Non-chordate (invertebrate) zoology practical 9788183185042, 8183185045

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NON-CHORDATE (INVERTEBRATE)

ZOOLO'GY PRACTICAL Dr. K. Pandey Head, Department of Zoology and Dean Faculty of Science, DDV - Gorakhpur University, Gorakhpur (U.P.)

Dr. J.P. Shukla Reader, P.G. Department of Zoology S. Kisan P.G. College, Basti (U.P.)

( FIRST EDITION: 2006 )

Rat GJIimalaya GPublishingGflou'se MUMBAI • DELHI • NAGPUR • BANGALORE • HYDERABAO

co

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FIRST EDITION: 2006

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CONTENTS

I

1.

Characters and Cfassification of Non-Chordates. Protozoa I. Porifera II. Coelenterata (Cnidaria. II. IV. Ctenophora V. Plathelminthes VI. Nemathelminthes (Ascheminthes. VII. Annelida VIII. Echiuroidea IX. Arthropoda Mollusca X. XI. Echinodermata XII. Hemichoradata

1-40 3 7 8 12 12 15 16 18 19 30 34 38

2.

Study of Museum Specimens and Slides of Different Invertebrate Phyla 41-374 43 Protozoa I. Porifera II. 72 87 III. Coelenterata IV. Platyhelminthes 127 V. Aschelminthes 153 VI. Annelida 165 VII. Arthropoda 212 VIII. Mollusca 277 • IX. Echinoder Mata 318 X. Minor Phyla 348 XI. Hemi Chordata 360

3.

Curios in Invertebrate Zoology Protozoa I. Porifera II. III. Coelenterata IV. Plathelminthes V. Annelida VI. Arthropoda VII. Mollusca VIII. Echinodermata IX. Important Sea Invertebrates

375-388 377 379 379 380 381 381 384 385 386

4.

M'i nor and Major Dissections I. Ascaris Lumbricoides II. Pheretima Posthuma

389-434 392 393

III. IV. V. VI. VII. VIII. IX. X. XI. XII. XIII. XIV. XV.

397 400 402 410 414 417 422 424 428 429 430 432 433

Hinedinaria Granulosa Nereis Prawn Scorpion Poeciloceres Periplaneta Americana Unio Pila Globose Mytilus Loligo Sepia Holothuria Echinus

5.

Preparation of Important Fixatives, Stains, and other Reagents Fixatives I. II. Stains III. Other Reagents

435-444 437 439 443

6.

General Procedure of Microscopic Preparations I. Single Staining II. Double Staining III. Microtomal Staining

44"5-452 448 449 450

7.

Invertebrates Culture Methods I. Phylum - Proto-=r-oral groove J:::::..~~~ vestibule

oesophagus

:~~$:;-

trichocysts

15. There is a prominent oral groove

;~~-

endoplasm

leading posteriorly into vestibule which continues as buccal cavity.

foodvacluoIE'--~~~~

I-:-~~=---myonemes

posterior -~~wTi contractile . vacuole

16. Locomotion ciliary, at a speed of 1.5 mm per second. Beating of cilia is effected by effective stroke and recovery stroke. 17. Nutrition holozoic. Digestion starts in acidic medium of pH 1.4-3.4.

Fig. 2.23 Paramecium 18.

14. Anterior and posterior contractile vacuoles are fixed with 5-7 radiating canals.

Digestion occurs in food vaculoes during cyclosis. The path followed by food vacuole resembles the figure of '8'.

19.

Undigested food is removed through cytopyge situated venterolaterally .

20.

Reproduction is by binary fission, conjugation, cytogamy, autogamy, endomixis and hemixis . Endomixis was first described by Kloodruff and Eromann (1914) in P. aurelia and in 1916 in P. caudatum.

21 .

It is the most familiar and extensively studied protozoan type . It has great experimental value in cytological studies. Sonneborn, T.M. (1937) reported that P. aurelia occurs in two strains. One is killer strain having Kappa particles and other is sensitive strain having no Kappa particles.

22.

Kappa particles produce toxic proteins. Lambda particles, Mu particles and Pi particles have also been reported in certain strains of Paramecium.

23.

The most common species is P. caudatum.

Special. Ress (1922) and Lund (1933) described neuromotor system in Paramecium. •

A single Paramecium can devour 2.5 million Bacterium coli in 24 hours .

•

In P. bursa ria green algae about 200 chlorellae remain as symbiont.

Habit and Habitat

.

It is found in freshwater ponds, lakes, ditches, pools, streams and rivers.

Distribution: Cosmopolitan.

Non-Chordate (Invertebrate) Zoology Practical

]0 .

Identification Since it contains slipper-shaped body with 2 star-shaped contractile vacuoles. hence it is

Paramecium .

24. PARAMECIUM IN BINARY FISSION

Comments I.

Binary fission is the asexual mode of reproduction.

2 .. It takes place under favourable temperature and other con ditions. 3. A median transverse tonstriction appears which deepens and divides the body transversely into two equal · halves.

new oral

groo'/e

Fig. 2.24 Paramecium, Binary Fission 4.

Micro and Macro nuclei elongate and divide by mitosis and amitosis respectively.

5.

Each half receives a daughter micro - and macro nucleus and a contractile vacu o le.

6.

Cytopharynx also divides into two.

7.

By the time of separation, each half develops all the essential structures.

8.

In binary fission, two daughter individuals are formed.

9.

The fission takes about two hours to complete and may occur one to four times per day, producing 2 - 16 individuals.

to.

The Paramecia produced from one inoividual by fission are termed as clones.

II.

During this process, the animal after attaining maximum size, stops feeding .

25. CONJUGATION IN PARAMECIUM

Comments

conjugenta

cilia

Fig. 2.25 Conjugation in Paramecium

I. Conjugation is the sexual mode of reproduction. 2. It involves the temporary union of two Paramecia to facilitate the nuclear exchange. 3. Two Paramecia come in contact vertica)ly and unite by their oral surface. 4. The pellicle and ectoplasm between two paramecia degenerate and a protoplasmic bridge is formed between the two individuals which are called conjugants or gametocytes.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

71

5.

In each conjugant, macronucleus degrades.

6.

Micronucleus in each conjugant divides twice forming 4 haploid daughter micronuclei. Comparison between Macronucleus and Micronucleus S. No. I.

Macronucleus

Micronucleus

It is large granular and roughly kidneyshaped.

It is small round in shape and lodged in the depression of macronucleus.

2.

Nuclear membrane is absent.

Nuclear membrane always present.

3.

It is vegetative or trophic nucleus .

It is reproductive nucleus.

4.

It controls day to day metabolic activities of the cell.

It controls reproductive activities of the cell.

5.

It always divides amitotically.

It always divides mitotically.

6.

It is derived from the micronucleus during reproduction.

It gives rise to micronucleus during reproduction.

7. Of the four daughter micronuclei, three degenerate and disappear in each conjugant, while the remaining one again divides forming two unequal pronuclei. 8. The smaller one is the active migratory and potentially male pronucleus and the bigger one is the inert stationary and potentially female pronucleus. 9. Migratory pronudeus of one conjugant moves through the protoplasmic bridge into the other conjugant and fuses with stationary female pronucleus to form zygote nucleus or synkaryon and vice versa. 10. Zygote nucleus is diploid and is also called as conjugation nucleus or amphinucleus. 11. The complete fusion of two nuclei from the different individuals forming a zygote nucleus is called as amphimixis. 12. After an union of about 12 - 48 hours the two paramecia separate and are called

exconjugants. 13. The zygote nucleus of each exconjugant at the end of the conjugation divides further and produces four daughter Paramecia. 14. Process of conjugation is conditioned as it occurs in deficiency of nutrition, at a certain temperature and forms smaller individuals. 15. Conjugation occurs among different strains. 16. Conjugation has significance, as it imparts rejuvenation and nuclear reorganization and hereditary variations. However, Woodruff and Jennings did not support that conjugation helps in rejuvenescence. 17. Conjugation also aids in the formation of better resistant paramecia.

Non-Chordate (Invertebrate) Zoology Practical

72

IUNIT II-PORIFERA I Spuimens: I. uucosolmia 2. Clathrina (Olynthus) 3. Sycon (Scypha) 4. Grantia 5. Euplectdla 6. Hyalon"ma 7. Chondritla 8 . Cliona 9. SponRiIla 10. Chulina II . Eu.fponRia

Slides: I. T.S. of Sycon or Scypha 2. L.S. of Sycon or Scypha 3. T.S. of Gruntia 4. L.S. of Grantia 5. SponRe spicule.f 6. Gemmule 7. Amphibla.flllla larva.

ISTUDY OF MUSEUM I 1. LEUCOSOLENIA

Classification ' Phylum Class Order Genus -

Porifira Calcaria Homocoela Leucosolenia

Multicellular, Symmetrical or Asymmetrical and pore-bearers. Calcarious spicules of

CaCO~

from the skeleton.

Unbranched. smooth spongocoel, Simple canal system.

Commen ts 1. The Leucosolenia (Gr., leukos = white, solen = pipe) is whitish yellow. vertical pipe-like colonial delicate branching sponge. 2. Each vertical tube bears an opening. the osculum. at their free distal ends while united at the bases by horizontal tubes through adhesive disc. 3. The upright cylinders or tubes of the colony may attain a height up to 25 mm. and produce a number of buds in their basal part.

P- i-g-.-2-.2-6-Le-u-c-o-so-l-e-n-ia-,-A-p-o-r-ti-o-n-o-if-c-o-l-o-n-'y

L..-

4. The thin, simple body wall consists of an outer epidermis or pinacoderm and an inner gastrodermis or choanoderm layers seperated by a gelatinous layer of mesogliea.

5.

Skeleton consists of calcarious spicules made of mesenchyme.

6.

The unbranched, simplest canal system called "asconoid type" is found in Leucosolenia.

7.

The porocites are contractile and serve to close the ostia when required.

8.

It is an asconoid sponge with simplest and most primitive structural plan .

9.

Body is cylindrical and radially symmetrical.

CaCO~

spicules embedded in

Study of Museum Specimens and Slides of Different Invertebrate Phyla

73

10.

Sizo maximum upto 10 cm height. colour whitish or yellowish.

II.

Spicules may be of monaxon. triaxon or tetraxon type.

12.

Nutrition is holozoic and digestion is intracellular.

13.

The principal nitrogenous waste is ammonia.

14.

Different types of amoebocytes are: Archaeocytes. Chromocytes. Thesocytes. Myocytes. Trophocytes. Gland cells and Sex cells.

15.

The asexual reproduction takes place by means of budding and sexual reproduction through gametes (ova and spermatozoa).

regen~ration

while

16.

Fertilization is internal.

J 7.

Cleavage is equal and holoblastic.

J8.

Zygote develops into a hollow blastula cal!ed coeloblastula.

19.

Further development results in the formation of stereogastrula or parenchymula larva.

20.

Parenchymula swims freely and finally gets attached to substratum and becomes sessile adult.

Habit and Habitat It is a sessile. delicate. simple. colonial. marine sponge growing in shallow water below low tide mark on the rock etc. near the sea shores where waves are intense and rough.

Distribution: Very much common in Europe.

2. CLATHRINA (OLYNTHUS)

Classification Same as that of Leucosolenia.

Comments I.

Clathrina is a marine. colonial simple sponge with a vaseshaped cylindrical body being narrower at the base.

2.

Externally the body surface bears numerous incurrent pores or ostia communicating with the spongocoel. The spongocoel or paragastric cavity opens out through the osculum. Skeleton consists of calcarious triaxon spicules with equal rays. Canal system asconoid type. The central cavity (spongocoel) is lined by choanocYlcs. Asexual reproduction by budding and sexual by fusion of ova and spermatozoa. Olynthus in considered to be a hypothetical ancestor of sponges. Development is complicated.

3. 4. 5. 6. 7. 8. 9.

~------------,--~

Fig. 2.27 Clathrina (= OIynthus)

74

Non-Chordate (Invertebrate) Zoology Practical

Habit and Habitat Clathrina is a sedentary marine colonial sponge usually found attached to the rocks or stones in shallow sea-water.

Distribution Martha's Vineyard to Gulf of St. Lawrence, Casco Bay to Arctic Ocean. It is abundant in Europe.

3. SYCON OR SCYPHA

Classification Phylum Class Order

Genus

Porifera Calcarea Heterocoela Sycon or Scypha osculum

Multicellular. Symmetrical or asymmetrical pore-bearers. Calcareous spicules of CaCO) form the skeleton. cyconoid types of canal system .

Comments I. Sycon is commonly called "Crown Sponge" due to crown like oscular fringe and "Urn Sponge" due to its shape like an urn (water vessel) . 2.

is a vase - shaped branching or individual cylinder sponge measuring about 15 to 30 mm. in length and 5 to 6 mm . in diameter.

SyCOfl

3. Solitary or colonial. 4. Each cylinder is centrally swollen and bears an opening, the osculum at its tip. 5. The body surface is rough and perforated by numerous poresthe ostia or incurrent pores.

Fig. 2.28 Sycon or Scypha

6. The body wall consists of two loosely organised layers - an outer pinacoderm and the inner gasteroderm with an intermediate mesenchymatous layer.

7.

The choanocytes are shifted and being restricted to the radial canals only.

8.

The calcareous monaxon, triaxon and tetraxon spicules form the skeleton .

9.

Due to infolding of body wall, the canal system becomes complicated and is called syconoid type. The water passage is : Water ~ Ostia ~ Prosopyles ~ Radial canal ~ Apopyles ~ Spongocoel ~ Osculum ~ Outside.

10.

The ostia and canal system is absent in collar and basal parts.

I I.

Asexual reproduction by budding and sexual by fusion of gametes.

12.

Bisexual.

Habit and Habitat Scypha is a widely distributed, solitary or colonial marine sponge, found permanently attached to the submerged rocks and alike objects in the shallow coastal water.

Distribution: Common in Europe. From Rhodes Islands to Greenland.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

75

4.GRANTIA

Classification Same as that of Sycoll. osculum

Comments I.

The slender, vase-shaped body measures from 20-25 mm. in height and 5-8 mm. diameter.

2.

There tubes slightly bulge in the middle and bear an external opening at their tips - t~e osculum, which is encircled and fringed by large monaxon spicules forming the sphinctered oscular fringe.

3.

The dermal layer becomes thick and spreads over the surface of body forming a cortex of varying thickness embedded with triradiate calcareous spicules mostly arranged parallel to the body surface.

4.

Owing to the thicker cortex, the incurrent canals have branched and become more irregular.

Fig. 2.29 Grantia 5.

Similarly, the development of a gastral cortex around spongocoel has shifted and displaced the radical canals. These canals may branch off at their outer ends and become more uniform.

6.

Canal system syconoid type.

7.

Hermaphrodite.

8.

Reproduction sexual and asexual both.

9.

Development through amphiblastula larva. Gralltia is almost similar to sycon in all respects but for its outer surface of body is formed of thick dermal layer or cortex which is entirely absent in sycon. Due to this thickening the canals do not show their uniform pattern and are thus displaced .

Habit and Habitat It is a colonial marine sponge found attached to the submerged rocks or other alike objects in well oxygenated shallow waters.

Distribution: It is abundantly found in Gulf of SI. Lawrence. 5. EUPLECTELLA

Classification Phylum Class Order Genus

Porifera Hexactinellida (Hyalospongiae) Hexasterophora - Euplectella

Characters as that of Grantia. Skeleton made of triaxon or hexactinal (six ./ rayed) siliceous spicules. Spicules exclusively hexasters (star-shaped).

Non-Chordate (Invertebrate) Zoology Practical

76

Comments 1.

Popularly known as 'venus's flower basket' is the intricately latticed dried glossy skeleton of Euplectella.

2.

It is long curved, thin walled, cylindrical tube like measuring about 15-30 cm. in length and 2-5 cm. in . diameter.

3.

The curved rigid structure is regarded as an adaptation to the slow, constant water current at the sea bottom.

4.

The body is fastened in the bottom mud of deep sea by a mass of long siliceous root spicules.

' - - - - - - - - - - - - - - ' 5. Fig. 2.30 EuplecteUa

6.

The colour is white

transp~nt.

Usually six rayed siliceous spicules are fused at their tips to form the skeleton with net like parietal gaps.

7. 8.

Parietal gaps communicate with the spongococl.

9.

Simple syeonoid type of canal system presenL

An opening at terminal end in covered by an oscular sieve plate.

10.

Small choanocytcs are restricted to finger sbaped simple or branched radial canals.

II.

It is solitary, marine sponge found in deep water at a variable depth of 500-5000 metre.

12.

It is perhaps the most beautiful glass sponge. Cleaned and bleached skeletons of BupkcteUa form costly wedding gift in Japan and much mythological significance is related to it for a "Union till death".

In the young Euplectella a male and a female crustacea called Spongicola enter the spongocoel and remain prisoned there due to the formation of oscular sieve. Thus, only death·can separate the two life partners. Therefore, such skeletons are given as a wedding gift in Japan which symbolises "a life long companionship."

Habit and Habitat Solitary glass sponge is found in slow running deep sea water.

Distribution: These are abundantly found 'in Philippines islands. 6. BYALONEMA

Classification Phylu", - Porifera

C/tul

- HeoedneDld.

Charac&cr same as that of Grantia. Skeleton made of lriaxon or hexactinal (six rayed) siliceous spicules.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

77

Comments I. Popularly known as "glass rope sponge ". Hyalonema possesses variable forms of body approximately 30-40 cm. long. 2. The body is radially symmetrical. rounded or oval with a simple spirally twisted root tuft of glassy spicules. 3. The root tuft is made up of very long spicules which traverses the body as an axis or columella and projects above as the gastral cone. 4. The middle part of the columella usually bears epizoic or symbiotic anemones of the genus Epizoanthus. 5. The spicules of the root tuft are spirally twisted like a rope. 6. If the columella projects upwards to form the gastral cone. the spongocoel does not exist. 7. Though the skeleton is chiefly composed of amphidiscs. however, small branching six rayed .spicuJes resembling christmas trees may also be present. 8. Osculum contains sieve plate. 9. Flagellated chambers are arranged radially and in parallel . planes in the sponge wall. Fig. 2.31 Hyalonemtl

Habit and Habitat Hyalonema is a widely distributed sponge inhabiting 10-15 metres deep water of sea.

Distribution: It is abundant along New England coast. ' 7. CHONDRILLA Classification Phylum. Class

Porifera - Demaspongia Tetractinelllda Carnosa

Sub-class Order

Characters same as that of Grantia. Skeleton either of siliceous spicules or spongin fibres or a combination of these two or none. Skeleton of tetraxon siliceous spicules. Simple spicules of similar size, asters may be present.

- Chondrilla

Comments

t.

Chondrilla is popularly known as 'chicken-liver sponge ' found attached with the substratum.

2.

III body is smooth, almost round bearing one to a few oscula and numerous pores on the distal body surface.

78

Non-Chordate (Invertebrate) Zoology Practical 3. Skeleton mainly of siliceous multiactinate microscleres ca\led asters and are present as spherasters. 4. Chondrilla possesses only spherasters spicules embedded in the cortex between cones.

oscula

5. The spicules in the cortex may project from the surface making it thick har.d and stony . '--_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _-' 6. Canal system is leuconoid type. Fig. 2.32 Chondrilla 7. Hermaphrodite.

Habit and Habitat It is a marine sponge attached with the substratum.

Distribution:

It is found in British and U.S.A. sea waters.

8. CLIONA Classification Phylum - Porifera Class - Demospongia Sub-class Monaxonida Hadromerina

Order

Genus

-

}Characters same as those of Chondrilla. Skeleton of diactinal monaxon and megascleres with or without spongin. Broad and knobbed megascleres the tylostyles, microscleres star shaped, (asters) if present, spongin absent.

Cliona

Comments 1.

Cliona is often of a bright sulphur yellow colour and able to bore into calcareous structures like the mollusc and coral shell. It is, therefore. popularly known as 'boring' or 'sulphur

sponge'.

Fig. 2.33 Cliona

2.

The sponge forms a compact mass of 20 to 40 cm. in diameter with sulphur smell.

3.

Their larvae bore in dead or living she\ls, corals and calcareous objects forming tunnels and burrows. growing in a compact mass which finally occupies them.

4.

The exposed surfaces of these shells etc. show the channels burrowed by the sponge.

5.

The surface shows elevated openings or papillae bearing an osculum or a group of ostia leading to the incurrent canal.

6.

Skeleton generally comprises of siliceous monaxon spicules or spongin fibres .

Study of Museum Specimens and Slides of Different Invertebrate Phyla

79

7.

Cliona is regarded as an important agent for the decomposition of shells and corals.

8.

Canal system is of Leuconoid type. According to Gorean and Hartmen (1963), the larvae bore into the shell by chipping away small fragments of CaCO} through localized chemical dissolution.

Habit and Habitat It is a cosmopolitan genus inhabiting molluscan shells, corals and other calcareous objects in the shallow sea water.

Distribution Cosmopolitan. Abundantly found in South Carolina.

9. SPONGILLA Classification: Same as that of Cliona.

Comments Spongilla is the most commonly occurring freshwater sponge with a characteristic odour. 2. Its colony is profusely branched and shows different shades of green colour because of the presence of the symbiotic algae Zooehlorella. 3. The thin dermal membrane forms the body wall and is perforated with ostia and oscula. I.

L -____________________________________~

Fig. 2.34 Spongi/la

4. 5. 6.

7.

The canal system is rhagon type. Skeleton consists of siliceous monaxon spicules in the form of network of smooth or spiny large and small oxeas embedded in spongin. Reproduction asexual and sexual both. Asexual reproduction, like many freshwater sponges by gemmule. Sexual reproduction takes place by syngamy with an unusual free swimming larva typical of spongilla. The protective covering of gemmules posses needle like spicules but amphidiscs are absent.

Habit and Habitat It is a colonial branching sponge found abundantly on submerged sticks and plants in freshwater ponds and lakes.

Distribution It is abundantly found in Atlantic, European and American freshwater bodies.

80

Non-Chordate (Invertebrate) Zoology Practical

lO.CHALINA

Classification Characters same as that of Spollgilla.

Comments I. It is popularly known as " merl1Ulid 6'oves" or "dead man's

fingers". 2. It is yellowish brown or orange or

~ven

red in colour.

3. The flattened body surface bears group of finger like branches. 4. These branches are perforated by a large number of oscula. 5. Skeleton consists of spongin fibres in which siliceous oxea spicules are embedded. 6. Canal system is of leucon type.

Fig. 2.35 Chalina

7. Reproduction both asexual and sexual. Asexual by regeneration and budding while sexual through syngamy by producing free swimming larva.

Habit and Habitat ChaNna is a deep water sponge found in Rhode Islands to Labrador. But when broken from the stalk. it may be washed ashore and can be even found in shallow waters.

Distribution Found in Europe. Abundantly found from Rhodes Islands to Labrador.

11. EUSPONGIA

Classification Phylum Class Sub-class

- Porifira - Demospongia Keratosa

Gellus

- Euspongia

}

Characters same as that of spongiIJa. Horny sl'0nges with leathery surface without spicules bUI spongia fibres present.

Comments I.

2. 3. 4. 5.

n.

Euspongia is the popular "bath sponge". It is also known as "commercial sponge." The body is massive and the shape may vary from rounded to lamelliform and may be dark brown or even black in colour. The body surface is perforated with a number of oscula on the elevated partition:;. Due to the infolding of the body wall, the sponge become:) more complex. Spongin fibres form the skeleton and spicules are altogether absent, The bath sponge for household use is prepared hy decaying their ntlih. squeezing and bleaching the undecomposed skeleton .

Study of Museum Specimens and Slides of Different Invertebrate Phyla

81

7. Thus the marketed bath sponge consists of horny close meshed reticulum of spongin fibres with immense capacity of holding water. 8. It is commonly used as a bath sponge and also in offices and banks etc. for wetting postal stamps and counting currency notes. However. synthetic sponge has now completely replaced it. 9. The body exhibits a large number of small projections called conuli which are due to strands of spongin fibres. substratum

10. Areas between conule are perforated by dermal ostia leading into incurrent canals through subdermal cavity.

Fig. 2.36 Ellspongia

II. Inside the sponge are numerous incurrent canals. flagellated chambers and excurrent canals.

12. The passage of water circulation is same as described in T.S. sycon and may be shown diagrammatically as : water -+ ostia -+ incurrent canal -+ prosopyles -+ radial canals -+ apopyles -+ spongocoel -+ through osculum -+ outside.

Habit and Habitat Euspongia is a sedentary form. found attached to the rocks by horny spongin secretion in warm shallow waters of tropical and subtropical regions . .

Distribution Cosmopolitan. Most abundant in Eastern Mediterranean. West Indies. Asia and Australia.

I STUDY OF PREPARED SLIDES I 1. Transverse Section of Sycon or Scypha

Comments T.S. of Sycon or Scypha depicts following charac~ teristic histological features: I. The diploblastic body wall possesses an outer ectoderm and an inner endoderm layer with in which a layer of gelatinous mesenchyme is sand~\ witched. These layers fold and form two types of alternating canals - the radial and incurrent canals.

Fig. 2.37 Sycon T.S.

Non-Chordate (Invertebrate) Zoology Practical

82

2.

The ~todenn is formed of a single layer of scaly, thin pinacocyte cells forming the body covering and lining the incurrent canals and the large spongocoel.

3.

The endoderm is made up of a single layer of large flagellated collared cells choanocytes bordering the radial canals only.

4.

The intermediate layer of mesenchyma forms the substance of body and is particularly thick at the outer and inner foldings of the body wall. This is called dermal cortex and gastral cortex respectively and possesses several types of amoeboid cells.

the

The amoebocytes can be differentiated into several functional cell types. Example collencytes -+ branching and radiating; chromocytes -+ pigmented; trophocytes -+ nurse cells; thesocytes -+ storage cells; scleroblasts -+ spicules production; archaecytes -+ undifferented embryonic 'totipotent' cells that can produce other cell types.

6.

