The Essential Guide to Rockpooling 9780691232430

Citation preview

The Essential Guide to

Rockpooling

000 Rockpooling.indd 1

15/04/2019 12:39

By the same authors THE ESSENTIAL GUIDE TO BEACHCOMBING AND THE STRANDLINE IN THE COMPANY OF SEAHORSES

Published in 2019 by Wild Nature Press Ltd Registered address 7 Sandy Court, Ashleigh Way, Plymouth PL7 5JX Copyright © 2019 text Julie Hatcher and Steve Trewhella Copyright © 2019 photographs Steve Trewhella, except those credited on page 294 The rights of Julie Hatcher and Steve Trewhella to be identified as the authors of this work has been asserted by them in accordance with the Copyright, Designs and Patents Act 1988. All rights reserved. No parts of this publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publishers. A CIP catalogue record for this book is available from the British Library. ISBN 978-0-9955673-1-3 Printed and bound in Slovenia on behalf of Latitude Press 10 9 8 7 6 5 4 3 2 1

www.wildnaturepress.com

000 Rockpooling.indd 2

15/04/2019 12:39

The Essential Guide to

Rockpooling Julie Hatcher and Steve Trewhella

000 Rockpooling.indd 3

15/04/2019 12:39

Contents Introduction 7 What are rockpools? 7 What is found there? 7 When is the best time for rockpooling? 7 Tides 8 What is zonation? 9 Recognising the different rocky shore zones 10 Challenging conditions 11 Threats to rockpool wildlife 12 The Seashore Code 13 Kit list 14 Keeping safe 16 Types of rockpools Pink-lined rockpools Brackish pools Super-saline rockpools Deep rockpools Sandy pools next to rocky outcrops Surge gullies and overhangs Crevices Artificial rockpools Curious rockpools

19 19 20 20 21 21 22 23 23 24

Seaweeds 27 Green seaweeds 30 Blue-green algae 34 Brown seaweeds 34 Red seaweeds 50 Lichen

65

Sponges 69 Bryozoans 75 Cnidarians 79 Hydroids 79 Stalked jellyfish 84 Anemones and corals 87 Worms Bristle worms Flatworms Ribbon worms Spoon worms Peanut worms

000 Rockpooling.indd 4

99 99 117 119 120 121

15/04/2019 12:39

Crustaceans 123 Crabs 123 Lobsters, shrimps and prawns 139 Isopods 148 Tanaids 157 Cumaceans 158 Nebaliidae 158 Ostracods 158 Amphipods 159 Skeleton shrimps 163 Barnacles 164 Sea spiders 170 Insects and other air-breathing arthropods Springtails and bristletails Beetles Flies Bugs Centipedes Arachnids

175 175 177 179 182 183 183

Molluscs 187 Gastropods 187 Bivalves 223 Cephalopods 230 Chitons 232 Echinoderms 235 Starfish 235 Brittlestars 239 Featherstars 241 Sea urchins 242 Sea cucumbers 244 Sea squirts

247

Fish

257

Birds

276

Mammals 283 Eggs

287

Glossary 292 Acknowledgements 294 Photographic credits

294

References 295 Index

000 Rockpooling.indd 5

296

15/04/2019 12:39

Introduction

000 Rockpooling.indd 6

15/04/2019 12:39

F

or most people, the marine environment is almost entirely inaccessible and impossible to explore. It is an unfamiliar place but a source of endless fascination. The rockpools and shore, where the land ends and the sea begins, offer us a glimpse into this mysterious world. It is no wonder that rockpooling is a popular activity, which we enjoy as children but do not outgrow as adults. In this book we introduce the reader to the extraordinary diversity of wildlife that can be found in rockpools and on rocky shores around the coast at low tide. Many people will be familiar with the crabs and small fish found on trips to the seaside. Our aim is to enhance this knowledge and create a better understanding of these animals and the myriad others that can be found using a bit of simple detective work. We have included a selection of activities that will add a new dimension to this popular pastime.

What are rockpools? Rockpools are pools of seawater left behind when the tide retreats. The natural process of coastal erosion results in the formation of hollows, gullies and crevices which trap water and form microhabitats supporting a fascinating and diverse array of marine life. Rockpools are dependent on the local geology and vary from soft, easily eroded chalk pools to hard, granite exposures.

What is found there? Rockpools are formed in areas of intertidal bedrock and the activity of rockpooling necessarily includes the surrounding rocky seashore. This book encompasses the whole experience of the rocky shore and explains why some creatures are found within the rockpools while others survive on the surrounding rock. It is sometimes assumed that the animals found in rockpools have been temporarily trapped, caught out by the ebbing tide. While this may be the case for some species, for the majority, the rockpool is their permanent home. Many are permanently attached, for example seaweed and barnacles, and moving is not an option.

