesad to the strand of dark tissue (Fig. 86B). This streak of luminous tissue, which appears to be continuous with the Dn, is the incipient Vn. From the 17-mm stage until a size of approximately 24 mm, when the Ant becomes distinguishable, the luminous organs of the head look similar to those of D. fragilis. Within the size range of 26-32 mm, the Dn and Vn grow rapidly; the Dn acquires its rectangular shape and the Vn spreads behind the olfactory ap-

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FIGURE 87. Diaphus pmpicilUtus, a tropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and Parin et al. (1974).

paratus, both organs eventually coining into contact with the median ethmoid ridge. Size. This fish does not seem to grow much larger than 70 mm. It apparently reaches sexual maturity at sizes between 50 and 55 mm. Remarks. A comparison of a detailed drawing of the mutilated holotype of Ogilby's Aethoprora perspicillata with specimens from off Sydney, Australia (both kindly provided by John R. Paxton of the Australian Museum) and with specimens of D. elucens from the

Atlantic and Indian Oceans revealed no differences. Therefore, Brauer's D. elucens is here placed in the synonymy of D. perspicillatus (Ogilby) 1898. Atlantic Distribution. Diaphus perspicillatus (Fig. 87) is an uncommon tropical species nowhere more abundant than in the Caribbean Sea. It is a frequent waif in the Gulf Stream and apparently also in the Brazil Current. It is absent from the Mauritanian Upwelling and occurs but little in the Gulf of Mexico.

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FIGURE 88. Diaphus effulgens:

young female, 72 mm.

Extra-Atlantic Occurrence. Diaphus perspicillatus has been collected in the western Indian Ocean west of 70 °E between 7°N and 25 °S. In the Pacific, the species is quite common off the east coast of Australia to about 35°S. It has been reported from near Hawaii (Clarke, 1973) and from 3°30/N, 145°W (Hartmann and Clarke, 1975). Records from as far north as 30°N in the eastern and western Pacific, and from as far south as 22°S in the central and 12°S in the eastern Pacific need to be confirmed. (N) Vertical Distribution. In the WHOI collections, D. perspicillatus occurred between 375 and 750 m by day, with maximum abundance at 400-500 m, and between the surface and 125 m at night, with maximum abundance at 75 m. Four specimens of D. perspicillatus were captured with opening-closing devices near Bermuda, one (possibly a contaminant) at 1,500-1,550 m by day and three at 20-70 m at night. Synonyms and References: Aethoprora perspicillata Ogilby, 1898: 36 (orig. descr., type-locality: Lord Howe Island ["... having been washed ashore after the recent heavy gale"]; holotype, Queensland Museum No. I. 794 ["... badly mutilated"]).

Myctophum (Nyctophus) elucens Brauer, 1904: 392, 401, Fig. 8 (orig. descr., Indian Ocean). Diaphus elucens. Parr, 1928: 121, 138 (key; taxonomic discussion); Bekker, 1967b: 107 (records from west equat. Atlantic; depths of capture); Nafpaktitis, 1968: 66, Figs. 41—43 (key; descr.; distr. in the North Atlantic); Clarke, 1973: 406, 413 (growth; vertical distr. off Hawaii). Diaphus (Lamprossa) perspicillatus. Fraser-Brunner, 1949: 1072, fig. erroneous. Diaphus (Lamprossa) elucens. Fraser-B'runner, 1949: 1073, fig. (in key).

Diaphus effulgens (Goode and Bean) 1896 Figures 88-90 Study Material. Four specimens, 62-139 mm, taken by the NMFS vessel OREGON in the western Caribbean Sea and the northern Gulf of Mexico; in LACM.

Distinctive Characters. Characters in the key will separate this species from D. fragilis and D. perspicillatus. From D. roei it is distinguished by its lower PLO and SAO8, its Ant, and lower gill-raker counts. Description. Fin rays: dorsal 16 (15); anal 15 (14); pectoral 12 (11). Gill rakers: 6 - 7 + 1 + 13 (12-14), total 20-21 (19-22). Photophores: AO 6 (5-7) + 5 (6), total 11 (12).

Fishes of the Western North Atlantic ,.-• nr

FIGURE 89. Diaphus effulgent:

147 j*"***^

A, front view of head of female in Fig. 88; B, young, 19 mm.

Lateral-line organs: 36-37. Head. Length of head 28.J-33 percent of SL. Mouth moderately large; length of upper jaw 1.4-1.6 in hi and extending O.J-0.7 of the diameter of eye behind vertical through posterior margin of orbit. Eye very large, its diameter 1.8-2 in length of upper jaw and 2.6-3 in hi. Operculum tapering posteriorly to a point at PLO. Fins. Origin of dorsal fin in advance of base of ventral fin. Origin of anal fin on or behind vertical through end of base of dorsal fin. Pectoral fin nearly reaching base of ventral fin in fish smaller than about 60 mm, extending to a little beyond PO4 in larger individuals. Base of adipose fin on or somewhat in advance of vertical through end of base of anal fin. Luminous Organs. Dn very large, massive, directed forward, its entire medial border in contact with median ethmoid crest, and extending considerably higher than dorsal margin of orbit (Fig. 89A). Vn also very large and massive, occupying entire lower half of snout, spreading behind nasal apparatus to ethmoid crest, continuing along anteroventral border of orbit, terminating just in front of vertical through anterior margin of pupil. Dn and Vn in contact with each other. Ant well developed, large, roughly triangular, in contact with Dn at dorsolateral margin of of latter. PLO nearer to base of pectoral fin

than to lateral line. VLO midway between base of ventral fin and lateral line or slightly lower. SAO on a straight or very nearly straight, subvertical line; SAOi behind and above VO6; SAO3 about over origin of anal fin and 1.5-3 times its own diameter below lateral line. AOa forming a trough, with 1st and, to a lesser degree, last photophore elevated. Pol 1.5-2 times its own diameter below lateral line, often appearing continuous with AOa. AOp behind base of anal fin, evenly spaced and level. Prc forming a gentle curve, with Prc4 2-3 times its diameter below lateral line. A roundish luminous scale at PLO. Development of Headlights. In specimens up to about 1J.J mm the only luminous organ to be found on the head is a relatively large, massive Dn, somewhat smaller than the lens of the eye. This organ is framed, except for its ventral margin, by dark tissue which extends all the way down to the anteroventral aspect of the eye. Fishes about 16 mm long begin to show traces of Vn immediately posterolaterally to the olfactory organ. The Vn grows fast, spreading behind the olfactory organ (22 mm) and eventually reaching the median ethmoid crest (about 30 mm). Before this stage, however, the Ant has begun developing. This latter organ begins to form in individuals 24—25 mm long, but unless the specimen at that stage is in very good condition and the dark tissue associated with

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FIGURE 90. Diaphus effulgens, a bipolar subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and Hulley (1972b).

the Dn is intact, the Ant can not be distinguished. In fish larger than about 32 mm the Ant is readily distinguishable. Size. This myctophid grows larger than If 0 mm. The best developed ovaries and eggs were found in a 139-mm specimen from the Caribbean Sea off Nicaragua (OREGON Sta. 3J71). Atlantic Distribution. Diaphus effulgent (Fig. 90) is a bipolar subtropical species found but little outside the subtropical seas. However, significant numbers are found in the

Slope Water, whence they may be carried by warm-core eddies of the Gulf Stream. Extra-Atlantic Occurrence. Diaphus effulgens has been collected in the Indian Ocean west of 70°W between J°S and 38°S. The species is also known from the central South Pacific east of 1JO°W between 37°S and 40°S (McGinnis, 1974) as well as from the eastern South Pacific near 31°S, 92°W (Craddock and Mead, 1970). (N) Vertical Distribution. Opening-closing devices took a few D, effulgens near Bermuda

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FIGUKE 91. Diapbus roeii holotype (USNM 210553), male, 89 mm.

at 500-700 m by day and at 90-200 m at night. In the WHOI collections, D. effulgens occurred between 325 and 650 m by day, with maximum abundance at 450-500 m, and mostly between 40 and 175 m at night, with maximum concentration at 100 m. Individuals larger than 80 mm were, however, dispersed between 200 and 850 m at night; specimens larger than 100 mm may not migrate vertically. Synonyms and References: Aethoprora effulgens Goode and Bean, 1896: 87, Pi. 27, Fig. 103 (orig. descr.; Brown's Bank, North Atlantic, from stomach of cod; holotype, USNM 43770). Diaphus effulgens. Taning, 1928: 62 (in key); Parr, 1928: 138, Fig. 29 (compar. of related forms); Parr, 1929: 42, Fig. 20 (descr. of holotype); Bigelow and Schroeder, 1953: 142, Fig. 60 (occur, in Gulf of Maine, descr.); Nafpaktitis, 1968: 70, Figs. 44—46 (key, descr., distr. in North Atlantic); Craddock and Mead, 1970: 3.27 (records from east. South Pacific); Kotthaus, 1972a: 12 (records from east. North Atlantic, char., photo of otol.); Kretft and Bekker, 1973: 177 (synon., ref., distr.). Diapbus macrophus Parr, 1928: 136, Fig. 27 (orig. descr.; 24°ll'N, 75°35'W, 7,500 f.w.o.; holotype, BOG 2172).

Diapbus (Lamprossa) macrophus. Fraser-Brunner, 1949: 1071, fig. (in key). Diapbus (Lamprossa) effulgens. Fraser-Brunner, 1949: 1073, fig. (in key).

Diaphus roei Nafpaktitis 1974 Figure 91 Distinctive Characters. The high position of the PLO and SAO8, the absence of Ant, and the high gill-raker count will separate this fish from its closest relative, D. effulgens. Description. Fin rays: dorsal 15; anal 14 (13); pectoral 11 (12). Gill rakers: 7 (6-8) + 1 + 15-16, total 23-24 (22-25). Photophores: 6 + 5 (4-6), total 11 (1012). Lateral-line organs: 36. Head. Length of head 29.5-32 percent of SL. Mouth large, oblique; length of upper jaw 1.3-1.4 in hi and extending 0.6-0.8 of the diameter of eye behind vertical through posterior margin of orbit. Eye very large, its diameter 1.9-2.1 in length of upper jaw and 2.7-3 in hi. Operculum tapering posteriorly to a point somewhat below PLO,

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Fins. Origin of dorsal fin slightly in advance of base of ventral fin. Origin of anal fin behind end of base of dorsal fin. Pectoral fin not reaching base of ventral fin. Ventral fin reaching origin of anal fin in specimens smaller than about 90 mm, somewhat shorter in larger individuals. Base of adipose fin in advance of vertical through end of base of anal fin. Luminous Organs. Dn very large, directed forward, its medial border in contact with median ethmoid crest, and extending higher than dorsal margin of orbit. Vn also very large and massive, occupying nearly entire lower half of snout, reaching ethmoid crest dorsad to nasal apparatus, continuing along anteroventral border of orbit and terminating at or slightly behind vertical through anterior margin of pupil. Dn and Vn in contact with each other above olfactory organ. Ant absent. PLO nearer to lateral line than to base of pectoral fin. VLO midway between base of ventral fin and lateral line or a little lower. SAO on a straight or very nearly straight, subvertical line; SAOi well above and behind VO6; SAO8 slightly in advance of vertical through origin of anal fin and immediately, or less than its own diameter, below lateral line. AOa forming a deep trough with 1st, 5th, and 6th AOa elevated. Pol 11.5 times its own diameter below lateral line and almost continuous with AOa. AOp behind base of anal fin, evenly spaced and level. Prc forming a gentle, ascending curve, with Prc4 2-3 times its own diameter below lateral line. A small luminous scale at PLO. Size. The species grows to at least 110 mm. Nafpaktitis (1974) reported two gravid females, 104 and 108 mm, respectively. Atlantic Distribution. Diapbus roei> a pseudoceanic (land-associated) species, is known from only three near-shore localities in the western tropics and subtropics: off the Leeward Islands, off Puerto Rico, and off Dominican Republic (Nafpaktitis, 1974).

D. roei has not been reported from outside the North Atlantic. Vertical Distribution. Diaphus roei has been collected only by bottom gear by day between about 300 m and 560 m (Nafpaktitis, 1974). Reference: Diaphus roei Nafpaktitis, 1974: 4, Fig. 2 (orig. descr.; 17°20/N, 62°52'W, 550 m; holotype, USNM 210553).

Diaphus metopoclampus (Cocco) 1829 Figures 92, 93 Study Material. Four specimens: 2 (58—60), taken by the WHOI vessel CHAIN (Sta. RHB 1296) at 23° 06'N, 94°53'W; 1 (74) and 1 ( 7 5 ) , taken by the NMFS vessel SILVER BAY at 27°53'N, 79°09'W (Sta. 442) and "Blake Plateau" (Sta. 3 4 5 5 ) , respectively; in LACM.

Distinctive Characters. This species is easily distinguishable from all of its North Atlantic congeners by its deep and short head and its very large luminous organs on the head, especially the Vn which occupies much of the ventral margin of the orbit. Description. Fin rays: dorsal 15 (16); anal 15 (14-16); pectoral 10-11. Gill rakers: 8-9 (7) + 1 + 13-16, total 23-26 (22). Photophores: AO 6 (5-7) + 6 (5-7), total 12 (11, rarely 13). Lateral-line organs: 36-37. Head. Head almost as deep as it is long, its anterior profile round; hi 27-33 percent of SL. Mouth of moderate size, its cleft oblique; length of upper jaw 1.4—1.5 in hi and extending 0.6-0.9 the diameter of eye behind vertical through posterior margin of orbit. Eye large, its diameter 2-2.2 in length of upper jaw and 2.8-3.3 in hi. Operculum truncate posteriorly, forming a prominent, distinctly serrate (in adults) lobe dorsally. fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin on or slightly in

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FIGURE 92. Diaphus metopoclampus: female, 55 mm; A, front view of head of same; B, head of specimen, 60 mm, from southwestern Gulf of Mexico.

advance of vertical through end of base of dorsal fin. Pectoral fin extending about to PO4. Base of adipose fin in advance of end of base of anal fin. Luminous Organs. Dn very large, thick, forward directed, reaching median ethmoid crest and extending higher than supraorbital ridge. Vn massive, extending along entire anterior and much of ventral orbital margin, but not reaching ethmoid crest medially, terminating behind vertical through center of lens, its posterior end somewhat expanded and protruding into iris (see under Geographic Variation). Dn and Vn in contact with each other above olfactory organ. A large, roughly triangular Ant in contact with Dn. Body

photophores distinctly smaller than average Diaphus photophores. PLO nearer to lateral line than to base of pectoral fin, about midway between the two in specimens from the southwestern Gulf of Mexico. VLO behind base of ventral fin and about 3 times nearer to lateral line than to base of ventral fin. SAO on a straight or very nearly straight, subvertical line; SAOi above and well behind VOB; SAO3 on or behind vertical through origin of anal fin, immediately or less than its own diameter below lateral line. AOai more or less elevated, last AOa often somewhat raised. Pol about its diameter below lateral line. AOp evenly spaced, level, with AOpi behind, sometimes on or even slightly

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FIGURE 93. Diaphus metopoclamfrus, a bipolar questionably temperate-semi subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Bolin (1959), Cocco (1829), Gibbs et al. (1971), Goodyear et al. (1972), Krefft (1974, and unpublished), Maurin (1968), Nafpaktitis (1968), Parin et al. (1974), and Rossi (1958).

in front of vertical through end of base of anal fin. Prc forming a straight or slightly curved line, with Prc* lying at bases of middle caudal-fin rays and about its own diameter below midlateral line. A small, roundish luminous scale at PLO. Development of Headlights. In about 19mm-long juveniles the Vn has not only appeared but has also spread along much of the ventral margin of the orbit. The Ant is readily

distinguishable in individuals about 22 mm long. Size. This species becomes sexually mature at sizes between 55 and 60 mm and grows to at least 75 mm. Geographic Variation. In addition to slightly lower gill-raker counts (total 22 as compared to 23-26), the two specimens from the southwestern Gulf of Mexico have a distinctly lower PLO (midway between base of

Fishes of the Western North Atlantic pectoral fin and lateral line or slightly higher) than their conspecific representatives from the North Atlantic. But a more striking difference is found in the structure of the Vn. In the two specimens from the Gulf the posterior, expanded portion of the Vn is clearly separated from the rest of this organ, essentially forming a distinct So (Fig. 92B). The same feature has been found in specimens from the Indian Ocean (unpublished data). It should be added here that this difference in the Vn is not related to sex. Atlantic Distribution. Diaphus metopoclampus (Fig. 93) is a bipolar, questionably temperate-semisubtropical species everywhere quite rare in midwater trawls. In WHOI collections it was more abundant in the Slope Water than anywhere else. Although Cocco (1829) described the species from Messina, it has been considered rare in the Mediterranean (Bolin, 1959; Krefft and Bekker, 1973); it was not treated in Taning's "Mediterranean Scopelidae" (1918), nor did Nafpaktitis (1968) have Mediterranean specimens for his study of North Atlantic Diaphus and Lobianchia. Goodyear et aL (1972) found but a single Mediterranean specimen, and WHOI collections from the Mediterranean contain only two specimens. However, Maurin (1962, 1968) reported it as common, even abundant, in bottom trawls made between 300 or 400 and 650 m off Corsica, Sardinia, and Tunisia, especially in nets with a large vertical opening. Maurin also said that Rossi (1958, not seen by us) found D. metopoclampus to be one of seven fishes characteristic of a certain type of muddy bottom in the Ligurian Sea between 200 and 700 m. Thus, it appears that D. metopoclampus may not be a truly mesopelagic species, but how its mesopelagic occurrence relates to its nearbenthic occurrence is unknown. Extra-Atlantic Occurrence. Both variants of Diaphus metopoclampus (see Geographic Variation) occur in the southwestern Indian Ocean. Representatives of the typical form

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have been collected in the Agulhas Current to about 36°S. The species has also been reported from near Hawaii (Clarke, 1973) and is known to occur in the tropical western North Pacific. (N) Vertical Distribution. Opening-closing devices took D. metopoclampus by day at 500850 m and at night at 300-800 m near Bermuda. Individuals 13-24 mm were taken shoaler than 500 m at night; non-migrants were 13-79 mm. In the WHOI collections, D. metopoclampus occurred between 375 and 850 m by day, with maximum abundance at about 500 m, and between 90 and 850 m at night, with maximum abundance at 200-250 m. Synonyms and References: Myctophum metopoclampum Cocco, 1829: 144 (orig. descr.; Messina). Aethoprora metopodampa. Goode and Bean, 1896: 86, PI. 27, Fig. 101 (descr.); Bolin, 1959: 22 (char., distr.); Bini, 1971: 183, illus. (morphol., biol., distr.). Diapkus metopoclampus. Taning, 1928: 61 (in key); Parr, 1928: 137, Fig. 28 (char.); Taning, 1933, fig. (diag., distr.); Bekker, 1967b: 107 (records from North Atlantic); Nafpaktitis, 1968: 74, Figs. 36, 47-48 (key, descr., distr. in North Atlantic); Kotthaus, 1972a: 13 (records from east. North Atlantic, char., photo of otol.); Clarke, 1973: 406 (record from off Hawaii); Krefft and Bekker, 1973: 179 (synon., ref., distr.). Diaphus (Lamprossa) metopoclampus. Fraser-Brunner, 1949: 1074, fig. (in key).

Diaphus vanhoeffeni Brauer 1906 Figures 94-96 Distinctive Characters. Characters in the key will separate this fish from the rest of its North Atlantic congeners. Description. Fin rays: dorsal 14 (13); anal 15 (14); pectoral 10-11. Gill rakers: 7-8 + 1 + 14-15, total 2224.

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FIGURE 94. Diaphns vanhoeffeni:

male, 27.5 mm.

B

FIGURE 95. Diapkus vanhoeffeni: young, 11.5 mm.

A, head of female, 27 mm; B, broad-based, recurved premazillary teeth; C,

Fishes of the Western North Atlantic Photophores: AO 5-6 (7) + 4-5 (6),

total 10-11.