The surface of the body is perforated with small openings, the ostia communicating with incurrent canals which open through prosopyles into radial canals and. the radial canals through apopyles open into large central cavity the spongocoel, opening outside via terminal osculum. The water circulates through these passages in sponge body and the system is known as canal system which ' is syconoid type in sycon.

7.

The calcareous spicules - mainly monaxon, oxeote and triradiate are embedded in the body wall.

8. 9.

Each choanocyte cell contains a basal body, having nucleus and a single flagellum. Flagellated chambers are quite distinct in circular way.

Representation of Canal System (Syconoid type). Water current

J,

Ostia

J,

Incurrent canal

J,

Prosopyle

J,

outside

t

Radial canal

J,

Osculum

, Apopyle

I

t I

2. Longitudinal Section of Sycon or Scypba Comments L.S. of the sycon body shows similar cellular structures as in the transverse section. 1.

The body wall with an outer ectodenn and inner endodenn enclosing the intennediate layer of mesenchyme.

2.

Due to the infolding of body wall, two types of vertically and alternatively placed canals or tubes - the incurrent and the radial canals are fonned.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

83

3. Ectodermal epithelial cells cover the entire outer body surface along with the lining of incurrent canals and spongocoel.

'f--oscular fringe

4. The mesenchyme composed of gelatinous transparent matrix into which different types of amoebocytes (Ref. to T.S . SycolI) and calcareous. monaxon. oxeotes and triaxon spicules are embedded. 5. Gastral epithelium or endoderm comprises of a single layer of flagellated choanocyte c.ells lining the radial canals exclusively. .flagellated chamber

6. The passage of water circulation is same (syconoid type) as described in T.S. and may be shown diagrammatically as' -7 water -7 ostia -7 incurrent canal -7 prosopyles -7 radial canals -7 apopyles -7 spongocoel -7 through osculum -7 outside. 7. Spongocoel opens exterior by osculum. 8. Flagellated chambers open apopyles.

inside spongocoel by

Fig. 2.38 L.S. of Sycon

3. Transverse Section of Grantia Comments ..... ..........

\

\

\ I

,"

spongocoel

I

I I

,/

--_ .... " radial canal

choanocytes

Fig. 2.39 Grantia T.S.

The T.S. of Grantia shows following histological features. 1. Diploblastic body wall. 2. The outer body surface is formed of t-hick dermal layer or dermal cortex . 3. The calcareous triradiate cortical spicules are tangentially embedded in the dermal cortex. 4. Due to the enormous development of dermal cortex. the incurrent canals are irregularly placed and channelized. 5.

Similarly. the radial canals have also been displaced and branched due to the development of thick gastral cortex and spongocoel.

6.

Canal system of syconoid type and the course of water is similar to that of sycon.

7.

Grantia differs histologically from sycon only in the development of dermal cortex which invades and narrows the spaces of the incurrent canal.

8.

Spongocoel is lined with gastral cortex.

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Non-Chordate (Invertebrate) Zoology Practical

4. Longitudinal Section of Grantla Comments

Intemal ostium

L.S. through the body of Grantia shows followimt histological features. 1. 2.

radIai canals

incunant canals

dermal ostia

e~

spoclgOCOll

spicules

'exo-pinac:oderm

Body wall is diploblastic. Dermal membrane forms a . thick dermal cortex which covers· the entire body surface. 3. Calcareous monaxon. oxeote and triradiate cortical spiCules are tangentially embedded in the dermal cortex.

Fig. 2.40 Grantia LS. 4. 5. 6. 7.

8.

The extensive development of dermal cortex has pushed the incurrent canals which became branched and irregular. Similarly. the radial canals have also been narrowed and branched. The gastro vascular cavity is Iine4 with gastral cortex. Canal system syconoid type and the passage of water circulation is similar to that of sycon. Water current -+ ostia -+ incurrent canals -+ prosopyles -+ radial canal -+ apopyle -+ spongocoel -+ osculum -+ outside. The section shows extensive development of dermal cortex occupying more space between successive canals which have accordingly narrowed and thus differ from that of sycon.

S. Sponge • Spicules Comments

ox.. Tetractlne A. Monaxon spicules

Triaenea

y Triod C. T8IIIXon epIcuIM

D.OeImI

Fig. 2.41 Various type, of SpicU'" in Sponge,

1. Sponges possess the most peculiar type of skeleton either as spicules or spongin fibres or both. 2. The spicules are produced by scleroblasts present in the mesenchyme. 3. Spicules are formed of an axis of organic materials around which either the calcium carbonate or silica is deposited. Spicules arc of two types (I) Megucleres, and (ii) Microscleres.

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85

The spicules (megascleres) are of different shapes which form the basis of their classification into main six types. (i) Monaxons Having a single axis growing in one or both direction. (ii) (iii)

Triaxons Tetraxdns

With three equal axes crossing each other forming six rays. With four rays. When all the 4 rays are more or less equal. the spicule is called CALTHROPS. When a single ray is elongated. bearing a crown of three smaller rays. it is called TRIAENES.

With several axes and many rays radi~ting from a centre and are popularly called asters. Round in shape in which growth is concentric around a cen(v) Spheres tral point. (vi) Desmas Formed by the deposition of irregular successive layers of silica: on any type of spicules. These are usually united into a network called LITHISTID. Microscleres are found throughout the mesenchyme and include spines and asters. These are non-supporting. Spicules protect and support the sponge body. Spicules constitute the basis of classification of poriferons.

(iv) Polyaxons

5. 6. 7.

6. Gemmule Comments

Fig. 2.42 Gemmule of Spongilla

I.

Gemmules are asexual reproductive bodies formed as internal bud in all the freshwater and a few marine sponges like Ephydatia .

2.

These are either formed in excessive cold or dry conditions to tide over the unfavourable weathers.

3.

A gemmule is a small hard round body consisting of an outer chitinous capsule and an internal food ladden mass of archeocytes.

4.

Th~

resistant chitinous capsule is made of two membrane!i usually pierced at one end by an opening the micropyle.

5.

The chitinous layer of capsule is strengthened by siliceous amphidiscs but are absent in spongilla.

6.

The archeocytes are enriched with food reserve. formed by trophocyte cells or nurse cells.

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Non-Chordate (Invertebrate) Zoology Practical 7.

Under favourable conditions the living contents (histoblast) pass out through the micropyle and develops into a new sponge which later produce ova and spermatozoa . Such sponges thus show the phenomenon of alternation of generatiqn.

8.

Gemmules of freshwater sponges can be leept for two years.

9.

They hatch at a lemperature of 13" - 21°C in about 3 days .

Sig~ificance

of Gemmule

I.

It is a means of asexual reproduction .

2.

It helps the sponge to tide over the unfavourable seasons.

3.

It helps the disposal of sponges.