When is the best time for rockpooling? Rockpools only appear as the tide recedes, so you will need to have a knowledge of tide times. These vary around the coast and from day to day. As there is no point turning up at the beach when the tide is in, a certain amount of planning is required. Tide times for a particular area can be found either by buying a tide table, available from chandlers and tackle shops, or by looking online. Plan to visit as the tide is going out so you will have more time to explore, following the tide down the shore. It is important to ensure you will not be cut off by the incoming tide. Remember that the incoming tide will flood low-lying gullies and channels before it reaches higher ground, so plan your retreat carefully. As the tide varies each day throughout the lunar cycle you should be aware of the difference between spring and neap tides. The lowest part of the shore, home to the widest variety of marine life, is only uncovered during spring tides.

Introduction  7

000 Rockpooling.indd 7

15/04/2019 12:39

The returning tide brings relief to creatures of the intertidal zone

Tides Tides are governed by the moon and sun and their relative position to the Earth. At times of new and full moon, when the Earth, sun and moon are all in alignment and their gravitational pull on the ocean is combined, the tidal range is larger, which means the low tide is lower and the high tide reaches higher up the shore. These are called spring tides. At times of half-moon, the moon and sun form right angles with the Earth so that the gravity of the moon and sun are pulling in opposing directions. The result is a smaller tidal range with a not-so-low low tide and not-so-high high tide on the shore. These are neap tides. sun

last-quarter moon

new moon

moon

first-quarter moon

spring tides

earth

full moon

last-quarter moon

LUNAR CYCLE high spring tide

neap tidal range

spring tidal range

neap tides

high neap tide mean tidal level low neap tide low spring tide

day

1

2

3

4

5

6

7

8

9 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

8  Introduction

000 Rockpooling.indd 8

15/04/2019 12:39

The tidal range – the maximum vertical height between high and low tide – varies around the country, with some locations experiencing large tidal ranges of up to 15m and others very small tidal ranges of just 2 to 3m. This variation is caused by the topography of the seabed and coastline which may restrict the normal flow of the tide, for example by funnelling water through a narrow channel or by creating an obstruction and causing the water to ‘pile up’ against it. The weather can also have an influence on the tide. A high atmospheric pressure may push down the sea surface and make a predicted low tide even lower, whereas a low pressure area increases the height of the tide. In addition, winds blowing from the shore out to sea may help to push the tide further out, while onshore winds will help the waves to pile up on the shore. While these effects may be insignificant in areas with a large tidal range, they can make a big difference in locations with a small tidal range.

What is zonation? Seashore wildlife is not randomly scattered throughout the intertidal area. Instead, species are restricted to particular levels or zones, depending on how long they can survive exposure to the air when the tide is out, and on competition from other species. This ‘zonation’ is governed by the tides. Animals and algae (seaweeds) that are adapted to survive for longer periods out of water can live higher up the shore, while those less well adapted are confined to lower zones. The further up the shore a species can survive, the less competition it will have for food and space. However, an upper shore species may find it is outcompeted lower down the shore, restricting it to a particular level. The different zones on the seashore are often visible as coloured horizontal bands. The colour of each zone is dictated by the dominant species found there. For example, on a wave-exposed shore the splash zone is often dominated by orange-coloured splash zone high tide

lichen

low tide

barnacles

mussels

red seaweed

wracks and kelps

Representation of zonation on a rocky shore

Introduction  9

000 Rockpooling.indd 9

15/04/2019 12:39

Lichen colonises the highest rocks with various wrack zones beneath

lichens. Below this will be zones of differing colours dominated by pale barnacles, blue mussels, black tar lichen and brown algae. These coloured bands are most obvious on steeply sloping shores.

Recognising the different rocky shore zones The location and the direction a rocky shore faces determine how exposed it is to wave action. Those sheltered from the prevailing wind, for example within estuaries, tend to be dominated by algae, while those exposed to the full force of ocean waves and storms tend to have less algae but more barnacle or mussel cover. The more waveexposed a shore is, the higher up the shore the zones extend, with a well-defined splash zone above the high water mark. Conversely, on sheltered shores the zones are more compressed, with a very narrow splash zone.