Lateral-line organs: 35-36. Head. Length of head 32-35 percent of SL. Mouth large, oblique; length of upper jaw 1.4—1.5 in hi and extending 0.7-1 time the diameter of eye behind vertical through posterior margin of orbit; a series of forwardhooked, broad-based teeth on posterior half of premaxilla (Fig. 95B). Eye of moderate size, its diameter 2.3-2.9 in length of upper jaw and 3.4^.2 in hi. Anterior, spinelike portion of frontal supraorbital ridge extending forward and downward nearly reaching posterodorsal border of olfactory organ. Operculum tapering posteriorly to a point at or a little below PLO. Fins. Origin of dorsal fin directly over or slightly in advance of base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin extending to base of ventral fin. Base of adipose fin on or slightly in advance of vertical through end of base of anal fin. Luminous Organs. Dn apparently fused with Vn, the compound structure in adult females beginning at or somewhat higher than dorsal margin of nasal apparatus, extending along anterior margin of orbit, expanding ventrally, its posteroventral tip not reaching vertical through anterior margin of pupil. A strip of dark tissue separating the Dn-Vn complex from orbit and extending along ventral orbital margin, its posterior end forming a small, round, pocketlike expansion in advance of vertical through posterior margin of pupil. Inside the pocketlike structure there is a tiny, roundish So connected with the DnVn complex by a very narrow streak of luminous tissue distinct in well-preserved, adult specimens. PLO nearer to base of pectoral fin than to lateral line. VLO nearer to base of ventral fin than to lateral line. SAO on a straight or nearly straight, subvertical line; SAOi behind and above VO6; SAO3 on or slightly in advance of vertical through origin of anal fin and about its own diameter below

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lateral line. AOai 1-2 times its own diameter anterodorsad to AOa2; last AOa in line with or somewhat higher than preceding organ of same series. Pol less than its own diameter below lateral line. AOp evenly spaced, level; AOpi on or immediately behind vertical through end of base of anal fin. Prc forming an ascending arc, with Prcs-Prc4 interspace enlarged; Prc4 about twice its own diameter below lateral line. A luminous scale at PLO. Sexual Dimorphism. Males are easily distinguished from females by the presence in the former of a conspicuous, roughly triangular Ant immediately above the Dn-Vn complex. Development of Headlights. A small Dn, framed by dark tissue can be seen in fishes 11 nun long (Fig. 95C). Even at this early stage, luminous tissue has already begun spreading from the Dn downward between the nasal organ and the eye. As the Vn grows larger it greatly obscures the Dn which, in adult fish, is a very small, roundish structure on top of and continuous with the large Vn. The small So first appears in indivduals 16-17 mm long. The Ant begins developing as a small, diffuse patch of luminous tissue in males 1819 mm long, attaining its maximum size and definitive shape at sexual maturity. Size. This diminutive member of the genus becomes sexually mature at a size of about 27 mm and does not seem to grow larger than 40 mm. Atlantic Distribution. Diaphus vanhoeffeni (Fig. 96) is a tropical species found only in the eastern Atlantic. It is a ranking myctophid in the Atlantic Tropical Region, in spite of the fact that it is restricted to the Guinean Province of that region. It is a ranking myctophid as well in the Mauritanian Upwelling, where it is restricted to the southern province. We collected less than 10 specimens of this abundant myctophid from outside the two provinces mentioned.

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FIGURE 96. Diaphus vanhoeffeni, a tropical species. Distribution, based on the WHOI collections. Additional records are from Nafpaktitis (1968).

Diaphus vanhoeffeni has not been recorded from outside the Atlantic Ocean. Vertical Distribution. In the WHOI collections, D. vanhoeffeni occurred between 275 and 750 m by day and between 40 and 125m at night, with maximum concentration at 50 m. Synonyms and References: Myctophum (Diaphus) vanhoeffeni Brauer, 1906: 222, Fig. 143, both fig. and descr. inaccurate [orig. descr.; "... deutschen Sudpol-Expedition." Lectotype: ZMHU, designated by Nafpaktitis, 1968].

Diaphus vanhoeffeni. Parr, 1928: 117 (in key); Bekker, 1967b: 100, Fig. 4 (records from Gulf of Guinea, char.); Nafpaktitis, 1968: 77, Figs. 4952 (key, descr., distr. in east. trop. Atlantic, desig. of lectotype). Diaphus lewisi Nafpaktitis, 1966: 410, Figs. 7-11 (orig. descr.; 13°3l'N, 18°03'W; ZMUC P2329207).

Diaphus rafinesquii (Cocco) 1838 Figures 97, 98 Study Material. Eleven specimens, 66.5-83 mm, taken by the NMFS vessels OREGON and SILVER BAY north of Haiti and in the northern Gulf of Mexico.

Fishes of the Western North Atlantic

FIGURE 97. Diapbus rafinesquii:

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female, 61 mm.

Distinctive Characters. Characters in the key will differentiate this species from its North Atlantic congeners D. mollis9 D. holti, andD. subtilis. Description. Fin rays: dorsal 13-14; anal 13-14 (15); pectoral 10-11. Gill rakers: 7-8 + 1 + 14-15 (16), total 22-24 (25). Photophores: AO 6 (5-7) + 4 (3-5), total 10 (9-11). Lateral-line organs: 35-36. Head. Length of head 30.5-32.5 percent of SL. Mouth moderately large; length of upper jaw 1.4—1.5 in hi and extending 0.50.6 of eye diameter behind vertical through posterior margin of orbit. Eye large, its diameter 1.8-2 times in length of upper jaw and 2.6-3 in hi. Operculum rounded posterodorsally, truncate posteriorly, ending at PLO. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin extending to PO6. Ventral fin extending somewhat beyond origin of anal fin. Base of adipose fin directly over or slightly in advance of end of base of anal fin. Luminous Organs. A round, forward directed Dn, set in deep, cup-shaped recess above nasal apparatus. Vn large, elongate, extending along ventral border of eye from about under

anterior margin of orbit to about under middle of lens, its anterior end slightly bifurcating and wider than its posterior end. A small, round So framed by black tissue, in advance of vertical through posterior margin of pupil and in contact with posterior end of Vn. PLO nearer to base of pectoral fin than to lateral line. VLO midway between base of ventral fin and lateral line or slightly lower. SAO in a straight line or very nearly so; SAOi above and somewhat behind VOB; SAO3 about over origin of anal fin and 1-1.5 times its own diameter below lateral line. AOat rather abruptly elevated; AOa5 and AOa6 progressively raised. Pol about its own diameter below lateral line. AOp behind base of anal fin, evenly spaced and level. Prc forming an ascending arc, with Prc* 2-3 times its diameter below lateral line. A large, luminous scale at PLO. Sexual Dimorphism. In adult males the Vn is distinctly larger than the same structure in females of comparable sizes. Size. The species probably grows to 90 mm. It apparently reaches sexual maturity at a size of about 65 mm. Development. Taning (1918) described and illustrated larval (4.5-9.5 mm) and metamorphosis (10 mm) stages of this species on the basis of material from the Mediterranean Sea.

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FIGURE 98. Diaphus rafinesquii, a temperate-semhubtropical species. Distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971), Krefft (1961, and unpublished), and Taning (1918).

Atlantic Distribution. Diaphus rafinesquii (Fig. 98) is a fairly common temperate-semisubtropical species most abundant in the Mediterranean Sea and in the Northern Mauritanian Upwelling. Its numbers are considerably less in the northern subtropics than in the temperate part of its range; in the former place it co-occurs with its close relative, the tropical-subtropical D. mollis, which is the more abundant. D. rafinesquii is present, but rare, in the Gulf of Mexico.

D. rafinesquii is not known from outside the North Atlantic. Vertical Distribution. Opening-closing devices took D. rafinesquii during the day from 400-500 m to 650-700 m near Bermuda, near the Canary Islands, and in the Mediterranean Sea; maximum abundances were at 450-550 m near Bermuda and at 500 m in the Mediterranean. At night, the species was taken at about 40-200 m and about 300-600 m in all three areas; only juveniles were taken in the

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FIGURE 99. Diaphus mottis: female, 37 mm.

shoaler stratum near Bermuda and near the Canaries, while juveniles and adults, but mostly subadults were taken in that stratum in the Mediterranean. Large subadults and/ or adults were taken from the deeper stratum in all three regions. In the WHOI collections, D. rafinesquii occurred between 325 and 750 m by day, with maximum abundance at about 500 m, and at 40-275 m and 500 m at night, with maximum abundance at 100 m. Synonyms and References: Nychtophus rafinesquii Cocco, 1838: 180 (orig. descr.; Messina). Collegia rafinesquei. Goode and Bean, 1896: 88, Pi. 26, Fig. 100 (descr.). Myctophum (Diaphus) rafinesquei. Brauer, 1906: 223, Fig. 144 (descr.); Taning, 1918: 83, Figs. 33, 34 (develop., reprod., distr., in Mediterranean). Diaphus rafinesquei. Taning, 1928: 60 (in key) ; Bolin, 1959: 20, 21 (key, char., distr.); Bekker, 1967b: 101 (records from North Atlantic, distr.); Nafpaktitis, 1968: 81, Figs. 53, 54 (key, descr., distr.); Bini, 1971: 181, illus. (morphol., biol., distr.); Kotthaus, 1972a: 13 (records from east. North Atlantic, char., photo of otol.); Goodyear et al., 1972: 182 (abund., growth, vert, distr. in Mediterranean); Krefft and Bekker, 1973: 180 (synon., ref., distr.). Diaphus (Diaphus) rafinesquei. Fraser-Bnmner, 1949: 1075, fig. (in key). Diaphus intermedium Borodin, 1930: 89 (orig. descr.; North Atlantic; MCZ 32289). Diaphus (Panthophos) intermedium. Fraser-Brunner, 1949: 1069, fig. (in key).

Diaphus mollis Tining 1928 Figures 99-101 Distinctive Characters. Characters in the key will separate D. mollis from D. holti. Description. Fin rays: dorsal 13; anal 12-13; pectoral 10-11.

Gill rakers: 4-5 + 1 + 11 (10-12), total 16-17 (15-18). Photophores: AO 5 (4-6) + 4 (3-5), total 9 (8-10).

Lateral-line organs: 34-35. Head. Length of head 29.5-33 percent of SL. Mouth relatively small; length of upper jaw 1.6-1.8 in hi and extending 0.3-0.5 of the eye diameter behind vertical through posterior margin of orbit. Eye very large, its diameter 1.5-1.7 in length of upper jaw and 2.5-3 in hi. Operculum truncate posteriorly, angular or forming a distinct, posteriorly directed lobe posterodorsally. fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin extending to PO6. Ventral fin just about reaching origin of anal fin. Base of adipose fin over end of base of anal fin. Luminous Organs. A round, forward directed Dn, set in cup-shaped recess above nasal apparatus. Vn along ventral border of eye, elongate, about % as long as diameter of lens; much larger in adult males. A small,

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FIGURE 100. Diaphus mollis: sexually dimorphic Vn of male, 37.5 mm.

round So framed by dark tissue, in advance of vertical through posterior margin of pupil. Vn and So connected by a band of dark tissue. PLO nearer to base of pectoral fin than to lateral line. VLO midway between base of ventral fin and lateral line or slightly lower. SAO forming an obtuse angle; first 2 SAO in line with VOs; SAO3 distinctly smaller than rest of organs of same series, on or slightly in advance of vertical through origin of anal fin and 1-1.5 times its own diameter below lateral line. AOa forming a shallow trough.

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FIGURE 101. Diaphus mollis, a tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et al, (1971).

Fishes of the Western North Atlantic Pol smaller than AO and about its own diameter below lateral line. A Op behind base of anal fin, evenly spaced and level. Prc forming an ascending arc, with interspaces becoming progressively wider; Prc4 about twice its diameter below lateral line. A small luminous scale at PLO. Sexual Dimorphism. In adult males a large patch of luminous tissue fills almost the entire space bordered by the olfactory organ, the anteroventral margin of the orbit and the upper jaw (Fig. 100). This luminous tissue first appears in males 22-23 nun long. In fish about 28 mm long this tissue is so well developed that it can not be overlooked. Development of Headlights. At a size of 9 mm, which must be soon after metamorphosis, D. mollis shows a large, round Dn and a thin streak of luminous tissue in the place of the Vn. In specimens about 11.5 nun long all three luminous organs of the head are clearly distinct under the dissecting microscope. Size. D. mollis grows to about 60 nun. It becomes sexually mature at a size of about 30 nun. Atlantic Distribution. Diaphus mollis (Fig. 101) is a common myctophid conforming to the tropical-subtropical pattern. It is a ranking myctophid in the Gulf of Mexico and in the North and South Atlantic Subtropical Regions. Also, it is common in the temperate Slope Water to which it is probably carried by Gulf Stream eddies. The species occurs in negligible quantities in the Mauritanian Upwelling and was absent from the southeastern part of the Guinean Province off west Africa. The range of D. mollis is more or less complementary to that of its close relative, the temperate-semisubtropical D. rafinesquii. The two overlap in the north subtropics, where D. mollis is the commoner and in the Slope Water, where D. rafinesquii is the commoner. Extra-Atlantic Occurrence. Diaphus mollis has been collected in the Indian Ocean west of 70 °E between the equator and 25°S. The

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species appears to be quite common in the western South Pacific west of 170°W and south of about 20°S. It has repeatedly been taken in the Tasman Sea to 37°S. A single confirmed record comes from the western North Pacific at 2f°ll'N, 122°35'E. (N) Vertical Distribution. Opening-closing devices collected D. mollis by day at 300-800 m near Bermuda, with maximum abundance at 450-600 m, and at 300-500 m near the Canary Islands. Very few individuals were taken shallower than 4JO m or deeper than 700 m during the day near Bermuda. At night, the species was taken at about 33-350 m in both areas; near Bermuda maximum abundance was at 33-100 m. In the WHOI collections, D. mollis occurred mostly between 32 J and 6JO m by day, with maximum abundance at 400 m, and between the surface and about 225 m at night, with maximum abundance at 100 m. References: Diaphus mollis Taning, 1928: 60 (orig. descr.; in key); Bolin, 1959: 20, 21 (key, synon., char.); Bekker, 1967b: 102 (records from North Atlantic); Nafpaktitis, 1968: 84, Figs. 55-57 (key, descr., distr.); Kotthaus, 1972a: 13 (records from east. North Atlantic, char., photo of otol.); Nafpaktitis, 1973: 32, Fig. 29 (desig. and descr. of lectotype; 19°22'N, 24° 06'W, 600 m.w.o.; ZMUC P2329211). Diaphus (Diaphus) fulgens. Fraser-Brunner, 1949: 1075, fig. (D. mollis in synonymy of D. fulgens).

Diaphus holti Tuning 1918 Figures 102-104 Distinctive Characters. Characters in the key will differentiate this species from D. mollis. Description. fin rays: dorsal 14 (13); anal 13 (12-14); pectoral 11 (10-12). Gill rakers: 5-6 + 1 + 12-13 (11), total 18-20. Photophores: AO 5 (4-6) + 4 (3-5), total 9 (8-10). Lateral-line organs: 34-35.

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FIGURE 102. Dtaphus holtii female, 44.5 mm.

Head. Head large, its length 32.5-35.8 percent of SL. Mouth moderately large; length of upper jaw 1.4—1.6 in hi and extending 0.4-0.5 of eye diameter behind vertical through posterior margin of orbit. Eye very large, its diameter 1.7-1.9 in length of upper jaw and 2.5-3 in hi, Operculum rounded posterodorsally, truncate posteriorly. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin extending to PO6, reaching base of ventral fin in young fish. Ventral fin just about reaching origin of anal fin. Base of adipose fin over end of base of anal fin. Luminous Organs. A round, forward directed Dn, set in cup-shaped recess above nasal apparatus. Vn along ventral border of eye, elongate, equal in length to, or somewhat longer than, diameter of lens; much larger in adult males. A round So in a black, pocketlike structure protruding into iris, its posterior margin somewhat in advance of vertical through posterior margin of pupil. Vn and So close to each other, sometimes confluent, but usually connected by dark tissue. Body photophores larger than average Diaphus photophores. PLO much nearer to base of pectoral fin than to lateral line. VLO nearer to base of ventral fin than to lateral

line. SAO on a straight or slightly curved line; SAOi close behind and above VOB; SAOs often slightly smaller than rest of organs of same series, over base of anal fin and 2-2.5 times its own diameter below lateral line. First through 3rd or 4th AOa in a straight line or AOai slightly raised; AOas and sometimes AOa4 raised, the posterior part of this series thus forming a gentle arc. Pol often smaller than AO and about twice its own diameter below lateral line. AOp behind base of anal fin, evenly spaced and level. Prc forming an ascending arc with interspaces becoming progressively somewhat larger; Prc4 2.5-3 times its own diameter below lateral line. A small luminous scale at PLO.

FIGURE 103. Diaphus holti: sexually dimorphic Vn of male, 48 mm.

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FIGURE 104. Diapkus holti, an *tfj/*r» species. Distribution, based on the WHOI collections. Additional records are from Geistdoerfer et al. (1971), Nafpaktitis (19*8), and Taning (1918). The records lying southeast of the short broken line off South Africa and thence west along the southern edge of the South Atlantic Subtropical Region pertain to a form of D. holti that perhaps warrants recognition as a species.

Sexual Dimorphism. In adult males the Vn is greatly enlarged, reaching the olfactory organ and growing between it and the eye. Growth of this additional luminous tissue appears to begin along the ventral margin of the Vn proper. It soon spreads downward and forward partially or completely obliterating the outlines of the original Vn. The sexually dimorphic growth of this organ begins in fish about 32 mm long (Fig. 103).

Development of Headlights. Fish about 11 mm long have a small but sharply distinct Dn and a very long and thin Vn. In specimens about 12.5 mm long a tiny So can be seen differentiating at the posterior tip of the Vn. The two organs soon separate from each other (about 13.5 mm), the Vn becomes deeper, and the dark tissue associated with the So attains its characteristic form. Size. D. holti apparently becomes sexually

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mature at about 38 mm and grows to 55, possibly 60 mm. Development. In his study of Mediterranean myctophids, Tining (1918) described and illustrated larval (5-10 mm) and metamorphosis (10-12 mm) stages of this species on the basis of material from the Mediterranean. Atlantic Distribution. Diaphus holti (Fig. 104) is one of two eastern myctophids. It occurs in the eastern provinces of the temperate and tropical regions and in the Mauritanian Upwelling, but is absent from the subtropics. It is the ranking myctophid in the Mauritanian Upwelling. The records on our distribution map lying southeast of the short broken line off South Africa and thence west along the southern edge of the South Atlantic Subtropical Region pertain to a form of D. holti that perhaps warrants recognition as a species. So far as is known, D. holti is confined to the Atlantic. Vertical Distribution. Opening-closing devices captured D. holti in the Mediterranean Sea by day at 100-235 m and 500-675 m and at night at 80-235 m and 400-600 m. Maximum abundances were at 500-600 m by day and at 150-190 m at night. The shallow day and deep night captures were mostly 10-13 mm specimens, but included one adult from 235 m by day. In the WHOI collections, D. holti occurred between 225 and 650 m by day and between 40 and 275 m at night, with maximum abundance at 75-200 m. Synonyms and References: Myctophum (Diaphus) holti Taning, 1918: 88, Figs. 35, 36 (orig. descr.; Mediterranean). Diaphus holti. Taning, 1928: 59, 60 (in key); Bolin, 1959: 20, 21 (key, synon., char.); Nafpaktitis, 1968: 88, Figs. 58-60 (key, descr., distr.); Kotthaus, 1972a: 13 (records from east. North Atlantic, char., photo of otoL); Goodyear et al., 1972: 186 (abund., growth, vert, distr. in Mediterranean); Nafpaktitis, 1973: 33, Fig. 30 (desig. and descr. of

lectotype: 36°53'N, 03°09'E, 300 m.w.o.; ZMUC P2329204); Krefft and Bekker, 1973: 178 (synon., ref., distr.). Diaphus (Diaphus) theta. Fraser-Brunner, 1949: 1074, fig. (D. holti in synon. of D. theta).