7. Amphiblastula Larva Comments

~~~~~~::-., flagellated cells

granular cells or non·flagellated cells

I.

Amphihlasttila is the larva of most of Ihe sponges.

2.

The stomoblastula stage undergoes a process of inversion and thus its inner flagellated surface of micro meres becomes the outer surface and is now called amphiblastula larva.

3.

This larva' 5 almost oval in shape whose anterior half comprises of small slender flagellated cells while the posterior half of large rounded, non-flagellated cells.

Fig. 2.43 Amphiblastula larva 4.

The fully grown larva first enters the radial canal and then passes to exterior through osculum along with the water to lead a free swimming life.

5.

Swimming freely for sometime, the larva attaches to some weeds or rocks etc., and gastrulation takes place through the invagination of the flagellated micromeres called epiboly and subsequenlly develops the spongcoel and an osculum.

6.

During epiboly the flagellated half sinks inside the non-flagellated half.

7.

The flagellated cells, (choanocytes) form the inner lining of spongocoel while the non-flagellated ones form the dermal covering.

8.

After the above changes, the larva develops into the alynthus or asconoid stage and subsequently changes into the young syconoid stage.

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Study of Museum Specimens and Slides of Different Invertebrate Phyla

IUNIT - III. COELENTERATA

I

Specimens I . Hydra 2. Ceratella 3. Hydractina 4. Mi/lepora 5. Styla.fUr 6. Diphyes 7. Phy.falia lI. Porpita 9. Velella 10. Aurelia II. Charybdeo 12. Cyanea 13. Rhizostoma (Pilema) 14. Tubipora mU.fica 15. Alcyonium 16. Gorgonia 17. Corallium Ill. Pennatufa 19. Metridium 20. Adamsia showing commensalism 21. Madrepora or Aeropora 22. Dendrophylia 23. Fungia 24. Astrea 25. Favia 26. Meandrina 27. Edward.fia 28. Pteroeides . . Slides I . L.S. through the body of Hydra 2. T.S. pa.f.finll throullh the body of Hydra 3. Hydra : T.S. paHinll thrr>ullh te.;p"..".

Comments I.

Alc\"OI/iUIIl is commonly known as Dead Man '.I' Finger.

2.

It is marine. coloni al anthozoan .

3.

It is fleshy hence also referred as soft coral.

4.

The colony consists or a stalk and soft thick leathery lohes .

S.

Zooids are found di stally.

6.

The pol y ps are emhedded in the gc lntinous mass of coencnch y ma . a fleshy ma ss from which only antilOcodia protrude OUI.

7.

The proximal part of the colony is devoid of anthocodia and hence it is sterile.

8.

Each polyp contains 8 pinnate tentacles, mouth, gastrovaseular cavity and 8 mesenteries . It is delicate. elongated and yellow coloured and looks like tiny star on stuby leathery branches of the colony.

' - - - - - - - - - - - - - - - - - ' 9. Fig. 2.58 AlcYOlliul1I

Skeleton consists of isolated calcareous spicules secreted hy the sclcrohlasts of the mcsogloea.

10.

Spicules are distrihuted coenenchyma .

throughout

the

mesogloea

and

impart

solidity

to

II.

Fertilization is external.

12.

Life cycle includes a free-swimming planula larva which fixes itself to some ohject and gives rise to new colony hy hudding.

Habit and Habitat It is a marine sedentary and colonial anthozoan. Many of its species live hetween tidal zone at the depth of 200 m and few even at a depth of 3000m. It is found attached to rocks and stones in Indo-Pacific Oceans.

Distribution Cosmopolitan, chiefly in temperate and cold sea-waters.

NOI/-Chonlrlf(' (1IiverlebrOIC) Z(loI08Y PracliNJI

102

16. GORGONIA (Sea-Fan) Classification

}

Phylum

Coelenterata

Class

Anthozoa

Sub-class

Octocorallia

Order

Gorgonacea

Horny corals . polyps short not reaching IIplO hase.

Family

Gorgonida

Colony plant like. axial skeleton or calcareous ~picules or horn like m-IJ""-

seminal vesicle

stomach

ventral blood vessel

ventral nerve ,cord

Fig. 2.166 Earthworm. T.S. through Seminal vesicles.

Comments T.S. of Pheretima passing through the seminal vesicles (11th segment) shows following histological details . I.

Section through the middie of the I I th segment exhibits finger-like testes and girdle - shaped seminal ,vesicles.

2.

Body wall consists of a thin cuticle, epidermis, thin circular muscle layer and thick longitudinal muscle bundles separated by septa.

Non-Chordate (Invertebrate) Zoology Practical

208

3.

A pair of elongated seminal vesicles are visible on the lateral sides of the oesophagus .

4.

Below the seminal vesicle, a pair of testis enclosed in testis sacs, and a pair of vasa deferentia are present.

5.

Seminal vesicle contains numerous spermatozoa.

6.

Sperm ducts show internal ciliated epithelial layer.

7.

Testes sacs are supposed to be closed coelomic chambers, while seminal vesicles as extension of septa.

8.

Seminal vesicles are enclosed in the testes sac of the same segment.

9.

A circular septum separates oesophagus and body wall layers.

10.

Ventral nerve cord is present outside the intersegmental septum.

11.

The body cavity is greatly reduced due to the enlargement of internal structures.

Identification Since the section reveals girdle shaped seminal vesicles enclosing finger like testes , hence it is the T.S. of earthworm through II th segment.

18. EARTHWORM: T.S. PASSING THROUGH PROSTATE GLANDS AND GENITAL PAPILLAE coelom

ventral nerve cord

. sub·neural vessel

Fig. 2.167 Earthworm. T.S. through prostate gland and genital papilla

Comments T.S. of Pheretitna passing through prostate glands and genital papillae (18th segment) shows following histological details. I.

Prostate gland single pair and genital papillae are seen in the section .

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209

2.

Body wall is composed of thin cuticle, epidermis, thin circular muscle layer and thick longitudinal muscle bundles separated by septs.

3.

Prostate glands are of irregular shape differentiated into glandular and non-glandular regions.

4.

Latter part forms prostatic duct, which joins sperm duct and is enclosed in a common sheath.

5.

The common duct, comprising of sperm and prostate duct opens through male genital pore on genital papillae.

6.

Section also shows the presence of dorsal vessel, ventral vessel, ventral nerve cord and intestine.

7.

Prostate glands synthesize a nuid of unknown function.

Identification Since the section contains prostate gland, genital papillae, common prostatic and spermatic duct, hence it is T.S. of Pheretima passing through 18th segment.

19. EARTHWORM: T.S. PASSING THROUGH TYPHLOSOLAR REGION

Comments

cuticle

T.S. of earthworm passing through Typholosolar region reveals fo)]owing histological features.

circular muscle layer '

I. Intestine is divided into 3 regions:

longitudinal ~"liffJj'.it..ij muscle layer· .endoderm cells

(ii) Typhlosolar (from 26th to Rectum) (iii) Post-typhlosolar (Rectum)

coelom

intestine

(i) Pre-typhlosolar (from 15-26 segments)

septal . nephridium

2. Typhlosolar region has median dorsal internal fold. 3. In the centre a section of intestine with typhlosole is present.

4. Typh!osle is a median internal fold of dorsal wall, having chloragogen cells and a capillary blood vessel. sub·neural ·vessel ' - - - - - - - - - - - -_ _ _ _ _ _ _ _ _-' 5. Body wall comprises of a thin cuticle, columnar epidermis, thin Fig. 2.168 Earthworm. T.S. through circular muscle layer and thick typhlosolar region. longitudinal muscle layer separated by septa. 6.

Intestine is made up of outer layer of peretonial epithelium, the layer of longitudinal and circular muscle fibres and the internal epithelial lining of the gut.

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Non-Chordate (Invertebrate) Zoology Practical 7.

Internal epithelium of intestine is thrown into numerous folds · to increase the absorptive surface.

8.

The typhlosole projects in the lumen of the gut.

9.

Typhlosole encloses a capillary blood vessel.

10.

Sections of dorsal, ventral and subneural blood vessels. supra-intestinal excretory canal. nephridia and ventral nerve cord are also seen.

II.

The nephridia are also found in the coelom.

Identification Median dorsal internal folding in the intestine shows that it is a T.S. of Pheretima passing through Typhlosolar region.

20. EARTHWORM: SETAE IN SITU Comments I. Earthworm has a ring of setae in the middle of each segment. epidermis circular muscles

?~~~~I

__

""===-
formed of 6 cephalic and 8 thoracic segments.

6.

The head contains 2 prominent compound eyes, and 5 pairs of cephalic appendages, namely antenna, antenuleles, mandibles, I maxillae and II maxillae.

7.

The abdomen contains 6 segments which distinguish both dorsally and externally.

8.

The six pairs of abdominal appendages are called pleopods.

9.

There are 19 pairs of appendages, one pair in each segment.

10.

The pleura of the second abdominal segment do not overlap to those of the first.

II.

In female, the endopodite of the first pleopod is reduced.

12.

The sternum of the last thoracic segment of female is modified into a structure known as thelycum.

13.

In male, the endopodites of the first pair of pleopods unite to form petasma.

14.

The development includes nauplius, protozoaea, zoaea and mysis stages. cephalothorax rostrum

\

thoracic legs

Fig. 2.176 Penaeus

Study of Museum Specimens and Slides of Different Invertebrate Phyla

217

Habit and Habitat Penaeus is marine and found in most of the sea.

Distribution It is abundan.tly found in American sea water.

6. CAPRELLA

Classification Phylum

Arthropoda } Crustacea Malacostraca

Class Subclass Order

Amphipoda Caprella

Genus

Same as that of Balanus. Carapace absent; body elongated and laterally compressed.

free thoracic, segments

Fig. 2.177 Caprella. A - Female; B - Ma!e.

Comments I.

It is a no-body crab consisting of cephalothora and abdomen.

2.

Body is externally slender and elongated.

3.

Cephalothorax is formed by the fusion of head and first 2 thoracic segments

5.

Antennules are larger than antennae.

6.

Thorax comprises 6 free segments and contains heart.

7.

Abdomen is reduced to a minute stump.

8.

Male is smaller than the female.

9.

First antennae is longer than the second.

10.

Gills are confined to third and fourth free segments.

I I.

Thoracic legs are sub-chelate.

Habit and Habitat Caprella lives on colonies of Hydrozoa and Polyzoa.

Distribution Cosmopolitan in distribution specially found in U.S.A., Alaska to Santa Barbara.

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218

7.GAMMARUS

Classification Arthropoda

Phylum Class Subclass Order Genus

Crustacea Malacostraca Amphipoda Gammarus.

Characters same as that of Penaeus Body elongated and laterally compressed; carapace absent.

free thoracic segments

cephalothorax

1st abdominal segment

Fig. 2.178 Gammarus.

Comments I.

Commonly called as sand-flea or freshwater shrimp.

2.

Body bilaterally compressed and differentiated into head, thorax and abdomen.

3.

1st thoracic segment is fused with head and without carapace.

4.

Head comprises of a pair of antennules, a pair of antennae and a pair of small sessile eyes.

5.

Walkings legs present in 7 free thoracic segments.

6.

1st two pairs of legs are subchelate and the remaining are non-chelate.

7. 8.

Coxopodites of walking legs contain branchiae. Posteriorly abdomen ends in a telson, which is deeply left.

9. 10.

Heart is thoracic. Unisexual.

II.

Fertilization external.

12.

Eggs and embryos are carried by female which in tum are carried by males.

Habit and Habitat It is found in all types of aquatic habitat. It is mainly scavenger, eating dead and decaying animals and vegetation.

Distribution It is found in U.S.A. and Europe.

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219

8.SQUILLA Classification Phylum Class Sub-class Order Genus

Arthropoda Crustacea Malacostraca Stomatopoda Squilla

Characters same as that of Penaeus Abdomen broader than cephalothorax.

Comments I.

It is commonly hown as Mantis shrimp.

2.

Body is differentiated into cephalothorax, thorax and abdomen.

3.

It is very active and predatory. The body has a short carapace.

4. 5. legs

In the head region, there are two movable seg- ments which bear bilobed eyes and antennules and antenna.

6. The 5 pairs of thoracic appendages are modified as maxilIipedes and are subchelate.

7. The second maxilIipede is large and prehensile. 8. The last 3 pairs of thoracic appendages are 9. 'telson

Fig. 2.179 Squilla

10.

biramous and without epipodites. Abdomen six segmented which is broader and elongated than cephalothorax. It contains large and biramous pleopods. The antennal glands are absent.

11. J 2.

Heart is greatly elongated extending through the thoracic and abdominal regions. The body is whitish. semitransparent and is differentiated into cephaJothorax. thorax and abdomen measuring about 22-25 cm in length.

13.

Larvae are pelagic and resemble zoaea of crab in morphology.

Habit and Habitat It is a large. marine, crustacean. found in burrows in the sand or mud at the bottom. It catches prey with powerful maxillepedes.

Distribution It is found in India. Gulf of Mexico and Southern coast of Florida.

Non-Chordate (lnverfebrate) Zoology Practical

220

9. PALAEMON

Classification Same as that of Penaeus.

Fig. 2.180 Palaemon

Comments I.

P. malcolmsoni' is commonly called Indian freshwater prawn.

2.

Body is elongated. spindle-shaped. bilaterally symmetrical and dee!? orange coloured when preserved and measures about 22-26 cm. in length.

3.

Body is divisible into cephalothorax. abdomen and telson.

4.

It has two stalked compound eyes. These are located beneath the rostrum.

5.

The cephalothorax is formed by the fusion of two regions. namely the head and the thorax.

6.

The head is formed of 5 segments and the thorax is formed of 8 segments.

7.

The body and the appendages are covered by chitin which forms the exoskeleton and protects the body.

8.

In each segment the exoskeleton has a dorsal piece called tergum and a ventral piece called sternum.

9.

The terga of the anterior 13 segments [cephalothorax] fuse together to form a broad plate called carapace or dorsal shield.

10.

Anteriorly the carapace is produced into a median spine called rostrum. It is serrated.

II.

Prawn has jointed biramous appendages. Each segment bears a pair of appendages on the ventral side.

12.

As there are 19 segments. prawn has 19 pairs of appendages. Of these 19 pairs. 5 pairs are located in the head and are called cephalic appendages. 8 pairs are present

- Study of Museum Specimens and Slides of Different Invertebrate Phyla

221

in the thorax and are called thoracic appendages and 6 pairs are pre~ent in the abdomen and are called abdominal appendages. The appendages are named as follows. I st appendages are called - antennule. 2nd appendages are called - antenna. 3rd appendages are called - mandible. 4th and 5th appendages are called - I and II maxillae respectively. 6th, 7th, 8th appendages are called - I, II and III maxillipedes respectively. 9th to 13th are called - I to V walking legs respectively. 14th to 18th are called - Pleopods. 19th are called - Uropods. 13.

Each appendage is formed of many segments called podomeres.

14.

The month lies ventrally in between the mandibles.

15.

The anus lies ventrally at the base of the tel son.

16.

True coelom absent.

17.

Circulatory system is of open type.

18.

Blood is colourless. Plasma contains a blue respiratory pigment called haemocyanin.

19.

The excretory system is formed of a pair of antennary glands or green glands.

20.

It has a pair of statocyst, located inside the precoxa of the antennules.

21.

Sexes are separate.

22.

In male there is petasma, which is male copulatory organ.

23.

In the female thelycum is present.

24.

Development is indirect. The fertilized egg hatches into a larva called nauplius. followed by metanauplius, protozoea, zoea, and mysis.

25.

Prawns are of great food and laboratory value.

Habit and Habitat It is found in freshwater, streams, rivers, lakes and ponds, It is omnivorous and nocturnal.

Distribution Commonly found in India.

10. ASTACUS FLUVIATILIS

Classification Same as that of Penaeus.

Comments I.

It is popularly known as cray-fish.

2.

Body is sub-cylindrical. small. about 10 em in length and divided into anterior cephalothorax. middle flexible abdomen and posterior telson.

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Non-Chordate (Invertebrate) Zoology Practical

3.

Cephalothorax consists ofl1ead and thorax and is covered by carapace. Carapace is produced into unserrated short rostum. On the sides carapace covers the gills. 4. Antennae elongated. antennules short and eyes slalked. 5. Appendages are 19 pairs - 5 cephalic. 8 thoracic and 6 abdominal. 6. Abdomen contains 6 pairs of swimming appendages or pleopods and a telson. 7. Walking legs are chelate. 8. Telson forms a tail - fan together with uropods. 9. Sexes are separate. 10. Female carries hundreds of small, rounded egg on the ventral side of her abdomen. 11. It has food value.

Habit and Habitat Commonly found in streams. lakes and rivers. It is omnivorous and acts as scavenger.

Fig. 2.181 Astacus

Distribution It is found on the pacific slope. Europe. U.K. U.S.A. Australia. New Zealand and Asia.

11. PALINURUS

Classification Same as that of Penaeus.

Comments I.

It is commonly known as spiny lobster or marine rock lobster.

2.

It can swim or crawl over the rocks.

3.

The body is divided into cephalothorax and abdomen.

4.

The body consists of 19 segments.

5.

The carapace bears spines.

6.

There are no appendages in the first abdominal segment.

7.

The remaining abdominal segments bear leaf like appendages.

8.

The tel son bears the tail fin.

9.

The walking legs are non-chelate in male.

10.

In female the last legs is chelate.

.'

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223

II. Cephalic appendages are antennae, antennules, and eyes. antenna rostrum

12. Antennal sac is absent and antennae are much elongated. 13. Unisexual. 14. Larva is called Phyllasoma which is broad and thin schizopoda larva.

cervical groove

15. Its flesh is delicious an it is an important export item in the international market.

Special Feature It produces a peculiar sound like creaming of leather by rubbing antennal pad against a sternal keel.

Habit and Habitat It is a marine crustacean found in the rocky region.

Distribution It is found in Asia and Europe.

telson.

Fig. 2.182 Palinurus

12. EUPAGURUS [HERMIT CRAB]

Classification Phylum Class Subclass Order Sub order

Genus

Arthropoda Crustacea Malacostraca Decapoda Anomura Eupagurus

Characters some as that of Penaeus. Carapace and statocyst present. Abdomen flexed.

Comments I.

It is popularly known as Hermit crab.

2.

The body consists of broad cephalothorax and a large soft abdomen.

3.

It lives in the empty shells of gastropod molluscs.

224 4.

Non-Chordate (Invertebrate) Zoology Practical In order to adjust in the coils of molluscan shells. hermit crab is having extreme modifications: (a)

Body is reduced in varying degree and asymmetrical but shows sexual divisions i.e. cephalothorax [head + thorax] and abdomen.

(b) Carapace reduced. (c)

Rostrum absent.

(d)

Head contains antennules. antennae and stalked eyes: Thoracic appendages protrude through the opening of the shell.

(e)

1st thoracic leg is chelate and rest reduced.

(f)

Right chelate leg is very large as compared to left and it acts as lid or operculum.

(g)

Abdomen is asymmetrical soft. fleshy. elongated and twisted or bent under the thorax.

(h)

Vlth left abdominal appendages (uropod) adopted for holding the body in hollow objects.

(i)

Uropods are hooked and notched in the shell. great chela of first thoracic leg mouth

tentacles

compound

eye...-l~~~~

8th thoracicappendage

·B

Fig. 2.183 A - Hermit-crab. B - Commensalism between Hermit-crab and Sea-anemone.

Special Features Eupagurus inside the empty gastropod (mollusc) shell and sea-anemone (coelenterate) over the shell associate themselves to lead a commensal life. The hermit crab by its appendages takes sea-anemone to distant places for food and in turn sea-anemone protects itself as well as the crab by its stinging cells. When the growth of the body demands. the hermit crab selects a new empty large gastropod shell and deserts the old one. There is no metabolic dependency in above association.

Habit and Habitat Eupagurus is a popular sea-shore crustacean found inhabiting the empty shells of gastropods.

Study of Museum Specimens and Slides of. Different Invertebrate Phyla

225

Distribution Cosmopolitan. In India. it is found at Mumbai and Goa beaches.

13. HIPPA [EMERITA]

Classification Same as that of Penaeus.

Comments I. Hippa or Emerita is popularly known as mole crab or sand crab. 2. The body is ovate with large cephalothorax. 3. Carapace is smooth and mouth parts are poorly developed. 4. Head bears paired eyes. a pair of biramous antennules and a pair of uniramous large antennae. 5. Rostrum is simple and pointed. 6. Legs are flattened and curved. applied in burrowing.

A

B

Fig. 2.184 Hippa A • Dorsal view; B • Ventral view

7. Abdomen 6 segmented. first 3 abdomen segments bear swimming appendages and produce water current to bathe the gills. The last 3 are posteriorly directed and are called as uropods. which are used for darting.

8.

Antennules are long and feather - like. These help in filter feeding.

9.

There are no chelate legs.

10.

Hippa exhibits tidal and living shore migration.

II.

Unisexual.

12.

The males are smaller and show neoteny.

13.

The females carry the eggs in their pleopods.

Habit and Ha'bitat Hippa is a marine crustacean. It is commonly found in the sand bottoms and beaches near the coastal region. It burrows rapidly with its back when the wave recedes. It is planktophagic.

Distribution It is found on the Pacific coast, U.S.A. and Organ to Mexico.

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14. CARCINUS [CANCER OR CRAB]

Classification Phylum Class Sub class Order Suborder Genus

Arthropoda } Crustacea Characters same as that of Eupagurus. Malacostraca Decapoda Abdomen reduced. Brachyura Carcinus or Cancer

Fig. 2.185 Carcinus. The Commo n Crab.

Comments I.

It is popularly known as rock - crab or true - crab.

2.

The body is oval and dorso - ventrally flattened.

3.

The body is divided into large and broad cephalothorax and a stumpy abdomen.

4.

The carapace is fused with epistome at the sides and nearly always in the middle.

5.

Rostrum absent.

6.

Eye stalks and antennules.are contained in sockets of carapace.

7.

Antennules and antennae are small.

8.

I1Ird maxillipedes are broad, flat and valve like and cover the other mouth parts.

9.

Five pairs of thoracic legs are well developed.

10.

The first pair of legs is chelate.

II.

Abdomen is greatly reduced and folded permanently under cephalothorax.

12. '"

Pleopods are much reduced. The male has only 2 pairs to act as copulatory organ while the female has 4 pairs for the attachment of the eggs.

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13.

Dioecius.

14.

Uropods are absent.

15.

Development is indirect.

227

Habit and Habitat It is found burried among rocks or in sand.

Distribution Cosmopolitan.

15. PAUROPUS

Classification Phylum

Arthropoda

Triploblastic; metamericaIIy segmented, jointed appendages.

Class Genus

Chilopoda

Genital apertures situated near the anterior end of the body.

-

Pauropus

Comments

head

I. Body is smaII, measuring 2 mm in length. 2. Head distinct and bearing a pair of triflageIIate antennae, a pair of mandibles and a pair of maxillae. 3. Eyes are absent. 4. Trunk comprises of 12 segments. 5. Nine pairs of trunk appendages. 6. Anus is at the hind end. 7. Sexes separate and gonads are unpaired.

Habit and Habitat Pauropus is found under stones, wood etc. in damp places.

Distribution Fig. 2.186 Pauropus

Cosmopolitan.

16. JULUS

Classification t Phylum

Arthropoda Diplopoda

Class

(Millipedes)

Genus

Limb jointed. Trunk bears numerous segments each of which bears 2 pairs of legs. Herbivorous. Poison jaws absent.

Julus

Comments I.

It is commonly caIIed as wire worm.

2.

Body elongated and cylindrical and comprising large number of segments.

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228 3.

4. 5. 6.

7.

Body is differentiated into head; thorax and abdomen. Head consists of a pair of short and jointed antennae, a pair of mandibles and a pair of maxillae forming gnathochilarium. The thorax consists of 4 segments. The abdominal segments are double. Poisonous jaws are absent. Stink (odoriferous) glands present along the sides of the body.

8. 9. 10.

Genital opening on the third segment behind the head.

II.

There is no tracheal system.

12.

It moves slowly.

Sexes are separate.

openings of stink glands -

eye

Fig. 2.187 lulus

Habit and Habitat Julus is found hidden usually in dark and damp places under stones or wood or in decaying leaves. It is herbivorous.

Distribution Cosmopolitan in distribution. Generally found in India, U.S.A. and Europe.

17. SCOLOPENDRA

Classification Arthropoda Chilopoda (Centipedes) Scolopendramorpha : Scolopendra

Phylum Class

Order Genus

Limbs jointed. Numerous trunk segments, each bearing a single pair of legs. Poison jaws present. Carnivorous.

Comments I.

It is commonly called as centipede.

2.

The elongated and dorsoventrally flattened body is divided into head and trunk having numerous segments.

3.

Head bears a pair of mandibles and 2 pairs of maxillae.

4.

Trunk segments bear a pair of legs.

5.

Mouth is guarded by labrum, mandibles and first maxillae.

6.

Body has 21 segments with 21 pairs of walking legs. The forwardly directed first pair of legs form maxillipedes or poison claws.

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7. The walking legs are identical. 8. Each leg is composed of coxa. trochanter. femur. tibia and 3 tarsi ending in a single claw.

9. The stigmata lie on segments 4. 6. 9. II. 13. 15. 17. 19 and 21.

10. The end segment bears the anus. II. Genital opening situated at the hind end of the bod). stigmata

12. Sexes are separate. 13. Carnivorous. feeds upon insects. spiders. worms. slugs etc. 14. Scolopendra is harmful to mankind when enters the ear during sleep. 15. It moves fastly.

Habit and Habitat It commonly occurs under stones in rotten logs and houses in damp places.

Distribution It is found in India, America (Austin and Texas).

Fig. 2.188 ScolOpendra

18. LEPISMA

Classification Phylum

Arthropoda

Jointed limbs.

Class

Insecta

Air breathing; terrestrial or aquatic. body divisible into head. thorax and abdomen. 3 pair of legs.

Subclass

Apterygota

Primitive wingless insects; metamorphosis little or absent.

Order

Thysanura

A pair of many segmented cerci and a long median caudal filament. Body covered with small scales.

Genus

Lepisma

Comments I.

Popularly known as silver fish.

2.

The flattened body covered with silvery scales; measures about 1.25 cm in length and divided into head, thorax and abdomen.

3.

Head bears a pair of many segmented antennae an'd a pair of ocelli.

4.

Thorax has 3 pairs of small walking legs but devoid of wings.

5.

Abdomen has 11 segments bearing styles.

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6. Mouth parts biting and chewing type. 7. Malpighian tubules present. 8. The development is epimorphic. 9. Body colour is silvery while. 10. It is a primitive delicale fish-shaped wingless insect. 11. Anal segment possesses two or three circi.

Habit and Habitat Mostly found in damp cool places and in books. It is very commonly found in amidst books. It avoids light.

Distribution Found all over Asia. Europe and U.S.A.

Fig. 2.189 Lepisma

19. SCHISTOCERCA GREGARIA Classification Arthropoda Insecta Pterygota Exopterygota Orthoptera Scistocerca gregaria

Phylum Class Sub-class Division Order Genus Species

Jointed limbs. 3 pairs of legs. Winged insects Wing develop externally. Straight wings

Comments I.

It is the well known desert locust.

2.

Body is divisible in to head thorax and abdomen.

3.

Head bears short antennae and well developed compound eyes.

4.

Thorax bears 3 pairs of legs and 2 pairs of dissimilar wings.

5.

Abdomen has 11 cylindrical segments.

6.

Fore-wing are elongated. thick. leathery and straight. while hind wings are large and membranous.

7.

Sexes are separate.

8.

They have stridulating organs and organs of hearing.

9.

They have 2 phases. (i)

Solitary or nonmigratory phase with yellow colour.

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231

(ii)

Migratory phase with pinkish body.

10.

Causes great damage to vegetation.

Habit and Habitat Schistocerca is found in the deserts in tropical region of the world.

Distribution It commonly occurs in Africa, Arabia, India, Mexico, Japan, Philippines, Afghanistan and U.S.A.

Fig. 2.190 Schistocerca gregaria.

20. GRYLLUS

Classification Same as that of Schistocerca

Comments

thorax \

I.

Commonly called as house cricket.

2.

The body is divisible into head, thorax and abdomen .

3.

Head comprises a pair of compound eyes and a pair of antennae which are longer than body.

forewing

4. Thorax contains wings and 3 pair of ")

walking legs.

abdomen

5. The abdominal segment contains a pair of anal cerci.

hindwing

6.

Mouth parts are mandibulate type and well developed.

7.

Fore wings are hardened and hind wings are membranous .

8.

Female possesses a long ovipositor. which serves for depositing the eggs in soil.

9.

It produces a familiar sound with its stridulating organs.

anal cercus

Fig. 2.191 Gryllus

10.

They are very destructive to clothes, books, food etc.

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Non-Chordate (Invertebrate) Zo%RY Practical

Habit and Habitat It is nocturnal and omnivorous and commonly found during rainy season under wall and crevices in kitchen.

Distribution Found in India. Sri Lanka. Burma. Asia. Europe. U.K .• U.S.A . and Canada .

21. MANTIS RELIGIOSA Classification Phylum

Arthropoda

Class

Insecta

Sub·class

Pterygota

Division

Exopterygota

Order

Mantodea

Genus

Mantis

}

Cha,"ctecs same as that of Schistoc.cca.

Mouth parts biting type. prothorax greatly elongated.

Comments

compound ' head

I . It is commonly called as

f!oje

praying mantis. antenna

Body is divided in to head. thorax and abdomen .

mouth parts

3. Head is triangular. bears large compound eyes and three ocelli.

raptorial torelegs

4. Prothorax is much elongated . mid legs

abdomen

hind legs

5. The 10th segment abdomen contains a pair of anal cerci.

' - - - - - - - - - - - - - - - - - - - - - - - - - ' 6. The middle and hind legs are Fig. 2.192 Praying mantis elongated. 7.

The raptorial tibia of sub-chelate fore legs are modified for grasping prey.

8.

Ovipositor is not erected.

9.

It is carnivorous. feeding on other insects.

10.

Eggs are laid in ootheca.

I I.

Mantis waits for their prey. the fore legs remain in an attitude of prayer. hence the Mantis is called as praying mantis.

12.

Mouth parts are of biting type.

13.

The forelegs are raptorial and clasped like hands while in praying.

14.

The males have anal styles.

Habit and Habitat Praying mantis is found among green vegetation. It is canibolic. predacious and pugnacious.

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Distri bu tion It is found in U.S.A., Africa , South Europe and Western Asia .

22. PERIPLANETA AMERICANA Classification Same as that of Schistocerca.

Comments

head

I. It is popu larly known as cockroach . The generic name Periplaneta was given by Burmeister (1838). 2. The body is bilaterally symmetrical and covered with a hard exoskeleton of sclerites.

metathorax ~~-!!I:lIJ~~

'

V1I1 "

R IX

. sternum

x

anal cercus anal siyle

VI

..L- sternum

f1= VII '

anal cercus

,

A

salivary gland - """"'",'

trachea .~;.....;.~- oesophagus

visceral_-T.,r;~~

thoracic ganglion

ganglion , crop .- -",:,;,.-r,

1~~~~~t~::~abdominal ganglion ~ 'gizzard ~I::::i;~;';"'~~' hepatic (meseniric)ceeca '

'\ .:;;:;.;;.;::.,,::..-;,... ileum testis

B

Fig. 2.193 Anatomy of Periplaneta.

3. Body is divisible into three parts - head, thorax and abdomen. 4. The head bears a pair of compound eyes, long antennae, maxillae, mandibles, labium, labrum, ocelli or fenestrae and a hypopharynx. 5. Mouth parts are cutting and chewing type (mandibulate type). 6. Thorax is divisible into prothorax, mesothorax and metathorax . 7. Thorax has three pairs of walking legs. The mesothorax and metathorax each, possess a pair of wings, namely forewings and hind wings respectively. 8. Abdomen contains 10 segments . It is without appendages. 9. Tenth segment has a pair of anal circi, and in male as additional pair of anal styles are present.

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Non-Chordate (Invertebrate) Zoology Practical 10.

Anal cerci bear minute sensory hairs which are sensitive to sound and other vibrations .

II.

Leg of cockroach is five segmented . Segments from base are : coxa, trochanter, femur, tibia and tarsus .

12.

The most swollen segment in the leg is coxa and the longest segment is tibia.

13.

The body cavity of cockroach is haemocoel filled with blood.

14.

Cockroach is omnivorous.

15 .

Circulatory system is open or lacunar type.

16.

Heart is neurogenic having 13 chamhers.

17 .

Respiratory system of cockroach consists of tracheal system.

18.

Excretory organs are malpighian tuhu les . Cockroach is uricotelic.

19.

Endocrine system consists of corpora allata, corpora cardiaca and prothoracic gland .

20.

Each compound eye is composed of about 2000 visual units called ommatidia.

21.

During day time mosaic vision or apposition image and in dim n ight superposition o r dull image forms.

22.

It is dioeciou s.

23 .

The egg of cockro ach is centrolecithal type.

24.

Metamorphosis in cockroach is incomplete or paurometabolous type.