A sheltered rocky shore (left) showing the predominance of brown seaweed, and an exposed rocky shore (right) with less seaweed and more barnacle and mussel cover

10  Introduction

000 Rockpooling.indd 10

15/04/2019 12:39

Challenging conditions For sea creatures, spending even a short period of time out of water may be difficult. Their respiratory organs, such as gills, must remain moist in order to function and if these dry out, the animal will be unable to obtain oxygen and will die. On hot and windy days, the dehydrating effect on seashore animals can be intense. For animals permanently submerged in the sea, the temperature remains relatively constant compared with that of air. In the UK, sea temperature rarely varies more than 15°C throughout the year. Air temperature can range from below freezing to over 30°C, and rocks warmed by the sun’s heat can get even hotter. Intertidal species must be able to cope with this range of temperature, especially those higher up the shore, where they may spend several hours each day out of water. The temperature in rockpools can also vary widely, particularly if they are small and shallow. Try putting your hand in a small rockpool on a hot day to feel how warm it can be. If you reach down below the covering of seaweed the water will feel a lot cooler. Conversely, the water may freeze over on a cold winter’s day, particularly if it is brackish. In coastal waters, the salt content of the sea is slightly lower than that in the open ocean, fed as it is by freshwater from rivers and streams. However, on the seashore and in rockpools the salinity can vary substantially between almost freshwater in heavy rain and the very high salinity of upper shore rockpools where the water has evaporated on a hot day. Other changes to the chemical composition of rockpools occur during the day when algae is photosynthesising rapidly, absorbing carbon dioxide from the water and producing oxygen. Add to these factors the intense UV light these marine species are exposed to, the battering by waves and predation by terrestrial animals and it is clear that life is hard on the seashore.

A freshwater stream reduces the salinity of nearby rockpools

Introduction  11

000 Rockpooling.indd 11

15/04/2019 12:39

So why do species colonise this incredibly inhospitable habitat? Living space below the sea is at a premium and competition is intense. For those that can adapt to survive the harsh environment of the intertidal zone, especially on the middle and high shore, there is less competition for space and food. The adaptations that enable algae and animals to survive include being able to lose and rapidly reabsorb almost all the water from their cells without dying (algae), sheltering inside a tough shell (barnacles and many molluscs), reducing their surface area exposed to the air (sea anemones) and retreating into cool, damp, shady areas at low tide (crabs and fish).

Threats to rockpool wildlife As with all wildlife, species living in rockpools and on rocky seashores face a number of threats from human activity. These include direct disturbance at a local level such as trampling and bait collection and global problems such as climate change and marine litter. The more accessible shores can suffer from heavy trampling and over-collection of animals, resulting in sparser seaweed cover, rocks being left overturned and removal of keystone species that are fundamental to the whole habitat, such as limpets. Rockpoolers should always follow the Seashore Code in order to prevent such impacts. In some locations, commercial collection of species such as limpets, periwinkles and algae, and bait collection, for example of peeler crabs, can affect seashore populations and have a detrimental impact on the whole ecosystem. Over-foraging is also a potential threat if too many people are regularly removing species from the same site. In some locations, coastal development can result in the loss of rocky shore habitat. This can happen when land is reclaimed or hard structures such as sea walls and sewage pipes are installed. Pollution and marine litter have the potential to affect any rocky seashore, from the devastating effects of an oil spill to the persistent threat of agricultural run-off carrying excessive nutrients into the sea. Storm overflows release sewage and cleaning products directly onto the beach during periods of heavy rainfall and storm drains wash contaminated water and litter from our roads into the sea. Marine litter can smother habitats, or trap and entangle wildlife, while microplastics are ingested by filter-feeding animals and enter the food chain. Non-native marine species arriving on our shores, often transported here by shipping or accidentally escaping from aquaculture farms, have the potential to become invasive, settling around the coast and out-competing our native species. They may carry diseases to which native species have no immunity, and can devastate native populations as well as becoming pests in their own right. The biggest long-term threat to all marine wildlife is climate change. Already the distribution of intertidal species is changing, with warmer water species arriving and spreading as the sea temperature increases. Climate change is also resulting in an increase in ocean acidity, which reduces an animal’s ability to build a calcareous shell. This will have untold consequences for species from corals and crabs to snails and plankton.

12  Introduction

000 Rockpooling.indd 12

15/04/2019 12:39

The Seashore Code To minimise your impact on wildlife while rockpooling, please remember to follow the Seashore Code. Always return rocks and seaweed exactly as you found them. They provide shade and shelter and if not returned, will leave animals exposed to light and air. Watch where you walk to avoid trampling seaweed and creatures hiding beneath it. Leave attached animals and seaweed where they are. Limpets, anemones and algae may not survive if removed. Handle animals gently and with wet hands. Return all animals to where you found them. They may be guarding eggs or territory. They will not survive away from the beach. If temporarily holding animals in a tank or bucket, be sure to refresh the water regularly to keep it cool and oxygenated. Do not put animals together that might harm each other. It is best to return them to their homes immediately once they have been observed. Avoid long-handled nets from seaside shops. Sweeping these around in rockpools damages and scares away the wildlife. If necessary, use a shorthandled aquarium net gently and carefully. Take all your litter home as well as any litter you find in the rockpools.