Diaphus subtilis Nafpaktitis 1968 Figures 105-107 Study Material. Nineteen specimens, 15—85 mm, from the Gulf of Mexico (WHOI and NMFS vessels CHAIN and OREGON) , the Caribbean Sea (WHOI vessel CHAIN), and the eastern North Atlantic (WHOI vessel ATLANTIS II); in LACM

Distinctive Characters. The following combination of characters will separate this species from the rest of the North Atlantic members of the rafinesquii-species group: the position of the 1st AOa which is not, or very slightly, raised; the high number of AOp which are continuous, or very nearly so, with the Prc; and the number of gill rakers (2023). Description. Fin rays: dorsal 13(12); anal 13; pectoral 10-11 (12). Gill rakers: 6-7 + 1 + 13-15, total 20-23. Photophores: 5 (6) +6-7 (5), total 1112 (10). Lateral-line organs: 35-36. Head. Length of head 31.5-34 percent of SL. Mouth moderately large; length of upper jaw 1.6-1.7 in hi and extending 0.3-0.5 of eye diameter behind vertical through posterior margin of orbit. Eye very large, its diameter 1.6-1.8 in length of upper jaw and 2.7-3 in hi; pupil horizontally elliptical with considerable aphakic space in front of lens. Operculum truncate posteriorly, rounded or somewhat angular posterodorsally. Fins. Origin of dorsal fin directly over or somewhat behind base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin extending to PO5. Ventral fin long, extending to base of 4th or 5th ray of anal fin. Base of adipose fin over end of base of anal fin.

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FIGURE 105. Diapbus subtilisi holotype (ZMUC P2329216), female, 78.5 mm.

Luminous Organs. A round, forward directed Dn, set in cup-shaped recess above nasal apparatus. Vn along ventral orbital margin, short and deep in females, much larger in adult males. A small, roundish So in vertically elongate, slipper-shaped structure of dark tissue protruding into iris and lying immediately in front of vertical through posterior margin of pupil. Vn and So separated by a space about equal to width of So. All 3 luminous organs are present and distinct in fish about 11 nun long. PLO nearer to base of pectoral fin than to lateral line. VLO midway between base of ventral fin and lateral line or somewhat lower. SAO in a straight line or very nearly so; SAOi above and behind VO5; SAO8 often smaller than rest of organs of same series, on or a little behind vertical through origin of anal fin and 1-1.5 times its own diameter below lateral line. AOai not at all or very slightly raised; last AOa somewhat elevated. Pol about its diameter below lateral line. AOp behind base of anal fin, evenly spaced, level and usually continuous with Prc. Prc widely spaced, in a slightly curved line; Prc4 3-4 times its diameter below lateral line. A small luminous scale at PLO. Sexual Dimorphism. In adult males the Vn grows into a prominent bar of luminous tis-

sue which is as long as the horizontal diameter of the pupil in specimens larger than about 74 nun, somewhat shorter in smaller individuals (Fig. 106). The structure is slightly oblique and extends from about under the center of the pupil to or a little beyond a vertical through the posterior margin of the nasal rosette. A thinner bar of what appears to be denser luminous tissue can be seen within the large Vn, extending through-

FIGURE 106. Diaphus sub tilts: sexually dimorphic Vn of male, 79 mm.

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FIGURE 107. Diaphus subtilts, a tropical-scmisubtfopical species. Distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971), Nafpaktitis (1968), and Parin et al. (1974).

out the length of this organ. Male specimens about 32 mm long already show a forward projection or expansion from the ventral half of the Vn. Size. This fish grows to at least 8J mm. It apparently reaches sexual maturity at a size of about 70 mm. Atlantic Distribution. Diaphus subtilis (Fig. 107) is a tropical-semisubtropical species nowhere very abundant. Diaphus subtilis has not been recorded from outside the Atlantic Ocean.

Vertical Distribution. In the WHOI collections, D. subtilis occurred between 375 and 7JO m by day and between 40 and 5 50 m at night, with maximum concentration at about 100 m. References: Diaphus subtilis Nafpaktitis, 1968: 92, Figs. 61-63 (orig. deacr.; 13°47'N, 61°26'W, 4,JOO m.w.o.; holotype, ZMUC P2329216); Kotthaus, 1972a: 13 (records from east. North Atlantic, char., photo of otol.); Krefft and Bekker, 1973: 318 (synon., ref.).

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FIGURE 108. Diaphus brachycephalus: female, 50 mm.

Diaphus brachycephalus Tining 1928 Figures 108-110 Distinctive Characters. The very long Vn, the So which is behind the vertical through the posterior margin of the pupil, the short, heavy body, and large, closely set photophores readily differentiate D. brachycephalus from the rest of the members of the North Atlantic rafinesquii species group. Description.

Fin rays: dorsal 13 (12); anal 13 (14); pectoral 11 (10-12). Gill rakers: 6 (5-7) + 1 + 12-13 (14), total 18-20 (21). Photophores:

beyond PO6. Ventral fin extending to anus in young fish, nearly reaching origin of anal fin in adult individuals. Base of adipose fin somewhat in advance of vertical through end of base of anal fin. Luminous Organs. A small, round, forward directed Dn, set in cup-shaped recess above nasal apparatus. Vn very long, about 1.5 times the horizontal diameter of pupil, extending along anteroventral and much of ventral border of eye, narrow with slightly expanded ends in females, much wider in

AO 5 (4-6) + 4 (3-5),

total 9 (8-10). Lateral-line organs: 34(33-35). Head. Length of head 34-38 percent of SL. Mouth moderately large; length of upper jaw 1.4-1.6 in hi and extending 0.3-0.4 of eye diameter behind vertical through posterior margin of orbit. Eye very large, its diameter 1.6-1.8 in length of upper jaw and 2.4—2.7 in hi. Operculum rounded posterodorsally, bluntly angular posteriorly. Fins. Origin of dorsal fin over base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin extending to or slightly

FIGURE 109. Diaphus brachycephalus: morphic Vn of male, 49 mm.

sexually di-

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FIGURE 110. Diaphus brachycepbalus, a tropical-semisubtropical species. Atlantic Ocean distribution, based on the WHOl collections. The additional record is from Gibbs et aL (1971).

adult males. A small, round So almost immediately behind Vn, its posterior margin behind vertical through posterior margin of pupil. A large, profusely ramified melanophore immediately posteroventrad to So. All three luminous organs of the head appear and are clearly distinct upon metamorphosis (i.e., about 9-mm-long individuals). Body photophores markedly larger than average Diaphus photophores. PLO much nearer to base of pectoral fin than to lateral line. VLO nearer to base of ventral fin than to lateral line. SAO

in a straight line or very nearly so; SAd above and close behind VOB; SAO3 often smaller than rest of organs of same series, over base of anal fin and about 3 times its own diameter below lateral line. AOai not or very slightly raised; AOa5 and sometimes AOa4 raised. Pol usually a little smaller than AO and about twice its own diameter below lateral line. AOp behind base of anal fin, evenly spaced and level. Prc forming a steeply ascending arc with interspaces becoming progressively wider; Prc4 2-3 times its own diam-

Fishes of the Western North Atlantic eter below lateral line. No luminous scale at PLO. Sexual Dimorphism. In males, luminous tissue originating primarily from the anterior half of the Vn grows anteriorly until, eventually, it occupies the entire space bordered by the olfactory organ, the eye and the upper jaw (Fig. 109). Even in mature males the anterior end of the Vn proper can be distinguished from the additional luminous tissue which appears in males about 22 mm long. Specimens 26-28 mm long can readily be sexed on the basis of the size and shape of the Vn. Size. This fish becomes sexually mature at a size of about 3 0 mm and grows to about 60 nun. Atlantic Distribution. Diaphus brachycephalus (Fig. 110) is a tropical-semisubtropical species. It is a ranking species in the Atlantic Tropical Region. It occurs but little in the Gulf of Mexico and is absent from the Mauritanian UpweUing. Apparent waifs in the Slope Water are common. Extra-Atlantic Occurrence. Only two records of Diaphus brachycephalus are known from the eastern Indian Ocean (4°N, 93°E and 12°S, 96°E). However, numerous records are available from west of 70 °E between the equator and 25°S. North of about 10°S in the Mozambique Channel this species has been taken along with its close relative, D. richardsoni Taning. Young of the two species are difficult to differentiate. In the Pacific, D. brachycephalus has been reported from near 3°30'S, 145 °W (Hartmann and Clarke, 1975). It has also been collected at about 3°N, 129°E, and in the South Pacific off Sydney, near 33°30'S, and further east in, and in waters influenced by, the South Equatorial Current (Nafpaktitis, unpublished) . No confirmed records are available from east of 145°W. Material from near Hawaii (Clarke, 1973) may include D. richardsoni. (N) Vertical Distribution. Opening-closing de-

169

vices took D. brachycephalus near Bermuda at 150-250 m at night; none was taken during the day. In the WHOI collections, D. brachycephalus occurred between 175 and 5 5 0 m during the day and from near the surface to about 225 m at night, with maximum abundance at 100 m. References: Diaphus brachycephalus Taning, 1928: 59 (orig. descr.; in key); Bolin, 1959: 20 (in key); Bekker, 1967b: 101 (records from North and South Atlantic, distr.); Nafpaktitis, 1968: 96, Figs. 64-66 (key, descr., distr.); Nafpaktitis, 1973: 34, Fig. 31 (desig. and descr. of lectotype; 19°22'N, 24°06'W, 600 m.w.o.; ZMUC P2329197); Clarke, 1973: 406, 414 (vert, distr. off Hawaii); Kretft and Bekker, 1973: 176 (synon., ref., distr.). Diaphus (Diaphus) brachycephalus. Fraser-Brunner, 1949: 1076, fig. (in key).

Diaphus widerseni Taning 1932 Figures 111, 112 Study Material. The 20.5-mm holotype from the western South Pacific and a single North Atlantic specimen 25 mm, taken by the DANA at 15*08'N, 61°31'W.

Distinctive Characters. The characters in the key will separate this species from D. holti and D. brachycephalus. Description. Because the North Atlantic specimen is in rather poor condition measurements are mainly from the holotype. Fin ray si dorsal 12-13; anal 12; pectoral 10-11. Gill rakers: 5 + 1 + 11. Photophores: AO 4 + 4-5. Head. Length of head 35 percent of SL. Mouth large; length of upper jaw 1.5 in hi and extending 0.2-0.3 of eye diameter behind vertical through posterior margin of orbit. Eye very large, its diameter 1.6 in length of upper jaw and 2.4 in hi. Operculum bluntly angular posteriorly, produced into a distinct lobe posterodorsally.

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FIGURE 111. Diaphus anderseni: holotype (ZMUC P2329194), 20.5 mm.

Fins. Origin of dorsal fin directly over or slightly behind base of ventral fin. Origin of anal fin behind base of dorsal fin. Pectoral fin extending to PO5. Base of adipose fin over end of base of anal fin. Luminous Organs. A round, forward directed Dn, set in cup-shaped recess above nasal apparatus. Vn roundish, about % the size of a general body photophore, at the anteroventral border of eye and in advance of vertical through anterior margin of pupil. So in advance of vertical through posterior margin of pupil, slightly larger than Vn and separated from it by a space 2-3 times its own horizontal diameter. Body photophores larger than average Diaphus photophores. PLO nearer to base of pectoral fin than to lateral line. VLO much nearer to base of ventral fin than to lateral line. SAO in a straight line or very nearly so; SAOi close behind and above VO5; SAO3 somewhat smaller than rest of organs of same series, over base of anal fin and about 3 times its own diameter below lateral line. First three AOa level, AOa4 slightly raised. Pol smaller than AO and about twice its own diameter below lateral line. AOp behind base of anal fin, very close to each other and level. Prc forming an

ascending arc; Prc4 about 3 times its own diameter below lateral line. A very large luminous scale at PLO. Size. This is a diminutive species, as suggested by the fact that the single North Atlantic specimen reported by Nafpaktitis (1968) is a 25-nun-long gravid female. The largest specimen in the WHOI collections measures 31 mm. In the waters near Hawaii the species reaches sexual maturity at about 20 mm (Clarke, 1973). Atlantic Distribution. Diaphus anderseni (Fig. 112) is a waif in the North Atlantic. It is a subtropical species occurring regularly in the Atlantic only in the southern hemisphere, where, in the South Atlantic Subtropical Region it is a ranking myctophid. Extra-Atlantic Occurrence. Diaphus anderseni is not known from the Indian Ocean. In the Pacific it has been collected near Hawaii (Clarke, 1973) and in the eastern North Pacific between about 20°N and 35°N. In the South Pacific it occurs between about 20°S and 27°S and from approximately 167°E to 110°W, with records to the east of 160°W in need of confirmation. (N) Vertical Distribution. In the WHOI collections, D. anderseni occurred between 225

Fishes of the Western North Atlantic -

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FIGURE 112. Diaphus anderseni, a subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Nafpaktitis (1968) and R- Baird (in litt.).

and 375 m by day and between 60 and 17J m at night. References: Diaphus anderseni Taning, 1932: 134, Fig. 6 (orig. descr.; SW of Fiji Island, 20°00/S, 174°29'E, 600 m.w.o.; holotype, ZMUC P2329194); Nafpaktitis, 1968: 99, Fig. 67 (key, descr.); Nafpaktitis, 1973: 30, Fig. 27 (descr. of holotype); Clarke, 1973: 406, 414 (vert, distr. off Hawaii). Diaphus (Diaphus) andersoni. Fraser-Brunner, 1949: 1074, fig. (misspelling, in key).

Genus Lampadena Goode and Bean 1896 Lampadena Goode and Bean, 1896: 85 (type-species Lampadena speculigera Goode and Bean 1896, by monotypy); Fraser-Brunner, 1949: 1077 (description, subdivision of genus into subgenera Lampadena and Lychnophora); Bolin, 1959: 23 (characters); Paxton, 1972: 46 (definition, osteological characters). Lychnophora Fraser-Brunner, 1949: 1080 [as subgenus of genus Lampadena; type-species Lampadena nitida Taning 1928 (= Myctophum luminosum Garman 1899), by original designation].

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Characters. Mouth moderate to large; jaws extending from a little over % to about 1% times the diameter of eye behind vertical through posterior margin of orbit; maxillary not or slightly expanded posteriorly. Pterotic spine well developed. Base of anal fin equal in length to or somewhat shorter than base of dorsal fin; origin of dorsal fin directly over or in advance of base of ventral fin; origin of anal fin behind vertical through end of base of dorsal fin; procurrent caudal fin rays stiff. Lateral line well developed. Dn absent; Vn small; PVd about under PVO2; 5-6 PO, level or PO4 elevated; VLO nearer to lateral line than to base of ventral fin, sometimes midway between the two; 3-6 VO; 3 SAO, weakly angular, with SAOi about midway between last VO and SAO2, but with SAO3 displaced dorsally, lying its own diameter or less below lateral line; one Pol; 2 + 1 Prc, Prca at level of lateral line; supracaudal and infracaudal glands large, single organs bordered by darkly pigmented tissue, and present in both sexes; no luminous tissue at bases of procurrent caudal fin rays or at any other part of trunk or head. Size. Relatively large myctophids, several species growing larger than 100 mm and at least one, L. urophaos, attaining a size of over 200 mm. Range. In all three major oceans, between approximately 50°N and 50°S. Species. The genus includes eight described species: L. anomaly L. chavesi, L. dea, L. luminosa, L. notialis, L. pontifex, L. speculigera, L. urophaos. Two of these, L. dea and L. notialis, are restricted to the southern hemi-

sphere. The rest of the species all occur in the North Atlantic. Of these, L. pontifex Krefft 1970 is known only from the eastern North Atlantic. No species seems to enter the Mediterranean Sea. Remarks. Fraser-Brunner (1949) erected the subgenus Lychnophora to include L. luminosa and L. nitida. The distinguishing characters of the subgenus were given as follows: PQs (= PO4) much elevated (vs. PO all on same level); diameter of eye more than four times in length of head (vs. eye diameter less than four times in head); and inner row of entopterygoid teeth conspicuously enlarged (vs. entopterygoid teeth uniformly small). Nafpaktitis and Paxton (1968) indicated that Fraser-Brunner's character differences were not sufficiently strong to warrant maintenance of the subgenus. On the other hand, a number of evolutionary trends and relationships are quite obvious within the genus. Krefft (1970) suggested that the species could be assigned to three groups (the luminosa, speculigera, and the chavesi groups) with the members of each group "being more closely related to each other than to those of the remaining groups" (Krefft, 1970). In the absence of comparative osteological studies, this, in my opinion, is as far as we can go in the systematics of this tightly knit genus. The species descriptions are based mainly on the works of Nafpaktitis and Paxton (1968), Maul (1969), and Krefft (1970). Where additional material has been examined it is so indicated in the Study Material under the particular species involved.

Key to the Atlantic Species of Lampadena Lampadena notialis does not occur in the North Atlantic. Its inclusion in the following key is for purposes of comparison with the North Atlantic L. pontifex. la. PO4 abruptly and highly elevated, about over PO3. luminosa (Carman) 1899, p. 173 Ib. None of the PO abruptly and highly elevated 2 2a. VO plus SAO 5-6; AOa 3-4; Pol more than its diameter below lateral line; gill rakers 5 + 1 + 11 (10-12), total 17 (16-18). anomala Parr 1928, p. 184

Fishes of the Western North Atlantic

173

2b. VO plus SAO 7-9; AOa 5-7; Pol its diameter or less below lateral line 3 3a. Prci-Prc2 interspace 3 or more times the diameter of a photophore of this series; last 2 (sometimes 3) AOa behind base of anal fin; infracaudal luminous gland very long, its length more than 14 percent of SL; a crescent of whitish tissue on dorsal half of iris chavesi Collett 1905, p. 182 3b. Prci-Prc2 interspace much shorter than 3 times the diameter of a photophore of this series; no AOa behind base of anal fin; length of infracaudal luminous gland less than 14 percent of SL; no crescent of whitish tissue on dorsal half of iris 4 4a. Gill rakers 3-5 + 1 + 8-10; supracaudal luminous gland equal in length to, or somewhat longer than, infracaudal gland; medial and posterior mesopterygoid teeth markedly enlarged. urophaos atlantica Maul 1969, p. 176 4b. Gill rakers 6-8 + 1 + 12-17; supracaudal luminous gland shorter than infracaudal gland; mesopterygoid teeth uniformly small 5 5 a. Distance between end of base of anal fin and anterior margin of infracaudal gland equal to, or greater than, length of this gland; gill rakers 19-22. speculigera Goode and Bean 1896, p. 178 5b. Distance between end of base of anal fin and anterior margin of infracaudal gland much less than length of this gland; gill rakers 22-26 6 6a. Distance between end of base of anal fin and anterior margin of infracaudal gland more than % of length of this gland; last AOa not raised. pontifex Krefft 1970, p. 180 6b. Distance between end of base of anal fin and anterior margin of infracaudal gland about 1A of length of this gland; last AOa distinctly raised. notialis Nafpaktitis and Paxton 1968. Southern Ocean

Lampadena luminosa (Garman) 1899 Figures 113, 114 Study Material. Thirty-six specimens, 35-163 mm, from off British Guiana and Surinam, the Caribbean Sea off the coasts of Venezuela, Colombia and Panama, and from the northern Gulf of Mexico; in LACM.

Distinctive Character. This species is readily distinguishable from the rest of its North Atlantic congeners by its abruptly and highly elevated PO4. Description. The following measurements, expressed in percent of SL, are from 10 specimens, 22-151 mm: Diameter of eye: 7.3-9.4. Length of caudal peduncle: 19.8-22.9. Depth (least) of caudal peduncle: 9.510.7. Tip of snout to origin of anal fin: 64.368.0. Length of supracaudal luminous gland: 7.0-9.4.