25 .

Metamorphosi s is regulated by two hormones: ecdysone secreted by prothoracic glands and juvenile hormones secreted by corpora allata .

26.

Cockroach are regarded nuisance and sign of unclean condition.

Special Two species of cockroaches commonly found in India are:

Periplaneta americana and Blatta orientalis. P. americana is the largest and most common. Salient difference between these two is tabulated below . .

Difference Between Periplaneta and Blatta P. americana

B. orientalis

I. Larger in size.

I.

Smaller in size.

2. Colour shiny brown

2.

Colour dark brown .

3. Wings well developed extending upto abdomen (females) tip and beyond (males).

3.

Wings developed in males but upto thorax only; vestigial in femals .

4 . Pronotum narrower having yellow border.

4.

Pronotum broader with dark border.

5.

Arollum present.

5.

Arollum absent.

6.

Invertase absent in saliva.

6.

Invertase present in saliva.

7.

Lactase absent in midgut juice.

8.

Male 2n = 47 and Female 2n = 48.

7. Lactase present in midgut juice. 8.

Male 2n = 33 and Female 2n = 34

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235

Habit and Habitat It is a nocturnal creature, avoiding the daylight and found in damp and warm places like kitchens, bakeries , hotels, godowns, stores, restaurants, bathroom etc.

Distribution Its original native place is Mexico but has travelled to all parts of the world, thus it is cosmopolitan .

23. CARAUSIUS (STICK INSECT) Classification Same as that of Schistocerca.

Comments eye

I.

Popularly known as stick insect or walking stick .

2.

The body resembles to a twig or stick.

3.

It measures about 23-33 cm in ler.gth .

4.

The body is differentiated into head , th orax and abdomen.

).

Head contains compound eyes and filiform antennae.

6.

Thorax is divisible into pro, meso and metathorax.

7.

Prothorax is short while meso and metathorax are elongated .

8.

Abdomen elongated and contains J 0 segments.

9.

Tegmina reduced or absent.

10.

Walking legs 3 pairs. These are simple and adapted for walkin g.

II. The tarsi are usually 5 jointed. 12.

changes in colour like its surroundings and jumps swiftly.

Fig. 2.194 Carausius 13 .

14.

Carausius has great power of mimcry and represents

Sexes are separate. The male is small, active and winged whereas female is large, sluggish and apterus.

Ovipositor rudimentary.

Habit and Habitat It is found in tropical forests and thick vegetation. Its all species are leaf feeders . They move very slowly and act as dead if disturbed.

Distribution It is found in Sri Lanka, Burma, India and other Asian countries as well as Europian countries.

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24. PHYLLIUM SCYTHE (LEAF INSECT) Classification Same as that of Schistocerea. Commen~s

I . Popularly known as leaf insect.

2. Body is broad and flat, divisible into head thorax and abdomen . 3. Head is small bearing small paired antennae. ~-~L--prolhorax

4. Thorax is also small bearing 3 pairs of flattened leaf coloured legs. 5. Wings are remarkable colouration and venation.

in

having

leaf-like

6. Abdomen comprises of 10 segments. 7. Dioecious. 8. Male has small well developed wings and relatively narrow body. 9. In female the tegmina is extensive leaf like expansion, the wings are vestigial and the body is expanded . Fig. 2.195 Phyllium scythe

II.

10. It shows extreme degree of mimcry because it matches very much with the leaves and becomes practically invisible.

The leaf insects are so named because their green bodies, wings and the flattened legs look leaf like.

Special Feature It shows mimcry which is a protective device to enemies.

Habit and Habitat Phyllium is found in the tropical forests.

Distribution It is almost entirely confined to the moist parts of the oriental region, islands of the Indian ocean and forests of Assam.

25. QUEEN TERMITE Classification Phylum

Arthropoda

Class Sub-class

Insecta

3 pairs of leg.

PterYJIota

Wings present.

Jointed limbs.

Study of Museum Specimens and Slides of Different Invertebrate Phyla Division Order Type

Exopterygota Isoptera Queen termite

237

Wings developed externally. Equal wings and caste system in colony.

Comments I. Queen termite is the sexually mature fertile female of the colony . 2. The body is elongated and cylindrical. 3. Head usually not covered by pronotum. metathorax

4. The antennae are monilliform. 5. Head and thorax are comparatively small.

terga

1

abdomen distended with eggs

6. Abdomen is enormously swollen to accommodate the large number of fertilized eggs. 7. Eggs laying rate is 60 per minute. 8. Legs are adapted for walking. 9. The tarsi are 4 jointed. 10. The cerci are very short.

>-=A--anal cercus

Fig. 2.196 Queen Termite.

II. Compound eyes are well developed. 12. Social and polymorphic forms exhibiting caste system. The main castes are: kings. queens. workers and soldiers.

13.

Mouth parts are of biting and chewing type.

14.

They feed upon cellulose.

15.

Colony comprises sexually mature males and females (kings and queen). sterile workers. soldiers and Naustes.

16.

Ovipositor absent.

17.

Termites are externally destructive in houses since they destroy wooden beams. door frames. window frames. furniture and other wooden portions. They also cause great loss to libraries.

18.

The main function of queen is to lay eggs. hence she is called the veritable egglaying machine.

19.

All the members of a colony are her daughters and sons.

20.

The queen can live for 15 or more years.

21.

The bee colony has only one queen. But there are many queens in the termite colony.

22.

The queen lives inside the queen cells which may be I or 2 having cylindrical and vas-shaped.

23.

Trichonympha. a flagellate protozoan is found in the gut of termite; it digests cellulose showing symbiosis.

Habit and Habitat It inhabits underground of galleries, termitaria etc. Some are found burrowing in wood and form chambers.

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Distribution Cosmopolitan, usually in temperate and tropical countries.

26. DRAGON·FLY (pALAEOPHLEBIA)

Classification Phylum

Arthropoda

Class Division

Insecta Pterygota Eropterygota

Order

Odonata

Genus

Palaeophelbia

Sub-class

Characters same as that of Queen Termite.

Incomplete metamorphosis; niads (nymphs), aquatic with or without exterior gills.

Comments I. Dragon flies are commonly known as mosquito - hawks. 2. These are found in the vicinity of water. 3. Body is slender divisible into head, thorax and abdomen. 4. Head is exceptionally mobile and bears a pair of large compound eyes and a pair of short inconspicuous antennae. 5. Mouth parts are biting· and masticatory. 6. Prothorax is reduced, meso and metathorax are intimately fused together forming synthorax. 7. Legs are 3 pairs and weak.

Fig. 2.197 Dragon-Fly. 9.

8. Two pairs of membranous wings present and are held in a horizontal position during rest and flight.

Abdomen is greatly elongated consisting of 10 distinct segments. According to Heymons vestiges of 11 th and 12th segments are also present. The 12th segment contains a pair of caudal furca.

10.

Abdomen with male copulatory organ on the 2nd and 3rd sternites.

I I.

Dioecious.

12.

Oviposition endophytic or exophytic.

13.

Metamorphosis incomplete.

14.

Nymphs are aquatic and breathe by caudal or rectal gills and feed upon aquatic insects and other organisms.

15.

Dragon flies are strong hunters.

16.

Copulation takes place when they fly in the air.

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239

Habit and Habitat Dragon flies are abundantly found du..-ing rainy se-ason resting on twigs, grass stalk and leaves. These fly in the vicinity of water.

Distribution Cosmopolitan .

27. EPHIMERA (MAY FLY)

Classification Phylum Class Sub-class

-

Arthropoda } Hexapoda Insecta Pterygota

Division

Eropterygota

Order

Ephemeroptera Ephimera (May Fly)

Genus

Characters same as that of Queen Termite.

Very short span of life (one or two days of adult).

Comments I.

Ephimera is popularly known as May Fly.

2.

Body soft, small to large and slender.

3.

Body is divisible into head, thorax and abdomen.

4.

Head is small having short setaceous antennae, vestigial mouth parts, a pair of compound eyes and 3 ocelli between compound eyes.

5.

Thorax has 3 pairs of walking legs.

6. Pro and metathorax are small but mesothorax in large. 7. Two pairs of membranous, triangular and fragile wings present. Forewings are larger than the hindwings .

caudal \filament

8. 9'.

Pterostigma in the wings absent. Abdomen has 10 segments with a reduced tergum .

10. Caudal filament single and anal cerci one pair. Both are very long.

Fig. 2.198 Ephimera (May Fly) 13. 14. 15. 16.

II. Dioecious .. 12. The male has three jointed clasping organs. The female has no ovipositor. Nymph is aquatic and breathe by means of abdomen trachial gills. Naiad lives for a long time up to 3 years in water, feeds on aquatic plants and animals. Naiads also act as intermediate hosts for nematode parasites of vertebrates.

17.

The imago moults prior to mating and is extremely short lived.

18. 19.

The adult lives for one day. The alimentary canal is functionless .

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Non-Chordate (Invertebrate) Zoology Practical

Habit and Habitat It is commonly found on the margins of lakes, streams and rivers.

Distribution It is found in India, Sri Lanka, Burma and U.S.A (Florida, Illinois).

28. NEPA (WATER SCORPION)

Classification Phylum

Arthropoda } Insecta or Hexapoda

Class Sub-class

-

Pterygota

Division

Eropterygota

Order

Hemiptera

Genus

Nepa raptorial lore-leg

Characters same as that of Queen Termite.

Metamorphosis gradual. Wings if present are leathery.

Comments 1. Nepa is commonly called as water scorpion.

2. The body is short, dorso-ventrally compressed and divisible into head, thorax and abdomen . 3. Head contains a pair of eyes and 3 jointed antennae. 4. Mouth parts form a long rostrum adapted for piercing and sucking. 5. The respiratory tube is most peculiar. It consists of two spine - like processes. 6. 3 pairs of "false spiracles" are located on 3th, 4th and 5th ventral abdominal segments. 7. The tarsi usually with 3 joints. 8. Thorax contains walking legs. 9. Fore wings are not uniform. At rest the wings overlap and lie flat above the abdomen . 10. Dioecious.

Fig. 2.199 Nepa.

II . The female is provided with a pointed toothed, ovipositor. 12. The eggs are deposited in chains.

13. The fore legs are modifed for holding the prey.

Habit and Habitat It is very commonly found in the shallow water of ponds, ditches, lakes and streams.

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241

Distribution It has cosmopolitan distribution.

29. BELOSTOMA Classification Same as that of Nepa. raptorial foreleg

Fig. 2.200 Belostoma.

9. 10. II . 12. 13. 14.

Comments I . Belostoma is popularly known as Giant-Water Bug. 2. Body is elongated dorso-ventrally compressed , covered by leathery exoskeleton . 3. It is large insect. measuring about IOcm in length and is adapted for crawling and swimming. 4. Body is divisible into 3 parts: Head. thorax and abdomen. 5. Head bears large compound eyes and small inconspicuous four segmented antennae. 6. Mouth parts adapted for piercing and sucking. 7. Thorax contains walking legs. posterior legs adopted for swimming. Tarsi 3 jointed. Tebia flattened and fringed with hairs. 8. Wings membranous. Forewings not uniform.

Abdomen is having two retractile apical appendages. Legs flat. Middle and hind legs serve for swimming. The forelegs are raptorial. It is carnivorous, feeds chiefly on insects, snails, fry and tadpoles. Legs inflict injuries on prey. It also inflects heavy wound on man which is very painful. There is a pair of respiratory processes at its hind end . Dioecious and predatory.

Habit and Habitat Belostoma is found in rivers, ponds and lakes.

Distribution It is found in India, U.K. North America and South Africa.

30. APHID (PLANT LICE) Classification Same as that of Nepa.

Comments 1.

Aphids are cO{T\monly known as plant lice.

2.

Body oval and dorso-ventrally flattened with a pair of siphons. These are dull yellow, green or black in colour.

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3. Body is divisible into head-thorax and abd9men .

4. Head is having long straight antennae. small compound eyes and long thread like mouth parts extruded from a short proboscis.

5. Mouth parts are piercing and sucking type. 6. Thorax and abdomen robust. Abdomen is elongated. 7. Nine pairs of lateral abdominal spiracles are present.

8. These may be winged or wingless forms. 9. Dioecious. 10. These exhibit phenomena of parthenogenesis. Fig. 2.201 Aphid.

II. Life cycle involves asexual and sexu al phases.

12.

Harmful pests on different kinds of crops.

13.

These cause a great loss in mustard yield in V.P.

Habit and Habitat Aphids are found on plants and suck their juice.

Distribution They occur mostly on mustard. wheat and cotton and plants belonging to family solanaceae.

31. PIERIS (BUTTERFLY)

Classification

Order

Arthropoda Hexapoda (Insecta) Pterygota Endopterygota Lepidoptera

Genus

Pieris (Butterfly)

Phylum ClIlss

Sub-class Division

Jointed limbs. 3 pairs of legs. Winged insects. Wings developed internally. Body and wings completely covered by nat overlapping scales and hairs.

Comments I.

Butterfly is a large and the most beautiful among insects.

2.

Being an insect, the body is divided into 3 parts - head - thorax and abdomen .

3.

The head is small and freely movable, having a pair of large compound eyes and a pair of clavate antennae (swollen tips).

4.

Mouth parts sucking type provided with a spirally coiled suctorial proboscis.

Study of Museum Specimens and Slides of Different Invertebrate Phyla head

antenna

'compound eye

fore-wing

243

5. Thorax bears 3 pairs of legs and 2 pairs of wings which are covered by pigmented scales. 6. The wings are held vertical during rest. 7. Abdomen consists of 10 segments covered with scales. 8. Cerci absent. 9 . Ovipositor rarely present. 10. Larva is called as Caterpillar. II . It is diurnal i.e. day flier and sucks the nectar from the flowers.

12. Metamorphosis complete. 13. Common butterflies of India are:

Fig_ 2.202 Butterfly

Monarch, Cabbage, Swallowtail and Dead-leaf butterflies:

Habit and Habitat Butterflies are commonly found in gardens, flying over the flowering plants.

Distribution Cosmopolitan.

32. MOTH

Classification Same as that of Butterfly (Pieris).

Comments I. It closely resembles the butterfly. 2. It is night flier. 3. Head, thorax, and abdomen are the divisions of the body. 4. Head is very small and bears very short paired feathery antennae. 5. Mouth parts sucking type. I -_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _....J

6. Thorax bears 3 pairs of legs and 2 pairs of wings which are co v-

Fig. 2.203 Moth

ered with scale~.

7.

Hind pair of wing is smaller than that of fore-pair.

8.

The wings are held horizontally during the resting period (differentiation from butterfly).

9.

Abdomen 10 segmented.

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Non-Chordate (Invertebrate) Zoology Practical ~ome

10.

Nocturnal and

II.

Wings are membranous. They are coupled and beat together.

on the light usually during the rainy season.

12.

Metamorphosis complete.

13.

There are several varieties of moths such as cloth moths. sphinx moths and cerropia moths. 14. Tinea Pelliozeda is the common cloth moth.

Habit and Habitat These are found on the lamps. bulbs and candle flames etc . during the rainy season.

Distribution Cosmopolitan.

33. LIFE CYCLE STAGES OF SILK WORM Silk is a valuable natural protein fibre. produced by the catterpillars of silk producing insects. called silk worms. Silk worms are the larva of silk moths. The rearing of silk worm for the production of silk is known as sericulture. Four species of silk worms are extensively used in sericulture. They are as follows : I.

Mulberry silk worm

2.

Eri silk worm

3.

Tasar silk worm

Bombyx mo,; Attacus rechinii Antheraea paphia .

4.

Muga silk worm

A. assama

Comments Silk worm (Bombyx mori) is a holometabolous insect. It passes through four distinct stages during its life cycle. namely the egg. the larva. the pupa and the adult.

1. Egg: Female moth lays 300-500 eggs at a time in clusters upon the mulberry leaves. The female dies after laying the eggs. The eggs are sticky. The eggs are first yellowish white and become darker later on . 2. Larva: Egg hatches into larva known as caterpillar larva. Its mandibulate mouth parts help in feeding upon the mulberry leaves. As it grows. undergoes moulting. Fully mature larva stops feeding and secretes liquid silk by its salivary glands. The liquid silk comes out through spinnerts and hardens into silk filaments. Another gland secretes sericin which sticks to silk filaments forming silk threads. The larva feeds voraciously on mulberry leaves and grows very fast. During the larval period it represents moulting or ecdysis four times. The secretion of the silk is to build cocoon. The larval period lasts for 20-24 days . 3. Pupa: The caterpillar larva after passing through four moults within a fortnight becomes pupa or chrysalis inside the cocoon . Body becomes shortened. Actually silk threads wrap around the larval body to give rise to cocoon. A single caterpillar may secrete about 100015000 meters of silk in 2 to 4 days. The pupal period lasts for 10 to 12 days. 4. Adult: Within 3 to 4 months. pupa metamorphoses into adult moth. A single egg may either develop into male or female. Males are smaller than females. The adult secretes a fluid which softens the cocoon. It pierces the cocoon and comes out. Soon after emergence. moths mate. lay eggs and die within 2 or 3 days.

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Study of Museum Specimens and Slides of Different Invertebrate Phyla

forewing

thoracic legs

ADULT

.. .•

: . Ci. Q,.

..:-.. .1

. ~

. ~ ~

PUPA IN , COCOON ·

silk thread

EGGS

.

eggs on mulberry leaf

dorsal horn

CATERPILLAR LARVA (LATERAL VIEW)

Fig. 2.204 Silk worm. Life cycle stages.

34. LIFE CYCLE STAGES OF HONEY BEE. Comments Honey bees are highly beneficial social insects. They belong to the genus Apis. A. indica is the common Indian honey bee. The life cycle stages of honey bee are as follows:

1. Egg: Queen bee after mating during nuptial flight with a drone returns to hive and lays eggs. The eggs are bean shaped. In the whole life span of 2-5 years. a queen lays about 15,00,000 eggs. In a day, one queen lays about 1,500-2,000 eggs. 2. Larva: Eggs hatch into small larvae after 72 hours. Each larva possesses head and body segments containing spiracles. Larva may develop either into worker or queen depending upon the types of food they take. A larva which feeds upon royal jelly develops into a queen and which feeds upon honey develops into a worker. 3. Pupa: In the sealed chamber of hive larva develops into the pupa, The pupa possesses mouth parts, rudiments of wings, walking legs and eye. Pupal body is divisible into head, thorax and abdomen. After completion of metamorphosis, pupa is metamorphosed either into

Non-Chordate (Invertebrate) Zoology Practical

246

drone or worker or queen in 21 or 18 or 13 days respectively . All of them possess head, thorax and abdomen .

. compound

abdomen

WORKER

wing rudinents

walking leg

antenna head

thorax

PUPA spiracles

DRONE

Fig. 2.205 Honey bee. Life cycle stages 4. Worker: Smaller in size than queen or drone. Colour is blackish or brownish. It collects nectar and secretes wax from the wax glands present in the abdomen . The tibia of metathoracic legs bear pollen basket. 5. Drone: Intermediate in size. About 14-18 mm in length . Head contains one pair of large compound eyes. Only these mate with queen. 6. Queen: It is the fertile female and measures 15-20 mm in length. It has long tapering abdomen, ·short legs and wings. It only lays the eggs. Except drones all forms possess sting.

35. LlMULUS

Classification Phylum

Arthropoda

Jointed limbs, triploblastic.

Class

Arachnida

Air breathing, without antennae, 4 pairs of legs.

Order

Xiphosura

Prosoma convex, covered by horse shoe shaped

Genus

Limilus

car~pace .

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Study of Museum Specimens and Slides of Different Invertebrate Phyla

lileral eye (compound) carapace ,

pits Ie/son

A anus B

Fig. ,2.206 Dorsal view of Limulus.. A - Dorsal view. fJ - Ventral view.

Comments I.

It is commonly known as king crab or horse-shoe crab.

2.

Body is divided into prosoma and opisthosoma.

3.

Prosoma is convex, bears three longitudinal ridges, one median and 2 lateral.

4.

The dorsal surface of prosoma contains a pair of simple median eyes and a pair of lateral compound eyes.

5.

Prosoma bears 6 pairs of appendages grouped around the mouth.

6.

The prosoma is covered by a large semicircular carapace.

7.

The carapace also bears one pair of median and 2 large composite sub-dorsal or lateral eyes.

8.

Opisthosoma is roughly hexagonal comprises 6 segments, the mesosoma, a vestigial metasoma and a long spine like telson.

9.

Opisthosoma comprises 6 pairs of appendages, first pair forms genital operculum, the remaining 5 pairs carry book - lungs.

10.

Mesosoma contains 6 pairs of spines.

II.

The legs are biramous.

12.

Respiration by book gills or lungs.

13.

Excretion by coxal or brick red glands.

14.

Sexes are separate.

15.

The post and caudal spine is hinged.

16.

Development is indirect. The life cycle includes a larva called trilobite.

17.

It was regarded as quite akin to extinct trilobites.

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Non-Chordate (Invertebrate) Zoology Practical 18.

Limulus retains many primitive characters 'unchanged for the past 200 million years. Hence, it is called a living fossil.

Habit and Habitat Limulus is a marine form found burrowing in the sand.

Distribution Eastern coast of Asia and its Island and eastern coast of North America from Nova Scotia to Florida. It represents discontinuous distribution.

36. PALAMNAEUS

Classification Phylum Class

Arthropoda } Arachnida

Order

Scorpion idea

Genus

Palamnaeus (Scorpion)

Same as that of Limulus. Body consists of prosoma, mesosoma and metasoma, respiration by 4 pairs of book lungs.

Fig. 2.207 Palamnaeus (Scorpion) A - Dorsal view; B - Ventral view.

I

Comments I.

It is commonly known as Scorpion.

2.

Body is elongated and segmented.

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249

3. 4.

Body divisible into anterior prosoma. middle mesosoma and posterior metasoma. Prosoma is covered by carapace and is 6 segmented.

5.

Prosoma bears a pair of median eyes, 2-5 pairs of lateral eyes and 6 pairs of appendages. 1st pair is called chelicerae which is used to hold the food; lInd pair is called pedipalp which is used to seize the prey and from IIIrd to IVth segments are walking legs.

6.

Mesosoma is composed of 7 broad segments.

7.

Metasoma has 5 narrow segments without appendages. The last segment is tel son containing a sting.

8.

Ventrally the sternum of first mesosomatic segment contains a pair of genital opening. Respiration by means of 4 pairs of book lungs.

9. 10.

Excretion by malpighian tubules and coxal gland.

II.

Sexes are separate but without sexual dimorphism.

12.

Scorpion also exhibits cannibalism.

13.

It is harmful to mankind. The sting has a poison duct from the sting gland.

14. 15.

The body cavity is the haemocoel, which is filled with haemocoelonic fluid. Circulatory system is of open type.

16.

Heart is tubular and muscular.

17.

Fertilization is internal preceded by' copulation.

18. 19.

During copulation the male digs a hole where copulation takes place. After copulation. the female eats the male. The development is internal.

20.

Scorpions are viviparo,us.

Habit and Habitat Scorpion is a nocturnal carnivorous. terrestrial arthropod. found in sand. crevices, under stones and the bark of dead trees. It usually lives on hills. They are regarded as first land arthropods.

Distribution Its distribution is cosmopolitan but particularly found in India. Europe and U.S.A.

37. ARANEA (SPIDER)

Classification Phylum Class

-

Order Genus

-

ArthroPoda} Arachnida Arancida Aranea

Character same as that of Limulus. Chelicerae subchelate with poison gland.

Non-Chordate (Invertebrate) Zoology Practical

250

Comments

chelicera

I. It is commonly called as spider. 2. Body consists of prosoma and an opisthosoma. the two being connected by a narrow delicate pedicel. 3. Prosoma is covered by carapace and bears eights eyes dorsally and six pairs of appendages. 4. Opisthosoma is unsegmented. soft. rounded and without telson. 5. Chelicerae are subchelate and contain poison glands and six jointed pedipalps. 6. Opisthosoma contains 4 pairs of spinnerets which produce silken threads for making web. 7. Respiration by book lung and tracheae.

posterior spinnerels

Fig. 2.208 Aranea 8.

Excretion by mulphighian tubules and coxal glands.

9.

Sexes are separate. Sexual. dimorphism is often well marked.

10.

Carnivorous.

11. 12.

Walking legs 4 pairs. Aranea constructs complex webs of different shapes.

Habit and Habitat Aranea is found in houses and gardens.

Distribution' It is found in South East Asia and U.S.A.

38. GALEODES

Classification Phylum

Order

Arthropoda Arachnidha Solifugae

Genus

Galodes

Class

~}

Same as that of Aranea. Body consists of prosoma and opisthosoma. chelicerae large and chelate.

Comments 1.

Body divisible into prosoma and opisthosoma.

2.

Prosoma consists of head and thorax having last three free segments and six pairs of appendages.

3.

Chellecerae are long and chelate.

4.

Pedipalpi are leg like and sensory.

5.

Opisthosoma is composed of ten segments not marked off from the prosoma.

Study of Museum Specimens and Slides of Different Invertebrate Phyla 6.

Poison glands are absent.

7.

Respiration by tracheae.

8.

Body possesses large number of setae.

251

Habit and Habitat Galeodes is found in warm dry regions.

Distribution It is found in Asian countries.

Fig. 2.209 Galeodes.

39. CHELIFER Classification Phylum Class Order

Arthropoda

Genus

Ch~lifer.

-

Arachnida

}

Pseudoscorpionida

Characters same as in Aranea. Appearance like scorpion. or chelonethida. tel son absent.

Comments cephalothorax

1.

It is commonly known as Pseudoscorpion.

2. 3.

Body consists of prosoma and opisthosoma.

4.

Prosoma is broad and continuous having six pairs of appendages. Chelicerae and pedipalpi are like those of scorpion.

5. A pair of spinning gland are present on the tips of chelicerae.

Fig. 2.210 Chelifer.

6. 7. 8.

Opisthosoma is ten segmented without telson. Respiration by tracheae. Dioecious.

Habit and Habitat Chelifer is found commonly under the bark of trees.

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Non-Chordate (Invertebrate) Zoology Practical

40. PERIPATUS

Classification Phylum ClIlss

-

Arthropoda Onychophora

Genus

-

Parpitus.

Jointed legs. Primitive arthropods with unjointed legs revealing anneIidan characteristics.

ringed preantennae

Fig.2.211·Peripatus.

Comments 1.

Body is elongated like caterpillar and measuring 2-3 inches in length.

2.

The outer covering of body is velvety. The skin shows many transverse wrinkles and numerous conical papillae.

3.

The body consists of a head and trunk.

4.

The anterior end is marked by preantennae and ventral mouth and posterior end by anus.

5.

Head is not distinct and bears a pairs of antennae, a pair of jaws, a pair of oral papillae and a pair of simple eyes.

6.

There are about 15 pairs of walking legs.

7.

Trunk bears a series of paired short stumpy appendings which vary in number 1442.

8.

The body cavity is haemocoel.

9.

Slime glands open on the surface of oral papillae.

10.

Crural glands are absent.

I I.

Respiration by tracheae having spiracles.

12.

Excretion is carried out by segmentally arranged metanephridia.

13.

The nervous syste'm is ladder like.

14. 15.

Sexes are separate and gonads are paired. Mostly viviparous, while some are oviparous.

16.

It is uricotelic animal.

17.

Carnivorous.

18.

Fertilization is internal.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

19.

253

Due to the presence of both annelidan and arthropodan characters it is al!io said to be a connecting link between Annelida and Arthropoda.

Habit and Habitat It is nocturnal, lives in crevices of rocks, tinder bark and stones in, other dark moist places of tropical region. It is insectivorous. -

Distribution Having discontinuous distribution. found in damp forests of. Africa, Malaya. Alfstralia. South America and New Zealand.

Special Features Paripatus was first described by Guilding in I S2S. 'H~ placed it in Phylum Mollusca because of its slug-like appearance. In 1874 Mosley placed'it 'under the phylum Arthropoda. It exhibits annelidan characters too, hence referred to as a connecting link between annelida and' arthropoda.

Annelidan Characters I.

The

se~mentation

2. 3. 4. 5. 6.

The The The The

lJbdY is vermiform. body wall is dermomuscular. legs are hollow and unjointed like those of parapodia. eyes are simple.

7. 8.

Genital ducts are ciliated. Alimentary canal is straight.

is mpre or less homonomous.

The nephridia are segmentally arranged.

Arthropodan Characters I. 2. 3. 4. 5. 6.

The antennae are jointed. Haemocoel present. Respiration by tracheal system. Salivary glands are connected with the digestive system. Body covered with chitiQous cuticle. Appendages are provided with claws.

Unique Features 1. 2. 3. 4. S.

Segmentation not distinct. Stigmata arranged in scattered" pattern. Nervous system is ladder like and without segmented ganglia. Skin is soft, velvety with many transverse wrinkles and papillae. Only one p~ir of jaws ,present.

254

Non-Chordate (Invertebrate) Zoology Practical

ISTUDY OF SLIDES I 1. CULEX: EGG RAFr water

egg raft

,=-",'. - ~

Comments

-~:-:=-----'

Female Culex lays eggs in clusters in the form of egg raft on L the surface of stagnant water. __ --- : 2. Eggs are whitish. cigar-shaped having two ends - one is broad and round and the other narrow and pointed.

Fig. 2.212 A Culex. Egg raft

3. Each egg raft usually contains 200-400 eggs. 4. The eggs are held together by their sticky surfaces.

5.

Eggs contain air-bubbles in the anterior tip which help in floating.

6.

Eggs hatch out into free-swimming larva in 2 or 3 days.

2. CULEX: LARVA Comments I. Culex larva is transparent. about 1 mm long and divisible into head. thorax and abdomen. 2. Head contains a pair of compound eyes. simple antennae (one pair) feeding brushes. chewing mandibles and maxillae. 3. Thoracic segments are fused into a single rounded region which bear 3 pairs of lateral tufts of hairs.

Fig. 2.213 Culex. Larva

4. Abdomen with 9 - segments. each provided with tufts of bristles and hairs. 5. A respiratory siphon with two spiracles arises from the dorsal surface of the 8th segment.

6.

Last segment of abdomen bears 2 pairs of tracheal gills and ventral brush distally.

7.

It hangs with head downwards at an angle with the surface of water in resting condition.

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Study of Museum Specimens and Slides of Different Invertebrate Phyla

3. CULEX: PUPA

Comments 1. Larva of culex moults four times to change into colourless pupa. 2. It is comma-shaped and consists of cephalothorax and abdomen. antenna

~~

paddles or ~za;.2Il1 tracheal gills

3. Cephalothorax contains a pair of long and tubular respiratory trumpets. 4. Abdomen is 9-segmented having tufts of bristles. 5. Last abdominal segment possesses single pair of chitinous leaf like paddles by which pupa swims.

Fig. 2.2 14 Pupa of Culex.

4. HEAD AND MOUTH PARTS OF FEMALE AND MALE CULEX A - Male I.

Mandibles and maxillae are reduced and nonfunctional.

2.

The hypopharynx is fu'sed to the labium or proboscis

3.

The maxillary palps are as long as the proboscis but are not club shaped.

4.

Mouth parts are of sucking type. .probosCis or labium

labella

.maxillary 'paJp

A

head

B

'MAle

~_--=~-- head

.·FEMALE·,

Fig. 2.215 Culex. '. A - Head and mouth parts of male. B - Head and mouth parts of female•

. B-FEMALE

Comments. 1.

Mouth parts are piercing and sucking type.

2.

It comprises of labrum - epipharynx, needle like mandibles. maxillae and hypopharynx.

3.

Maxillary palps are short and three-jointed.

256

Non-Chordate (Invertebrate) Zoology Practical 4. 5. 6. 7.

Head is freely movable on a slender neck having large compound eyes and antennae. The mandibles and maxillae are raper-like skin piecing structures. The labrum-epipharynx and the hypopharynx form two sucking tubes. It transmits the filarial worms in human being which ultimately gives rise to elephantiasis.

S. EGGS OF ANOPHELES

Comments I. Anopheles lays eggs horizontally and singly on the surface of the water. 2. Eggs are whitish and boat-shaped. 3. Each egg has two lateral air floats which help in floating. 4. The number of eggs is usually 40-100. 5. They hatch into free swimming larval stage after 24-48 hours.

Fig. 2.216 Anophelex. Eggs.

6. ANOPHELES LARVA 1.

It has the same general body plan as that of culex except the following differences: (i) Respiratory siphon absent. (ii) Head lies horizontally parallel to the surface of water. (iii) Palmate hairs on the abdomen. (iv) A quadrilateral plate with two spiracles on the 8th segment. (v) Comb is absent.

2.

It is surface feeder.

Ihoral' .

Fig. 2.217 lAna Anopheles.

0/

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- Study of Museum Specimens and Slides of Different Invertebrate Phyla

7. ANOPHELES: PUPA

Comments I. The larva of Anopheles (wriggler) moults four times to become a pupa.