The seashore code  13

000 Rockpooling.indd 13

15/04/2019 12:39

Kit list The following items may be useful to carry with you on your rockpooling expeditions. It is also worth remembering that beaches tend to be very exposed to the weather and offer little opportunities for shelter, either from wind and rain, or from strong sunlight. It is important to wear appropriate clothing, including a hat and strong, non-slip footwear and to take waterproofs and/or sunscreen. Always check the tides beforehand to avoid being cut off by the rising tide. While you are on the seashore, it is good practice to do your bit by collecting a few items of litter for safe disposal or recycling. This is a useful habit to get into and sets a good example for others. Your rockpooling kit list could contain the following equipment: Buckets, pots and trays to temporarily hold your catch for identification Small, short-handled aquarium net Headband magnifier or hand lens Camera or phone camera Knee pads or a gardener’s kneeling mat (for comfort) Notepad and pen Pooter (for collecting seashore insects) Turkey baster (for collecting small delicate invertebrates) Drink – in a refillable bottle Tip Mark your kit items with a piece of yellow tape as it is easy to put things down and lose them on the seashore when you move on to the next rockpool.

14  Introduction

000 Rockpooling.indd 14

15/04/2019 12:39

000 Rockpooling.indd 15

15/04/2019 12:39

Keeping safe Beaches can be hazardous places for a number of reasons and it is important to have these in mind before heading out on a rockpooling trip. Exposure to the weather, the sea and tides, slippery, uneven rocks and unstable cliffs all present dangers to the unwary visitor. In order to keep safe we advise taking the following precautions. Check tide times for the beach you are visiting before venturing out. At high tide the beach, or parts of it, may be inaccessible, or you may be cut off by a rising tide. Tide times for the week ahead are available online, or you should be able to purchase a tide book for the year at a local fishing tackle shop or chandlers. Check the weather forecast for your area and dress and pack accordingly. Also be aware that freak waves may reach much higher up the beach than anticipated. Beware of slippery, uneven rocks – surfaces covered in seaweed or lichen are extremely slippery, while it is easy to trip over uneven rocks, so extra care must be taken when walking on a rocky shore. Old trainers, walking boots or wellington boots are the recommended footwear, as flip flops and sandals offer no support and increase the hazard when wet. Beware of cliff falls – in some parts of the country cliff falls can be frequent and unexpected. It is always advisable to keep a safe distance from the foot of cliffs to avoid being hit by falling rocks. Carry a mobile phone in case of emergency situations, but be aware that signal coverage can be patchy around the coast. A waterproof carrying case is a good investment, as handling your phone with wet, salty hands can cause damage.

16  Introduction

000 Rockpooling.indd 16

15/04/2019 12:39

RECORDING YOUR FINDS It is useful and interesting to keep a record of your seashore finds as a reference tool. By creating a rockpool logbook you can record your memories as well as notable species and locations. Keeping a written and photographic record can highlight that certain locations and times of year are better for particular species.

A pencil and waterproof notebook A camera or camera phone in a waterproof case ● A hand-held GPS if not built into your phone/camera (optional) ● ●

What to record ● ● ● ● ● ● ●

Date Location (name of beach or area) Ordinance Survey grid reference or latitude/longitude (if using a GPS) Seashore level, i.e. upper, middle or lower Species name Species number or abundance Description of habitat, e.g. gully or rockpool (or take a photo showing this)

activity

What you need

17

000 Rockpooling.indd 17

15/04/2019 12:39

Types of rockpools

000 Rockpooling.indd 18

15/04/2019 12:39

R

ockpools are found in an infinite variety of shapes and forms. Each one is unique and offers a different microhabitat. Here are a few examples of the types of rockpool you may find.

Pink-lined rockpools Pink-lined rockpools are shallow depressions lined with encrusting red algae. The alga is sometimes mistaken for paint, especially when it has turned white around the pool edges where it has dried out and lost its photosynthesising pigment. These pools generally lack other types of seaweed but may contain a variety of molluscs such as limpets, topshells and periwinkles, whose grazing prevents other seaweed from settling.

Encrusting red algae bleaches to a paler colour in strong sunlight

FIRST SETTLERS Encrusting red alga produces a chemical which attracts juvenile limpets when they first settle on the shore. For the tiny limpets, measuring just 1mm in length, this indicates a safe place to settle, where they will not dry out at low tide. The alga benefits from having a herbivore keeping other seaweeds at bay and preventing it from being grown over and shaded. As the limpets grow bigger and their shells thicker, they can move out of these pink-lined pools and further up the shore.