Length of infracaudal luminous gland: 6.69.4. Fin rays: dorsal 15 (14); anal 14 (13-15); pectoral 16 (15-17). Gill rakers: 4 + 1 + 9 (8-10), total 14 (13-15). Photophores: PO 5; VO 5 (4); AO 5-6 (7) + 2. Lateral-line organs: 37-38. Vertebrae: 36 (37). Dentition. Medial and posterior mesopterygoid teeth greatly enlarged in specimens larger than about 65 mm. Fins. Origin of dorsal fin somewhat in advance of base of ventral fin. Pectoral fins extending to vertical through 2nd or 3rd VO. Ventral fins reaching anus. Base of adipose fin somewhat in advance of vertical through end of base of anal fin. Luminous Organs. PLO 1.5-2 times its diameter below lateral line. PVOi slightly in

174

Memoir l y Part 7—Sears Foundation for Marine Research

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advance of PVO2. PO4 highly and abruptly elevated, directly over, slightly in front of or behind PO3 and about at level of PVOi. AOa level. Pol behind base of adipose fin and its diameter or less below lateral line. First AOp slightly in front of, or directly over anterior end of infracaudal luminous gland. Prc2 1-2.5 times its diameter behind PrciSupracaudal and infracaudal luminous glands about equal in length, in general slightly shorter than diameter of eye; distance between end of base of anal fin and anterior margin of infracaudal gland equal to, or slightly shorter than, length of gland. Size. This species grows to about 180 mm. Sexual maturity is apparently attained at sizes larger than 150 mm. Remarks. A direct comparison of the type specimens of L. luminosa and L. luminosa nitida Tining 1928, revealed no differences (Nafpaktitis and Paxton, 1968). Tdning introduced his subspecies on the basis of the division of the VO series into two groups. A grouping of the VO into 1 + 1 + 3 is clearly visible in Carman's type. Irregularities in the spacing of VO are not uncommon. Some specimens have 5 VO evenly spaced, others have the same number of VO but the series is divided into two groups (2 + 3). Still others have only 4 VO either evenly

spaced or with the VO2-VO3 interspace distinctly enlarged. Finally, in some cases where there are 5 VO, the 3rd is markedly reduced in size. With these differences considered to be expressions of intraspecific variation and in the absence of other, consistent differences, the maintenance of L. luminosa nitida is not warranted (Nafpaktitis and Paxton, 1968). Atlantic Distribution. Lampadena luminosa (Fig. 114) is a questionably tropical-semisubtropical species. The largest WHOI collections come from the Caribbean Sea and Straits of Florida. Extra-Atlantic Occurrence. Lampadena luminosa has been reported from the western Indian Ocean between about 7°N and 18°S and 60°E and 65°E (Nafpaktitis and Nafpaktitis, 1969) and the species is known in the eastern part of that ocean between approximately 7°N and 10°S. Further, it has been collected in the Mozambique Channel and off the east coast of South Africa to about 32°S. Elsewhere, L. luminosa has been taken in the Southeast Asian seas to about 15°N. The specimen reported from off Owase, Mie Prefecture, Japan (Matsubara, 1952) represents the northernmost record in the western North Pacific. The species has also been reported

Fishes of the Western North Atlantic

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FIGURE 114. Lampadena luminosa, a questionably tropical-semisubtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and Krefft (1970).

from off Hawaii (Clarke, 1973), near 3°30' N, 145 °W (Hartmann and Clarke, 1975), and from 4°J6TST, 142°54'W (Nafpaktitis and Paxton, 1968). Available data indicate that it occurs eastward in tropical waters of the South Pacific to about 105°W. (N) Vertical Distribution. In the WHOI collections, L. luminosa occurred mostly between 425 and 850 m during the day and between 40 and 225 m at night, with maximum catch at 75 m. Only juveniles 30 mm and smaller were

taken near Bermuda, where day captures were from 700-850 m (one specimen from 1,2501,300 m) and night captures were from 50300 m and from day depths, with maximum abundance at 100-150 m. Synonyms and References: Myctophum luminosum Carman, 1899: 263, PI. 55, Fig. 2 (orig. descr.; 0°57'30"S, 89°03'30"W; holotype, MCZ 28498). Lampadena luminosa nitida Taning, 1928: 62 (orig. descr.; in key); Nafpaktitis, 1973: 36, Fig. 33

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FIGURE 115. LampaJena urophaos atlanticai young, 33 mm. (desig. and descr. of lectotype: 17°43'N, 64°S6'W; ZMUCP2330214). LampaJena (Lychnophora) nitida. Fraser-Brunner, 1949: 1080, fig. (in key). Lampadena (Lychnophora) luminosa. Fraser-Brunner, 1949: 1080, fig. (in key). LampaJena nitida. Bekker, 1967b: 108 (records from North Atlantic). LampaJena luminosa. Nafpaktitis and Paxton, 1968: 4, Fig. 1 (descr., otol., taxon., distr.); Nafpaktitis and Nafpaktitis, 1969: 33, Fig. 39 (records from Indian Ocean, char.); Krefft, 1970: 276 (records from trop. Atlantic, char.); Clarke, 1973: 415 (vert, distr. off Hawaii).

Lampadena urophaos atlantica Maul 1969 Figures 115, 116 Study Material. Thirty-four specimens, 17-33 mm, taken by the WHOI vessel CHAIN (Sta. RHB 1740) at 31°31'N, 67°31'W; in LACM.

Distinctive Characters. The character differences that distinguish this subspecies from the Pacific L. urophaos are the position of the PVd (slightly in front of or directly under PVO2 in Pacific L. urophaos vs. behind, seldom directly under, PVO2 in L. urophaos atlantied), and, in specimens larger than about 50 mm, the relative sizes of the caudal luminous glands (supracaudal gland somewhat longer than infracaudal in Pacific specimens vs. supracaudal gland equal in length to infracaudal in L. urophaos atlantica).

Description. The following measurements, expressed in percent of SL, and counts are taken from Maul (1969) and are based on 19 specimens, including the holotype, ranging in size from 20.8 to 229 mm. Diameter of eye: 6.6-8.7. Depth of caudal peduncle: 8.7-13.9. Tip of snout to origin of anal fin: 62.867.7. Fin rays: dorsal 15 (16); anal 14; pectoral 16 (17). Gill rakers: 4 (3) + 1 + 9 (8), total 14 (13). Photophores: PO 5; VO 5; AO 5 + 2. Dentition. Medial and posterior mesopterygoid teeth markedly enlarged in specimens larger than about 90 mm. Fins. Origin of dorsal fin somewhat in advance of base of ventral fin. Pectoral fins extending to about bases of ventral fins. Base of adipose fin directly over or somewhat in advance of end of base of anal fin. Luminous Organs. PLO 1-3 times its diameter below lateral line. PVOi slightly behind, seldom directly under, PVO2. PO4 slightly elevated. AOa evenly spaced and level or nearly so. Pol behind base of adipose fin. Both AOp over anterior half of infracaudal luminous gland. Prci and Prc2 about one organ diameter apart from each other. Supracaudal and infracaudal glands equal in

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FIGURE 116. Lampadena uropbaos atlantica, a subtropical species. Distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and KrefFt (1970).

size or very nearly so, equal in length to or slightly longer than diameter of eye. Size. Members of this subspecies grow to a size well over 200 nun, the holotype measuring 229 nun. Remarks. The differences, as stated by Naf paktitis and Paxton (1968) and Maul (1969), between the Pacific and Atlantic populations are indeed very small and, in view of the geographic isolation of the two populations, not at all unexpected. The addition therefore of yet another name to the already overburdened

myctophid nomenclature might be argued against were it not for apparent marked differences in otolith morphology between Pacific and Atlantic specimens [see Naf paktitis and Paxton (1968: 24, Fig. 10) for otolith from Pacific and Kotthaus (1972a: 26, No. 76) for otolith from Atlantic specimens]. A more thorough comparative study of otoliths is needed for a clearer definition of the taxonomic status of the two populations. Atlantic Distribution. Lampadena urophaos atlantica (Fig. 116) is a subtropical

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FIGURE 117. Lampadena speculigera: young, 66 mm.

subspecies that is restricted to the North Atlantic. The largest WHOI collections come from the Northern Sargasso Sea. Extra-Atlantic Occurrence. L. urophaos urophaos is known in the North Pacific from North America west to about 160°W between about 25° and 42°N (Nafpaktitis and Paxton, 1968; Clarke, 1973). (BC) Vertical Distribution. Opening-closing devices took L. urophaos atlantica near Bermuda by day at 600-7 JO m; all were juveniles smaller than 30 mm. At night, the species was taken from JO to about 200 m, with one specimen each at 300-3JO m and JJ0-600 m. Opennet samples near Bermuda caught most specimens at 100-1 JO m at night. In the WHOI collections, L. urophaos atlantica occurred between JJO and about 1,000 m during the day, with no apparent maximum, and between 60 and 22J m at night, with maximum abundance at 100-1 JO m. References: Lampadena urophaos atlantica Maul, 1969 (orig. descr.; Camara de Lobos, Madeira; holotype, MMF Reg. No. 2464); Krefft, 1970: 275 (records from east. North Atlantic, char.); Kotthaus, 1972a: 13 (record from east. North Atlantic, char., photo of otol.); Krefft and Bekker, 1973: 185 (synon., ref., distr.).

Lampadena speculigera Goode and Bean 1896 Figures 117, 118 Study Material. Ten North Atlantic specimens, 20.597 mm; in ZMUC.

Distinctive Characters. The characters in the key will separate this species from the eastern North Atlantic form, L. pontifex. Description. The following measurements, expressed in percent of SL, are from 4 specimens 24—109 mm; the counts are from 30 specimens 20-130 mm: Diameter of eye: 10.4-10.9. Length of caudal peduncle: 22.7-24.4. Depth (least) of caudal peduncle: 11.212.9. Tip of snout to origin of anal fin: 63.063.6. Length of supracaudal luminous gland: 5.0-5.8. Length of infracaudal luminous gland: 7.3-10.1. Finrays: dorsal 14 (13-15); anal 14 (15); pectoral 14 (13-15). Gill rakers: 6-7 + 1 + 12-14, total 1922. Photophores: PO 5 (6); VO 5 (4-6); AO6-7 + 3-4 ( 5 ) . Lateral-line organs: 39—41.

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FIGURE 118. LampaJena speculigera, a bipolar temperate species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971), G. Krefft (in litt.), and Parin et aL (1974).

Vertebrae: 38-39 (40). Dentition. Mesopterygoid teeth uniformly small. Fins. Origin of dorsal fin over base of ventral fin. Pectoral fins extending to about vertical through 1st VO. Ventral fins reaching origin of anal fin. Base of adipose fin over end of base of anal fin. Luminous Organs. PLO about its own diameter below lateral line. PVOi slightly behind PVO2. AOa level, about one photophore diameter (1-2 diameters in fishes less than

30 mm) apart from each other. Pol under or slightly behind base of adipose fin and about its own diameter below lateral line, AOp evenly spaced, in a straight, gently ascending line; 1st and usually 2nd AOp in front of anterior end of infracaudal luminous gland. Prci and Prc2 about one photophore diameter apart from each other. Length of supracaudal gland %-% of that of infracaudal; distance between end of base of anal fin and anterior margin of infracaudal gland 1-1.5 times as great as length of this gland.

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FIGURE 119. Lampadena pontifex:

female, 76 mm.

Size. The largest specimen examined measured 130 mm. Atlantic Distribution. Lampadena speculigera (Fig. 118) is a bipolar temperate species. Unlike most "northern" species, it is not found in the Mediterranean Sea. Gibbs et al. (1971) report it from Ocean Acre off Bermuda, but otherwise it is unrecorded from subtropical seas. Extra-Atlantic Occurrence. Records summarized by Nafpaktitis and Paxton (1968) showed L. speculigera to occur in the southern Indian and Pacific oceans between about 31°S and 42°S and, so, to be circumglobal in the southern hemisphere. (BC) Vertical Distribution. Only juvenile L. speculigera smaller than 30 mm were taken by opening-closing devices near Bermuda. Except for a single specimen at 1,250-1,300 m, all day captures were at 700-850 m. The species was taken at night at 50-300 m and at day depths; maximum abundance was at 100-150 m. In the WHOI collections, L. speculigera occurred between 475 and 950 m by day, maximum catch at 800 m, and between 60 and 750 m at night, with maximum abundance at 100 m.

Synonym and References: Lampadena speculigera Goode and Bean, 1896: 85, PL 26, Fig. 99 (orig. descr.; 39°48'N, 70°36'W, 551 fms; holotype, USNM 43797); Bolin, 1959: 24 (synon., char., distr.) ; Bekker, 1967b: 108 (records from North Atlantic); Nafpaktitis and Paxton, 1968: 10, Fig. 3 (descr., otol., distr.); Nafpaktitis and Nafpaktitis, 1969: 34, Fig. 41 (records from South Indian Ocean, descr.); Craddock and Mead, 1970: 3.28 (record from off Chile, 33°42'S, 73° 3S'W) ; Krefft and Bekker, 1973: 184 (synon., ref., distr.). Lampadena braueri Zugmayer, 1914: 2 (orig. descr.; 40°15'N, S6°2J'W, 0-4,000 m; MOM, fide Krefft and Bekker, 1973).

Lampadena pontifex Krefft 1970 Figures 119, 120 Distinctive Characters. The characters in the key will separate this species from its North Atlantic congener L. speculigera. Description. Measurements in percent of SL, counts as well as the description that follows are from Krefft (1970) and based on the holotype (91.5 mm) and five paratypes (26.6-93.4 mm). Diameter of eye: 9.4—10.9. Length of caudal peduncle: 24.3-25.4. Depth of caudal peduncle: 10.7-11.4.

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FIGURE 120. LampaJena pontifex, a Mauritanian Upwelling species. Distribution, based on the WHOI collections.

Tip of snout to origin of anal fin: 58.961.8. Length of supra caudal luminous gland: 8.2-9.9. Length of infracaudal luminous gland: 10.4-11.3. Fin rays: dorsal 14; anal 14; pectoral 14 (13-15). Gill rakers: 7 + I + 14-16, total 22-24. Photophores: PO 5; VO 5; AO 6 (7) + 3 (4). Lateral-line organs: 39-40. Vertebrae: 38.

Dentition: Mesopterygoid teeth uniformly small. Fins. Origin of dorsal fin slightly in advance of bases of ventral fin. Pectoral fins extending a little beyond bases of ventral fins. Ventral fins reaching base of 3rd ray of anal fin. Base of adipose fin about over end of base of anal fin. Luminous Organs. PLO 1-2 times its diameter below lateral line. PVd from slightly in advance of to slightly behind vertical through middle of PVO2. VO evenly spaced or VOi-VO2 interspace somewhat enlarged,

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FIGURE 121. Lampadena chavesi: young, 54.5 mm.

the series forming a slight arc. AOa level and 1-1.5 photophore diameters apart from each other. Pol under or somewhat behind base of adipose fin and about its own diameter below lateral line. AOp along dorsal margin of infracaudal gland. Prci and Prc2 0.5-1 photophore diameter apart from each other. Length of supracaudal gland about % of that of infracaudal; distance between end of base of anal fin and anterior margin of infracaudal gland less than half as great as length of this gland which is somewhat longer than diameter of eye. Size. The largest specimen reported measures 110 mm. Atlantic Distribution. Lampadena pontifex (Fig. 120) has the most restricted range of any North Atlantic myctophid, being limited to the Mauritanian Upwelling and apparently to the southern province of that region. L. pontifex is not known from outside the North Atlantic. Vertical Distribution. In the WHOI collections, L. pontifex occurred between 27 5 and 750 m during the day and between 90 and 275 m at night. Reference: Lampadena pontifex Krefft, 1970: 277, Figs. 1, 2 (orig. descr.; 14°3l'N, 17°39'W, 0^100 m; holotype, ISH, 662/64a).

Lampadena chavesi Collett 1905 Figures 121, 122 Distinctive Characters. The wide PrciPrc2 interspace and the very long infracaudal luminous gland, which occupies nearly the entire length of the caudal peduncle, readily differentiate this species from its North Atlantic congeners. Description. The following measurements, expressed in percent of SL, are from 5 specimens 34—60 mm (Nafpaktitis and Paxton, 1968); the counts are from 31 specimens (Nafpaktitis and Paxton, 1968, and Krefft, 1970): Diameter of eye: 8.8-11.3. Length of caudal peduncle: 25.8-27.9. Depth (least) of caudal peduncle: 9.511.5. Tip of snout to origin of anal fin: 58.060.9. Length of supracaudal luminous glands about 11. Length of infracaudal luminous gland: 15.1-18.6. Fin rays: dorsal 14 (13-15); anal 13-14 (12); pectoral 15-17. Gill rakers: 6-7 + 1 +13 (12-14), total 20-22. Photophores: PO 5; VO 5 (4-6); AO 7-8 (6) + 2 (1-3).

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FIGURE 122. Lampadena chavesi, a bipolar questionably subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971), Krefft (1970, 1974), and Parin et al. (1974).

Lateral-line organs: 38 (39). Vertebrae: 37-38. Eyes. A conspicuous crescent of whitish tissue, best seen in preserved specimens, on dorsal half of iris. Dentition. Mesopterygoid teeth uniformly small. Fins. Origin of dorsal fin over base of ventral fin. Pectoral fins reaching bases of ventral fins. Ventral fins extending to origin of

anal fin. Base of adipose fin behind base of anal fin. Luminous Organs. PLO 1-1.5 times its diameter below lateral line. PVd directly under or slightly behind PVO2. VO evenly spaced or distinctly grouped (2 + 3), the series forming an arc. Last 1-3 AOa behind base of anal fin. Pol about under base of adipose fin and its own diameter or less below lateral line. AOp widely spaced, about over

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Memoir 1, Part 7—Sears Foundation for Marine Research

FIGURE 123. Lampadena anomala: male, 126 mm.

middle of and in contact with infracaudal gland. Distance between Prci and Prc2 equal to, or somewhat smaller than, distance between Prc2 and Prc3. Caudal glands largest in genus; infracaudal gland very long, flat in cross section and tapering posteriorly rather than anteriorly; distance between end of base of anal fin and anterior margin of infracaudal gland equal to about twice the diameter of a photophore. Size. Members of this species do not seem to grow much larger than about 75 mm. Sexual maturity is apparently attained at a size of about 58 mm (Krefft, 1970). Atlantic Distribution. Lampadena chavesi (Fig. 122) is a bipolar questionably subtropical species. It appears to be most abundant in the poleward parts of the sub tropics; most WHOI specimens come from close to the temperate-subtropical boundary. Extra-Atlantic Occurrence. Lampad-ena chavesi is known from the southwestern Indian Ocean between about 26°S and 32°S (Nafpaktitis and Nafpaktitis, 1969) and from the southeastern Pacific Ocean off Chile between and 31°S and 34°S (Craddock and Mead, 1970). (BC) Vertical Distribution. The few captures of L. chavesi near Bermuda with opening-closing devices were at 600-800 m by day and at 50}20 m at night, except for one juvenile takeq

at day depth at night. Near the Canary Islands the few specimens were taken in the upper 150 m at night. In the WHOI collections, L. chavesi was taken at 700-800 m by day and at 40-175 m at night, with maximum catch at 75-100 m. References: Lampadena chavesi Collett, 1905: 728 (orig. descr.; off the Azores; Zoologisk Museum, Oslo, holotype, J 693, fide Krefft and Bekker, 1973); Bolin, 1959: 24 (synon., char., distr.); Nafpaktitis and Paxton, 1968: 18, Fig. 7 (descr., otol., distr.); Nafpaktitis and Nafpaktitis, 1969: 37, Fig. 45 (records from South Indian Ocean, char., distr.); Craddock and Mead, 1970: 3.28 (records from off Chile); Krefft, 1970: 274 (records from Atlantic Ocean, char., distr.); Kotthaus, 1972a: 13 (records from east. North Atlantic, char., photo of otol.); Krefft and Bekker, 1973: 185 (synon., ref., distr.).

Lampadena anomala Parr 1928 Figures 123, 124 Study Material. One (about 50 mm), DANA Sta. 1230 III, 23°13'N, 82°21'W, in ZMUC; 1 (134 mm), OREGON II Sta. 10638, 28°36'N, 87°07'W, in LACM.