~~~

antenna

2. Body comprises of cephalothorax and abdomen. 3. Pupal stage is green-coloured and known as tumbler.

4. Cephalothorax contains a pair of short and broad respiratory trumpets with a large terminal opening and antennae. '--_ _ _ _ _ _ _ _ _ _ _ _ _ _ _-' 5. Abdomen is 9 segmented and is more strongly curved than in culex. Fig. 2.218 Pupa of Anopheles. 6. Bristles are unbranched. 7.

8th abdominal segment bears a pair of paddles for swimming.

8.

Rudiments of some of the prospective appendages are also present.

8. HEAD AND MOUTH PARTS OF FEMALE AND MALE ANOPHELES A·FEMALE

r--------------,

Comments I. Head is freely movable on a delicate and slender neck. 2. Head contains a pair of large compound eyes and antennae. 3. Antennae possess a few short hairs at joints. 4. Mouth parts" are piercing and sucking type. It comprises labrum - epipharynx. "needle shaped mandibles and maxillae. hypopharynx. maxillary palps and labium. 5. Maxillary palps are simple and equal to labium or proboscis.

1-\

A I...-_ _ _ _ _ _ _ _ _ _ _..J

Fig. 2.219 (A) • Anopheles. Head and mouth parts of female

6. Clypeus articulates with labrum and epipharynx. 7. It transratits malarial disease and acts as intermediate host for plasmodium (Malarial Parasite).

,

Non-Chordate (Invertebrate) Zoology Practical

258

B-Male ANOPHELES maxillary

I--!f-- palp IHf4!---proboscis I/JIlIL..--antenna

,0 ~I-. ~I~O egg boat

I

maxillary palp

single eggs

I

siPIi71n '"Q'Wl4t abdomen I ,anal gills thorax : LARVA breathing I trumpet I ~

maxillary palp

'anlennul cas~ 1;:t;9 • leg case I eye _, wing case PUPA paddle

maxillary palp

B,

Fig. 2.219 B • Anopheles· Mouth parts with comparative account of Culex and Anopheles The head and mouth parts of male Anopheles has the same general plan as that of female except: I.

Maxillary palps are club-shaped and are nearly equal to labium or proboscis.

2.

Antennae have long. bushy hairs at

3.

It does not help in transmission of malarial diseases and feeds on plant juices.

th~ir

joints.

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259

9. HOUSE FLY: HEAD AND MOUTH PARTS Comments ocellar plate with ocelli

compound eye'

1. Head of house fly (Musca domestica) contains a pair of large compound eyes, three ocelli. a pair of antennae and mouth parts. 2. It lacks cutting apparatus. 3. Mouth parts sponging type. 4. Mouth parts comprise of proboscis, short maxillary palps, labrum - ephipharynx and hypopharynx. 5. Mandibles are totally absent. 6. Maxillae are represented by short and unjointed maxillary palps before the rostrum. 7. Labrum fused with epipharynx. 8. Hypopharynx is narrow blade like having salivary duct and fits into the tube formed by labrum-epipharynx. 9. Maxillary palps are small and unjointed.

pseudolracheae

Fig. 2.220 Head and mouth parts of housefly.

10. Proboscis is retractile and consists of 3 parts a basal large rostrum, middle haustellum and upper labella or oral lobes. II. Labella or oral lobes form an oral disc crossed by the pseudotracheal channels.

12. All the pseudotracheal channels open into a common channel or aperture-which finally leads into the mouth opening.

13.

Labium forms a tube enclosing the labrum - epipharynx and hypoPharynx.

14.

Food channel is formed by labrum - epipharynx and hypopharynx.

10. BUTI'ER FLY: HEAD AND MOUTH PARTS Comments I.

Mouth parts sucking or siphoning type.

2.

Head is broad and bears a pair of compound eyes, and a pair of small antennae.

3.

Mouth parts composed of a small labrum and coiled proboscis.

4.

Mandibles and labium are highly reduced.

5.

Proboscis is in coiled shape and composed of elastic cuticle.

Non-Chordate (Invertebrate) Zoology Practical

260 6.

Proboscis is formed by the greatly elongated galeae of maxillae which is grooved internally forming food canal for nectar.

7.

Labrum is triangular and plate-like containing labial palps.

8.

Maxillary palps are vestigial.

9.

Compound eyes and having omJ1latidia.

10. Labium lies in between the rudimentary maxillary palp. II. Long and coiled proboscis is the salient feature, of mouth parts of, butterfly.

Fig. 2.221 Head and mouth parts of butterfly. \

11. APIS (HONEY BEE): MOUTH PARTS

Comments I.

Mouth parts of Apis are well adapted for collection of nectar and pollen. It is of rasping and lapping type.

2.

Mouth parts are located on head which is triangular having compound eyes, 3 ocelli, and antennae.

3.

Mouth parts consists of spoon shaped mandibles, labrum, and maxillae devoid of lacinia.

4.

Labellum is spoon-shaped, grooved internally forming a tube and is known as tongue.

glossae

(llgi.lla)--~~

5.

Mandibles are smooth and spatulate type, located on either side of the labrum.

6.

Maxillary palps are vestigial and '--------------~---""" galea are. blade-like. . Fig. 2.222 Honey-bee. Mouth parts of water.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

261

7.

Epipharynx is soft and triangular,located below the labrum. Cardo and stipes are well developed.

8.

Labium consists of.an elongated prementum and small mentum.

9.