Types of rockpools  19

000 Rockpooling.indd 19

15/04/2019 12:39

Brackish pools Brackish water rockpools are found in places of freshwater input, for example where a stream crosses a beach or in the splash zone where rain-water collects but the high tide rarely reaches. The salinity in these pools is lower than that of seawater and this restricts what can live there to a few tolerant species. These pools tend to be dominated by the green Ulvae seaweeds, and both Rough and Small Periwinkles.

Super-saline rockpools Under certain conditions, shallow, splash-zone pools can become super-saline. During the summer, when there has been little rainfall or rough weather, splash-zone rock pools can become stagnant, with salinity increasing as the water evaporates. At first glance these pools appear to be devoid of life, with rotten seaweed forming a sludge at the bottom. However, there are opportunistic species that rely on these conditions to complete their life cycles. These include tiny water beetles, various species of midge and the rat-tailed maggots of the coastal hoverfly, Eristalinus aeneus.

20  Types of rockpools

000 Rockpooling.indd 20

15/04/2019 12:39

Deep rockpools Deep rockpools are places where larger animals can be found, such as large dahlia anemones, spiny starfish or lobsters. As they offer more shelter, they may temporarily trap larger fish or shoals of small fish at low tide. However, because of their size and depth they can be harder to explore than smaller rockpools. Often the best way is to sit quietly and observe as animals go about their business in relative safety.

Sandy pools next to rocky outcrops Pools of seawater collect in depressions around rocky outcrops on sandy beaches. They can offer an insight into some sandy shore species that become temporarily trapped there, as well as some rocky shore animals that can cope with some sand scour. Examples of creatures to look out for in the sand include shrimps, sand eels and flatfish, while Strawberry Anemones inhabit the base of the rocky sides. If you have seen stranded jellyfish on the beach it is worth looking in these pools for any free-swimming individuals.

Types of rockpools  21

000 Rockpooling.indd 21

15/04/2019 12:39

Surge gullies and overhangs While not strictly rockpools, these are damp, shaded places of high wave energy, where particular types of animal can be discovered. Hanging from the walls and overhangs of these gullies robust, filter-feeding animals such as Dead Man’s Fingers, cup corals and a colourful variety of sponges may be found. When the tide comes in, large volumes of water are funnelled through these passages, carrying lots of fresh food for filter feeders. The animals that live here include some normally associated with deeper water as well as those found intertidally.

22  Types of rockpools

000 Rockpooling.indd 22

15/04/2019 12:39

Crevices Cracks and fissures in the rock are ideal retreats for creatures at low tide, offering shelter in dark, damp places. They can be tucked away behind a curtain of seaweed and may extend far back into the rock. A small torch can be useful for investigating these habitats and you might see a clingfish or Shanny guarding its eggs, breeding aggregations of Dog Whelks, or a variety of crabs and starfish wedged in place.

Artificial rockpools Around the coast over the centuries, rockpools have been created by people, either as a by-product of quarrying or deliberately as a safe seawater bathing area. When they become disused, the sea can reclaim them. The fact that they are man-made does not prevent species from colonising them so they are worth exploring. Research has shown that hard coastal defences like sea walls and groynes limit the natural dispersal of seashore animals. The addition of small, artificial pools enable these structures to act as stepping stones for the spread of species and increase the biodiversity on these otherwise unnatural habitats.

An artificial rockpool built into a rock groyne

Types of rockpools  23

000 Rockpooling.indd 23

15/04/2019 12:39

Hexagonal pools form where basalt columns are eroded

Curious rockpools In a handful of locations around the UK you may come across rockpools resulting from an extraordinary geological history. In Northern Ireland and the Scottish Hebrides, where the basalt columns made famous by the Giants Causeway have worn, they have resulted in hexagonal-shaped rockpools. On the Isle of Skye, tracks left as dinosaurs walked across soft mud have fossilised to produce rockpools in the shape of dinosaur footprints (opposite).

The remains of an ancient man-made fish trap. Rocks placed across the inlet trapped fish when the tide retreated

24  Types of rockpools

000 Rockpooling.indd 24

15/04/2019 12:40

000 Rockpooling.indd 25

15/04/2019 12:40

Seaweeds

000 Rockpooling.indd 26

15/04/2019 12:40

O

n the seashore, seaweed forms the base of the food web, providing food for herbivores which are preyed upon by carnivores with predators of their own. It also provides shade and shelter, a base for attachment and a home for many invertebrates. On shores that are sheltered from wave action, for example at the mouths of estuaries and harbours, in sea lochs or in sheltered coves, seaweeds can completely cover the intertidal zone. However, on very wave-exposed shores it is difficult for all but the most hardy of seaweeds to withstand the constant pounding by waves, and these areas are dominated by animals such as barnacles and mussels.