Distinctive Characters. The poorly developed photophores and caudal glands, the low numbers of VO and AOa, and the gillraker counts (16-18) which are higher than those in the low-count members of the genus

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FIGURE 124. LampaJena anomala, a questionably tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections, and records from Gibbs et aL (1971), Krefft (1970), and W. Kmeger (in litt.).

(L. luminosa, L. urophaos at Ian tica; 13-15) but lower than those in the high-count species (L. speculigera, L. pontifex, L. chavesi\ 1924) distinguish this uncommon species from its congeners. Description. The measurements (in percent of SL) given below are from the OREGON II specimen mentioned above, followed, in parentheses, by those from 6 specimens reported by Krefft (1970). The counts are based on the holotype and all specimens reported so far, except for 3 (30-49 mm) listed by Clarke (1973) from off Hawaii.

Diameter of eye: 6.7 (6.2-9.5). Length of caudal peduncle: 21.6 (22.925.0). Depth of caudal peduncle: 10.8 (9.210.6). Tip of snout to origin of anal fin: 63.2 (59.0-62.9). Length of supracaudal luminous gland: 9.3 (8.7-11.0). Length of infracaudal luminous gland: 9.7 (8.8-11.3). Fin rays: dorsal 14-16; anal 13-14; pectoral 16-18.

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Gill rakers: 5 + 1 + 11 (10-12), total 17 (16-18). Photophores: PO 5; VO 3; AO 3 (4) + 2. Lateral-line organs: 36-37. Vertebrae: 36. Dentition. Mesopterygoid teeth enlarged, needle-like, widely spaced. fins. Origin of dorsal fin in advance of base of ventral fin. Pectoral fins broken in all specimens examined. Ventral fins extending about to anus. Base of adipose fin about over end of base of anal fin. Luminous Organs. PLO 2-3 times its diameter below lateral line. PVd on or slightly behind vertical through center of PVO2. VO evenly spaced or distinctly grouped (2 + 1). AOa widely spaced, level. Pol about twice its own diameter below lateral line. AOpi usually in front of anterior end of infracaudal gland. Prci and Prc2 about one organ diameter apart from each other. Supracaudal gland equal in length to, or slightly shorter than infracaudal; distance between end of base of anal fin and anterior margin of infracaudal gland slightly shorter to somewhat longer than length of same gland. Size. The largest specimen reported so far measures 149.7 mm (Krefft, 1970). Atlantic Distribution. Lampadena anomala (Fig. 124) is a rare deep-living species possibly conforming to the tropical-subtropical pattern. Extra-Atlantic Occurrence. A single specimen of Lampadena anomala has been reported from the western Indian Ocean at 6°OlTsf, 64°59'E (Nafpaktitis and Nafpaktitis, 1969) and three specimens from near Hawaii (Clarke, 1973). A single individual has also been taken north of New Guinea at 1°20'S, 138°42/E. (N) Vertical Distribution. The single L. anomala taken by an opening-closing device near Bermuda was caught during the night at 450500 m. In the WHOI collections, one L. anomala

was taken by day at 800 m and two at night, one at 500 m, one at 1,500 m. Krefft (1970) reported six WALTHER HERWIG specimens— two by day each at about 2,000 m and three at night, one at 330 m and two between 500 and 600 m. References: Lampadena anomala Parr, 1928: 150, Fig. 35 (orig. descr.; 32°24'N, 64°29'W, 10,000 f.w.o.; holotype, BOG 2272); Nafpaktitis and Pazton, 1968: 23 (single specim., 13°12'N, 72°47'W, descr., otol, relationships); Nafpaktitis and Nafpaktitis, 1969: 38 (single specim. from Indian Ocean); Krefft, 1970: 280, Fig. 4 (6 specim., central Atlantic, descr., distr.); Clarke, 1973: 406 (3 specim. from off Hawaii).

Genus Taaningichthys Bolin 1959 Taaningichthys Bolin, 1959: 25 (type-species Lampadena bathyphila Taning 1928, by original designation); Pazton, 1972: 46 (definition, osteological characters).

Characters. Eye very large, its diameter less than 3.5 times in hi; a crescent of whitish tissue on posterior half of iris (best seen in preserved specimens). Mouth rather large; jaws extending 0.5-0.7 of eye diameter behind vertical through posterior margin of orbit; palatines and mesopterygoids sparsely toothed; no teeth on vomer. Origin of dorsal fin behind base of ventral fin. Origin of anal fin behind end of base of dorsal fin. Lateral line very poorly developed or absent. Dn absent; Vn very small, poorly defined. Photophores present or absent; if present, PO 57; VLO usually nearer to horizontal septum than to base of ventral fin; VO 3-10, level; a single SAO; a single Pol; Prc 2 + 1 . Both sexes with large, undivided, translucent, supracaudal and infracaudal luminous glands bordered by heavy black pigment. Size. Small to moderate-size myctophids, not growing larger than about 100 mm. Range. In all three major oceans, between about 40°N and 40 °S, with one 67-mm-long

Fishes of the Western North Atlantic specimen taken by the USNS ELTANIN at 67°31'Sf 90°26'W. Species. The genus includes three known species all of which occur in the North Atlantic: !T. bathyphilus, T. minimus, and T. paurolychnus.

187

Remarks. No material has been examined for the present study. Data and descriptions are based on works by Bolin (1959), Nafpaktitis and Nafpaktitis (1969), Davy (1972), and Nafpaktitis (1973).

Key to the Species of Taaningichthys la. Photophores absent. paurolychnus Davy 1972, p. 191 Ib. Photophores present 2 2a. VO 3-5; AO 1-4 + 1-2, total 2-5; Pol behind base of adipose fin; Prci-Prc2 interspace equal to, or less than, one photophore diameter, bathyphilus (Tining) 1928, p. 189 2b. VO 8-10; AO 5-7 + 4-6, total 9-13; Pol directly under or in front of base of adipose fin; Prci-Prc2 interspace greater than one photophore diameter. minimus (Tining) 1928, p. 187 Taaningichthys minimus (Tining) 1?28 Figures 125, 126 Distinctive Characters. In addition to the characters in the key, the presence on the dentaries near the symphysis of one or more enlarged, broad-based, posteriorly-hooked teeth and the higher number of vertebrae distinguish this species from its two congeners. Description. Fin rays: dorsal 11-13; anal 12-13 (1114); pectoral 15-17. Gill rakers: 4-5 + 1 + 11 (10-13), total 16-17 (15-18).

Photophores: VO 8-10; AO 5-7 + 4-6, total 9-13. Vertebrae: 40-41. Fins. Pectoral fins extending well beyond bases of ventral fins. Base of adipose fin directly over or slightly behind end of base of anal fin. Luminous Organs. PLO midway between base of pectoral fin and horizontal septum or somewhat higher. PVOi directly under or a little behind PVO2. VO forming a wavy line. Single SAO directly over or in advance of last VO and about 1.5 times its diameter below

FIGURE 125. Taaningichthys minimus: lectotype (ZMUC P2329221), female, 53 mm.

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FIGURE 126. Taaningichthys minimus, a questionably subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Badcock and Merrett (1976), Gibbs et al. (1971), Kotthaus (1972a), W. Krueger (in litt.), and Parin et al. (1974).

horizontal septum. Pol directly under or slightly in front of base of adipose fin and about 1.5 times its own diameter below horizontal septum. Prci and Prc2 about 2 photophore diameters apart from each other. Supracaudal gland about % as long as infracaudal in adult males (over 40 mm), somewhat shorter in adult females of comparable sizes; infracaudal gland occupying about % of length of caudal peduncle. Size. Members of this species, the smallest

in the genus, grow to about 65 mm. Sexual maturity is apparently reached at a size of about 40 mm. Remarks. As already noted, T. minimus is the smallest of the three species in the genus. It is also the shallowest. Perhaps correlated with this occurrence in shallower waters is the fact that a number of features, such as photophores, scalation, musculature, etc., are better developed in this species than in its two, deeper-dwelling congeners.

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FIGURE 127. Taaningichthys bathyphilus: male, 43.5 mm.

Atlantic Distribution. Taaningichthys minimus (Fig. 126), unlike its congeners, is a mesopelagic species (Gibbs et aL, 1971; Clarke, 1973). It is uncommon and tentatively regarded as a bipolar subtropical species. Extra-Atlantic Occurrence, Taaningichthys minimus has been reported from the Indian Ocean between about 20° and 30°S (Nafpaktitis and Nafpaktitis, 1969; Davy, 1972). Elsewhere, the species has been collected in the central and eastern North Pacific between 12° and 35°N (Berry and Perkins, 1966; Davy 1972; Clarke, 1973). (N) Vertical Distribution. Near Bermuda, T. minimus was collected with opening-closing devices between 600 and 800 m by day and was dispersed between 200 and 600 m at night. Contrary to the findings of Davy (1972), a substantial proportion of the population does migrate vertically (Gibbs et aL, 1971). The WHOI records are similar, except that at night specimens were taken as shallow as 90 m. Synonym and References: Lampadena minima Taning, 1928: 63 (orig. descr.; in key); Parr, 1928: 154, Fig. 37 (record from west. North Atlantic, descr.). Taaningichthys minimus. Bolin, 1959: 25 (in key); Berry and Perkins, 1966: 659 (records from east. North Pacific); Backus et aL, 1969: 96 (records

from west. North Atlantic); Nafpaktitis and Nafpaktitis, 1969: 39, Fig. 48 (record from west. South Indian Ocean, descr.); Davy, 1972: 69, Figs. 1, 2, 5 (descr., otol., distr.); Kotthaus, 1972a: 13 (record from east. North Atlantic, char., photo of otol.); Clarke, 1973: 406, 416 (records from off Hawaii, vert, distr.); Nafpaktitis, 1973: 37, Fig. 34 (desig. and descr. of lectotype: 15°50'N, 26°32'W, 1,000 m.w.o.; ZMUC P2329221); Krefft and Bekker, 1973: 198 (synon., ref., distr.).

Taaningichthys bathyphilus (Tining) 1928 Figures 127, 128 Distinctive Characters. In addition to the characters in the key, the lower number of gill rakers and the absence of enlarged, broadbased, posteriorly-hooked teeth on the dentaries near the symphysis distinguish this species from T. minimus. The presence or absence of photophores is the most reliable character which will separate T. bathyphilus from T. paurolychnus. Description. fin rays: dorsal 12-13 (11-14); anal 13 (12-14); pectoral 12-14. Gill rakers: 3 (2-4) + 1 + 7 - 8 ( 5 - 9 ) , total 11-12 (9-14). Photophores: VO 4 (3-5); AO 3 (1-4) + 1 (2), total 4 (2-5). Vertebrae: 34^36. Fins. Pectoral fins extending to or slightly beyond bases of ventral fins. Base of adipose

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FIGURE 128. Toaningichtbys batbyphilvs, a bathypelagic species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Badcock and Merrett (1976), R. Baird (in litt.), Bolin (1959), Davy (1972, and papers cited therein), Rotthaus (1972a), and Parin et al. (1974).

fin directly over or slightly behind end of base of anal fin. Luminous Organs. PLO varying in position, usually somewhat nearer to horizontal septum than to base of pectoral fin. PVOi directly under or slightly behind PVO2. VO level. SAO behind last VO and about its diameter below horizontal septum. Pol behind base of adipose fin and about its diameter below horizontal septum. Prci and Prc2 one organ diameter or less apart from each

other. Minute secondary photophores on head. Supracaudal gland about % of length of infracaudal, the latter occupying about % of length of caudal peduncle. Size. This species grows to about 80 mm. A gravid female reported by Davy (1972) measured 57 mm. Atlantic Distribution. Taaningichthys bathyphilus (Fig. 128) is an uncommon myctophid better regarded as bathypelagic than as mesopelagic. WHOI collections and the

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FIGURE 129. Taaningichthys paurolychnus: female, 79 mm.

Atlantic Ocean literature records for this species (Davy, 1972) come mainly from the North Atlantic Subtropical Region, although there are some from the adjacent tropical and temperate regions. It may be that bathypelagic species in no way conform to the biogeographic system used here, which has been worked out using mesopelagic species. Extra-Atlantic Occurrence. Taaningichthys bathyphilus is known from the Indian Ocean east of 60 °E between about 8°N and 30°S (Nafpaktitis and Nafpaktitis, 1969; Davy, 1972; and unpublished data). The species has also been collected in the South China Sea, the Tasman Sea, and across the Pacific Ocean between approximately 41 °N and 40°S, with a single record from 67°31/S,90°26'W (Davy, 1972; Clarke, 1973; McGinnis, 1974; and unpublished data). (N) Vertical Distribution. There is no evidence that T. bathyphilus migrates vertically. It was taken with opening-closing devices near Bermuda between 800 and 1,550 m by day and between 800 and 1,000 m at night. Most WHOI specimens were likewise from deeper than 800 m; the shallowest was from 625 m. Synonym and References: LampaJena bathyphila Taning, 1928: 63 (orig. descr.; in key); Parr, 1928: 151, Fig. 36 (records from west. North Atlantic, descr.). Taaningichthys bathyphilus. Bolin, 1959: 25, Fig. 6

(key, descr., distr., desig. of lectotype: 25°ll'N, 20°57'W, 6,000 m.w.o.; ZMUC P2329220); Berry and Perkins, 1966: 659 (record from east. North Pacific); Nafpaktitis and Nafpaktitis, 1969: 39, Figs. 46, 47 (records from west. Indian Ocean, char.); Davy, 1972: 70, Figs. 3, 5 (descr., otol., distr.); Kotthaus, 1972a: 13 (records from east. North Atlantic, char., photo of otol.); Clarke, 1973: 406, 415 (records from off Hawaii, vert, distr.); Nafpaktitis, 1973: 38, Fig. 35 (illus. and char, of lectotype); Krefft and Bekker, 1973: 197 (synon., ref., distr.).

Taaningichthys paurolychnus Davy 1972 Figures 129, 130 Distinctive Character. The absence of photophores will separate this species from its two congeners. Description. Fin rays: dorsal 12-13 (11); anal 13 (1114); pectoral 14 (13-15). Gill rakers: 3-4 + 1 + 9-10 (8-11), total 13-15 (12-16). Photophores: absent. Vertebrae: 35-36. Dentition. No enlarged, broad-based, posteriorly-hooked teeth on dentaries near symphysis. Fins. Pectoral fin reaching base of ventral fin. Base of adipose fin directly over or somewhat behind end of base of anal fin. Luminous Organs. Minute secondary photophores on head and interradial mem-

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branes of caudal fin. Supracaudal gland %% of length of infracaudal, the latter occupying approximately % of length of caudal peduncle. Size. This species grows to about 95 mm. It apparently attains sexual maturity at a size of about 65 mm. Remarks. T. paurolychnus is the largest, rarest, and deepest-dwelling member of the genus. It may be scarce because it occurs at depths greater than 900 m. Like T. batbyphilus, T. paurolychnus does not seem to migrate vertically.

Atlantic Distribution. Taaningichthys paurolychnus (Fig. 130) is a rare bathypelagic species, and there are but four Atlantic records (Davy, 1972; Badcock, unpublished). Extra-Atlantic Occurrence. One specimen of Taaningichthys paurolychnus is known from the Indian Ocean at 4°S, 60°E (Davy, 1972) and one from off Luzon, the Philippines, at 14°37/N, 119°S2'E. However, there are numerous records from California to Hawaii between 20°N and 37°N (Berry and Perkins, 1966; Davy, 1972; Clarke, 1973) and three records from east of 115°W be-

Fishes of the Western North Atlantic tween the equator and 17°S (Davy, 1972). (BC) Vertical Distribution. Taaningichthys paurolychnus is the deepest living myctophid and probably does not migrate vertically; all known specimens are from deeper than 900 m (Davy, 1972). Three specimens of T. paurolycbnus have been taken in the North Atlantic with opening-closing devices, all by DISCOVERY: one near the Cape Verde Islands between 1,300 and 2,000 m (Davy, 1972), and two near Bermuda between 1,500 and 2,000 m (Badcock, personal communication). References: Taaningichthys spp. Berry and Perkins, 1966: 659 (records from east. North Pacific Ocean). Taaningichthys paurolychnus Davy, 1972: 71, Figs. 4-6 (orig. descr.; 31°18.S'N, 119°02.7'W; SIO 7019); Clarke, 1973: 406 (record from off Hawaii).

Genus Lampanyctus Bonaparte 1840 Lampanyctus Bonaparte, 1840 (type-species Nyc tophus bonapartii Cocco 1838 = Gasteropelecus crocodilus Risso 1810, by monotypy) ; Fraser-Bnmner, 1949: 1081 (description; subdivision of genus into subgenera Lampanyctus, Stenobrachius, Triphoturus and Lepidophanes) ; Bolin, 1959: 26 (definition of genus; accorded Lepidophanes full generic status and proposed similar status for Stenobrachius and Triphoturus); Pazton, 1972: 48 (definition, including osteological characters) . Nannobrachium Giinther, 1887: 199 (type-species Nannobrachium nigrum Giinther 1887, by monoNyctimaster Jordan, 1921: 645 (type-species Lampanyctus jordani Gilbert 1913, by original designation) . Serpa Whitley, 1933: 64 (type-species Gasteropelecus crocodilus Risso 1810, by original designation). Parvilux Hubbs and Wisner, 1964: 448 (type-species Parvilux ingens Hubbs and Wisner 1964, by original designation). Paralampanyctus Kotthaus, 1972a: 13 (type-species Nannobrachium nigrum Giinther 1887, by original designation) .

Characters. Mouth large, extending far behind orbit; maxillary slender, slightly but

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abruptly expanded posteriorly. Dn absent; Vn present, small; PVOi always well below PVO2, the two organs below level of upper end of base of pectoral fin; 5 PO, the 4th elevated; 4 VO, level, arched, or VO2 elevated; SAO usually angulated; 2 Pol in an oblique line; 4 Prc, often continuous with AOp; supracaudal and infracaudal luminous glands present in both sexes and consisting of overlapping scalelike structures not framed by black pigment; one or two similar structures sometimes present at base of adipose fin; secondary photophores present in some species. Size. Small to large myctophids, many species growing larger than 100 mm and at least one attaining a size of about 240 mm. Range. In all three major oceans and from antarctic to northern temperate waters. Species. Our knowledge of this speciose genus is by no means clear. Least known and understood are the taxonomic status and relationships of the several forms characterized by very short pectoral fins. Much of the difficulty in studying these fishes arises from the fact that many forms, especially those with short pectoral fins, are very fragile. As a result, a great deal of the available material is in such poor condition that specific identification is extremely difficult, if at all possible. Thirty-one species are currently recognized. These are L. acant hums, L. achirus, L. alatus, L. ater, L. australis, L. boschmai, L. crocodilus, L. cuprarius, L. fernae, L. festivus, L. hubbsi, L. idostigma, L. ingens, L. intricarius, L. isaacsi, L. iselinoides, L. jordani, L. lepidolychnus, L. lineatus, L. macdonaldi, L. macropterus, L. niger, L. nobilis, L. omostigma, L. parvicauda, L. photonotus, L. pusillus, L. regalis, L. ritteri, L. steinbecfd, and L. tenuiformis. Of these, 13 (L. alatus, L. ater, L. crocodilus, L. cuprarius, L. festivus, L. intricarius, L. isaacsi, L. lineatus, L. macdonaldi, L. nobilis, L. photonotus, L. pusillus, and L. tenuiformis) occur in the North Atlantic. Two, L. crocodilus and L. pusillus, are found also in the Mediterranean Sea.