Prementum bears four segmented labial palp, paraglossae and glossae.

to.

Paraglo!)sae are greatly reduced whereas the glossae are,~airy. elongated and united forming the ligular tongue which terminates into a small lobe called flabellum.

II.

Liquid food is taken along the tongue and is converted into honey in honey sac by the enzymes secreted from salivary glands.

12.

Honey-bee also moulds waxes in it hive.

12. APIS (HONEY BEE): STING APPARATUS.

Comments polson sac

I.

It is a complicated structure.

2.

Sting apparatus is a modified ovipositor located at the posterior extremity of the abdomen in queens and workers.

3.

It is composed of terebra or sting, bulb, levering plates and glands.

4.

Sting is composed of two pairs of ganapophyses: those of the 8th segment forming sty lets and of the 9th segment stylet sheath, which enclose poison canal.

5.

Distally the stylet sheath and.stylet contain pointed spines or barbs.

6.

Stylet sheath is expanded into the bulb at the base of the sting.

7.

The sty lets can move up and down.

8.

Attached to the stylets proximally is a median poison sac into which opens two acid glands and one alkaline gland.

9.

The poison is secreted in acid and alkaline glands and stored in poison sac.

polson gland gland

sting--~1

Fig. 2.223 Sting Apparatus of honey-bee.

10. The sting has a set of 3 chitinous plates. II. During stinging, the sty lets and stylet sheath enter the victim, the secretions of two types of glands mix and pass down the poison canal into the wound.

12.

Sting along with glands remains inside victims body and bee dies after sometimes.

13.

The bite of the sting causes burning sensation, pain and swelling.

Non-Chordate (llIvertebrate) Zoology Practical

262

13. COCKROACH: MOUTH PARTS

~ :-":': ":"

: ~:

'.:-.: ..'::' .:

.

.. .

superli~nua . :.

. '.' .

.. .... salivary ducl

Mouth parts of cockroach are biting and chewing type.

2.

It consists of labrum, a pair of mandibles, a pair of maxillae, a labrum and a hypopharynx.

3.

Mandibles afe simple chitinous and toothed. They are for culting.

4.

Labrum protects the mouth and is broad oblong plate and forms the upper lip.

5.

Maxillae is located below the mandibles.

6.

Maxillae has two parts - carbo and stipes.

7.

Stipes internally conlains lacinia, externally maxillary palp and medially galea .

LEFT MANDIBLE

.:- '..

':'.'

I.

' ..:~:: ... ..

LABIUM

dentlcles

RfGHT MANDIBLE

Comments

fj): . . .:. .

molar area U-ClypeUS

.• '..

cardo

'. :

IHYPOPHARYNX

maxillary palp

RIGHT FIRST MAXILLA

LEFT FIRST MAXILLA

labial palp paraglossa

. SECOND MAXILLA OR LABIUM

Fig. 2.224 Mouth parts of cockroach. 8.

Labium forms the lower lip and is composed of distal prementum, middle mentum and proximal submentum.

9.

Prementum carries glossa internally, paraglossa medially and palpiger externally.

10.

Hypopharynx is a median tongue like structure which lies above the labium and between the maxillae. It is provided with sensory bristles.

II.

Maxillary and labial palps are tasting organs.

14. CIMEX [BED BUG]: MOUTH PARTS Comments compound eye cJypeus

Fig. 2.22S Bed bug. Mouth parts.

1.

Head is broad but short and bears compound eyes, antennae and mouth parts.

2.

Mouth parts located on the head are of piercing and sucking type.

3.

Antennae are 5 joints.

4.

Mouth parts consist of elongated larrum, rostrum or proboscis, niddle - shaped mandibles and maxillae.

5.

Proboscis is grooved.

6.

Maxillary palps and labial palps are absent.

7.

Mouth parts are well adapted to suck the human blood.

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263

15. GRASSHOPPER: MOUTH PARTS

labrum

mandible

lacinia

hypopharynx

stipes

ligula

cardo

maxilla

Fig. 2.226 Mouth parts of grasshopper. (Biting and chewillg type)

Comments I.

The head bears one pair of compound eyes, three simple eyes called ocelli, one pair of segmented antennae and a set of mouth parts.

2.

Mouth parts are of mandibulate type.

3.

Mouth parts consists of upper lip or labrum, hypopharynx, mandible, maxillae and labium or lower lip.

4.

The labrum is rectangular attached to the ventral edge of the clypeus.

5.

Beneath labrum hypopharynx is located which is a tongue like structure.

6.

Mandibles are hard, heavy, horny and triangular whose inner margin is toothed.

7.

Lying behind the mandibles a pair of maxillae are situated.

8.

Each maxilla is composed of 4 parts: basal cardo, middle stipes, distal elongated curved lacinia and rounded galea and a slender 5 segmented sensory maxillary palp which arises from a palpifer.

9.

The maxillae are applied in manipulating the food as it enters the mouth.

10.

The broad, median lower lip or labium is considered as a fused second pair of maxilJae.

II.

The labium consists of a basal submentum, a central mentum and two movable flaps. The ligulae and a three segmented sensory labial palp on eit.her side.

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Non-Chordate (Invertebrate) Zoology Practical 12.

The labrum and labium jointly serve to hold food between the mandibles and maxillae which move laterally to grind it.

16. CIMEX [BED BUG]

Classification Phylum Sub phylum Class Sub-class Division Order Genus

Arthropoda

Jointed limbs.

Mandibulat

Jaws and antennae present.

Hexapoda [Insecta]

3 pairs of legs. Winged insects.

Pterygota Exopterygota

Wings develop externally. Metamorphosis gradual.

Hemiptera Cimex (Bed Bug)

Comments ,antenna

L..-_ _ _ _ _ _ _ _ _ _ _ _- - '

Fig. 2.227 Cimex.

10. I 1. 12. 13.

I. It is

popula~ly

known as Bed bug. 2. The body is some what oval. dorsoventrally flattened and reddish brown in colour. 3. Wings absent [first pair represented by very short pad or hemelytra cn mesonotum]. 4. The head is short, bro .. d and lateraIIy carries a pair of compound eyes. 5. 6. 7. 8.

Ocelli absent., Piercing and sucking type of mouth parts present. Antennae four jointed. Tarsi 3 jointed.

9. The thorax is divided into a large prothorax. a very small mesothorax and a metathorax.

Abdomen with 8 distinct segments. Dioecious. Abdomen of male is pointed at the tip whereas that of female is rounded.

Cimex is a blood sucking ectoparasite of man. It transmits many diseases from infected persons to healthy ones.

Habit and Habitat Cimex is found inhabiting the human dwellings such as the crevices of cots and furnitures. folding of beds etc.

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265

17. PEDICULUS [HUMAN HEAD LOUSE]

Classification

Order

Arthropoda Mandibulata Insecta Pterygota Exopterygota Anoplura

Genus Species

Pediculus humanus.

Phylum Sub phylum Class Sub-class Division

r---'antenna "'I. ....I"" .....:--eye

a:---' thoracic , spiracle

Fig. 2.228 Pediculus

Characters same as that of Cimex.

Wingless insects, no metamorphosis, mouth parts piercing and sucking type, ectoparasite.

Comments I.

Pediculus humanus is popularly called human head louse.

2.

Wingless.

3.

Pale yellow body is dorso-ventrally flattened, divisible into head, thorax and abdomen.

4.

Head carries a pair of feebly developed compound eyes and a pair of 5 jointed antennae.

5.

Mouth parts are piercing and sucking type.

6.

Thorax 3 segmented but fused in one mass and bears one pair of spiracles between first 'and second thoracic legs.

7.

Each leg bears a large curved claw adapted for clinging to the hairs of the host.

8.

Abdomen is 9 segmented.

9.

Sexes are separate. Females are larger than males. Female measures about 3-4 mm in length whereas male 2-3 mm in length.

10.

In male, the posterior end is turned upwards but not in female.

II.

The abdomen of male is pointed at the tip whereas that of female is rounded.

12.

Female lays scattered eggs which do not attach to the hairs.

13.

Mandibles are rudimentary.

Special There are two species of Genus PedicuLus - P. human us, the human head louse and P. corporis, the human body louse. P. humanus is mainly responsible for typhus, relapsing and trenche fever.

Habit and Habitat It is found as an ectoparasite of man.

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18. XENOPSYLLA [RAT FLEA]

Classification Phylum Sub phylum

Arthropoda Mandibulata

Class

Hexapoda or Insecta

Sub-class

Pterygota

Division

Endopterygota

Wings originate internally; Metamorphosis complete.

Order

Siphonaptera

Secondarily wingless ectoparasites of birds and mammals; mouth parts piercing and sucking type; cerci absent.

Genus

Xenopsylla

Species

cheopis anal styles

abdomen

}

antenna

Characters same as that of Cimex.

Comments J. It is popularly known as rat-flea. 2. The body is laterally compressed suited for glidding.

3. Without wings. 4. Head is broadly jointed to the small thorax.

5. Abdomen of 10 segments. 6. Antennae are clavate. short and concealed in grooves.

Fig. 2.229 Xenopsylla. 7.

The mouth parts comprising of serrated mandibles. triangular maxillae and maxillary palps. reduced labium. hypopharynx and large labrum - epipharynx. are of piercing and sucking type.

8.

Compound eyes are absent.

9.

Body is furnished with backwardly projecting bristles. which help the flea in forcing its way between dense hairs and prevent it from slipping backwards.

10.

Legs are long and powerful and modified for jumping.

1 I.

Dioecious.

12.

Last 3 abdominal segments in males form copulatory apparatus.

13.

In males. the posterior end of abdomen is upwardly directed where as in females it is rounded.

14.

The adult flea is active and slips through hair with great ease.

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Special Rat fleas are prime transmitters of two diseases : I.

Bubonic plague

2.

Endemic typhus

These also transmit Tularemia in rodents and Myxomatosis in rabbits.

Habit and Habitat Xenopsylla cheopis is an ectoparasite of mammals specially rats. It transmits the bubonic plague from rats to man.

19. CYCLOPS Classification Phylum

Arthropoda

Jointed limbs, segmented.

Sub-phylum

Jaws and antennae present.

Sub-class

Mandibulata Crustacea Copepoda

Order

Eucopepoda

Free living and parasitic copepods, females having ovisacs generally.

Genus

Cyclops

Class

coelomate

and

metamerically

Aquatic arthropods with 2 pairs of antennae. Free commensal or parasite, carapace and abdominal appendages absent.

Comment median eye

I. 2.

3. 4.

,.d~~~'h-seminal receptacle

fused 6th thoracic and 1st abdominal segment

5.

6. 7. 8. 9. 10.

Fig. 2.230 Cyclops. Female

Cyclops is found in ponds and ditches. The body is elongated or pear shaped with somewhat broad anterior and narrow posterior end. It measures 1.5 to 5.3 mm in length. The body is divided into an anterior region in a single shield of chitin carapace and a segmented posterior region. The anterior region called cephalothorax includes the head and first 2 thoracic segments. A median eye is present dorsally over carapace. The remaining 5 thoracic segments are free and bear limbs ventrally. Abdomen is also 5 segmented. Fourth abdominal segment bears a caudal style or forked tail and anus dorsally. Body appendages are: uniramous antennules, short antennae, mandibles, maxillulae, maxillipedes and legs.

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Non-Chordate (Invertebrate) Zoology Practical II.

Mature female carries two lateral egg sacs or ovisacs attached to upper abdominal segment.

12.

Male Cyclops lack ovisacs and antennules are- modified to form clasping organs.

13.

Respiration rectal.

Special Cyclops besides food for fishes, also acts as an intermediate host for various heliminth worms. The important disease in Rajasthan, Dracunculiasis in human is communicated by cyclops.

Habit and Habitat Cyclops is a free-swimming copepod found in freshwater and sometimes in brackish water.

20. DAPHNIA

Classification Phylum

Arthropoda

Jointed legs, segmented.

Sub Phylum

Mandibulata Crustacea Poranchiopoda Cladocera Daphnia

Jaws and antennae present.

Class Sub-class Order Genus biramus antenna

coelomate

and

metamerically

Aquatic forms with 2 pairs of antennae. Free-living, compound eyes and carapace present. 4 to 6 pairs of thoracic limbs.

nerve to nuchal sense organ gut diverticulum

iir::r::::::~""~~'"

Comments I. Daphnia is commonly called water flea. 2. Body is soft, bilaterally compressed measuring 1-2 mm in length. 3. Segmentation is imperfect. 4.

Body except the head is enclosed in a bivalved shell or a large fold of carapace.

5. Carapace ends into a pointed dorsal spine.

6. Head not separated from the body and is rounded. It bears a pair of biramous antennae, a pair of small antennules and a compound sessile eye. ~_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _....J

Fig. 2.231 Daphinia.

7. Abdominal appendages are absent. , 8. Thorax contains 5 pairs of leaf like appendages.

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Dioecious.

10.

Female carries eggs in brood pouch.

II.

Brood pouch is located near the back.

12.

Male lacks the brood pouch.

Habit and Habitat It is found in freshwater ponds. streams and ditches.

21 CYPRIS (MUSSEL SHRIMP)

Classification Phylum Sub phylum Class

Arthropoda } : Mandibulata : Crustacea :

Sub-class

Ostracoda

Bivalved. carapace rudimentary.

Order

Podocopa

Antennal uniramous.

Genus

Cypris

Characters same as that of Cyclops. encloses

body.

abdomen

Comments bivalved shell

eye~

1. It is commonly called as Mussel shrimp.

...

2. Body is completely enclosed in a bivalved carapace. Both the valves are connected by a large adductor muscle. overy anlennae~-~"""'~

Fig. 2.232 Cypris.

3. A median eye is present at the anterior end. 4. Compound eyes absent. 5. Head bears four pairs of appendages. antennules. antennae, mandibles and maxillae. 6. Antennules and antennae are biramous and help in swimming.

7.

Thorax bears three pairs of appendages.

8.

Abdomen is deviod of appendages.

9.

Eggs develops parthenogenetically.

Habit and Habitat Cypris is free swimming crustacean and occurs in freshwater stagnant ponds.

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22. MYSIS

Classification

Class Sub-class Order

Arthropoda Mandibulata Crustacea Malacostraca Mysidaceae

Genus

Mysis

Phylum Sub phylum

}

Characters same as that of Cyclops. Eyes usually stalked. Body distinctly segmented. Carapace covers almost entire thorax and uropods form broad fan-like tail fin.

Comments I.

It is a small. transparent. shrimp like crustacean.

2.

Body is bilaterally compressed and elongated measuring from 2-6 mm in length.

3.

Carapace covers the entire thorax except the last two segments.

4.

Head contains antennules. antennae and a pair of stalked compound eyes.

5.

Thoracic limbs bear 8 pairs of biramous appendages. Two anterior appendages arc small and form maxillepedes.

6.

Posterior thoracic limbs bear a brood pouch within which the eggs develop.

7.

Dioecious.

8.

The appendages are rudimentary in the female. The telson is without candal styles.

9.

Statocyst is located on the endopodite of each uropod.

10.

Gills absent and the respiration through the lining of carapace.

I I.

Development is direct. mandibular groove

, thoracic appendages

brood pouch

Fig. 2.233 Mysis.

Habit and Habitat Mysis is a marine pelagic form. It is usually confined to the surface of water.

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271

23. NAUPLIUS LARVA Comments I.

Development in crustacea includes various larval stages. After cleavage egg hatches into first larval stage, called Nauplius larva.

2.

It is minute, free - swimming, conical, microscopic, unsegmented with broad anterior and narrow posterior end.

3.

Body is divided into indistinct head, trunk and bilobed anal region.

4.

Head contains a median eye and a pair of uniramous antennules bearing terminal setae.

5.

Trunk bears two pairs of biramous appendages i.e. antennae and mandibles. All the appendages help in swimming.

6.

Mouth opens at the anterior end while the linus lies on the posterior extremity.

7.

Ventral nerve cord and heart absent.

8.

It undergoes a series of moults to pass through several intermediate larval forms before it reaches the adult stage.

9.

It has great phylogenetic significance and is supposed to be arthropodised trochophore.

Fig. 2.234 Nauplius Larvae. A - of Penaeus. B - of Apus

24. ZOAEA LARVA Comments I.

Zoaea larva is the IVth larval stage of Crustacea. Nauplius

Metanauplius

Protozoaea

(I)

(2)

(3)

Zoaea Larva. '(4)

2.

Body comprises of cephalothorax and abdomen.

3.

Cephalothorax is unsegmented whereas abdomen is long and segmented.

4.

Carapace of Cephalo-thorax is produced into rostrum anteriorly, and median spine. dorsally.

5.

Head contains large paired compound eyes, antennules, antennae, mandibles. maxillae and maxillepedes.

Non-Chordate (Invertebrate) Zoology Practical

272 anlennule

cephalothorax

maxillipede

Fig. 2.235 Zoaea larva of crab.

6.

Compound eyes' are movable.

7.

Thoracic buds.

8.

Abdomen 6 segmented and devoid of appendages. The last segment bears caudal fork.

9.

Zoaea larva changes into metazoaea or megalopa larva.

10.

Heart is located laterally to the median dorsal spine.

II.

Second maxillipede is longer than the first.

12.

Thoracic appendages are much smaller than the abdominal.

13.

Zoaea is a zeoplanktonic form.

14.

It

appendages develop as

normally metamorphoses megalopa larva after moulting.

into

25. MEGALOPA LARVA

Comments

median spine

I. Megalopa larva is the larva of crab and develops from Zoaea larva through successive moultings. 2. It resembles the adult stage and has a broad and median cephalothorax. produced into median spine and abdomen. 3. Body is divisible into unsegmented cephalothorax and segmented abdomen. 4. Head bears large pedicellate compound eyes. small antennules and large antennae. 5. Thoracic appendages are 5 pairs of legs, out of which the 1st pair is chelate. uropod

lelson

pleopOds

' - -_ _ _ _ _ _ _ _ _ _ _ _ _...J

Fig. 2.236 Megalopa larva.

6. Abdomen 6 segmented bearing biramous pleopods. 7. It leads a pelagic life for sometime and later on sinks to the bottom and transforms into adu It.

26. MYSIS LARVA

Comments I.

The Zoaea larva in Anomura and Pennaeus, instead of converting into Megalopa changes into Mysis larva having 13 pairs of appendages.

2.

The name so called because it very much resembles adult Mysis.

3.

Body is

divisi~le

into cephalothorax and abdomen.

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4. Carapace projected anteriorly into rostrum. 5. Head bears stalked compound eyes. antennules and antennae. 6. Thoracic appendages are biramous. 7. Posterior thoracic legs have nagellar exopodites for locomotion. L--_ _ _-=:----=-c=-=-=::--:--::---:--=--_ _ _ _ _ _...J

Fig. 2.237 Mysis Larva. 9.

8. Abdomen is having 5 pairs of pleopods, one pair of uropodes and telson.

It directly metamorphoses into adult.

27. PERIPATUS: T.S. PASSING THROUGH BODY Comments T.S. passing through the body of the peripatus along with legs reveals following noteworthy points: I.

The body wall is composed of cuticle. epidermis. dermis and musculature.

2.

Cuticle is thin nexible. chitinous. water proof and covered by several velvety processes. pericardial cavity