4th trophic level second-level carnivores

3rd trophic level

carnivores

2nd trophic level

herbivores

1st trophic level

seaweeds

A simple seaweed-based foodchain

Seaweed is a type of alga, sometimes called macroalga, and is distinct from plants although, like plants, it uses pigment in its cells to trap energy from sunlight in a process called photosynthesis. However, the structure of seaweed is quite different as it does not have roots to absorb water and nutrients but instead absorbs them directly from the seawater through its outer surface. Some types of seaweed, such as kelp, have a structure with a holdfast (base), a stipe (stalk) and a frond or blade, while others may

Seaweeds  27

000 Rockpooling.indd 27

15/04/2019 12:40

form flat sheets, spongy cushions or even balloon-like structures. The variety is enormous but almost all need to be firmly attached to the seabed and have a holdfast for this purpose. They need to attach to a firm surface such as rock and so are mostly restricted to rocky shores. Seaweeds tend to be grouped according to their colour and are divided into red, brown and green algae. The brown algae are the dominant group on the seashore and include the kelps and wracks that people are most familiar with. Seaweed species found in the intertidal zone need to be specially adapted to spending some time exposed to the air at low tide. During this time they may have to withstand a wide variation in both temperature and salinity, exposure to high levels of UV light, the risk of desiccation and trampling by people. For instance on a hot summer day the air temperature may soar way above sea temperature, causing seaweeds to dry out and exposing them to strong sunlight, which can destroy their pigments and cause bleaching. At other times they may be flooded with rainwater and run-off or even suffer a coating of frost (above). For those species living higher up the shore, spending prolonged periods out of water, some very special adaptations are required e.g. Channelled Wrack on page 35.

28  Seaweeds

000 Rockpooling.indd 28

15/04/2019 12:40

Seaweed as a host for other organisms On a rocky seabed, attachment space is at a premium and some animals and algae take advantage of larger species by anchoring to them. The large kelps can host a variety of ‘hangers-on’, from tiny Blue-rayed Limpets grazing on their fronds to red seaweeds and hydroids attached to their tough stipes and a whole community of sponges, sea squirts, molluscs and crustaceans sheltering in their holdfasts.

Seaweed and people Farming of seaweed is big business around the world and it is widely used in the cosmetics and food industries. It contains a variety of vitamins, calcium, iodine and protein, all of which are essential to our health. Historically, seaweed washed up on beaches has been applied as fertiliser in agriculture. Some seaweeds can be used to clean polluted water as they grow quickly, absorbing excess nitrogen and phosphorus before being harvested to remove the unwanted nutrients from the water.

FILTERING LIGHT

water depth

On land, most plants have green leaves for absorbing energy from sunlight. Their colour comes from the pigment inside, which traps the energy and converts it for use by the plant. Different types of pigment can trap different wavelengths of light, for example red or blue light. As light penetrates seawater, some wavelengths are filtered out in the first few metres while others penetrate much deeper. For this reason, different types of seaweed use a variety of pigments to trap light and appear in a much wider range of colours than land plants. Red and brown seaweeds mostly absorb blue-green light and can live at greater depths than green seaweeds, which mainly use red light and are most common in the shallower parts of the sea.

100m

200m

300m

Depths to which different wavelengths of light can penetrate

Seaweeds  29

000 Rockpooling.indd 29

15/04/2019 12:40

Green seaweeds The species in this group (Chlorophyta) are classified as plants and have the same photosynthetic pigments as land plants. Most green algae are found in freshwater but a small proportion live in brackish or fully marine conditions.

Sea Lettuce Ulva lactuca

Size 30cm

This very common seaweed is found all around the UK. As the name suggests, it is green and forms broad, undulating sheets which are attached to the substrate by a tiny holdfast. The sheets are thin enough to be translucent. Sea Lettuce is tolerant of a wide range of salinities and often dominates the upper shore and splash zone pools where salinity is very high, but also in areas of brackish water with freshwater input from streams or rainwater run-off. However it can be found on all levels of the shore.

30  Seaweeds

000 Rockpooling.indd 30

15/04/2019 12:40

Gutweed Ulva intestinalis

Size 30cm

This very common seaweed is found all around the UK. It is green and forms narrow, hollow tubes which can have bubbles trapped inside. It is a short-lived species and by late summer the fronds, exposed to strong sunlight, often lose their pigment and turn white and papery. Like Sea Lettuce, it is tolerant of a wide range of salinities and often dominates upper shore and splash zone pools where salinity is very high, but also in areas of brackish water with freshwater input from streams or rainwater run-off. However, it can be found on all levels of the shore.