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la. Gill rakers 21-26. macdonaldi (Goode and Bean) 1896, p. 195 Ib. Gill rakers fewer than 20 2 2a. Pectoral fins short, not extending beyond bases of ventral fins. VLO high, in contact with, or less than twice its own diameter below lateral line (except for L. alatus which has a high VLO but very long pectoral fins) 3 2b. Pectoral fins long, extending beyond bases of ventral fins. VLO low, midway between base of ventral fin and lateral line or higher but more than 3 times its own diameter below lateral line (except for L. alatus which has very long pectoral fins but a high VLO) 6 3a. VO2 abruptly and highly elevated, lying over VOi. isaacsi Wisner 1974, p. 201 3b. VO2 well behind and only a little higher than VOi 4 4a. Prc continuous with AOp; AO 9-12; lateral-line organs 33; pectoral fin rays 1112. cuprarius Tining 1928, p. 197 4b. Prc usually distinctly separate from AOp; AO 12-16; lateral-line organs 35-38; pectoral fin rays ?-14 5 5 a. SAOi behind VO3; lateral-line organs 37-38; dorsal fin rays 16-18; origin of anal fin in front of vertical through middle of base of dorsal fin; pectoral fin rays 12-14. lineatus Tuning 1928, p. 199 5b. SAOi in front of VO8; lateral-line organs 35-36; dorsal fin rays 13-15; origin of anal fin behind vertical through middle of base of dorsal fin; pectoral fins extremely short and fragile, rays very difficult to count. ater Tining 1928, p. 203 6a. 1-3 cheek photophores 7 6b. No cheek photophores 11 7a. Luminous tissue at base of adipose fin 8 7b. No luminous tissue at base of adipose fin 10 8a. A single cheek photophore; VLO high, about its own diameter below lateral line (see 2a.); lateral-line organs 35-36. alatus Goode and Bean 1896, p. 223 8b. 1-3 cheek photophores; VLO low (see 2b.); lateral-line organs 38-40 9 9a. AOa 8-9; anterior two AOa abruptly depressed, a line through them passing below AOa8; 1-2, rarely 3, cheek photophores; pectoral fins extending beyond origin of anal fin. intricarius Tuning 1928, p. 209 9b. AOa 5-7; anterior two AOa not abruptly depressed, a line through them passing above AOa8; 3, sometimes 2, cheek photophores; pectoral fins not reaching origin of anal fin. crocodilus (Risso) 1810, p. 206 lOa. 2 cheek photophores; Prc separate from AOp; infracaudal luminous gland extending along entire length of caudal peduncle; lateral-line organs 37-38. photonotus Parr 1928, p. 211 10b. 1 cheek photophore; Prc continuous with AOp; infracaudal luminous gland occupying %, or less, of length of caudal peduncle; lateral-line organs 33-34. pusillus (Johnson) 1890, p. 221 11 a. SAOi behind VO8; Prc separate from AOp; Prc2-4 in a straight line. nobilis Tuning 1928, p. 214 lib. SAOi in front of, seldom directly over, VO3; Prc continuous with AOp; Prc2-4 not in a straight line 11

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12a. Pectoral fin rays 15-17; AO 15-16; Prc3 usually higher than Prci. festivus Tuning 1928, p. 216 12b. Pectoral fin rays 13-14; AO 12-13; Prc3 usually at level of Prci. tenuiformis (Brauer) 1906, p. 218 Lampanyctus macdonaldi (Goode and Bean) 1896 Figures 131, 132 Study Material. Six specimens, 64-137 mm, from the western North Atlantic; in MCZ and LACM.

Distinctive Characters. The species is easily distinguished from the rest of its North Atlantic congeners by the high number of its gill rakers. Description. Data within brackets are from Bolin (1959). Fin rays: dorsal 14-15 [14 (13-15) ]; anal 16-17 [17 (15-18)]; pectoral 12-13 [13 (12-13)]. Gill rakers: 7-8 + 1 + 15 (14-17), total 23 (22-26) [7 (6-8) + 1 + 16 (14-18), total 24 (21-26)]. Photophores: AO 6-7 + 7-8, total 13-15 [7 (6-8) + 7 (6-8), total 14 (13-15)]. Lateral-line organs: 37 [36 or 37]. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin under posterior half of base of dorsal fin. Pectoral fins

FIGURE 131. Lampanyctus macdonaldi: female, 96 mm.

delicate and short, not quite reaching vertical through PO5. Ventral fins extending to origin of anal fin. Base of adipose fin directly over or somewhat in advance of vertical through end of base of anal fin. Luminous Organs. Two cheek photophores, one about in middle of cheek, the other near preopercular margin. PLO 1-2 times its own diameter nearer to lateral line than to base of pectoral fin. PVOi directly under or slightly behind PVO2 which is in front of upper half of base of pectoral fin. PO4 on or a little behind vertical through PO3, at, or slightly higher than, level of PVO2. VLO midway between base of ventral fin and lateral line or slightly higher. VO level or nearly so. SAOi usually somewhat in advance of VO3 and on or a little below straight line through SAO2 and VLO; SAO2 about over origin of anal fin; SAO3 slightly behind SAO2 and less than its own diameter below lateral line. AOa series slightly arched. Poll behind straight line through last AOa and Pol2 which

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FIGURE 132. Ltmpanyctus macdonaldi, a bipolar *ubpol*r-tempe?ate species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from G. Krefft (in litt.), Jensen (1948), and Norman (1930, as L. intricarius).

is directly under or somewhat in advance of base of adipose fin and less than its own diameter below lateral line. AOp behind base of anal fin, evenly spaced, level. Prc continuous with AOp or very nearly so; first 3 organs about equidistant from each other and forming an arc; Prc4 on or somewhat behind vertical through Prc3 and in contact with lateral line. Supracaudal and infracaudal luminous glands consisting of 3-4 and 7-8 poorly

defined scalelike structures, respectively; infracaudal series occupying entire or nearly entire length of caudal peduncle. A poorly defined patch of luminous tissue at anterior end of base of adipose fin. Size. One of the larger myctophids. The largest specimen examined measured 137 mm, but a specimen 142 mm long has been reported by Bekker (1967b). Atlantic Distribution. Lampanyctus mac-

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FIGURE 133. Lampanyctus cuprarius: lectotype (ZMUC P2330213), female, 63 mm.

donaldi (Fig. 132) is a bipolar subpolar-temperate species. Most WHOI specimens come from the Atlantic Subarctic Region and from the northern part of the Azores-Britain Province. Extra-Atlantic Occurrence. It is probable that L. macdonaldi occurs circumglobally in the Southern Ocean between the Subtropical Convergence and the Polar Front, although there are few Atlantic sector records and no Indian Ocean sector records (McGinnis, 1974). (BC) Vertical Distribution. In the WHOI collections, L. macdonaldi occurred by day between 550 m and deeper than 1,000 m. At night, juveniles were between 60 and 175 m, adults, deeper than 850m. Synonyms and References: Nanobranchium mac donaldi Goode and Bean, 1896: 94, PL 29, Fig. 110 (orig. descr.; 39°48'N, 70°36'W, 551 fms; holotype, USNM 39478). Lampanyctus macdonaldi. Parr, 1929: 20, Fig. 9 (char.); Fraser-Bninner, 1949: 1084, fig. (in key); Bolin, 1959: 31, Fig. 7 (synon., descr., distr.); Bussing, 1965: 207 (records from southeast. Pacific between approx. 46° and 57°S and from Drake's Passage between approx. 61° and 77°W); Bekker, 1967b: 116 (records from east. North Atlantic); Craddock and Mead, 1970: 3.29 (records from off Valparaiso, Chile); Kretft and Bekker, 1973: 189 (synon., ref., distr.).

cuprarius Tining 1928 Figures 133, 134 Study Material. One hundred and sixteen specimens, 22-77 mm, from across the North Atlantic, the Caribbean Sea, and the Gulf of Mexico; in LACM.

Distinctive Characters. The position of the SAOi distinguishes this species from L. ater\ the position of the VO2 separates it from L. isaacsi; and the lower numbers of AO and lateral-line organs differentiate it from L. lineatus. Description. fin rays: dorsal 16-18; anal 17-19; pectoral 11-12. Gill rakers: 5 + 1 + 11-12. Photophores: AO 5-6 (7) + 5 (4-6), total 10^11 (9-12). Lateral-line organs: 32-33. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin in advance of vertical through middle of base of dorsal fin. Pectoral fins short, not reaching PO4; rays very delicate. Ventral fins extending to anus. Base of adipose fin on or slightly in advance of vertical through end of base of anal fin. Luminous Organs. No photophores on cheek. PLO 0.5-1.5 times its diameter below lateral line. PVOi somewhat in advance of, directly under, or a little behind PVO2. PO4 slightly higher than PVO2 and behind vertical

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FIGURE 134. Lampanyctus cuprarius, * bipolar subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and Parin et al. (1974).

through PO8. VLO immediately below lateral line. VO series distinctly arched. SAOi behind VOS and lower than SAO2 which is behind vertical through origin of anal fin, sometimes directly over 1st AOa; SAO3 on or somewhat behind vertical through 1st AOa and at lateral line; a straight line through SAO3 and SAO2 passing well behind VO4, often through, or even behind origin of anal fin. AOai usually depressed; AOai-AOa2 interspace enlarged. Pol2 in advance of base of adipose fin and in contact with lateral line.

First AOp usually over base of anal fin. Prc continuous with AOp; first 3 Prc forming an angle of approximately 110°; Prc4 behind Prc3 and at level of lateral line. Supracaudal luminous gland with 2-3 poorly defined scalelike structures; infracaudal gland with 3-4 similar structures occupying 50-65 percent of length of caudal peduncle. No luminous tissue at base of adipose fin. Minute secondary photophores on caudal-fin rays and along posterior margins of enlarged lateral-line scales.

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FIGURE 135. Lampanyctus lineat us: lectotype (ZMUC P2330212), male, 121.5 mm.

Size. Bekker (1967b) and Kotthaus (1972a) have reported L. cuprarius individuals as large as 92.7 and 110 mm, respectively. A number of gravid females, measuring 7075 mm, were found among the specimens examined. Atlantic Distribution. Lampanyctus cuprarius (Fig. 134) is a bipolar subtropical species. Although it is by far most abundant in the subtropics themselves, it is found also in significant numbers in the Lesser Antillean Region, Caribbean Sea, Gulf of Mexico, and Slope Water. The species is probably carried into the Slope Water as a waif by Gulf Stream eddies. It is absent from the Mauritanian Upwelling. L. cuprarius is not known from outside the Atlantic Ocean. Vertical Distribution. Opening-closing devices captured L. cuprarius by day at 6001,200 m near Bermuda, with maximum abundance at 750-850 m, and at 700-900 m near the Canary Islands. It was taken at night at 50-1,000 m near Bermuda, with no obvious maximum, and at 100-500 m near the Canaries with maximum abundance at 200-400 m. Near Bermuda, fish migrated to 50-150 m at night only in June and were all 31-51 mm juveniles; those taken deeper than 700 m at night were mostly larger than 45 mm. In the WHOI collections, L. cuprarius oc-

curred by day between 650 and about 1,000 m, with maximum abundance at 800 m, and at night between 40 and 275 m, with maximum abundance at 100 m. Synonym and References: Lampanyctus cuprarius Taning, 1928: 68 (orig. descr.; in key); Parr, 1928: 106, Fig. 18 (records from west. North Atlantic; descr.); Fraser-Brunner, 1949: 1086, fig. (in key); Bolin, 1959: 33 (char., distr.); Bekker, 1967b: 116 (records, vert, distr.); Nafpaktitis, 1973: 41, Fig. 39 (desig. and descr. of lectotype: 24°30'N, 80°00'W, 1,000 m.w.o.; ZMUC P2330213); Krefft and Bekker, 1973: 187 (synon., distr.). Paralampanyctus cuprarius. Kotthaus, 1972a: 14 (records from east. North Atlantic; char.; photo of otol.).

Lampanyctus lineatus Tining 1928 Figures 135, 136 Study Material. Thirty specimens, 44—183 mm, from the western North Atlantic and the Gulf of Mexico, and 3 specimens, 197—237 mm, collected by the FFS WALTHER HERWIG in the South Atlantic (18°36'S, 04°18'W); in LACM.

Distinctive Characters. This species differs from L. ater in the position of the SAd, from L. isaacsi in the position of the VO2, and from L. cuprarius in its higher numbers of AO and lateral-line organs.

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FIGURE 136. Lampanyctus lineatus, a subtropical or tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971) and G. Krefft (in litt.).

Description. Fin rays: dorsal 17-18 (16); anal 20-22 (19); pectoral 13 (12-14). Gillrakers: J (6) + 1 + 12 (11-13), total 18 (17-19). Photophores: AO 7-8 + 6-8, total 14-16. Lateral-line organs: 37-38. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin in advance of vertical through middle of base of dorsal fin. Pectoral fins short, very delicate, not reaching PO4. Ventral fins reaching anus. Base

of adipose fin about over end of base of anal fin. Luminous Organs. No photophores on cheek. PLO about its diameter below lateral line. PVOi in advance of PVO2. PO4 a little higher than PVO2 and directly over or slightly behind vertical through PO3. VLO its own diameter or less below lateral line. VO series distinctly arched. SAOi behind VO3 and lower than SAO2 which is about over origin of anal fin; SAO3 about over 1st AOa and in contact with lateral line; a straight line

Fishes of the Western North Atlantic through SAO3 and SAO2 passing somewhere between VO4 and origin of anal fin. First AOa often somewhat depressed; AOai-AOa2 interspace sometimes distinctly enlarged. Pol2 in advance of base of adipose fin and in contact with lateral line. First AOp often over base of anal fin. Prc separate from AOp, although occasional specimens may have the two series continuous; first 3 Prc evenly spaced or nearly so, forming a very obtuse angle; Prc4 behind Prc3 and at level of lateral line. Supracaudal gland with 3 (4) poorly defined scalelike structures; infracaudal gland with 4-5 (6) similar structures occupying 40-50 percent of length of caudal peduncle in fishes less than about 140 mm, and up to 65 percent in larger specimens. No luminous tissue at base of adipose fin. Minute secondary photophores on caudal-fin rays. Size. L. lineatus is a large myctophid attaining a size of over 235 mm. Three gravid females were found in the material examined; they measured 171-237 mm. Atlantic Distribution. Lampanyctus lineatus (Fig. 136) is an uncommon myctophid fitting no distribution pattern very well. It is either a bipolar subtropical species or a tropical-subtropical one. Our collections of it are widely scattered in the subtropics, northern tropics, and Gulf of Mexico. The species has been taken in the South Atlantic at 18° 36'S, 4°18'W (Krefft, personal communication) . Extra-Atlantic Occurrence. Lampanyctus lineatus has been collected in the western Indian Ocean between the equator and about 8°N (Nafpaktitis and Nafpaktitis, 1969). The species also occurs around the Philippine Islands (7°23/N-13°32'N, 121°21'E123°58 / E). (N) Vertical Distribution. Lampanyctus lineatus was caught in small numbers near Bermuda with opening-closing devices by day at 7001,150 m and by night at 150-350 m and 9001,000 m. During the day the largest specimen (92 mm) was caught at the deepest depth and

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the smallest (25 mm) at the shallowest depth. Migrants were 44—86 mm, the sole non-migrant, 44 mm. Near the Canaries L. lineatus was taken in the upper 150 m at night. In the WHOI collections, L. lineatus occurred between 650 and about 1,000 m during the day and mostly between 60 and 225 m at night. Maximum night catch (mostly juveniles) was at 100 m; a few large subadults were taken between 200 and 1,000 m. Synonym and References: Lampanyctus lineatus Taning, 1928: 6% (orig. descr.; in key); Parr, 1928: 108, Fig. 19 (records from west. North Atlantic, descr.); Fraser-Bnumer, 1949: 1086, fig. (in key); Bolin, 1959: 34 (char., distr.); Bekker, 1967b: 117 (records from North Atlantic); Nafpaktitis and Nafpaktitis, 1969: 41, Fig. 49 (records from west, equat. Indian Ocean, char.); Nafpaktitis, 1973: 40, Fig. 38 (desig. and descr. of lectotype: 17°S4'N, 64°54'W, 5,000 m.w.o.; ZMUC P2330212); Krefft and Bekker, 1973: 188 (synon., ref., distr.). Paralampanyctus lineatus. Rotthaus, 1972a: 14 (record from east. North Atlantic, char., photo of otolith).

Lampanyctus isaacsi Wisner 1974 Figures 137, 138 Study Material. Twenty-one specimens, 20-120 mm, from the eastern North Atlantic; in LACM.

Distinctive Characters. L. isaacsi is similar to L. lineatus and L. cuprarius. It differs from both in the position of the VO2 which is about over the Vd in L. isaacsi but well behind the VOi in the other two species. It further differs from L. lineatus in having its AOp continuous with the Prc, and in its lower numbers of dorsal and anal fin rays, and lateral-line organs. From L. cuprarius it is also distinguished by its higher numbers of AO and lateral-line organs. Description. Fin rays: dorsal 15 (14-16); anal 18 (1719); pectoral 11-13. Gill rakers: 5 (6) + 1 + 12-13, total 1819 (20).

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FIGURE 137. Lampanyctus isaacsi: male, 88 mm.

Photophores: AO 6 (5-7)

+ 7-8, total

13-14 (15). Lateral-line organs: 35-36. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin in advance of vertical through middle of base of dorsal fin. Pectoral fins short, delicate, not reaching vertical through PO6. Ventral fins extending to anus. Base of adipose fin over end of base of anal fin. Luminous Organs. No photophores on cheek. PLO about its diameter or less below lateral line. PVOi in advance of, occasionally directly under, PVO2. PO4 somewhat behind PO3 and at level of PVO2 or a little higher. VLO immediately below lateral line. VO2 abruptly and highly elevated, lying directly above, slightly in front of or behind VOi. SAOi behind VO3, at level of SAO2 or slightly lower; SAO2 on or behind vertical through origin of anal fin; SAO3 about over 1st AOa and in contact with lateral line; a straight line through SAO3 and SAO2 passing somewhere between VO4 and origin of anal fin. First AOa distinctly depressed; AOai-AOa2 interspace often somewhat enlarged. Pol2 in advance of base of adipose fin and in contact with lateral line. First AOp usually over base of anal fin. Prc continuous with AOp; first 2 Prc below level of last AOp and forming an obtuse an-

gle with Prcs which is on or slightly behind straight line through Prc2 and Prc4; Prc4 behind Prc3 and at level of lateral line. Supracaudal gland about % as long as infracaudal, consisting of 3-4 poorly defined scalelike structures; infracaudal gland with 6 (5-7) similar structures occupying 55-85 percent of length of caudal peduncle. No luminous tissue at base of adipose fin. Size. The largest specimen reported so far is 130 mm. One of the paratypes (USNM 206795) measures 126 mm. Two nearly ripe females found in the collections examined measured 117 and 120 mm, respectively. Atlantic Distribution. Lampanyctus isaacsi (Fig. 138) is a tropical species found only in the eastern Atlantic. In addition to occurring in the tropical Guinean Province, it is found in the Southern Mauritanian Upwelling. A few specimens, presumably waifs, were found in the eastern part of the Amazonian Province. L. isaacsi is not known from outside the Atlantic Ocean. Vertical Distribution. In the WHOI collections, L. isaacsi occurred by day between 550 and 750 m and at night between 40 and 325 m, with maximum abundance at 100 m. Reference: Lampanyctus isaacsi Wisner, 1974: 14, Figs. 6, 7 (orig. descr.; 01°10'N, 11°36'W; holotype SIO 63-560).

fishes of the Western North Atlantic

203

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FIGURE 138. Lampanyctus isaacsi, a tropical species. Distribution, based on the WHOI collections.

Lampanyctus ater Tining 1928 Figures 139-141 Study Material. Ninety-nine specimens, 22—106 mm, from across the North Atlantic and the Gulf of Mexico; in LACM.

Distinctive Characters. This species differs from all of the North Atlantic forms with short pectoral fins in the position of its SAOU which is in front of the VO3, and of the origin of its anal fin, which is behind a vertical through the middle of the base of the dorsal fin.