heart

cuticle

epidermis dermis circular and diagonal muscle

~~~~- dor&o longitudinal muscle

claw

Fig. 2.23'8 Peripatus. T.S. passing through body and legs. 3.

Beneath cuticle are single layered epidermis. basement membrane and dermis of connective tissue.

4.

Musculature consists of circular muscle fibres, transverse fibres, dorsal, lateral and ventral longitudinal fibres.

5.

Between body wall and gut wall lies perivisceral haemocoel.

6.

The appendages are conical and hollow and each ends with a muscular foot bearing claws.

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Non-Chordate (Invertebrate) Zoology Practical 7.

In the section cut parts of the heart, slime glands, salivary gland, nephridium. nephrocytic tissue and nerve cords are also present.

28. SCORPION: PECTINE Comments shaft of pectine

I. Pectines are comblike structures attached to the ventral side of the second segment of the prosoma. 2. Each pectine is formed of a shaft or handle. 3. The shaft is made up of three segments. 4. The shaft bear a row of skeletal pieces called Fulcra.

teeth of pecti~e

5. The fulcra bears teeth like structures as comb.

Fig. 2.239 Scorpion. Pectine 6. The pectine are tactile and olfactory in function. 7. Pectines brush over the ground when scorpion walks.

29. SCORPION BOOK LUNG Comments pulmonary chamber.

,lamellae,

. stigma

atrial chamber

L.--=::---:--::-:-::-::--_::----::---::--::-_ _--'

Fig. 2.240 Scorpion. Book lung.

I.

Book lung or pulmonary sac is a respiratory organ of scofnion.

2.

There are 4 pa,. s of book-lungs situated in the 3rd, 4th, 5th and 6th segments of the mesosoma. one pair in each.

3.

Each book lung opens outside by an oblique slit called stigma.

4.

The cavity of each book lung is lined by a thin cuticle which is thrown into numerous folds, called lamellae.

5.

The lamellae are arranged parallel to one another giving the appearance of the leaves of a book.

6.

There are about 150 lamellae.

7.

Lamellae are hollow containing blood.

8.

Each stigma leads into a small chamber called atrial chamber.

9.

The atrial chamber leads into a large pulmonary chamber in which the lamellae are arranged.

10.

Air from outside enters the chamber and passes into the spaces between the leaves.

II.

The blood flows continuously in the space inside the lamellae while the inter lamellar spaces are filled with air so that exchange of gases takes place through the thin walls of the lamellae.

12.

The impure blood from the ventral sinus is sent to each book lung. The blood is aerated in lamellae.

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275

13.

The aerated blood is collected by the pulmonary vein, which opens into the pericardial sinus.

14.

The inspiration and expiration of the air in the book lung are controlled by the dorso-ventral and atrial muscles.

30. PRAWN: HASTA TE PLATE Comments circular cuticular 'plate

combed plate anterior valve

-#='~¥H

longitudinal ,--""""- fold or guiding ridge bristles of combed plate

lateral valve

~--------------------------~

Fig. 2.241 Floor of cardiac stomach of Prawn showing hastate plate.

I.

Hastate plate is a large triangular chitinous structure embedded in the middle of the floor of the stomach.

2.

It looks like head of a spear.

3.

It is called as gastric mill.

4.

Its upper surface contains setae and a median ridge.

S.

It carries a distinct median ridge with gradually sloping sides.

6.

Each lateral side is supported beneath by a longitudinal cuticular supporting rod.

7.

Comb plate contains a row of delicate bristles.

8.

Posteriorly hastate plate communicates with cardio - pyloric aperture.

9. The main function of the hastate plate is propulsion and grinding of the food particles.

10.

Hastate plate called as gastric miIJ is formed by chitinous plate.

31. PRAWN: STATOCYST cuticle

sensory setae

Comments 1. Statocyst is a tiny, whitish. vesicle-like structure.

s

2. It is located in the precox a of each antennule. 3. It is supplied by nerves and opens by small aperture in concavity. 4. T.S. of statocyst reveals that it has a cavity containing sand particles which is surrounded by a ridge or an oval area provided with a number of elongated delicate receptor setae.

Fig. 2.242 Prawn statocyst; A • Statocyst in situ. B • T.S. of statocyst. C - A sensory seta.

S. Sand particles function as statolith. 6. Each receptor setae receives a fine branch of statocystic nerve.

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Non-Chordate (Invertebrate) Zoology Practical 7.

Statocyst is a hydrostatic structure and serves as on organ of orientation and equilibrium.

8.

Any change in,swimming 'position brings about change in position of sand particles, which stimulates setae and the prawn regains its proper position.

32. SARCOPTES

Classification Phylum

Arthropoda

Class

Arachnida

Characters same as in Chelifer.

Order Genus Species

Acarina

Body unsegmented. prosoma is fused with opisthosoma.

Sarcoptes scpiei

Comments

Fig. 2.243 Sarcoptes scabiei.

I.

Sarcoptes is microscopic.

2.

Body is oval or rounded in shape and dorso ventrally nattened.

3.

Body comprises transverse striations and few short bristles.

4.

Prosoma and opisthosoma are 'lot distinguished.

5.

Mouth parts are situated anteriorly.

6.

Four pairs of legs.

7.

Anterior 2 legs are projected beyond the body and provided with terminal stalked suckers.

8.

Posterior two legs are short with long bristles.

9.

Mouth parts are of piercing and sucking type.

Habit and Habitat It is an ectoparasite which attacks man, causing scabies which produces severe irritation that may lead to skin innamation and infections.

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277

I UNIT VIII - MOLLUSCA I Specimens: I. Chaeloderma 2. Chilon 3. Palel/a 4. Haliolis 5. Fissurel/a 6. Cypraea 7. Pila II. Murex 9. Doris 10. Aeolidia or Aeoli., /I. Aply.•ia 12. Helix 13. Limex 14. Planorb,s 16. Lymnaea 16. Peclen 17. O.flrea Ill. Pinelada (Oysler) 19. Mytillls 20. VIlIO 21. M)'u 22 Solenllcurtus 23. EII.,i.. 24. Teredo 25. V~nu .. 26. Denlalium 27. Loligo 211. Sepia 29. Octopu .. 30. Argollulltu 31. Nuutilus Slides: I. RadII/a of Pila 2. L.S. Osphradtum of Pila 3. Gill of Pila 4. T.S. Gill Lalllina of Vnio 5. T.S. Mantle and Shell of Vllio 6. Unio : T.S. through anterior region 7. Unio: T.S. through middle region 8. Unio : T.S. through posterior region 9. Gloehidium larva 10. Viliger larva

STUDY OF MUSEUM SPECIMENS 1. CHAETODERMA

Classification Phylum

Mollusca

It includes such forms as clams; oysters, squids; octopods; and snails. Body bilaterally symmetrical. unsegmented and consists of head. foot. mantle. and visceral mass. Ventral surface is flattened and muscular to form a creeping sole or foot. The dorsal surface is covered by an oval, convex. shield like shell. Several pairs of gills are housed within mantle cavity. Blood vascular system open type.

Class

Amphieura

Elongated body with reduced head.

Sub-class

Aplacophora

Worm-shaped molIuscs calIed solengasters. Head is poorly developed. Typical molIuscan features viz; shelI. mantle and foot absent. Bisexual.

Order

Chaetodermatoidea

Mid-ventral longitudinal groove having one or more ridges.

Genus

Chaetoderma.

Comments I.

Commonly known as Solenogaster. Body vermiform. bilateral symmetrical and elongated.

2.

Shell absent but body covered with several layers of calcareous spicules.

3.

Foot and nephridia absent.

4.

Mouth and anus are terminal and at opposite ends

5.

Heart with single auricle.

6.

Gills reduced to a pair found in cloacal cavity.

7.

Gut contains a style sac.

8.

Bisexual.

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278

Habit and Habitat -mouth

L-

,~,

constriction

"I

Chaetoderma is a marine form, inhabiting moderate to abyssal depths. They appear to feed on cnidarians.

Distribution Mostly found in U.S.A. and Europe.

:, I

epidermal papillae

Fig. 2.244 Chaetoderma.

2. CHITON OR ISCHNOCHITON Classification Phylum

Same as that of Chaetoderma

Class

Mollusca Polyplacophora

Order

Chitonoidea

Genus

Chitoll (Sea Mica) : first shell plate

It includes chiton. Shell divided into eight overlapping transverse plates. Foot broad, flat, and ventral.

Valves of the shell with insertion plates and teeth. Pericardial cavity is large and located beneath the last two shell plates.

Comments

mouth

I. There are about 500 existing

species of chiton. (See Mica) 2. Highly adapted for adhering to rocks and shells.

ctenidium

3. Bilaterally symmetrical and greatly flattened dorsoventrally ovid body consisting of shell, foot, mantle and the visceral mass.

sole of foot""+-!~~~

A

B

Fig. 2.245 Chiton. A Ventral view. B • Dorsal view.

4. Chitons range in size from 3 mm to 40 cm; and are drab shades of red, brown, yellow, and green.

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279

5.

Shell calcareous, divided into eight overlapping transverse plates.

6.

The shell plates are composed of several layers. The upper layer - the tegmentum composed of CaCO J , covered by a thin periostracum. Beneath the tegmentum lies a thicker, denser layer, called hypostracum, purely composed of CaC0 1 •

7. 8.

Head is not distinct. Eyes and tentacles absent. Ventrally situated foot is broad and flat, helps in adhesion and locomotion.

9.

Chi tons creep slowly in the same manner as snails. It may roll up into a ball if dislodged.

10.

Mouth opens into the chitin lined buccal cavity with radula which hears 17 teeth in each transverse row. The mantle cavity consists of trough or groove on each side of the hody hetween the foot and the mantle edge.

11. 12. 13. 14.

Large pericardial cavity located beneath the last two shell plates. Single pair of auricles collect blood from all of the gills. Nephridia 'U' shaped.

15.

Primitive nervous system with poorly developed ganglia.

16.

Most chitons are dioecious.

17.

Copulation does not take place. Sperms leave the male in the exhalant currents.

18. 19.

Fertilization may be external or internal. Free-swimming trochophore larval stage present.

Habit and Habitat Chiton is a marine and sluggish animal attached to rocks, empty sheilS and corals. Most chitons are microphagous and feed on fine algae and other organisms thilt they scrap from the surface of rocks and shells with the radula. They are usually negatively phototactic and thus tend to locate themselves under rocks and ledges. They are most active in the night if the tide is right. Some species exhibit homing. Sometimes chiton is used as food by man.

Distribution Cosmopolitan.

3. PATELLA Classification Class

Mollusca Gastropoda

Sub-class

Prosobranchia

Phylum

Characters as that of Chitol/. Shell is an asymmetrical and spiral, visceral mass spirally coiled exhibit torsion. Foot is . flat. It includes all gastropods that respire by gills and in which the mantle cavity, gills and anus are located anteriorly. They may be marine, freshwater and terrestrial forms. Shell and usually an operculum present.

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Non-Chordate (Invertebrate) Zool08Y Practical Mostly dioecious.

Archaeogastropoda

Order

Primitive forms.

Or Due to two auricles (although one may be reduced).

Diotocardia Or

Aspidobranchia

Due to bipectinate gills.

,------------------------------------------,

Genus

Patella

Comments I. It is commonly known as true

limpet. 2. Small, oval and sluggish gastropod. 3. Oral and rounded shell without operculum. 4. Shell consists of four layers. shell A

B

2.246 Patella.

5. Distinct head contains a pair of stout sensory tentacles and primitive eye in the form of a cup with photoreceptor and pigment cells.

6.

The underside of the limpet shows a large, flat foot used for creeping and adhering.

7.

True mantle cavity is restricted anteriorly and the true ctenidia are replaced by pseudoctinidia.

8.

A secondary pallial cavity extends all around between the fOQt and mantle.

9.

Radula having 3 marginals, 3 laterals but no central teeth. There is no siphon.

10.

Heart with single auricle.

II.

It shows homing ability.

12.

It possesses nutritive value.

Habit and Habitat Patella is a sluggish, marine gastropod found on rocky beaches between tidemarks, feeding upon micro sea-weeds.

Distribution Mostly found along Pacific-coast, Atlantic coast, Europe and U.S.A (California).

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281

4. HALIOTIS Classification Same as that of Patella.

Comments I. Haliotis is commonly knows as abalone as well as

ear shell. 2. Shell is ear shaped and above the cavity contains a line of five holes. 1. Operculum absent. 4. Eyes are stalked. 5. The foot is large and provided with epipodia having various sensory tentacles.

Fig. 2.247 Haliotis.

6. Mantle cavity is spacious having two bipectinate ctenidia or gills. the right being smaller.

7.

Two auricles and two nephridia are present.

8.

Shell is asymmetrical.

9.

It is microphagous.

10.

Haliotis is of great economic importance. Shell is used for the preparation of beautiful buttons. jewellery. etc. Flesh is eaten in Japan. China and Europe.

Habit and Habitat Haliotis is a marine proso-brachiate found attached to the rocks between tide marks.

Distribution It is commonly found in Japan. China. U.S.A. Pacific coasts and Europe.

5. FISSURELLA Classification Same as that of Patella. epical shell aperture

Comments I.

Fissurella is commonly called as key-hole limpet.

2. It has a conical, secondarily symmetrical shell having a hole at the apex. 3. Water enters the mantle cavity anteriorly, flows over the gills and tissues as a powerful stream from the opening at the shell apex. 4. The anus and urogenital openings are located just beneath the posterior margin of the shell opening.

Fig. 2.248 Fissurella.

5. The operculum is absent.

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Non-Chordate (Invertebrate) Zoology Practical 6.

The foot is large, sole-like and ventrally situated.

7.

The foot is used as sucker for clinging to rocks.

8.

Row of cirri are present around the base of the foot.

9.

The head bears sensory tentacles.

Habit and Habitat Fissurella is a marine gastropod found attached with locks.

Distribution It is found in U.S.A.

6. CYPRAEA

Classification Phylum

Mollusca

Class

Gastropoda

Characters same as that of Patella.

Sub-class

Prosobranchia

Order

Mesogastropoda

Genus

Cypraea

Single monopectinate gill. one auricle, and one nephridium, osphradium simple (ridge like).

,---------------, Comments shell

Siphon

I. Cypraea us popularly known as Kowry.

2. Shell is convolute, convex above and flattened below.

foot

tentacle

3. The ventral side is having narrow longitudinal opening extending the length of the shell in the form of toothed channel. mantie

'A

4. The solid shell is highly smooth, polished and often coloured.

'"' .

5. The mantle and the foot are more beautiful.

~ .

,

.

,"

shell aperture

B

Fig. 2.249 Cypraea. A - Entire animal B - Slzel in ventral I'eiw.

6. Mantle may be reflected over the shell laterally and provided with tentacular filaments. 7. Operculum is absent. 8. Expanded animals are having a pair of eyes, tentacles. pallial tentacles. foot and siphon. 9. The shells of kowry are used for ornaments and as coin in olden period in India. 10. It has also mythological signi ficance.

Habit and Habitat It lives on rocky ground in shallow marine water.

Distribution It is mostly found in Indian and Pacific oceans. U.S.A and Africa.

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283

7. PILA

Classification Phylum Class

Mollusca Gastropoda

Sub-class

Prasobranchia

Order

Mesogastropoda

Super family

Cyclophoraceae

Genus

Pila

Species

globosa

} Characters same as that of Cypraea.

Freshwater forms. radula having teeth.

Comments

apea

varix

I.

Pila globosa is popularly known as apple snail.

2.

Body covered in univalve shell.

3. Shell is spirally coiled around the axis. called the columella and opens exteriorly by mouth.

body whorl

4. Coiling of the shell is right handed and is called dextral. outer lip

5. The surface of the shell is marked by lines of growth.

6. Soft body consists of head. foot and visceral mass.

7. Mouth of the shell is wide and covered by Fig. 2.250 Pi/a globosa.

an operculum.

8.

Head lies on the upper side and contains I pair of eyes and two pairs of contractile tentacles.

9.

Foot is muscular and flat and serves for creeping.

10.

Visceral mass, the main organ of body is spirally coiled and covered by mantle or pallium.

11.

Respiration either(a)

Aquatic by ctenidium and/or

(b)

Aerial by pulmonary chamber.

12.

Radula have 7 teeth in each transverse row.

13.

It feeds on aquatic plants like pistia etc.

14.

Circulatory system is of open type.

15.

Heart two chambered.

16.

Blood is blue having haemocyanin pigments.

17.

Eyes, statocysts, osphradium and tentacles are the important sense organs.

18.

Fertilization is internal and development in direct.

J 9.

Dioecious but sexual dimorphism not clear.

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Habit and Habitat It is one of the most common freshwater gastropod abundantly found in ponds. tanks, rice fields, and in water having succulent vegetation and during drought, they remain dormant.

Distribution These are most common is India, U.S.A and Europe.

8. MUREX

Classification Phylum

Mollusca

Class

Gastropoda

Sub-class

Prosobranchia

}

Order

Neogastropoda or Stenoglossa

Genus

Murex

Character same as of Patella Similar to mesogastropoda

Comments

spirally coiled shell

opercular opening

Fig. 2.251 Murex.

I.

The shell is spirally coiled, dextral, with a long and prominent spire bearing 3 or more rows of spines.

2.

Long retractile proboscis and siphon well developed.

3.

Siphon leads into the mantle cavity.

4.

The foot is large and tough having nat creepIng sale.

5,

Eyes are placed at the base of the tentacle.

6.

Radula with two or three teeth in each row.

7.

It is carnivorous and feeds upon living and dead animals.

8.

Visceral hump is spirally coiled.

9.

Heart has single auricle.

10.

Nervous system is highly concentrated.

II.

Kidney is also single.

12.

Dioecious. Males have projecting muscular penis.

13.

Few species of Murex are destructive to oyster beds.

14.

It is also used for producing worshipping sound as Shankh.

Habit and Habitat It is a marine active and carnivorous gastropod.

Distribution It is found both in tropical and temperate seas.

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285

9. DORIS Classification

}

Phylum

Mollusca

Class

Gastropoda

Sub-class

Opisthobranchia

Have one gill, one auricle and one nephridium but display detorsion. Reduction and loss of shell and mantle cavity common. Many are secondarily and bilaterally symmetrical. Head commonly bears two pairs of cephalic tentacles. Buccal cavity with a pair of jaws. Hermaphroditic. Mostly marine.

Order

Nudibranchia

Adults naked, without mantle cavity and shell. Nudibranchs or sea slugs.

Genus

Doris mouth

foot

head

mantle

Characters same as of Patella.

Comments I.

Doris is commonly called as sea lemon.

2.

The body is bilaterally symmetrical, short, flat, and more or less ovoid with convex dorsal surface.

3.

It is purplish brown.

4.

Skin is tough and contains calcareous spicules of various types arranged symmetrically.

5.

Ventral surface bears mouth, head, tentacles and mantle.

6.

Head bears a pair of short retractile tentacles or rhinophores.

Fig. 2.252 Doris

7.

Foot is ventral with a broad sole for mantle.

8.

The mantle is usually pigmented having dorsal tubercles or calcareous spicules.

9.

The anus lies mid-posteriorly and is surrounded by secondary branchiae.

10.

Digestive gland unbranched compact mass.

II.

Nervous system of euthyneurons type.

12.

It exhibits complete detorsion as shown by the absence of shell, mantle and ctenidium.

13.

Monoecious.

14.

The gonopore is asymmetrically placed on the right side of the body.

15.

Cerata are lacking.

Habit and Habitat It is a sluggish marine and curious gastropod found under stones at low tide mark and between weeds. It feeds on the encrusting organisms like sponges.

Distribution Cosmopolitan.

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10. AEOLIDIA or AEOLIS or EOLIS Classification Same as that of Doris.

Comments

Fig. 2.253 Eo lis.

I.

Aeolidia is commonly known as sea slug.

2.

Shell, mantle and true gills absent.

3.

Escape swimming is a common ability.

4.

Up to 5 cm, elongated depressed body, tapering behind, gray or orange, yellow, red coloured with brown or white spots.

5.

Secondary gills present, arranged in a circle around the posteriorly situated anus.

6.

Many species have skin glands that produce sulphuric acid or a non acidic noxious substance that repels potential predators, especially fishe~.

7.

Some species have spicules embedded in the mantle.

8.

The dorsal body surface is greatly increased in many nudibranchs by numerous projections called cerata.

9.

Cerata are club shaped or branched.

10.

Head bears two pairs of cylindrical retractile tentacles and sessile eyes at the base of the posterior pair of tentacles.

II.

Foot is muscular and ventral and serves for locomotion.

12.

Hermaphroditic. Common gonad is protrandric.

Habit and Habitat It is a slug-like marine gastropod, living among seaweeds and under stones between tide lines. It usually inhabits shallow waters.

Distribution Found in U.S.A, Europe and Rhodes Island to Arctic ocean.

11. APLYSIA

Classification Phylum

Mollusca

Class

Sub-class

Gastropoda Opisthobranchia

Order

Aplyriacea

Genus

Ap/ysia

Characters same as that of Doris.

Sea hares. Large opisthobranchs with more or less bilaterally symmetrical external forms. Reduced shell buried in mantle; gill and mantle cavity present, foot with lateral parapodia.

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287

Comments anterior tentacle penis rhinophore

I.

It is commonly called as sea hare.

2.

The body is soft, slimy, fleshy and greenish or whitish in colour. Body with a thin flexible plate-like shell almost completely covered by mantle. Anterior end bears head and neck. Head bears two pairs of tentacles, the anterior being larger and ear shaped, while the posterior pair is olfactory, each bearing an eye at their bases. Mantle cavity opens on the right side with the ctenidium pointing backwards.

3. 4.

5.

opening of shell sac ctenidium

Anus is posteriorly located. Visceral mass raised into a prominent hump. 9. Foot broad and ventral and contains a pair of lateral fleshy out growths, the parapodia which aid in swimming. Foot is pointed posteriorly. 10. Mantle's wall contains a gland which secretes a Fig. 2.254 Aplysia purple pigment. Bisexual (Monoecious) with a single gonoduct and single aperture. It feeds mainly on the sea weeds. Shell is internal and rudimentary. parapodium

II. 12. 13.

6.

14. 15.

7.

8.

Foot terminates in tail. Single gill is present in the mantle cavity.

Habit and Habitat It is a marine gastropod found crawling among seaweeds. It is having remarkable power of colour changings according to the surroundings.

Distribution It is found in India, Asia, West Indies and on the Florida Coast.

12. HELIX Classification Phylum

Mollusca

Class

Gastropoda

Sub-class

Pulmonata

Characters same as that of Patella. Evolved from Prosobranchia; It includes land snails; the gills have disappeared and the mantle cavity modified into lungs. Nervous system concentrated and symmetrical. Shell usually present, but operculum lacking. Hermaphroditic.

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Non-Chordate (Invertebrate) Zoology Practical

Order

Stylommatophora

Genus

Helix

shell

Pulmonates with two pair of tentacles. the upper pair bearing eyes at the tip. Terrestrial.

Comments

anus

1. Helix is commonly called as Garden Snail. 2. Body is enclosed in a shell and consists of head, foot and the visceral hump. anterior tentacle

,::~W~~~~~~~=~;}!=~!;::'.·opening of headfootl

genital opening

pedal gland

3. The thin smooth shell with prominent lines of growth is external and heliciform with a low conical spire, measuring about 4 em in length.

Fig. 2.255 Helix. 4.

Head bears two pairs of tentacles and mouth. Posterior pair of tentacles has oculiferous eyes while the anterior is olfactory in function.

S.

The mouth is having three distinct lips and well developed radula.

6.

Respiration by pulmonary sac, since gills are absent.

7.

Hermaphroditic.

8.

Negatively phototropic.

9.

Herbivorous.

10.

The vagina contains an oval dart sac, which secretes calcareous spicules. When two snails are interwined, one drives its spicules dart into the body wall of the other.

I I.

Some species viz. H. pomatia are edible.

Habit and Habitat Helix is a terrestrial mollusc and found in damp places. In winter it hibernates in the soil.

Distribution Commonly found in palearctic region but less abundant in U.S.A.

13. LIMAX

Classification Same as that of Helix.

Comments I.

Limax is commonly called as grey slug.

2.

Shell reduction or loss has occurred independently a number of times, therefore. this is called as slug. Shell is buried within the mantle.

3.

Body is elongated and differentiated into head, foot. and visceral hump.

Study of Museum Specimens and Slides of Different III vertebrate Phyla anterior .tentacle

4.

Head bears two pairs of retractile tentacles.

5.

The posterior pair of tentacles consist of black eyes at their tips.

6.

The tentacles are non invaginating within head.

7.

Foot is well developed, blunt anteriorly and tapering posteriorly.

8.

The pneumostome is usually a conspicuous opening on the right side of the body.

9.

Visceral hump is elongated, flattened and pointed posteriorly.

eye

mantle position of internal shell

289

10. Ctenidium absent. II. Pulmonary aperture lies on the right side of the mantle. 12. Nocturnal and herbivorous.

13. Hermaphroditic.

Habit and Habitat Fig. 2.256 Limax

Limax is cosmopolitan in distribution. It is a terrestrial form found in cultivated lands, gardens and moist woody regions.

Distribution It is especially found in India, Europe and U.S.A (California).

14. PLANORBIS

Classification Same as that of Helix.

Comments I. This animal is enclosed in black, stout and spirally coiled shell. tentacle

2. The shell is somewhat grey, sinistral and discoidal having a depressed or flattened spire.

eye shell

3. The head is small with foliform tentacles and a pair of eyes.

4. The mantle lobe outside the lung or pulmonary cavity is modified into a functional gi II.

5. The foot is long and muscular. 6. Dioecious.

7. The eggs are laid in the form of gelatinous masses on stones and aquatic plants. Fig. 2.257 Planorbis

9.

8. Planorbis undergoes aestivation during summer.

It serves as an intermediate host for larval stages of liver flukes and schistosomes.

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Non-Chordate (Invertebrate) Zoology Practical

Habit and Habitat It is found in freshwater ponds attached to the submerged plants.

Distribution Commonly found in India and Europe.

15. LYMNAEA

Classification Phylum

Mollusca

Class

Gastropoda

Sub-class

Pulmonate

Order

Basommatophora

Genus

Lymnaea

Characters same as that of Helix.

Pulmonates with one pair of tentacles; eyes located near tentacle base. Primarily freshwater forms and ' few marine.

Comments 1. It is commonly called as pond snail.

foot

eye

Fig. 2.258

Limnaea.

2.

Shell is thin. horny and fragile with an acute sharp.

3.

Body whorl is large while the penultimate whorl and apex are small.

4.

Body whorl opens outside by a wide aperture which is covered by operculum.

5. Tentacles are broad and flat bearing eyes at the base. 6. The tentacles are noninvaginating.

7.

The foot is rounded behind.

8.

Respiration aerial by pulmonary sac.

9.

Species of Limnaea are resistant to freezing. They can servive for several weeks in ice.

10.

Some species like L. truncatula serves as an intermediate host for the larval stages of the liver fluke.

Habit and Habitat Limnaea is a typical freshwater snail. found in ponds. lakes and streams.

Distribution Cosmopolitan.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

291

16. PECTEN Classification Phylum

Mollusca

Characters same as that of Chitin.

Class

Bivalvia or Pelecypod a

It includes such common forms as clams, oysters, and mussels. Bivalves are laterally compressed and possess a shell with two valves, hinged dorsally that completely enclose the body. The foot is also laterally compressed Hence the name Pelecypoda - hatchet foot, the head is poorly developed.

Order

Pseudolamellibranchiata

Shell valves frequently unequal Gills form vertical folds; foot rudimentary; single large posterior adductor muscle present.

Genus

Pecten

Comments umbo

1.

Pecten is commonly called as scallop.

2.

It is enclosed by two unequal .bivalved

shell.

Fig. 2.259 Pecten. Dorsal view.

3.

Shell is beautifully ribbed by radiating lines.

4.

Each valve bears a dorsal protuberance called the umbo.

5.

The two valves are attached by an elastic protein called the hinge ligament.

6.

Foot is highly reduced.

7.

Two large and crescentic gills are present.

8.

The mantle is tentaculiferous and it encloses viscera.

9.

Numerous eyes with stalk are present at regular intervals along the edges of t~e mantle.

10.

It feeds on microorganisms caught during respiratory water current.

11.

The hinge line straight and toothless.

12.

After removing shell, large adductor muscle, gill, gonad, and velum are marked.

13.

Pectens are peculiar in having two layers of photo-receptors, one rhabdomeric and other of the ciliary type. Behind the retina is a layer of reflecting pigment (tapetum) which bounces the incoming light buck to the ciliary receptor layer, where the image is formed. The function of the rhabdomeric receptor is uncertain.

14.

Monoecious. Ovary is pink and testis is cream coloured.

Non-Chordate (Invertebrate) Zoology Practical

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Habit and Habitat It is marine, free-swimming and cosmopolitan in distribution. It is abundant among eel grass and over mud flats. It lives gregariously on the sea bottom of about ten fathoms deep.

Distribution Commonly found in India and U.S.A.

17.0STREA Classification Same as that of Pecten.

Comments

Fig. 2.260 Ostrea.

I.

Ostrea is commonly known as edible oyster.

2.

Shell valves are irregl!lar, coarse and thick, variable in shape often with folded layers.

3.

The two valves of the shell are unequal. The left being large. thick, convex, and attached to the substratum by byssus while the right is small and flattened forming lid.

4.

Foot is absent.

5.

Single adductor muscle i.e. monomyarian is divided into two parts.

6.

The umbo and hinge at forward end.

7.

Heart with two fused auricles.

8.

Ostrea functions alternatively as males and females. Most of the young oysters are male but later on roughly 50% of them change into female.

9.

Fecundity is very high.

10.

Mortality of the eggs is also high.

I I.

Development includes veliger larva. After settling down, it is called "spat".

12.

Ostrea edulis is used as food in many countries.

13.

Uni or bisexual.

Habit and Habitat It is a sedentary bivalve found attached to rocks or stones, abundantly found in shallow and brackish water and in all seas except colder ones.

Distribution It is found in Atlantic and Pacific coasts, India and Gulf of Mexico to Massachusetts.

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293

18. PINCTADA VULGARIS (Indian Pearl Oyster)

Classification Same as that of Pecten.

umbo

ear-like

Comments I.

Pinctada vulgaris is commonly kl'own as Indian Pearl Oyster.

2. The shell valves are unequal and the hinge line is straight. 3. The left shell valve is large, convex and permanently attached to the rocks. 4. The right shell value is smaller and thinner and covers the viscera. 5. The surface of the shell is coarse, irregular containing radiating bands. L -_ _ _ _ _ _ _ _ _ _ _----'

Fig. 2.261 Pinetada vulgaris.

9.

6. Single adductor muscle present. 7. Left and right mantle lobes are free. 8. Oyster's shell secretes pearls whenever any organism enters the shell and cause irritation.

These are cultivated in Pearl oyster industry.

10.

Most of the germ pearls are obtained from pearl oyster.

II.

Feeding is similar to that of clams.

Habit and Habitat Pinctada is widely distributed in sea water except in cold zones.

Distribution It is very common in the Gulf of Kutch, tropical and temperate seas, Pacific and Atlantic coast.

19. MYTILUS

Classification Phylum

Mollusca } Pelecypoda or Bivalvia

Class Order

Genus

Filibranchia

-

Mytilus.

Characters same as that of Pectell. Anterior adductor muscle reduced or absent; single pair of plate-like gills; foot small and byssal gland present.

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Non-Chordate (Invertebrate) Zoology Practical

Comments I. Myti[us is commonly known as sea mussel. 2. The shell of two equal values which are pointed in front and rounded behind. 3. Toothless hing but may bear crenulations. 4. Mantle is bilobed and forms an exhalent siphon posteriorly. fool

5. Foot cylindrical and elongated with byssus.

byssus

' - - - - - - - - - - - - - - - - - - - ' 6. The shell is marked with lines of growth. Fig. 2.262 Mytilus. 7.

The byssal filaments situated in byssal cavity are formed by byssal gland or byssogenous apparatus.

8.

Anterior adductor muscle is weaker, while posterior adductor muscle is strongly developed.

9.

Beneath the posterior adductor muscle in the exhalent chamber, there is a patch of sensory epithelium usually called ospharidium considered as an organ of chemoreception.

10.

Gills. foot, kidney, heart and alimentary canal are well developed.

II.

The gills are lamelliform. Each gill is provided with gill filaments.

12.

A pair of simple eyes present.

13.

Dioecious. Gonads extend into the mantle.

14.

It is edible in Europe. Also in India, it is relished as food by poor fellows living at seacoasts.

Habit and Habitat Myti[us is marine, sedentary, filter feeder, found attached to the rocks between the tidemarks.

Distribution Cosmopolitan.

20. UNIO

Classification Phylum - Mollusca Class -

Bivalvia

Order -

Eulamellibranchiata

Genus -

Unio

}

Characters same as that of Pecten. Gill filaments united by interfilamentar and interlamillar junctions; two equal sized adductor muscle present; foot large; byssus small or absent.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

Comments

hinge ligament

6. 7. 8. 9. 10. II. 12. 13. 14. 15. 16. 17.

295

I. Unio is commonly known as freshwater mussel or clam. 2. Body is soft. bilaterally symmetrical and flattened. enclosed in an equal bivalved shell. 3. The periostracum is generally smooth and without rays. 4. The two valves of the shell are joined together by hinge ligament along the dorsal side. Fig. 2.263 Unio. 5. Mantle consists of two lobes corresponding to the two valves of the shell. Anterior and posterior adductor muscles are well developed of same size and are responsible for the opening and closing of the valves. Umbo is situated near the anterior end of the dorsal side. Posteriorly on lateral margins. there are two openings: smaller one is exhalent sipho.n and the larger one is inhalent siphon. Foot is large. muscular. and wedge shaped used for burrowing. The ctenidia are 'W' shaped. These perform respiration. Digestion is intra as well as intercellular. Circulatory system is of open type. Blood is blue because of the presence of haemocyanin. Excretion is carried out by organs of Bojanus (kidneys) or by Keber's organ. Dioecious. but there is no sexual dimorphism. Development includes Glochidium larval stage. The shells are used in making buttons and ormanental sets.

Habit and Habitat It is found at bottoms in ponds. lakes. streams, and rivers, burried in the sand or mud. It is omnivorous and feeds by filter-feeding method.

Distribution Commonly found in India, Europe, Atlantic slope and U.S.A.

21. MYA Classification Same as that of Unio.

Comments I. 2. 3.

It is commonly known as mud clam and morphologically resembles to unio. Body is covered by two equal shell valves joined by hinge ligament. The shell is delicate and thin.

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Non-Chordate (Invertebrate) Zoology Practical posterior end

foot

umbo

shell

exhalent and inhalent siphons

4. Periostracum is wrinkled. 5. Whitish Umbo is directed forward. 6. Lines of growth clearly visible on the shellvalves. 7. The hinge is weaker than Un:o and valves may be separated easily. 8. Foot is feebly developed and without byssus threads in adults. 9. Inhalent and exhalent siphons are very long. partly retractile and covered with periostracum. 10. Since the siphons are long. it is also known as long fleck clam.

Fig. 2.264 Mya.

II.

Eyes, tentacles and radula absent.

12.

Pallial sinus large.

! 3.

Dioecious.

14.

It constitutes the food of walrus.

Habit and Habitat It is marine and found bwrowing into the mud or sand near the sea coast.

Distribution It is found in Arctic ocean to Cape Hatteras, San Fransico and Europe.

22. SOLENOCURTUS Ciassification ~

_ _ _ inhalent siphon

Same as that of Unio.

Comments 1. Solenocurtus is commonly known as razor fish or razor shell, or

razor clams.

'--_--.".--.,.-=,-;:-_~

Fig. 2.265 Solenocurtus.

2. Shell values are of equal size with parallel margins with lines of growth and cover part of the body. 3. Inhalent siphon is large and exhalent siphon is small and thus are unequal. 4. The foot is strong, large, cylindrical and muscular boring organ without byssus. It swells with the inflow of blood and protrudes from anterior end. 5. Muscles are isomyarian. Both adductor muscles are of equal size. 6. The pallial line forms the sinuses. 7. Mantle cavity is elongated tube like having a pair of long narrow gills. 8. Solenocurtus swims backwards by jerking movements of the foot. 9. Mantle lobes are fused ventrally to form a tubular mantle cavity.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

'.'

297

Habit and Habitat It is a marine burrowing bivalve.

Distribution It is found in India and U.S.A.

23. ENSIS Classification Same as that of Unio. exhalent siphon

inhalent siphon

Comments I. It is commonly known as razor clam or razor shell. 2. Shell is thin, long and narrow consisting of two equal valves. 3. Shell contains parallel margins and lines of growth and have truncated ends. 4. Both siphons i.e. exhalent and inhalent are short but inhalent is larger than exhalent siphon. 5. Foot is more or less cylindrical and used in burrowing. 6. Mantle cavity is elongated tube like and contains a pair of long narrow gills. 7. The pallial line is sinupalliate i.e. it forms sinuses. 8. Ctenidia are paired. 9. Muscles are isomyarian. 10. It can swim backwards by jerks of the foot.

Habit and Habitat Ensis is marine and found burrowing in the sand at low tide Fig. 2.266 Ensis.

mark.

Distribution It is found is India and U.S.A.

24. TEREDO Classification Same as that of Unio.

Comments I.

Teredo is commonly called as shipworm.

2.

Body is cylindrical, vermiform and elongated.

3.

The shell is reduced and consists of two small valves enclosing only the anterior region of the body, provided with a rough and ridged surface, serves as effective cutting and boring organ.

298

Non-Chordate (Invertebrate) Zoology Practical 4.

Foot is very much reduced.

5.

Mantle is tube like and opens anteriorly.

6.

Mantle cavity is long and contains a pair of elongated ctenidia or gills.

7.

The two long siphons are united most of their lengths and provided with calcareous pellates for protection.

8.

The siphons separate at a point called pallet which acts as operculum.

9.

Teredo bores into submerged wood reducing it into saw dust by the rotatory action of the two shell values.

10.

It feeds on the saw dust which is digested by thl': enzymes secreted by the digestive glands.

II.

The stomach is provided with a caecum for saw dust storage.

12.

Teredo can easily digest cellulose and lignin.

13.

Both adductor muscles are well developed.

14.

Causes great damage to ships and boats.

lmanlle

pallets

inhalent siphon

body

shell valves

B

Fig. 2.267 Teredo. A - A piece of wood borrowed by Teredo. B - Entire animal.

Habit and Habitat Teredo is a marine bivalve, living in burrows made in the submerged wood of the ships and boat etc.

Distribution It is found in India. U.S.A. and Europe.

25. VENUS

Classification Same as that of Unio.

Comments I.

Venus is commonly known as hard-shelled clam or little neck clam.

2.

The shell is composed of two symmetrical halves.

Study of Museum Specimens and Slides of Different Invertebrate Phyla 3.

Dorsally two shell valves are joined by a hinge ligament.

4.

Shell bears lines of growth and is ovate or heart shaped, anterior end short, posterior end rounded.

5.

On either sides of the hinge ligament, there is a protruded Umbo.

6.

Siphons short, unequal and more or less separated.

7.

Mantle margin fringed.

8.

Though it lies buried few inches, it keeps its siphonal end bit above the surface of the mud in order to maintain a current of sea-water through its body for feeding purpose,

Fig. 2.268 Venus. Inner surface of left value.

9.

299

The lunule is a heart-shaped configuration which lies anterior and ventral to the beak.

10.

Spawning occurs during rainy. season. Millions of eggs and sperms are produced.

II.

Fertilization is mostly external.

12.

The young clam lies dormant for two years.

13.

It is extensively used as food and for manufacture of wampum.

Habit and Habitat It is a marine and burrowing form. Mode of feeding is ciliary.

Distribution It is found in India, Europe and U.S.A. (Gulf of St. Lawrence to Taxes).

26. DENTALIUM

Classification Phylum.

Mollusca

Characters same as that of chiton,

Class •

Scaphapoda

Burrowing marine molluscs that are popularly known as tusk or tooth shells. Both ends of the tube are open. Eyes, tentacles and gills absent.

Genus·

Dentalium

Comments I.

Del/talium is commonly known as Elephant's tusk shell.

2.

The name is derived from the shape of the shell which is elongated. cylindrical tube usually shaped like an elephant's tusk.

3.

The shell measures about 15 em in length.

300,

Non-Chordate (Invertebrate) Zoology Practical 4.

Indian species of Dentalium is brilliant jade green.

5.

The body is greatly elongated along the anterior and posterior axis.

6.

The head and foot project from the larger and anterior aperture of the shell.

7.

It lives buried in sand, head downward with the body steeply inclined and only the small, posterior aperture projects above the surface.

8.

Adapted to a burrowing habit, the head is reduced to a short, conical projection or proboscis, bearing the mouth.

9.

Mouth is surrounded by a circlet of retractile tentacles, the captacula with adhesive knob (sucker like ends). which drive food particles to mouth.

10.

Foot is long and cone-shaped and is projected into the sand. It protrudes through the anterior opening of the shell and is used in burrowing.

) I.

The mantle cavity is large and extends the entire length of the ventra) surface.

12.

The posterior aperture serves for both exhalent and inhalent water currents.

~_ _ dorsal

shell opening

caplacula

Fig. 2.269

Dentalium. 13.

Water slowly enters the mantle cavity as a result of mantle ciliary action and perhaps foot protraction.

14.

There are no gills. Exchange of gases takes place through the mantle surface.

15.

Dentalium feeds on microscopic organisms, especially forams, in the surrounding sand and water.

16.

Thread like tentacles i.e. captacula has an adhesive knob at the tip and extends into the sand to capture food.

) 7.

Small food particles are conveyed back to the month by tentacular cilia, larger particles grasped by the tentacles tips and brought to the mouth by retraction of the tentacle.

) 8.

The buccal cavity contains a median jaw and a well developed radula with large tlattened teeth for ingestion and crushing of the prey seized by the captacula.

19.

The in~estine empties through the anus situated at the base of foot into the mantle cavity.

20.

Circulatory system is reduced to a system of blood sinuses and there is no heart.

2).