Green seaweeds  31

000 Rockpooling.indd 31

15/04/2019 12:40

Green Sponge Fingers Codium fragile

Size 30cm

This is one of several species that look almost identical in the field, which makes its UK distribution uncertain, although it has been recorded from locations all around the coast. It is dark green in colour and spongy in texture, forming long, dichotomously branching fronds with rounded tips. The holdfast is small and the plant often has red algae growing on it. This group of species, which includes C. tomentosum and C. vermilara, look very similar to each other and are unmistakable from any other UK species. C. fragile is a nonnative species, although the others are native to the UK. It is found in the middle and lower shore, often on the vertical sides of rockpools and ledges.

32  Seaweeds

000 Rockpooling.indd 32

15/04/2019 12:40

Codium adhaerens

Size variable

This rare encrusting seaweed is found on the south and south-west coast of England. It is very dark green, almost black in colour, forming a spongy mat on bedrock. Look for it on the middle or lower shore, especially on moderately exposed shores, where it can form mats exceeding 30cm in length.

Cladophora rupestris

Size 2cm

This common intertidal seaweed is widespread around the coast of the UK. It is dark green in colour and coarse in texture, forming finely branched, dense tufts. It can be found at all levels on the seashore, in rockpools, on exposed ledges and also forming an understorey beneath brown algae.

Green seaweeds  33

000 Rockpooling.indd 33

15/04/2019 12:40

Blue-green algae Rivularia bullata

Size 2cm

Despite its appearance, this is not a seaweed but a type of blue-green alga or cyanobacteria. These photosynthesise like algae and plants but consist of a colony of microscopic bacteria. The bright green, gelatinous, spherical colonies appear on intertidal rocks in the summer. They grow from crevices and around barnacles in the middle shore.

Brown seaweeds Unlike both green and red algae, brown seaweeds (Phaeophyceae) are not related to plants but have developed more recently, arising from a different evolutionary pathway. The members of this group are mostly marine and contain the pigment fucoxanthin, which gives them their brown coloration. Brown seaweeds dominate the intertidal zone and can completely blanket the shore in sheltered locations. This group also contains the largest seaweeds.

34  Seaweeds

000 Rockpooling.indd 34

15/04/2019 12:40

Channelled Wrack Pelvetia canaliculata

Size 15cm

This seaweed is found on rocky shores all around the UK. It is olive green to mid-brown, sometimes with yellow fruiting bodies at the tips of the fronds. It grows in tufts on the upper shore, where it can be left exposed to the air for several days, during which time it can become desiccated and very dark in colour. The name Channelled Wrack comes from the shape of the frond, which is rolled to form a shallow channel which retains moist air and enables it to survive for longer out of water. Look for this seaweed on the upper part of the shore above the level of other algae.

Spiral Wrack Fucus spiralis

Size 20cm

This common seaweed is found on coasts all around the UK. It is olive to mid-brown in colour and the frond twists or spirals as it hangs from upper shore rocks where it is found. The frond has a midrib but no air-bladders, although it may have swollen tips which are the reproductive bodies. These have a rim around the outside which is characteristic of this seaweed. This species lives on the upper shore immediately below the Channelled Wrack zone but above the Bladder Wrack zone.

Brown seaweeds  35

000 Rockpooling.indd 35

15/04/2019 12:40

Bladder Wrack Fucus vesiculosus Below: on wave-exposed shores

Size 80cm

This large seaweed is common on coasts all around the UK. It is olive green to brown with a midrib and pairs of oval air bladders at intervals along the frond. On older specimens the frond may become worn and some of the bladders lost. On sheltered shores, more bladders are produced, whereas on wave-exposed shores these are reduced in number or even absent. The air bladders help the fronds to float upwards in the water, maximising their exposure to sunlight. This seaweed is found in the middle shore below the Spiral Wrack zone but higher than the Serrated Wrack.

Serrated Wrack Fucus serratus

Size 65cm

This large seaweed is common all around the coast of the UK. It is olive green to brown with a visible midrib and a serrated or toothed edge to the frond. The fronds are covered in minute pores from which tufts of white hairs emerge. Older plants and those on sheltered shores can be heavily encrusted with spiral worm tubes (page 100) and these can ultimately impair the alga’s ability to photosynthesise. It grows on the lower shore, below the Bladder Wrack zone, where it can form a dense carpet covering the rock.

36  Seaweeds

000 Rockpooling.indd 36

15/04/2019 12:40

Horned Wrack Fucus ceranoides

Size 60cm

This seaweed is found all around the UK. The fronds are flat and can become inflated either side of the midrib, although they lack bladders. The forked fronds are yellow towards the ends. It is found in sheltered areas with brackish water or freshwater input, especially in estuaries and sea lochs where it can be very common. Horned Wrack is found on the middle shore attached to rocks and stones.