Description. Fin rays: dorsal 13-15; anal 18-19. Gill rakers: 5 + 1 + 11 (10-12). Photophores: AO 7 (6-8) + 7 (6-8), total 14 (13-15, rarely 12). Lateral-line organs: 35-36. Fins. Origin of dorsal fin behind base of ventral fin; end of base of same fin on or in advance of vertical through second AOa. Origin of anal fin behind vertical through middle of base of dorsal fin. Pectoral fins very small and fragile, but always present. Ventral fins extending to anus. Base of adipose

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FIGURE 139. Lampanyctus atcr: lectotype (ZMUC P2330209), male, 89 mm.

fin slightly in advance of end of base of anal fin. Luminous Organs. No photophores on cheek. PLO 1.5-2 times its diameter below lateral line. Position of PVd varying from slightly in front of to slightly behind PVO2. PO4 directly over or slightly behind POs and about at level of PVO2. VLO about its diameter below lateral line. VO series in a straight or somewhat arched line. SAOi in front of VO8 and at level of SAO2 or slightly lower; SAO2 in front of, rarely on, vertical through origin of anal fin; SAO8 directly over or somewhat behind origin of anal fin and in contact with lateral line; a straight line connecting SAO2 and SAO3 passing through or a little behind VO4. AOa series usually

distinctly arched, with AOai-AOa2 interspace often somewhat enlarged. Pol2 under base of adipose fin and in contact with lateral line. First AOp behind, rarely over, end of base of anal fin. Prc separate from AOp, although occasional specimens may have the two series continuous; first 3 Prc forming an obtuse angle, with Prc* usually directly over Prc3 and at level of lateral line. Infracaudal luminous gland extending over at least % the length of caudal peduncle and consisting of 5-7 poorly defined scalelike structures the anterior 1-2 of which may be smaller than, and isolated from the rest; supracaudal gland about % as long as infracaudal. Size. Available data indicate that members of this species attain a size of about 140 nun.

FIGURE 140. Lampanyctus niger: 103 mm (BMNH 1887.12.7.219).

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FIGURE 141. Lampanyctus ater, a bipolar questionably subtropical species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from Gibbs et al. (1971), G. Kretft (in litt.), and Parin et aL (1974).

Remarks. As noted earlier, of all the members of the genus Lampanyctus, those with very short or no pectoral fins are taxonomically the least well known and understood ones. A case at hand is that of L. niger-L. ater. The two forms are so similar that a careful study and analysis of extensive material from a very wide area is necessary before the status of L. ater can be established with reasonable certainty. Until such study is done, I have chosen to follow Bolin (1959) in maintaining the specific distinction of L. ater.

I have examined and directly compared the type specimens of both L. niger (Giinther) 1887, from "S. of Philippines," (BMNH 1887.12.7.219, Fig. 140) and L. ater (ZMUC P2330209, Fig. 139). The most obvious difference between the two forms is found in the positions of the SAO2 and SAOa which are more forward in L. ater than in L. niger. Other differences include: the more posterior position of the origin of the anal fin in relation to the middle of the base of the dorsal fin, the more posterior position of the Pol2

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in relation to the base of the adipose fin, and the somewhat longer infracaudal gland in L. ater than in L. niger. However, these differences are less obvious in material from areas other than the type localities; hence our present confusion regarding the identity of the two forms. Atlantic Distribution. Lampanyctus ater (Fig. 141) is best considered a bipolar questionably subtropical species. A discrepancy from the typical subtropical pattern is its relative abundance in the temperate AzoresBritain and Mediterranean Outflow provinces combined with its absence in the Southern Sargasso Sea and some other parts of the subtropics. Alternatively, L. ater could be considered a bipolar temperate-semisubtropical species, but numerous specimens collected near the tropical-subtropical boundary in the eastern Atlantic argue against this interpretation. Extra-Atlantic Occurrence. Nafpaktitis and Nafpaktitis (1969) report L. ater from the Indian Ocean between about 12°S and 44°S. McGinnis (1974) reports material of the niger-ater complex from the Atlantic, Indian, and western (west of about 165°W) Pacific sectors of the Southern Ocean. These records come from near or north of the subtropical convergence. In the North Pacific one or more forms of uncertain relationship to our material have been reported as L. niger (see, for instance, Clarke, 1973). (BC) Vertical Distribution. Opening-closing devices took L. ater by day at 700-1,200 m near Bermuda, with occasional specimens at 1,4501,550 m, and at 680-930 m near the Canary Islands. Maximum abundance near Bermuda was at 700-800 m. Fish taken near Bermuda at 700-900 m were 22-73 mm, while those at 1,000-1,200 m were 72-103 mm. The species was taken at night at 100-250 m and 600-1,250 m near Bermuda, with maximum abundance at 800-900 m, and at 110-925 m near the Canaries. Near Bermuda, migrants were smaller than 50 mm, while nonmigrants included all sizes.

In the WHOI collections, L. ater occurred between 550 and 850 m during the day and between 60 and 850 m at night, with maximum abundance at 100-150 m. Synonym and References: Lampanyctus ater Taning, 1928: 68 (orig. descr.; in key); Parr, 1928: 104, Fig. 17 (records from west. North Atlantic; descr.); Fraser-Brunner, 1949: 1086, fig. partim (in key); Bolin, 1959: 33 (char., distr.); Bekker, 1967b: 116 (records from North Atlantic, depth of occur.); Nafpaktitis and Nafpaktitis, 1969: 44, Fig. 52 (records from west. South Indian Ocean, descr.); Hulley, 1972a: 225 (record from off west coast of S. Africa, char.); Nafpaktitis, 1973: 38, Fig. 36 (desig. and descr. of lectotype: 30°17'N, 20°44'W, 7,000 m.w.o.; ZMUC P2330209); Krefft and Bekker, 1973: 187 (synon., ref., distr.). Paralampanyctus ater. Kotthaus, 1972a: 14 (records from east. North Atlantic, char., photo of otol.); and 1972b: 29 (records from west. South Indian Ocean, char., photo of otolith).

Lampanyctus crocodilus (Risso) 1810 Figures 142, 143 Study Material. Five hundred and two specimens, 18—48 mm, from the western North Atlantic; in LACM.

Distinctive Characters. The evenly arched anterior AOa, the lower position of the SAOi in relation to the VLO and the shorter pectoral fin will differentiate this species from L. intricarius. Description.

Fin rays: dorsal 14-15 (13); anal 17-18; pectoral 14-15 (16). Gill rakers: 4-5 + 1 + 11 (10-12), total 16-17 (15). Photophores: AO 6-7 (5) + 8-9 (7),

total 14-15 (13-16).

Lateral-line organs: 38-39. Fins. Origin of dorsal fin somewhat behind base of ventral fin. Origin of anal fin under base of penultimate dorsal fin ray. Pectoral fins long, extending beyond SAOi but not reaching origin of anal fin. Ventral fins reach-

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207

FIGURE 142. Lampanyctus crocodilus: young, 34 mm.

ing origin of anal fin. Base of adipose fin directly over or slightly behind end of base of anal fin. Luminous Organs. Three, sometimes 2, cheek photophores. PLO 1-2 times its diameter below lateral line. PVOi behind PVO2. PO4 at level of PVO2 and directly over or slightly behind POa. VLO somewhat nearer to lateral line than to base of ventral fin. VOi distinctly depressed. SAOi in front of VOa and at level of SAO2 which is in line with, and midway between SAO3 and VO4; a straight line through SAO2 and SAOi passing one photophore diameter or more below VLO; SAO3 a little in advance of, sometimes on, vertical through origin of anal fin and in contact with lateral line. First AOa depressed. Pol2 directly under or slightly in advance of base of adipose fin and in contact with lateral line. AOp behind base of anal fin. Prc continuous with AOp, although sometimes space between last AOp and 1st Prc distinctly enlarged; first 3 Prc evenly spaced; Prc4 slightly behind Prc3 and immediately below level of lateral line. Two (1-3) scalelike structures at anterior end of base of adipose fin. Infracaudal gland consisting of 9 (8-10) scalelike segments extending over entire length of caudal peduncle; supracaudal gland about % as long as infracaudal and consisting of 3-4 poorly defined segments. One minute sec-

ondary photophore immediately under each lateral-line organ. Size. In his study of Mediterranean myctophids, Tuning (1918) stated: "Of all known Scopelids, the present species [L. crocodilus] is the one attaining the greatest length, specimens of 200-300 mm being known from the Mediterranean." The largest individuals examined by Tining were 87 mm and 129 mm from the Mediterranean and the Atlantic, respectively. "Otherwise," Tining remarked, "there are... very few large specimens at all in the material." Similarly, in their recent study of Mediterranean myctophid collections, Goodyear et al. (1972) commented on the absence of adults and the predominance of juveniles in their material. Evidently the species lives at depths greater than those commonly sampled. Furthermore, while juveniles seem to migrate to shallower depths at night, subadults do not (Goodyear et al., 1972). As noted earlier, the largest of 502 individuals examined in the present study measured 48 mm. All specimens were collected at night between the surface and 150 mm. Development. Tining (1918) described a series of larval stages on the basis of material primarily from the Mediterranean and the Sea of Marmora. In the absence of specimens at metamorphosis stage, Tining reasoned that

Memoir Jf, Part 7—Sears Foundation for Marine Research

208

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FIGURE 143. Lampanyctus crocodilus, a trmperate-semisubtropical species. Distribution, based on the WHOI collections. Additional records are from Geistdoerfer et al. (1971), Gibbs et al. (1971), and G. Krefft (in litt.).

metamorphosis must take place at sizes between 19 and 22 mm. Atlantic Distribution. Lampanyctus crocodilus (Fig. 143) is a temperate-semisubtropical species. It is a ranking myctophid in the North Atlantic Temperate Region. It is found throughout the Mediterranean Sea, but is considerably less abundant there than in the temperate provinces of the open Atlantic. The species is found also in the Mauritanian Upwelling. Although there are numerous subarctic records, we do not consider it to be a regular inhabitant of that region, where it is

rare in comparison with its abundance within its principal range. L. crocodilus is not known from outside the North Atlantic. Vertical Distribution. Opening-closing devices captured L. crocodilus by day at 7001,000 m both near Bermuda, where only small individuals were collected, and in the Mediterranean Sea. A few juveniles, mostly smaller than 20 mm, were also taken at 100-200 m in the Mediterranean. Maximum abundance in the Mediterranean was at 700-800 m; near Bermuda there was no obvious maximum.

Fishes of the Western North Atlantic The species was taken in two strata at night in each area. The shoaler layer was at 1002JO m near Bermuda and at 45-150 m in the Mediterranean and the deeper at 400-1,000 m in both regions. In the Mediterranean, maximum abundance was in the shallower layer, but near Bermuda few individuals were taken in this layer. Migrants were mostly small juveniles in both regions, while nonmigrants included small and large juveniles at Bermuda and small juveniles to subadults in the Mediterranean. In the WHOI collections, L. crocodilus occurred between 275 and about 1,000 m during the day, with maximum abundance at 600700 m, and from near the surface to 650 m at night, with maximum abundance (mostly juveniles) at 75 m. Synonyms and References: Gasteropelecus crocodilus Risso, 1810: 357 (orig. descr.; off Nice). Nyctophus bonapartii Cocco, 1838: 189, Pi. 7, Fig. 10 (orig. descr.; off Messina) . Lampanyctus gemmifer Goode and Bean, 1896: 80, PL 23, Fig. 88 (orig. descr.; 39°39'45"N, 71°35' 15"W, 538 fms; holotype, USNM 35604). Myctophum (Lampanyctus) crocodilus. Taning, 1918: 112, Figs. 44, 45 (descr., develop., distr. in Mediterranean). Lampanyctus crocodilus. Taning, 1928: 67 (in key); Fraser-Brunner, 1949: 1089, fig. (in key); Bolin, 1959: 30 (synon., char., distr.); Bekker, 1967b: 111 (records from North Atlantic); Bini, 1971: 171, illus. (morphol., reprod., distr.); Goodyear et al., 1972: 190 (abund., growth, vert, distr. in Mediterranean); Kotthaus 1972a: 14 (records from east. North Atlantic, char., photo of otol.); Krefft and Bekker, 1973: 186 (synon., ref., distr.). Lampanyctus peculiaris Borodin, 1929: 111 (orig. descr.; holotype, MCZ 31628). Lampanyctus iselini Parr, 1934: 60, Fig. 7 (orig. descr.; 41°30'N, 45°57'W, 1,280-1,463 m; holotype, MCZ 33223); Fraser-Brunner, 1949: 1089, fig. (in key).

Lampanyctus intricarius Taning 1928 Figures 144, 145 Study Material. Sixty-six North Atlantic specimens, 25-168 mm; in LACM and MCZ.

209

Distinctive Characters. The abruptly depressed anterior 2 AOa, the higher position of the SAOi in relation to the VLO and the longer pectoral fin will separate this species from L. crocodilus. For comparison with the southern species L. lepidolychnus Bekker see under Remarks. Description. Fin rays: dorsal 14-15 (16); anal 18-20; pectoral 13-14. Gill rakers: 4 + 1 + 10 (11). Photophores: AO 8-9 + 7-9, total 16-17 (18). Lateral-line organs: 39-40. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin in advance of vertical through base of penultimate dorsal fin ray. Pectoral fins long, their relative length increasing with size of fish, reaching 3rd or 4th AOa in specimens larger than about 70 mm. Ventral fins reaching origin of anal fin. Base of adipose fin over end of base of anal fin. Luminous Organs. One or 2, occasionally 3, cheek photophores. PLO 1-2 times its diameter below lateral line. PVOi behind PVO2. PO4 about at level of PVO2 and directly over or slightly behind PO8. VLO midway between base of ventral fin and lateral line or slightly higher. VOi depressed; VO2-VO3 interspace often enlarged. SAOi in front of VO3, usually a little higher than SAO2; a straight line connecting SAOi and SAO2 passing through, or less than one photophore diameter below VLO; SAO2 midway between but rarely in line with SAO3 and VO4, a straight line through SAO3 and SAO2 usually passing behind VO4; SAQa on or a little in advance of vertical through origin of anal fin and immediately below lateral line. First and 2nd AOa abruptly depressed, a line through them passing below AOa3. Pol2 under or slightly in advance of base of adipose fin and immediately below lateral line. First AOp behind, rarely over, end of base of anal fin. Prc continuous with AOp; distance between Prc2 and

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Memoir 1, Part 7—Sears Foundation for Marine Research

FIGURE 144. Lampanyctus intricarius: lectotype (ZMUC P2330208), young, 30.5 mm.

Prc3 often larger than that between Prci and Prc2; Prc4 directly over Prc3 and at level of lateral line. A luminous gland at anterior end of base of adipose fin, usually consisting of an anterior median and 2 bilaterally placed posterior patches. Infracaudal gland consisting of 8-10 scalelike segments extending over entire length of caudal peduncle; supracaudal gland consisting of 2-3 similar segments. A small, secondary photophore immediately below each lateral-line organ. Size. The largest specimen examined (MCZ 42873) measured 168 mm and was a female with poorly developed ovaries. Remarks. L. intricarius has in the past been confused with the morphologically similar L. lepidolychnus Bekker 1967. The two species can be separated on the basis of the least depth of the caudal peduncle (twice or more in length of upper jaw in L. intricarius vs. less than twice in L. lepidolychnus). Further, L. lepidolychnus differs from L. intricarius in having shorter pectoral fins (not reaching origin of anal fin), in its lower PLO (more than twice its diameter below lateral line), its lower SAOi (a line through SAO2 and SAOi passing well below VLO), the larger and better developed luminous gland at the base of its adipose fin, and by its well developed secondary photophores on the trunk (one per scale pocket). Lampanyctus lepidolychnus has so far been reported only from the southern hemisphere

where its range overlaps with that of L. intricarius. Interestingly, however, L. lepidolychnus occurs in the western South Atlantic where L. intricarius is absent, and appears to be absent in the South Pacific east of about 165°W where L. intricarius is relatively common (McGinnis, 1974). Atlantic Distribution. Lampanyctus intricarius (Fig. 145) is a bipolar temperate or bipolar subpolar-temperate species. It was most abundant in WHOI North Atlantic collections in the temperate Azores-Britain Province and Mediterranean Outflow. However, the Overflow '73 Expedition collected specimens as far north as Iceland using the 1,600-meshes Engel trawl. In the Atlantic this species occurs mainly in the east, although but few specimens were taken in the Mauritanian Upwelling. Extra-Atlantic Occurrence. Lampanyctus intricarius is known from the South Indian Ocean between 23° and 40°S (Nafpaktitis and Nafpaktitis, 1969; McGinnis, 1974; and unpublished data). The species is also known from south of Australia and the Tasman Sea (McGinnis, 1974; and unpublished data). Further, it has been taken from the Fiji Islands to east of New Zealand at about 42°S, 177°E, eastward in the region of the Subtropical Convergence, and in the eastern South Pacific to about 52°S (McGinnis, 1974). (N) Vertical Distribution. In the WHOI col-

Fishes of the Western North Atlantic .^..g S . ° 7 f ^^>^A jc

}?.,". H°. 30 20 10 o f ^r ------^i-m..^

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FIGURE 145. Lampanyctus intricarius, a bipolar temperate or subpolar-temperate species. Atlantic Ocean distribution, based on the WHOI collections. Additional records are from G. Krefft (in litt.) and the study material.

lections, L. intricarius occurred by day mostly between 550 and 750 m, and at night between 40 and 550 m, with maximum abundance (mostly juveniles) at 75 m. References: Lampanyctus intricarius Taning, 1928: 67 (orig. descr.; in key); Fraser-Brunner, 1949: 1089, fig. (in key); Bolin, 1959: 31 (char., distr.); Bussing, 1965: 204 (records from off Chile, char.); Bekker, 1967b: 111 (records from east. North Atlantic, char.); Nafpaktitis and Nafpaktitis, 1969: 50, Figs. 60, 65 (records from west. South Indian Ocean, descr.); Craddock and Mead, 1970: 3.29 (records

from off Chile, 31°-34°S, 72°-92°W); Nafpaktitis, 1973: 43, Fig. 42 (desig. and descr. of lectotype: 38°10'N, 9°20'W, 300 m.w.o.; ZMUC P2330208); Krefft and Bekker, 1973: 188 (synon., ref., distr.).

Lampanyctus photonotus Parr 1928 Figures 146, 147 Study Material. One hundred and ninety-six specimens 18-59 mm, from the equatorial and western North Atlantic; in LACM.

Distinctive Characters. The non-overlapping dorsal and anal fins, 2 cheek photophores,

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Memoir 1, Part 7—Sears foundation for Marine Research

FIGURE 146. Lampanyctus photonotus: female, 58 mm.

Prc separate from AOp, the series of enlarged secondary photophqres along each side of the back, and the lack of luminous tissue at the base of the adipose fin will separate this species from all of its North Atlantic congeners. Description. Fin rays: dorsal 13 (12-14); anal 16-17; pectoral 13 (12-14). Gill rakers: 4 (3-5) + 1 + 9 (8-10), total 14 (13-15). Photophores: AO 6 (5-7) + 7 (6-8), total 13 (11-14). Lateral-line organs: 37-38. Fins. Origin of dorsal fin slightly behind base of ventral fin. Origin of anal fin directly under or just behind end of base of dorsal fin. Pectoral fins long, extending to 1st or 2nd AOa. Ventral fins barely reaching origin of anal fin. Base of adipose fin directly over or slightly in advance of end of base of anal fin. Luminous Organs. Two cheek photophores. PLO 1-2 times its diameter below lateral line. PVOi behind PV02. PO4 higher than PVO2 and slightly behind PO3. VLO midway between base of ventral fin and lateral line or a little higher. VO evenly spaced and level or very nearly so. SAOi in front of VO8 and on or slightly below a straight line through

SAO2 and VLO; SAO2 midway between, and in line with SAO8 and VO4; SAOa about over origin of anal fin and immediately below lateral line. AOa series arched. Pol2 directly under or slightly in advance of base of adipose fin and immediately below lateral line. First AOp behind, rarely over, end of base of anal fin. Prc distinctly separate from AOp, forming a gentle curve; Prc4 behind Prc8 and at level of lateral line. A series of relatively large secondary photophores, one at middle of posterior margin of each scale pocket along each side of back from nape to somewhere between end of dorsal fin and adipose fin; a similar photophore immediately below each lateralline organ. No luminous tissue at base of adipose fin. Infracaudal gland with 8 (7-9) scalelike segments extending along entire length of caudal peduncle. Sexual Dimorphism. Adult females with supracaudal gland consisting of 3-5 scalelike segments occupying 60 percent or less of length of caudal peduncle; same gland in adult males consisting of 7-8 segments occupying 85-95 percent of length of caudal peduncle. Size. Members of this species grow to about 70 mm. Sexual maturity is reached at sizes between 50 and 55 mm.

fishes of the Western North Atlantic .