The nervous system exhibits the typical molluscan plan i.e. it consists of cerebral. pleural, and pedal ganglia.

22.

Eyes and osphradia usually absent.

23.

A pair of nephridia is present, and the nephridiopores are located near the anus.

24.

It is dioecious.

25.

The unpaired gonad fills most of the posterior part of the body.

26.

The eggs are shed singly and are planktonic and fertilization is external.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

301

27.

There is a free-swimming trochophore larva succeeded by a bilaterally symmetrical veliger.

28.

This scaphopod may be regarded as an offshoot of the ancestral bivalve stock.

29.

The tusk shell is of economic importance. The ancient red Indian tribes of America used tusk shells as currency.

Habit and Habitat Dentatium is marine living in clean sand upto 2,500 fathoms.

Distribution Found in all seas except the polar.

27. LOLIGO Classification Phylum

Mollusca Capbalopoda

Class

Characters same as that of Chitin. Includes cuttle fish, squids, octopods and nautili. Except few cephalopods like octopus (bottom dwelling habit), the class as a whole is adapted for a swimming existence. Head projects into a circle of large, prehensile tentacles or arms. Cephalopods have attained the largest size among invertebrates. The class first appeared in the cambrian period.

Sub-class

Coleoidia or Dibrancbiata

Shell internal, reduced or absent. The eight or ten appendages bear suckers. One pair of gills and one pair of nephridia. Kidneys and hearts two each.

Order

Squids, shell or pen, a flattened blade or vane. Body elongated with ten arms and two tentacles.

Sub-order

Teutboidea or Decapoda Myopsida

Genus

Loligo.

Squids with a transparent corneal membrane over the eye.

Comments 1.

Loligo is commonly known as sea squid.

2.

The shell is reduced to a long, flattened, chitinous plate called a pen or gladius.

3.

The fastest movement is achieved in backward escape swimming.

4.

They attain the greatest swimming speeds of any aquatic invertebrate, upto 40 km per hour.

5.

The fleshy body is long and tapered posteriorly, dorsoventrally flattened and is distinguished into anterior head, having arms and tentacles and a posterior pointed long visceral hump with a pair of posterior lateral pointed fins functioning as stabilizers, rudders, and even for propulsion at low speeds.

6.

Mantle is thick and muscular, encloses the visceral mass and mantle cavity.

7.

It is metachromatic having colour changing habit.

Non-Chordate (Invertebrate) Zoology Practical

302 suckers

oral arms

8. The foot is represented by 10 arms, tentacles, and siphon. 9. Eight arms are short, stumpy and non - retractile, while two are long slender, and retractile tentacles (having suckers) used for capturing the prey. 10. Funnel is a muscular tube.

-~--,,:-,,:----head ~--..I-'---eye

II.

Ventral siphon is formed hy the modification of the foot.

12. In males, one of the eight arms is modified as copulatory organ and show hectocotylization.· 13. Loligo is highly adapted for raptorial feeding and a carnivorous diet. 14. Highly developed eyes contain cornea and can locate the prey. 15. There are two ctenidia, two nephridia, and two auricles.

16. Digestion is entirely extracellular. suckers

17. The circulatory system is closed type. 18. The blood contains a haemocyanin (pigment containing copper) that loads at the gills and unloads at the tissues at relatively high oxygen pressure. 19. Nervous system cephalization.

Fig, 2.270 Loligo.

•

shows

great

20. An ink sac is also present and serves for defence. Ink is alkaloidal in nature.

21.

Loligo is dioecious. A single gonad is located in the posterior part of the body.

22.

Spermatophores are received by the mantle cavity.

23.

Nidimental gland is present whose secretion surround the eggs in a gelatinous mass.

24.

Large number of Loligo come together to copulate and spawn at the same time and a "Community File" of egg strings is formed on the bottom. Death of the adult usually follows soon after spawning.

25.

Usually the development is direct. There is no larval stage.

26.

Loligos are having short lives (one to three years).

27.

Loligo has food value. It is eaten by chinese and Italians.

The males insert their modified arms containing sperms in the cups (suckers) of female's vagina which breaks inside during copulation. However. a new anterior part regenerates afterwards.

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303

Habit and Habitat Loligo is a marine fast swimmer cephalopod.

Distribution It has cosmopolitan distribution. Mostly found in warm seas and coastal shallow or deep waters.

28. SEPIA

Classification Phylum Class Sub-class

Mollusca Cephalopoda

Order

Coleoideal or Dibranchiata Sepioidea

Genus

Sepia

Characters same as that of Loligo.

Cuttle fish and sepioles. Eight arms and two tentacles. Shell with septa or shell greatly reduced or lost. Body mostly short and broad or saclike.

Comments

suckers on oral arms

I.

Sepia is commonly known as cuttle fish.

2. Sepia is well adapted for swimming by water jet. These are versatile swimmers but not as fast as the more streamlined squids.

3. The colour is brownish with white spots and head eye collar

trunk

stripes. The fins are violet and the chromatophores are present in the deeper layers of integument over the entire surface.

4. The body is bilaterally symmetrical, dorsoventrally flattened, brownish, fleshy and differentiated into head, and visceral hump or trunk.

5. The head region contains siphon and eight arms having many rows of stalked suckers and two large tentacles having suckers only at tips. 6. Siphon, tentacles and arms represent foot, 7. The shell of sepia is internal and helps in providing buoyancy.

Fig. 2.271 Sepia.

8. Spaces between the thin septa contain fluid and gas - largely nitrogen. By regulating the relative amounts of fluid and gas, the degree of buoyancy can be varied which decreases in light and increases in the dark.

Non-Chordate (Invertebrate) Zoology Practical

304

9.

During the day, sepia lies buried in the bottom; at night it becomes active, swimming and hunting for food.

10.

The digestive gland consists of diffused pancreas and paired solid liver.

II.

The eye is of the direct type as in the vertebrates.

12.

Mantle is thick and muscular, enclosing a large mantle cavity on the ventral side which contains the viscera.

13.

Funnel is tubular and opens into the mantle cavity.

14.

One pair of large plume-shaped ctenidia or gills, one on each side of the man lie cavity performs the respiratory function.

15.

Single kidney is an excretory organ.

16.

A pear-shaped ink sac is present over the posterior ventral surface which opens into the rectum just behind the anus.

17.

The ink gland secretes a brown or black fluid containing a high concentration of melanin pigment. When an animal is alarmed, the ink is released through the anus and the cloud of inky water is formed to camouflage the predator or enemy.

18.

Dioecious.

19.

Single gonad located in the posterior part of the body.

20.

In Sepia several rows of smaller suckers from an adhesion area for the transport of spermatophores.

21.

Before copulation, male sepia presents a striped colour pattern and establishes a temporary bond with a female, swimming above her.

22.

Sepia deposits its eggs singly but attaches them by a stalk to sea - weed or other objects.

23.

The eggs are very large and may reach 15 mm in diameter.

24.

Mostly, development is direct.

Habit and Habitat Sepia is a marine form found in the shallow water. Sepia swims over the bottom and feeds on surface inhabiting invertebrates, especially shrimps and crabs. Sepia may rest at the bottom and wait for passing pre~

Distribution Cosmopolitan in distribution. It is especially found is region.

Ind~a,

Europe, and Mediterranean

29. OCTOPUS Classification Phylum Class Subclass

Order

Mollusca Cephalopoda Coleoidea or Dibranchiata Octopod a

} Characters same as that of Loligo.

Body globular; possess eight arms. Shell usually absent.

Study of Museum Specimens and Slides of Different Invertebrate Phyla Sub order

Incirrata

Genus

Octopus

305

Octopods without fins.

plate:

c siphon

arm B

Fig. 2.272 A - Octopus, B - Lateral view of Octopus C - Octopus showing Hectocotylized arm.

Comments I.

Octopus is commonly known as Devil fish.

2.

It has reverted to more benthic habits.

3.

The body is globular and baglike.

4.

Fins are absent.

5.

The mantle edges are fused dorsally and laterally to the head. resulting in much more restricted aperture into the mantle cavity.

6.

Although this animal is capable of swimming by water jets with arms trailing. it more frequently crawls about over the rocks around which it lives.

7.

Globular body is differentiated into head and visceral hump.

8.

Shell is absent completely.

9.

Nidamental glands absent.

10.

Mantle cavity and visceral mass are enclosed by mantle.

Non-Chordate (Invertebrate) Zoology Practical

306 II.

Head contains a pair of eyes and eight elongated equal arms, having two rows of sessile cupped, suctorial pockets or suckers on inner side.

12.

In male octopus one of the arms is modified as spoon-shaped intromittent organ or hectocotylized arm.

13.

The arms are elongated, webbed and similar; used to pull the animal along or anchor to the substratum.

14.

The suckers present at arms are stalkless and lack horny rings and hooks.

15.

A radula is present, but more important is the pair of powerful, beak like jaws in the buccal cavity. The beak can bite and tear off large pieces of tissue which are then pulled into the buccal cavity by a tongue like action of the radula and finally swallowed.

16.

Two pairs of salivary glands empty into the buccal cavity. The posterior salivary gland secretes poison.

17.

Octopus leaps on motile prey such as crab. It may take away home several animals, all paralyzed by salivary toxin for consumption.

18.

Digestive glands comprise salivary gland, spongy diffused pancreas and large solid liver.

19.

Paired nephridia present.

20.

Circulatory system closed type.

21.

High degree of development of nervous system.

22.

Eye is of direct type.

23.

Octopus can discriminate objects as small as 0.5 cm from a distance of 1.0 metre, which is of considerable advantage in catching prey (Wells, 1978).

24.

In octopus. a large ink sac or gland opens into the rectum just behind the anus. The sac or gland secretes a black fluid containing a high concentration of melanin pigment, which is stored in the reservoir.

25.

When this animal is alarmed, the ink is released through the anus and the cloud of inky water forms a "dummy" confusing the predatvr.

26.

Dioecious. Single gonad is located at the posterior of the body.

27.

Octopus forms egg clusters that resemble a bunch of grapes and are attached with in rocky recesses.

28.

The females of Octopus vulgaris die after brooding their eggs.

29.

Development is mostly direct.

30.

Octopus have short lives. Octopus vulgaris dies after one brood, when it is two years.

31.

Giant Octopus can hold man in its arms.

Habit and Habitat Octopus is marine, deep sea form found at the bottom. It is purely carnivorous. It feeds on crabs, fishes, and other molluscs. It has colour changing habit.

Distribution Cosmopolitan.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

307

30. ARGONAUTA

Classification Same as that of Octopus.

Comments I. Argonauta IS commonly called as paper nautilus because of its thin and fragile dry shell.

2. It is not a nautilus but more closely associated to Octopus. 3. Sexual dimorphism is remarkable and well marked.

Fig. 2.273 Argonauta.

4. Male about 2.5 cm in length and without sheli. while female about 20-25 cm in length and possesses a thin. transparent unilocular shell which is secreted by extremities of two dorsal arms and is used for protection of eggs.

5.

Mouth is surrounded by 8 arms and elongated arms are provided with suckers.

6.

Eyes and funnel are well developed.

7.

Third arm in the male is hectocotylized and is applied for conveying spermatophores in the mantle cavity of female.

8.

The two dorsal arms of the female secrete a beautiful calcareous. bivalved case intG which the eggs are deposited which is carried about and serves as a brood chamber.

9.

Sperm storage chamber also present.

10.

Two plume -

like ctenidia and two kidneys are present.

11.

The body is short and rounded.

12.

The suckers have no horny rings.

13.

Dioecious.

Habit and Habitat Argoflauta is a marine cephalopod. Female lives in deep waters and comes up on surface only during the spawning season.

Distribution It is found in all warmer seas.

Non-Chordate (Invertebrate) Zoology Practical

308

31. NAUTILUS Classification Phylum

Mollusca

Class

Cephalopoda

Order

.Nautiloidea

Genus

Nautilus

}

Characters same as that of Loligo. Posses external shells. Shell may be coiled or straight; Sutures not complex. Tentacles sucker less. Two pairs of gills and two pairs of nephridia present. Ink gland absent. They appeared in cambrian period.

Comments empty chambers

I.

Nautilus is popularly known as pearly nautilus.

2.

Body is enClosed in a calcareous spirally coiled many chambered shell.

3. The shell is coiled over head. 4. The shell is divided by transverse septa into internal chambers. last body chamber

Fig. 2.274 Nautilus.

5. As the animal grows, it periodically moves forwards and the posterior part of the mantle secretes a new septum. 6. Each septum is perforated in the middle, and through the opening a cord of body tissue called the siphuncle, extends from the visceral mass.

7.

Gas and fluids are exchanged through siphuncle to the chamber and secretes gas into the empty chambers, making the shell buoyant and allowing the animal to swim or float.

8.

The shell is composed of an outer porcelaneous layer, containing prisms of CaCO, in an organic matrix, and an inner nacreous layer.

9. 10.

Shell measures upto 20-25 cm. Shell is differentiated into a large body chamber, containing head and tentacles and several small coiled chambers having p.olongation of visceral mass called as siphuncle.

II.

Nautilus is tetrabranchiate, having 2 pairs of ctenidia and two pairs of kidneys and

12.

Dioecious.

13. 14.

Body consists of head bearing eyes and a system of tentacles and a sac like trunk.

also two pairs of auricles.

Mouth is situated at the end of the head and surrounded by 38 lobes bearing two rows of retractile tentacles without suckers but have transverse ridges.

IS.

Outer row of tentacles borne on a muscular ridge forming the hood which serves as an operculum.

16.

Arms and suckers absent.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

309

17.

Ink gland and chromatophores absent.

18.

The large stalked eyes are open vesicles without cornea or lens but having a large number of photoreceptors.

19.

The siphonal funnel is formed Of two separate folds,

20.

Salts are actively pumped in by the living tissue of the siphuncle. Water then passively diffuses out of the chamber and is replaced by gas, chiefly N2 - that diffuses into the vacated space.

21.

Except when feeding, Nautilus swims backwards at about the same speed as a man doing a slow hreast stroke (Haven. 1972).

22.

Nautilus is a scavenger and predator over the bottom. catching decapod crustaceans. When feeding. it swims forward, searching with extended tentacles.

23.

The oesophagus is muscular and conducts food by peristalitic action into the crop which is an expansion of one of the oesophagus.

24.

Statocyst present.

25.

Osphradia are present too in Nautilus.

26.

Finger like copulatory organs present on head.

27.

The eggs are deposited and attached to the substratum singly within rather elaborate capsules.

28.

It is used extensively for ornamental purposes.

Habit and Habitat It is a gregarious, nocturnal deep-sea form crawling over the bottom in troops at night time in search of food.

Distribution It is commonly found is Indian and pacific oceans.

NOli-Chordate (lnvertehrate) Zoology Practical

3/0

I STUDY

OF SLIDES

I

1. RADULA OF PI LA

/?'/(;f6z~/~\~V

outer inner marginal marginal

lateral

median rachidian

lateral

inner outer marginal, marginal

A

B

Fig. 2.275 A - Single row of teeth of radula. B - COtnJ - 'ete radula.

Comments I.

The radula is found on the surface of the buccal cavity of Pila.

2.

It serves for masticating or breaking the food.

3.

It is situated posteriorly in the buccal cavity over the odontophore.

4.

Radula is formed of a nap and a narrow strip or ribbon - shaped chitinous plate.

5.

It consists of seven recurved, horny teeth, arranged transversely in several rows.

6.

Each transverse row of radula consists of seven teeth including two marginals and a lateral on either side of a central tooth (median Rachidian). The dental formula is: 2:1:1:1:2 The posterior part of the radula lies in the radular sac, which is short-band like structure.

7. 8. 9. 10.

The wall of the radular sac consists of odontoblast cells, which secrete teeth of redula. The food is broken into small pieces by to and fro movements called chain saw movement (Huxley) of the radular teeth. Radula is operated by complex muscles.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

311

2. L.S. OSPHRADIUM OF PI LA Comments I. Osphradium acts as rheoreceptor and chemoreceptor. 2.

It is small lobe like structurc, attachcd to the mantle near the left nuchal lobe.

3. It is bipectinate consisting of 22-28 thick, oblong, fleshy leaflets arranged around a central axis. Fig. 2.276 Pila. L.S. Osphradium.

4. One end of the leaflet is attached to the mantle, while inner side is attached to the central axis.

5.

The side leaflets are smaller and the middle ones are larger.

6.

Osphradium is covered with epithelium.

7.

The epithelium consists of ciliated and non-ciliated supporting cells, mucocytes, glandular cells, and neurosensory cells.

8.

Besides serving to test the physical and chemical qualities of water, osphradium also helps in selection of food material.

3. GILL OF PILA Comments transverse pleats

afferent side

Fig. 2.277 A gil/lamella of Pita globosa.

7.

I.

Aquatic respiration in Pila is performed by gill or ctenidium.

2. 3.

It is monopectinate (comb-like). It is an elongated structure located on the right side of the branchial chamber hanging from its dorso-Iateral wall.

4.

It consists of a long ctenidial axis.

5.

The ctenidial axis is traversed hy an afferent blood vessel and an efferent hlood vessel.

6.

The efferent hlood vessel carries oxygenated blood from the gill to the heart.

The afferent blood vessel carries deoxygenated blood to the gill.

8.

The axis bears a long series of flat triangu}ar leaflets known as lamellae.

9.

The two free sides of the lamellae are unequal. The shorter side receives blood from the afferent vessel and is thus called afferent side while the other is called efferent side as from it the blood flows into the efferent vessel.

10.

In the middle the lamellae are larger and decrease in size towards the two ends.

312

Non-Chordate (Invertebrate) Zoology Practical II.

The anterior and posterior faces of each lamella are provided with transverse ridges containing branches of blood vessels.

12.

The ctenidium is innervated by nerves from the left pleural and surra-intestinal ganglia.

4. T.S. GILL LAMINA OF UNIO Comments I.

Each gill-lamina of Unio is composed of outer and inner lamellae. In T.S. it appears like a ladder.

2.

The two lamellae are connected together by inter lamellar junctions at regular intervals, and spaces formed by them are called as water tubes.

3.

Water tubes open in supra-branchial chamber.

4.

Each gill-lamella is composed of a series of thin vertical gill-filament which are connected to one another by horizontal bars or inter-filamentar junctions.

5.

Between the gill filaments are minute apertures called ostia which open into the water tubes.

6.

Gill filaments are supported by internal chitinous rods and are covered by ciliated epithelium. interfilamentar junclion

interlamellar junction,

outer lamella

~1":;''':. "/"I

.':' I

chitinous rod

gill tilments

ostium

Fig. 2.278 T.S. Gill Lamina Unio 7.

Gill lamellae are supplied with blood vessels i.e. they are of eulamellibranchiate type.

8.

Afferent and efferent branchial vessels are present on the outer edges of each interlamellar junction.

9.

Cilia present on gill surface aid in filter feeding.

10.

Water tubes present in gills provide space for developing eggs and consequent hatching into glochidia larvae.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

313

S. T.S. MANTLE AND SHELL OF UNIO Comments palisade layer inorgenio layer

lamelJated layer

I.

The shell is secreted hy the mantic.

2.

Shell is composed of inorganic and organic materials.

3.

Shell of Unio is composed of three layer: (i) Periostracu m (ii) Prismatic or ostracum (ii i)l'I acreous .

nacreous layer

Fig. 2.279 Unio. T.S. shell.

4. The outer most layer is called periostracum which is composed of organic matter consisting of translucent chitin like substance called as conchiolin.

5.

Outer most layer is thin and horny and greenish brown in colour.

6.

Middle layer is known as prismatic or ostracum consisting of tiny CaCO, prisms or plates.

7.

The prisms are separated by thin layer of conchiolin, arranged vertically.

8.

Inner most layer is known as nacreous layer or mother of pearl. It consists of CaCO, and conchiolin arranged parallel to the surface.

9.

Mantle is also composed of three layer.

10.

Outer layer consists of nacre-secreting epithelial cells and lies close to the nacre layers.

II.

Middle layer of mantle comprises thick connective tissue.

12.

Inner most layer of mantle is composed of single layer of ciliated epithelium.

6. UNIO: T.S. THROUGH ANTERIOR REGION Comments I.

Section reveals shell, mantle, foot, and other structures of anterior region.

2.

Mantle is associated with gill laminae (external and internal).

3.

Each gill lamina is made up of two folds-outer and inner gill lamellae.

4.

Foot, gonads, nephridia and intestine present anteriorly.

5.

Keber's organ, pericardial cavity, rectum, anus and ventricle are also observed in the section.

Non-Chordate . (Invertebrate) Zoology Practical

314

ligament

gill·lamina

/J--'--

left shell valve

Fig. 2.280 Unio. T.S. Anterior region.

muscle fibres

Study of Museum Specimens and Slides of Different Invertebrate Phyla

315

7. UNIO: T.S. THROUGH MIDDLE REGION Comments This section shows gonads. outer and inner gill laminae and water tubes. besides shell. foot, mantle. ventricle. branchial chamber. reclum and nephridium.

auricle -~u.~ 'Ta':::::l'4

suprabranchial chambers

bladder kidney

outer lamella of outer gill lamina

Infrabranchial chamber of mentle cavity

Fig. 2.281 Unio. T.S. Middle region.

8. UNIO: T.S. THROUGH POSTERIOR REGION. Comments This section shows gill laminae. supra branchial chambers. adduclor muscles and visceral ganglia. visceral ganglion

suprabranchial chambers

shell

mantle

outer lamina of outer gill lamina

Fig. 2.282 Unio. T.S. through posterior region.

31()

Non-Chordale (Illverlehrale) ZOO/Of>?'\' Praclical

9. GLOCHIDIUM LARVA Comments I. Glochidium (means "the point of an arrow") larva is found in the development of Pelecypoda or Bivalvia. 2. It is microscopic larva measuring O. I to 0.4 mm. 3.

4. Larva feeds on mucous secreted hy the gills .

mentle

5. '.

hinge

adductor muscle

Fi$. 2.283 Unio. Glochidium larva. 9.

It lives in the water tubes of gills. Larva comprises of shell and mantle.

6. Shell contains two triangular valves united dorsally and free ventrally . 7. Ventral free end of each value of the shell is produced into a curved hook bearing spines. H. Shell valves are operated hy a large adductor muscle located at the hase.

Mantle lobes are small and bear hrush-like sensory organs.

10.

A byssus gland is situated near adductor muscle through which a long filament like structure originates, called as hyssus.

II .

Fully matured larvae are passed out through the outgoing water .

12 .

They sink to the hottom of the pond . Further development takes place in a fish .

13 .

Glochidium larva attaches itself to the gills or skin or fins of a fish hy the hyssus and leads an ectoparasit ic life about 9-10 weeks before it changes into adult form.

14.

[t is a highly modified veliger larva which is a salient characteristic of rn.:shwatcr mussels.

15.

The larva undergoes metamorphosis during its ectoparasitic life on fish . During metamorphosis, the following changes occur. (i) (ii)

Sensory cells disappear.

(iii)

The larval mantle is replaced hy new one.

(iv)

Single adductor muscle is replaced hy two.

(v)

A gut with a mouth and an anus develops.

(vi)

I n.

Provisional byssus and byssus gland disappear.

The foot and the gills appear.

(vii)

The shell valves increase in size.

(viii)

After complete metamorphosis, the tiny young one comes out by the rupture of the cyst. It sinks to the hottom and develops into an adult unio.

Advantages of parasitic life are as follows: (i)

Larva gets protected from the predators.

(ii)

Larva gtls nourishment.

(iii)

Larva is transported to distant places.

317

Study of Museum Specimens and Slides of Different Invertebrate Phyla

10. VELIGER LARVA Before Torsion Comments I.

Veliger is a modified trochophore larva and is typical of molluscs generally.

2.

A shell is present on the dorsal side cf the viliger.

3.

On the ventral side, a foot lying between the mouth and the anus.

4.

Ciliary swimming organ is velum which is a bilobed circlet with strong cilia.

5.

The ectoderm forms a mantle on the dorsal side between the velum and the anus.

mantle anus _ _--"

A

foot

mantle

shell B

Fig. 2.284 Veliger lArva A - Veliger larva. Before torsion B - Veliger larva. After torsion

After Torsion In torsion the whole visceral hump of the veliger rotates 180 0 relative to the rest of the body so that:

I.

The mantle cavity comes to lie anteriorly above the head.

2.

The gills are anterior.

3.

The anus, excretory pores, and gonopores, all are anterior in the mantle cavity .

4.

The digestive tract is twisted from a V -shape into a loop.

5.

The visceral nerve loop becomes twisted into a figure of 8.

6.

The heart is turned around.

Non-Chordate (Invertebrate) Zoology Practical

318

IUNIT IX-ECHINODER MATA I Specimens I. Anredon 2. Holothuria 3. Thyone 4. Cucumaria 5. Synapta 6. Asterias 7. Pentaceros II. A.ftropectm 9. Anthmea 10. Luidia II . Ophioderma 12. Ophiothrix 13. Ophiocoma 14. Ophiolepis 15. Echinus 16. Strongylocentrotus 17. Echinarachillus Ill. Clypea.fter 19. Echinocardium 20. Aristotle's Lantern. Slides, I. T.S. of Arm Starfish 2. Pedicel/ariae of Starfi.fh 3. Bipinnaria Larva 4. Brachiolaria Larva 5. Ophiopluteus Larl'lJ 6. Echillophaeus Larva.

ISTUDY OF MUSEUM SPECIMENS I 1.ANTEDON

Classification Phylum

-

Echinodermata

Exclusively marine. largely bottom dwellers. pentamerous radial symmetry. presence of internal skeleton which is composed of calcareous ossiclcs and bears projecting spines. hence the name echinoderm. - " Spiny skin". Presence of a unique system of coelomic canals and surface appendages composing the water vasular system. coelomate.

Sub-phylum

Pelmatazoa

Stalked and fixed forms. most primitive forms. mouth and anus located dorsally. tube feet absent.

Class

Crinoidea

Attachment by aboral stalk. body cup shaped. arms five and bifurcated at the base. madreporite absent.

Sub-class

Articulata

Mouth and ambulacral grooves exposed,

Comatulida

Stalkless and unattached forms .

Antedon

On each side of the arm is a row of jointed appendages called pinnules from which the name " Feather Star" is derived .

Order Genus

-

Comments I.

Antedon is commonly known as feather star or sea lily or comatulid.

2.

The body is composed of central disc or calyx and a series of five radiating arms which are bifurcated at the base. therefore. arms appear ten in number.

3.

The central disc or calyx is differentiated into an upper convex oral surface and lower flat aboral surface.

4.

The oral surface is covered with a soft and leathery skin. the tagmen hearing the mouth and anus on a papilla.

5.

The oral surface is directed upwards.

6.

Aboral surface bears many slender curved jointed cirri supported by small ossicles meant for attachment.

Study of Museum Specimens and Slides of Different Invertebrate Phyla

319

l'

The flexible arms with numerous lateral pinnules containing gonads.

8.

Five ambulacral grooves radiate from the centrally placed mouth towards the arms .

9.

Mouth is surrounded hy sensory tuhe feet or podia.

pinnules

10. The podia or foot are without suckers. I I. Water vascu lar system is well developed.

12. There is no medreporite. 13. Unisexual and gonads contained in the dilated base of pinnules. Gametes are produced in the arms which are also the site of brooding. '

Fig 2.285 Alltedon

14. Development includes a stalked larval stage called Pentacrinoid Larva.

Habit and Habitat Alltedofl is marine found at about 25-500 fathoms deep and remains attached to the rocks and stones by cirri from central disc. They are suspension feeders and the podia on touching zooplankton or other suspended particles, undergo flicking action, driving the particles into the ambulacral groove. Ambulacral cilia carry the mucus - entrapped particles down the arms into the mouth.

Distribution Cosmopolitan. Found in all seas at depths down to 5,800 meters. It is known from lower cambrian to Recent.

2. HOLOTHURIA Classification Phylum

Echinodermata

As Antedon.

Sub-Phylum

Eleutherozoa

Non-pedicellate and free living, tube feet having suckers, Mouth and anus are located at opposite poles, i.e., mouth on the oral and anus on the aboral surface.

Class

- Holothuroidea

Body is not drawn out into arms. There are ambulacraland inter - ambulacral areas arranged meridian ally around the polar axis. Polar axis greatly lengthened giving elongated cucumber shape. Buccal podia modified into circle of tentacles around the mouth.

320

Non-Choraate (tnvertebrate) Zoology Practical

Order

Aspidochirotida

Genus

Tentacles pelted or shield like. Podia present sometimes forming a well developed sole.

- Holothoria buccal tube leet

opening 01 gonoduct

locomotary tube leet

. tubercles or warts

Fig. 2.286 Holothuria Comments I.

It is popularly known as black coloured sea cucumber. measures roughly 25-30 cm. in length.

2.

Body is elongated. bilaterally symmetrical bearing the mouth and anus at opposite poles .

3.

Mouth is on oral end. surrounded by 10-30 peltate tentacles. which represent modified buccal podia and are thus part of the water vascular system.

4.

The tentacles are highly retractile.

5.

Anus is posteriorly placed .

6.

The tube feet contains suckers in rows.

7.

Nonciliated epidermis covered externally by a thin cuticle.

8.

The thick dermal layer contains microscopic ossicles. called sclerites which display a great variety of shapes.

9.

Respiratory tree and cuvierion tubules are well developed. Most of NH J exists by diffusion .

10.

Hemal system highly developed which is involved in some gas transport and also in absorption or food transport.

II .

Haemocytes in the coelomic fluid contain haemoglobin.

12.

Madreporite hangs just beneath the base of the pharynx and is connected to the water ring by a short stone canal.

13.

Circumoral nerve ring lies in the buccal membrane near the base of the tentacles. The buccal tentacles collect the food.

14.

Unisexual possessing a single gonad.

Study of Museum Specimens and Slides of Different Invertebrate Phyla 15.

16.

321

Development includes two larval stages: (a)

Auricularia larva

(b)

Doliolaria .

The cuvierion tubules of some species are not adhesive but liberate a toxic suostance known' as Holothurin.

Habit and Habitat It feeds on microorganisms and moves slowly on the sea bottom by the muscular contraction of the body wa)] and with the aid of its tube feet.

Distribution Holothuria is found in sha)]ow. tropical seas of India. Florida and West Indies.

3. THYONE Echinodermata Eleutherozoa Holothuroidea Dendrochirotida

Phylum Sub-phylum Class Order

Genus

-

Characters same as that of Holothuria. Buccal podia ar tentacles are dendritic and are not provided with ampu)]ae. Podia are scattered over the entire body surface.

Thyone.

Comments

dorsal papillate podia ·

Fig. 2.287 Thyone.

I.

Thyofle is commonly ca)]ed as sea cucumber having du)] brown or red or black above and whitish below.

2.

Body is ovate or elongated.

3.

Mouth and anus located at opposite ends.

4.

Podia are scattered over the entire body surface.

5.

Oral end bears the mouth surrounded by 10 dendritic or branched tentacles. The aboral end bears anus.

6.

Two tentacles attached to the mid - ventral ambulacral are much sma)]er than others.

7.

The tentacular region is fo)]owed by introvert.

8.

Cuvierion tubes absent. but respiratory trees present.

9.

Water vascular system we)] present.

10.

Haemocytes in the coelomic nuid contain Hb.

II.

Stomach in the form of muscular sac.

12.

Dioecious.

13.

Development takes place in the coelom and includes auricularia larva.

14.

Thyone exhibits great power of regeneration and autotomy.

322

NOli-Chordate (Invertehrate) Zoology Practical

Habit and Habitat Thyone is marihe and found buried in sandy and muddy bottoms.

Distribution It is found in United States.

4. CUCUMARIA Classification Same as thai of Thyone .

Comments J.

Cucumaria like Thyone is also commonly called as the "Sea cucumber".

2.

Cylindrical, elongated body having mouth and anus at anterior and portends poles in p()sition .

3.

The mouth at the oral end is surrounded by a circular lip and a thin peristomial membrane.

4.

Mouth contains a whorl of 10 dendritic bushy. pinnately branched tentacles which are modified tube feet.

5.

The smooth. thin. and collar - like region at the base of the tentacles is known as introvert.

6.

Anus is present at the aboral end having paired respiratory trees.

7.

Rest of the body is differentiated into 5 ambulac.al and 5 intermbulacral zones.

8.

The ambulacral grooves run longitudinally.

9.

Dermo - muscular body wall having very small separate ossicles.

10.

The haemocytes in the coelomic fluid contain Hb.

Fig. 2.288 Cucumaria

I I.

Lacunar network is absent.

12.

Cuvierian tubules are absent.

13.

Single genital aperture present.

14.

Dioecious, gonads are arranged in two tufts.

15.

Larva is auricularia which further develops into doliolaria larva before metamorphosis.

Study of Museum Specimens and Slides of Different In vertebrate Phyla

323

Habit and Habitat It inhabits about 200 fathoms deep fully or partially buried in the mud . It feeds on detritu s and planktons.

Distribution Cucumaria is marine and cosmopolitan in distribution. It is especially found in U.S.A.

and India .

5. SYNAPTA

Classification Phylum Sub-phylum

Eleutherozoa

Class

Holothuroidea

Order

Apodia

Genus

Echinodermata

-

Characters same as that of Holothuria . Worm like sea cucumbers with only buccal podia or tentacles present. Tentacles digitate or pinnate. Tube feet absent.

Synapta

Comments

. (.)

a;

30

::I 0-

~

~

u.. 20

E..

10

o 6

10

~ ~

n

X

12 14 16 18 20 22 24 and over

Tuberculin reaction in mm

Fig. 12.2. Histogram sh6wing tuberculin reaction in 206 persons, never vaccinated as shown in illustration 1.2.

2. FREQUENCY POLYGON It is again an area diagram of frequency distribution developed over a histogram. In simple words, a frequency polygon is a graph frequency distribution. A frequency polygon is obtained when the mid point of each rectangle in the histogram is joined by a straight line. Such a straight line is drawn on the assumption that the frequencies in any class are concentrated at the midpoints of the class interval. The area of the polygon is equal to the area of histogram because the area left out is just equal to the area included in it. Polygon means a figure with many angles (Fig. '12.3 and 12.4).

Illustration: 2.1 Draw a frequency polygon for the following data.

Marks of the students Marks No. of students

10-20

20-30

7

10

I 30-40 I 15

40-50

50-60

60-70

13

10

6

547

Biometry (Biostatistics) y

X (Marks) 1 em = 10 marks Y (No. of Students) 1 em = 2 students

16 14 12 10

8

6 4

2

o

10

20

30

40

50

60

70

80

X

Fig. 12.3 Histogram with frequency polygon showing marks of students as show in illustration 2.1. Illustration: 2.2 Draw a frequency polygon for the following data (Tuberculin reaction measured in 206 persons). Reaction in mm

8-9

10-11

12-13 14-15 16-17 18-19 20-21

Frequency in percent

11.7

25.2

20.4

23.3

5.8

3.9

6.8

22-23 2.9

25.2 Q)

25

01

as

'E Q) ~

20

Q)

a.. 15

g>-

10 6.8

Q)

::J

[5

u..

2.9 8

10 12 14 16 18 20 22 24 and over

Tuberculin reaction in mm

Fig. 12.4 Frequency Polygon showing tuberculin reaction in 206 persons never fascinated as shown in illustration 2.2.

3. FREQUENCY CURVE When the number of observations is very large and group interval is reduced, the frequency polygon tends to lose its angulations, giving place to a smooth curve called as frequency curve. This provides continuous graph giving the relative frequency for each value of an attribute such as that of marks in Fig. 12.5 of a normal curve. Such a curve is obtained in normal distribution of individuals in a large sample or of means in population or of differences in pairs of sample means.

548

Non-Chordate (Invertebrate) Zoology Practicals

Actually a frequency curve is drawn by smoothing the frequency polygon. It is smoothed in such a way that the sharp turns are avoided. The curve should begin and end at the base line. It is also called smoothed frequency curve.

Illustration: 3.1 Draw histogram with frequency curve for the following data. \ Marks

10-20

20-30

7

10

INo. of students

I 30-40 I 15

40-50 13

I 50-60 I

10

60~ 6

I

Histogram with frequency curve of the above data is shown in (Fig. 12.5) y

=

X (Marks) 1 em 10 marks Y (No. of Students) 1 em 2 students

16

=

14 12 10

8 6 4

2

o

10

20

30

40

50

60

70

80

X

Fig. 12.5 Histogram with frequency curve showing marks of students given in above table (Illustration 3.1)

4. LINE CHART OR GRAPH Actually it is a frequency polygon presenting var lations by a line. It represents the trend of an event occurring over a period of time-rising, falling or representing fluctuations such as AIDS deaths, cancer deaths, infant mortality, birth rate, death rate, etc. The class interval may be a month, a year, 5 years or 10 years. It may well be shown by taking an example of population trend in India from 1901 to 1981 (Fig. 12.6). Vertical axis should not start from zero but at some point above when frequencies start at high levels as shown in Fig. 12.6. The shape of the line chart may differ with the change of scale on the vertical or horizontal line but the trend indicated, will remain the same.

Biometry (Biostatistics) 700

600

"'c:

.9

:: 500

~

.S:

.§

400

OJ

:;

0.

~ 300

200 i--.--r---r---r--r---.--r---r---. 1901 1911 1921 1931 1941 1951 1961 1971 1981

Years

Fig.12.6. Hypothetical line chart showing the population trend ill India

5. CUMULATIVE FREQUENCY CURVE OR OGIVE To draw this, an ordinary frequency table in a quantitative data has to be converted into a cumulative frequency table as shown in illustration 5.1. Actually cumulative frequency is the total number of particular or items in each particular range from lowest value of the characteristic upto any higher group value. Illustration: 5.1 Cumulative frequency table: Height of groups in cm

Frequency

Cumulative frequency

160-161

10

10

162-163

15

25

164-165

17

42

166-167

19

61

168-169

20

81

170-171

26

107

172-173

29

136

174-175

30

166

176-177

22

188

178-179

12

200

200

200

Total

To sum up, when cumulative frequencies are plotted on a graph, then the frequency curve obtained is calIed "ogive" or "cumulative frequency curve ". The class limits are placed along the X-axis and cumulative frequencies on the Y-axis. In drawing an ogive, the cumulative frequency is plotted at the upper limit of the class interval. On joining the points by a smooth free hand curve, the diagram obtained is called 'ogive'.

Types of Ogives Ogives are of two types: 1.

Less than ogive, and

Non-Chordate (Invertebrate) Zoology Practicals

550 2.

More than ogive.

1. Less than ogive: It is also known as less than cumulative frequency curve. In this type, we cumulate the frequencies from above to below and the cumulated frequencies are plotted. The cumulated frequency is, therefore, minimum in the first group or class and gradually increases, with the result that the curve upwards from left side bottom to the right side top. So we obtain a rising curve. Thus the "less than cumulative frequencies" are plotted against the upper group or class boundaries of the respective groups or classes. The points so obtained are joined by a smooth free hand curve to yield "less than ogive."

Illustration: 5.2 Draw less than ogive for the following data. 30-40 Weight of fishes in gm. 0-10 10-20 20-30 40-50 15 6 Frequency 5 8 10 Solution: We will make cumulative frequencies of the data given above first and later less than ogive curve will be plotted.

Weights less than

c.! 5 15 30 38 44

10 20 30 40 50 y 50 I/)

~ 40

-'0 .!!!

zci

30 20 10 O+---r--'--~---r--~--r-~x

10

20

30

40

50

60

Weight of fishes (gm)

Fig. 12.7. Less than ogive curve showing weight of fishes 2. More than ogive: It is also known as more than cumulative frequency curve. For this, we accumulate the frequencies from below to above and the cumulated frequencies are plotted. The cumulative frequency is, therefore, maximum in the first group or class and gradually decreases. Ultimately we may have a declining curve representing more than ogive.

Illustration: 5.3 Draw more than ogive for the following data. Weight of fishes (gm) 0-10 10-20 20-30 30-40 15

8

40-50

5 10 6 Solution: We will make cumulative frequencies of the data given above first and later Frequency

more than ogive curve will be plotted.

551

Biometry (Biostatistics) Weight more than

c.f

0 10 20 30 40 50

44 39 29 14 6 0

y 50

en

~ 40

en

:;:

_ 30 o

zo 20 10

10

20

30

40

50

60

X

Weight of fishes (gm)

Fig. 12.8 : More than ogive curve showing weight of fishes

Combined Concept of Less than and More than Ogive (cumulative frequency curves) Illustration: 5.4 Draw less than and more than cumulative frequency curve for the following data: Weight of insects in gm Frequency

0-10 3

10-20 9

20-30 15

30-40 30

40-50 18

50-60 5

Solution: We will make first the cumulative table (less and more in one) and then we will plot the less than and more than ogive (cumulative frequency curve in one).

Weight less thall

c.!

Weight more than

c.!

10 20 30 40 50 60

3 12 27 57 75 80

0 10 20 30 40 50

80 77

68 53 23 5

552

Non-Chordate (Invertebrate) Zoology Practicals y

80 70 60 >-

g

.,

50

:J

~ 40 LL.

30 20

10 O~~-''-.--.--~~-.--r---

10

20

30

40 50 60 Weight In gm

70

80

Y

Fig. 12.9. Ogive showillg the weight of the insects ill gm

II. ILLUSTRATION OF QUALITATIVE DATA Illustration of qualitative, discrete or counted data is done by diagrams and those in common use are the following: I.

Bar diagram

2.

Sector or Pie diagram

3.

Picture diagram or Pictogram

4.

Spot map or map diagram and

5.

Dot or Scatter diagram.

1. Bar Diagram: In bar diagram or chart, length of the bars, vertical or horizontal, denotes the frequency of any specific character. It is a popular and quite easy procedure adopted in biostatistics for visual comparison of the magnitude of different frequencies in discrete data, such as natality, mortality, professions, immunization status of population in different sexes, ages, etc. Bars may be drawn in ascending or descending order of magnitude or in the serial order of events. Spacing between any two bars should be nearly equal to half of the width of the bar. Types of bar: In biostatistics bar is of generally of three types: I.

Simple bar diagram (Fig. 12.10 and 12.11)

2.

Multiple bar diagram (Fig. 12.12)

3.

Proportional bar diagram (Fig. 12.13)

These three types of bar are illustrated here.

553

Biometry (Biostatistics) Children 0-6 Months 7-12 Years 1-3 Years 3-5 Years

• 12011