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FIGURE 147. Lampanyctus photonotus^ a tropical-subtropical species. Atlantic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et aL (1971).

Atlantic Distribution. Lampanyctus photonotus (Fig. 147) is a tropical-subtropical species, but it is missing from the Gulf of Mexico, Straits of Florida, and Caribbean Sea, provinces in which tropical-subtropical species are generally present if not abundant. It is also absent from the Mauritanian Upwelling and the southeastern part of the Guinean Province. It is a ranking myctophid in the North and South Atlantic Subtropical Regions. The species exists in significant numbers in the

temperate provinces adjacent to the northern subtropics. Extra-Atlantic Occurrence. Lampanyctus photonotus is here reported for the first time from outside the Atlantic Ocean on the basis of two specimens collected off New Caledonia: 1 (48 mm), DANA Sta. 3611 IV, 20°53.2/S, 164°03.3'E; 1 (60 mm, nearly ripe female), DANA Sta. 3613 I, 22°43/S, 166°05.8/E. (N) Vertical Distribution. Opening-closing devices caught L. photonotus near Bermuda by

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Memoir 1, Part 7—Sears Foundation for Marine Research

FIGURE 148. Lampanyctus nobilis: lectotype (ZMUC P2330211), young, 53.5 mm.

day at 600-1,100 m, with no obvious maximum, and by night at 40-2 JO m and 850-900 m, with maximum abundance at 100-1 JO m. Occasional specimens were taken at 1,5001,JJO m by day, at which time larger individuals (>3J mm) were generally deeper than 7JO m; non-migrants were all juveniles 17-19 mm. Near the Canary Islands, a few specimens were caught in the upper 150 m at night. In the WHOI collections, L. photonotus occurred between 40 and 17 J m at night, with maximum concentration at 60-12 J m, and between 550 and deeper than 1,000 m during the day, with maximum concentration at about 800 m. Synonyms and References: Lampanyctus photonotus Parr, 1928: 102, Fig. 16 orig. descr.; 22°43'N, 74°23'W, 8,000 f.w.o.; holotype, BOG 2261); Fraser-Brunner, 1949: 1088, fig. (in key); Bolin, 1959: 29 (synon., char., distr.); Backus et al., 1965: 144 (records from central North Atlantic); Bekker, 1967b: 110 (records from Atlantic, depth of occur.); Backus et al., 1969: 95 (records from west. North Atlantic); Kotthaus, 1972a: 14 (records from east. North Atlantic, char., photo of otolith); Kretft and Bekker, 1973: 189 (synon., ref., distr.). Lampanyctus taaningi Parr, 1929: 27 (orig. descr.; Exuma Sound, Bahamas; holotype, BOG 2301); Fraser-Brunner, 1949: 1088, fig. (in key).

Lampanyctus nobilis Tining 1928 Figures 148, 149 Study Material. One hundred and fifty-two specimens, 21-113 mm, from the equatorial and western North Atlantic, the Caribbean Sea, and the Gulf of Mexico; in LACM.

Distinctive Characters. This species is distinguished from its North Atlantic congeners by the following combination of characters: SAOi behind VO3; Pol2 in advance of base of adipose fin; Prc separate from AOp; and 2nd, 3rd and 4th Prc in a straight line. Description. Fin rays: dorsal 15 (14-16); anal 18-19 (17-20); pectoral 14-15 (13). GUI rakers: 3-4 + 1 + 9-10, total 13-15. Photophares: AO 6 (5-8) + 9 (8-10), total 15 (14-16). Lateral-line organs: 38-39. Fins. Origin of dorsal fin slightly behind base of ventral fin. Origin of anal fin under posterior %-% of base of dorsal fin. Pectoral fins long, extending to 3rd or 4th AOa. Ventral fins reaching origin of anal fin. Base of adipose fin directly over or slightly behind end of base of anal fin. Luminous Organs. No cheek photophores. PLO 1-2 times its diameter below lateral line, x behind PVO2. PO4 at level of, or a

fishes of the Western North Atlantic

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FIGURE 149. Lampanyctus nobilis, a questionably tropical species. Atlantic Ocean distribution, based on the WHOI collections.

little higher than, PVO2 and behind PO3. VLO distinctly nearer to lateral line than to base of ventral fin and behind the latter. VO2 distinctly raised, the series forming an arc. SAd behind VO3 and well below level of SAO2, a line through SAO2 and SAOi running parallel to a line through SAO3 and VLO; SAO3 directly over or slightly in advance of origin of anal fin and in contact with lateral line. AOa series arched, sometimes strongly so, with AOai-AOa2 interspace often enlarged. Pol2 well in advance of base of adi-

pose fin and in contact with lateral line. First and sometimes 2nd AOp over base of anal fin. Prc separate from AOp; Prci and Prc2 at same level; 2nd, 3rd and 4th Prc on a straight line with Prc4 behind Prc3 and at level of lateral line. No luminous tissue at base of adipose fin. Infracaudal gland consisting of 8-10 scalelike segments extending along entire length of caudal peduncle; supracaudal gland much shorter, consisting of 3-4 scalelike segments. Size. The largest specimen found in the

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collections examined measured 113 mm. The ovaries of two females, 82 and 84 mm, were well developed and contained large eggs. Ripe females caught near Hawaii were over 97 mm (Clarke, 1973). Atlantic Distribution. Lampanyctus nobilis (Fig. 149) is a questionably tropical species, there being sufficient specimens in WHOI collections from the equatorward parts of the subtropics to allow the possibility that the species is a tropical-semisubtropical one. L. nobilis is a ranking myctophid in the Tropical Region; greatest catches were made in the tropical provinces of the open Atlantic, those in the Caribbean Sea being fewer and smaller. The species is absent from the southern part of the Guinean Province and occurred but little in the Mauritanian Upwelling. It is an occasional waif in the Slope Water, whence it is carried by the Gulf Stream. Extra-Atlantic Occurrence. Lampanyctus nobilis is distributed circumglobally. It has been collected across the entire Indian Ocean between about 10°N and 18°S (Nafpaktitis and Nafpaktitis, 1969; Bradbury et al., 1971; Kotthaus, 1972b; and numerous unpublished data), in the Southeast Asian seas between 10°N and 8°S, and in the South Pacific to about 135°W between the equator and 20°S (a single 24.5-mm specimen has been taken off Sydney, Australia, at 34°20/S, 152°46'E). Further, the species has been reported from off Hawaii (Clarke, 1973), and from near 12°N and 3°30/N on the meridian 145 °W (Hartmann and Clarke, 1975), and from off the west coast of Central America (Parr, 1931). (N) Vertical Distribution. In the WHOI collections, L. nobilis occurred between 475 and 750 m by day, with maximum abundance at 700 m, and between 40 and 32J m at night, with maximum abundance at JO m. Near Bermuda, a single fish was taken with an opening-closing device at about 300 m at dawn. Samples from Bermuda taken with a large, open Engel trawl, indicate that few fish

are found there above 900 m during the day and that they occur at about 100-200 m at night. Synonym and References: Lampanyctus nobilis Taning, 1928: 66 (orig. descr.; in key); Parr, 1931: 29, Fig. 11 (descr. from east. Pacific); Fraser-Brunner, 1949: 1087, fig., partim (in key); Bekker, 1967b: 110 (records from equat. and west. North Atlantic, depth of occur.); Nafpaktitis and Nafpaktitis, 1969: 47, Figs. 59, 60 (records from west. trop. Indian Ocean, descr.); Clarke, 1973: 406, 418 (vert, distr., abund. off Hawaii); Nafpaktitis, 1973: 41, Fig. 40 (desig. and descr. of lectotype: 17°4l'N, 60°58'W, 6,000 m.w.o.; ZMUC P2330211). Lampanyctus macropterus. Parr, 1928: 110, Fig. 20 (records from around the Bahamas, descr.).

Lampanyctus festivus Taning 1928 Figures 150, 151 Study Material. Forty-four specimens, 26—123 mm, from the North and South Atlantic; in LACM and USNM.

Distinctive Characters. This species differs from L. nobilis mainly in the positions of the SAOi and the Pol2, as well as in the position and arrangement of the Prc. For character differences between L. festivus and L. tenuiformis see under the latter. Description. Fin rays: dorsal 13 (14); anal 19 (18-20); pectoral 16 (15-17).

Gill rakers: 4+ 1 +9 (8).

Photophores: AO 7 (6-8) + 8-9 (10), total 15-16. Lateral-line organs: 39-40. Fins. Origin of dorsal fin somewhat behind base of ventral fin. Origin of anal fin under posterior %-% of base of dorsal fin. Pectoral fins long, extending to 2nd or 3rd AOa. Ventral fins reaching origin of anal fin. Base of adipose directly over or slightly in advance of end of base of anal fin. Luminous Organs. No cheek photophores. PLO 1.5-2.5 times its diameter below lateral line. PVOi behind PVO2. PO4 about at level

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FIGURE 150. Lampanyctus festivusi lectotype (ZMUC P2330215), male, 101 mm.

of PVO2 and behind PO3. VLO nearly twice as close to lateral line as to base of ventral fin. VO2 and, to a lesser extent, VO3 elevated. SAOi in advance of, seldom directly over, VO3 and a little below straight line through SAO2 and VLO; a line connecting SAOS with SAO2 passing behind, rarely through, VXX; SAO3 directly over or behind origin of anal fin and in contact with lateral line. AOa series arched, often strongly so, with AOai-AOa2 interspace distinctly enlarged. Pol2 usually in advance of base of adipose fin and immediately below lateral line. First AOp usually over base of anal fin. Prc continuous with AOp; Prc3 higher than Prci; Prc4 directly over or slightly behind Prc3 and at level of lateral line. No luminous tissue at base of adipose fin. Infracaudal gland consisting of 8 (7-9) scalelike segments extending along entire, or very nearly entire, length of caudal peduncle; supracaudal gland with 3 (2) similar segments. Size. This species apparently grows to a size well over 120 mm. No gravid females were found in the material examined. Atlantic Distribution. Lampanyctus festivus (Fig. 151) is a bipolar questionably subtropical species; it is absent or nearly so from a significant portion of the subtropics, seemingly the least productive parts. Extra-Atlantic Occurrence. Two speci-

mens of Lampanyctus festivus are known from the southwestern Indian Ocean: one from 24°33'S, 38°26'E, the other from 35° 49'S, 23°09/E. In the Pacific Ocean the species has been collected west of New Caledonia, north of New Zealand, and in the Tasman Sea to about 33°30/S. It has tentatively been identified from off Chile between approximately 31°S and 34°S (Craddock and Mead, 1970). (N) Vertical Distribution. Opening-closing devices took L. festivus by day at 700-950 m near Bermuda, with maximum abundance at 700-850 m, and at 700 m and deeper near the Canary Islands. It was taken at night at about 100-350 m near Bermuda, with maximum abundance at 100-150 m, and in the upper 150 m near the Canaries. A few 2125 mm juveniles were taken at daytime depths during the night near Bermuda. In the WHOI collections, L. festivus occurred between 475 and about 1,000 m during the day and between 40 and 325 m at night, with maximum abundance at 75-150 m. References: Lampanyctus festivus Taning, 1928: 67 (orig. descr.; in key); Fraser-Brunner, 1949: 1087, fig. (in key); Bolin, 1959: 29 (synon., char., distr.); Bekker, 1967b: 111 (records from North and South At-

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FIGURE 151. Lampanyctus festivus, a bipolar questionably subtropical species. Atlantic Ocean distribution, based on the WHOI collections. The additional record is from Gibbs et al. (1971). lantic, char.); Nafpaktitis and Nafpaktitis, 1969: 46, Fig. 58 (compar. with L. tenuiformis); Nafpaktitis, 1973: 42, Fig. 41 (desig. and descr. of lectotype: 35°44'N, 29°33'W, 1,000 m.w.o.; ZMUC P2330215); Krefft and Bekker, 1973: 188 (synon., ref.).

Lampanyctus tenuiformis (Brauer) 1906 Figures 1*2, 153 Study Material. Seventeen specimens, 20-93 mm, from the equatorial Atlantic, the Caribbean Sea, and the Gulf of Mexico; 2 specimens, 120 and 122 mm, from the South Atlantic; in LACM.

Distinctive Characters. See under Description. Description. fin rays: dorsal 13-14; anal 18 (17); pectoral 13-14.

Gill rakers: 4 + 1 + 9.

Photophores: AO 6-7 + 6-7, total 12-13. Lateral-line organs: 37-38. This species is so similar to L. festivus that its detailed description would, to a very large extent, be an unnecessary repetition of that given for Tuning's species. The character

Fishes of the Western North Atlantic differences tabulated below should, taken together, help distinguish the two forms. Unfortunately, the poor condition of the ma-

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jority of the available specimens precluded taking reliable measurements that might reVeal morphometric differences.

Distinguishing Character Differences L. festivus Pectoral fin rays AO

VO series 1st AOp

Prc3 Infracaudal luminous gland

L. tenuiformis

16 (15-17) 15-16 arched with VO2 markedly raised usually over base of anal fin

13-14 12-13 level or nearly so

higher than Prci extends along entire length of caudal peduncle

Size. The largest specimen examined measured 122 mm. Clarke (1973) reported "four females (123-138 mm) with ripened ova" taken near Hawaii. Atlantic Distribution. Lampanyctus tenuiformis (Fig. If 3) is an uncommon tropical species, occurring also in the Gulf of Mexico. It appears to be absent from the Mauritanian Upwelling. Extra-Atlantic Occurrence. Lampanyctus tenuiformis was originally described from the Indian Ocean (Brauer, 1906), and a single

FIGURE 152. Lampanyctus tenuiformis:

young, 52 mm.

behind, rarely over, end of base of anal fin at level of Prci does not extend along entire length of caudal peduncle

specimen has been reported from 7°36/S, 59° 56^ (Nafpaktitis and Nafpaktitis, 1969). However, the species has recently been identified from several DANA stations, all in the eastern Indian Ocean east of 70 °E and between approximately 7°N and 4°S. It is also known from the Celebes Sea, the South China Sea off the Philippines to about 19°N, 120°E, north of New Guinea (l°13/-24/S, 138°42' E), southwest of the Fiji Islands (20°S, 174° 29T) and further east at 18°53'S, 163°03'W. Interestingly, the specimen (75 mm) from

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20°S, 174°29'E has the meristic characters of L. tenuiformis but the photophore arrangement of L. festivus, which has been taken just south of that location. The specific distinction of the two forms is indeed questionable. The specimens from near Hawaii (Clarke, 1973) are tentatively assigned to L. tenuiformis, pending re-examination of this material and solution of the taxonomic problem involved. (N) Vertical Distribution. In the WHOI collections, L. tenuiformis occurred at night be-

tween 40 and 32 5 m, with maximum concentration at about 100 m, and by day between 300 and 750 m. Synonym and References: Myctophum (Lamptnyctus) tenuiforme Brauer, 1906: 243, Fig. 160 (orig. descr.; from Indian Ocean, 4° 34'8"S, 53°42'8"E). Lampanyctus tenuiformis. Fraser-Brunner, 1949: 1087, fig. (in key); Nafpaktitis and Nafpaktitis, 1969: 46, Fig. 57 (record from west, equat. Indian Ocean, char., compar. with L, festivus); Clarke, 1973: 406, 420 (occur, near Hawaii).

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FIGURE U4. Lampanyctus pusillus: female, 35 mm.

Lampanyctus pusillus (Johnson) 1890 Figures 154, 155 Study Material. Five hundred and ninety-two specimens, 14-38 mm, from across the North Atlantic; in LACM.

Distinctive Characters. The single cheek photophore, low number of anal fin rays, low position of VLO, lack of luminous tissue at the base of the adipose fin, and the short infracaudal luminous gland will separate this species from its North Atlantic congeners. Description. Finrays: dorsal 12 (13); anal 14-15 (16); pectoral 14 (13-15). GUI rakers: 3 + 1 + 8 (rarely 7 or 9). Photophores: AO 4 (4-6) + 6 (5-7), total 10 (9-12). Lateral-line organs: 33-34. Fins. Origin of dorsal fin behind base of ventral fin. Origin of anal fin under posterior % of base of dorsal fin. Pectoral fins long, extending to 1st or 2nd AOa. Ventral fins reaching anus. Base of adipose fin behind vertical through end of base of anal fin. Luminous Organs. A single photophore in middle of cheek. PLO 1,5-2 times its diameter below lateral line. PVOi behind PVO2. PO4 about at level of PVO2 and behind, rarely

directly over, PO3. VLO midway between base of ventral fin and lateral line or slightly higher. VO2 often distinctly raised, the series forming an arc, SAOi in advance of VO3 and on or slightly above line through SAO2 and VLO; SAO2 in line with VO4 and SAO8 which is on or behind vertical through origin of anal fin and less than its own diameter below lateral line. AOa series gently arched with AOai-AOa2 interspace often distinctly enlarged. Pol2 in advance of base of adipose fin and its own diameter or less below lateral line. First AOp behind base of anal fin. Prc continuous with AOp and forming a curve, with Prc4 in advance of, seldom directly over, Prca. No luminous tissue at base of adipose fin. Inf racaudal gland short, occupying %, or slightly less, of length of caudal peduncle and consisting of 3 (4) scalelike segments; supracaudal gland about % as long as infracaudal. Secondary photophores on trunk and head, those on trunk arranged in a definite pattern (one at anterior margin of each scale pocket). Size. A small fish, attaining a maximum size of about 43 mm. Numerous gravid females, ranging between 31 and 36 mm, were found in the collections examined. Development. Misled by a poor description and an erroneous illustration of L. alatus by

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SPECIHENS/HOUR Diaphus bertelseni Diaphus mollis

terms of the regions or parts or combinations of them (Fig. 2, Table IV): temperate, subpolar-temperate, temperate-semisubtropical, subtropical, tropical, tropical-subtropical, tropical-semisubtropical, eastern, and Mauritanian Upwelling. It is convenient, sometimes, to speak of the first three together in the northern hemisphere as "northern" patterns.

Diogenichthys atlanticus tGonichthys cocco ^Lampadena anomala Lampanyctus photonotus Lobianchia gemellarii lLoweina rara Myctophum nitidulum ^Myctophum selenops Notolychnus valdiviae ?Notoscopelus caudispinosus ^Notoscopelus resplenJens ^Symbolophorus rufinus Tropical-semisubtropical Bolinichthys photothortx Diaphus brachycephalus Diaphus splendidus Diaphus subtilis ^Lampadena luminosa Tropical Diaphus dumerilii Diaphus fragilis Diaphus garmani Diaphus lucidus Diaphus luetkeni Diaphus perspicillatus Diaphus problematicus iDiaphus termophilus Diaphus vanhoeffeni Hygophum macrochir ?Lampanyctus alatus Lampanyctus isaacsi ^Lampanyctus nobilis Lampanyctus tenuiformis Lepidophanes guentheri Myctophum affine Myctophum asperum Myctophum obtusirostre Mauritanian Upwelling Lampadena pontifex Eastern Diaphus holti Electrona risso

In describing the faunal boundaries, remarks concerning physical properties of the ocean pertain mainly to the water column from near the surface to about 700 or 800 m, that is, the habitat of mesopelagic fishes. A boundary once described is not redescribed in connection with another region or province. Sections of boundaries that are land

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TABLE V. Species composition of each Atlantic Ocean pelagic faunal region. Numbers are the percentage of the total myctophid specimens from each region in WHOI midwater-trawl collections made at night in the upper 200 m, with the ranks in parentheses for the ranking species in each region (see chapter Family Myctophidae). Region Species

North Atlantic Subarctic Temperate Subtropical

Benthosema glaciate 96.2(1) Benthosema suborbitale Bolinichthys indicus