Egg Wrack Ascophyllum nodosum

Size 150cm

This very large, yellow or olive-green seaweed is found all around the UK and can dominate on sheltered shores, where it stands out against the brown of other wracks. The narrow, tough, fleshy fronds can grow extremely long. The single large, egg-shaped bladders are produced at intervals at a rate of one per year; plants on sheltered shores can be aged by counting them. Egg Wrack is long-lived, with the holdfast producing new fronds for several decades. Individual fronds have been aged at up to 15 years. The reproductive bodies form rounded, grape-like structures on stalks which emerge along the length of the frond. This species is associated with an epiphytic red alga called Vertebrata lanosa (page 61), which grows in tufts from the frond.

Brown seaweeds  37

000 Rockpooling.indd 37

15/04/2019 12:40

Sea Oak Halidrys siliquosa

Size 200cm

This bulky brown seaweed is found all around the UK, although it is not always intertidal. It is golden to dark brown in colour, with zigzag-shaped main fronds from which short branches sprout. These short branches terminate in elongated, flattened air bladders or ‘pods’, hence its alternative name of Pod Weed. It can be found in deep rockpools on the mid to lower shore.

Brown Tuning Fork Weed Bifurcaria bifurcata

Size 50cm

This seaweed is restricted to the south and west coasts of England and Wales in the UK. It is yellow-brown in colour with cylindrical fronds which fork at intervals along their length. It forms a fringe around the edge of rockpools on the middle and lower shore and extends into the shallow sublittoral.

38  Seaweeds

000 Rockpooling.indd 38

15/04/2019 12:40

Rainbow Wrack Cystoseira tamariscifolia

Size 45cm

This colourful seaweed is found on south and west coasts in the UK. It is bushy and appears light brown when exposed to the air, but underwater exhibits a rainbow of colours from irridescent blue and turquoise to violet and indigo. This colour-change phenomenon has led to its English names of Rainbow Wrack and Magic Seaweed. It has a rough texture and the older stems can be thick and tough with an almost woody feel. It is found in lower shore rockpools and occasionally on open rock during an extreme low spring tide. This species is one in a complex of related species, but is distinguished by its colour when in water.

Brown seaweeds  39

000 Rockpooling.indd 39

15/04/2019 12:40

Bushy Berry Wrack Cystoseira baccata

Size 150cm

This large, bushy seaweed is found in south-west parts of the UK. It is closely related to the Rainbow Wrack, with the same rough appearance. However, it is golden with oval air bladders at the base of each branch. It can be found in lower shore rockpools.

Wireweed Sargassum muticum

Size 200cm

This invasive non-native seaweed, which first appeared on the south coast of England in 1973, can be found on south and west coasts of the UK and may well continue to extend its distribution. It is golden brown with many small, round air bladders and short, leafshaped fronds arranged along the stems, giving it a bushy appearance. It can be found in middle and low shore rockpools, where it can dominate.

40  Seaweeds

000 Rockpooling.indd 40

15/04/2019 12:40

Thongweed Himanthalia elongata

Size 200cm

This common seaweed is found all around the UK apart from the south-east of England. There are two stages to its growth, consisting firstly of small, brown buttons which look like leathery mushrooms, from which long thin straps emerge in the second stage. The buttons grow to about 3cm in diameter and when mature, they form a saucer on top of a short stalk. The branched, yellow straps are the reproductive parts of the alga. This species grows best on wave-exposed ledges and rocks as the reproductive straps are designed to be broken off and dispersed in rough weather. It can be found on the lower shore and sublittoral fringe, often amongst kelp.

Brown seaweeds  41

000 Rockpooling.indd 41

15/04/2019 12:40

Furbelows Saccorhiza polyschides

Size 400cm

This common kelp is our largest seaweed and is found all around the UK apart from the east coast of England. It is brown with a very distinctive hollow holdfast which is large, bulbous and warty in appearance. The stipe is broad and flattened with the lowest section folded into a frill reminiscent of an Elizabethan ruff. The leathery fronds are divided into long straps. It can be found on the very lowest part of the shore or occasionally in low shore rockpools, usually mixed with other kelp species.

42  Seaweeds

000 Rockpooling.indd 42

15/04/2019 12:40

Oarweed Laminaria digitata

Size 200cm

This common kelp is found on rocky shores all around the UK. It is glossy brown with a branched holdfast, a smooth, flexible stipe and a palm-shaped frond from which long, straps emerge. It can be confused with the very similar Cuvie, but in Oarweed the stipe is oval in cross section and smooth, with no epiphytes growing on it. It can be found on the lower shore on rock and in rockpools, often in dense beds and mixed with other kelp. The flexible stipes can be seen emerging from shallow water and bending over like croquet hoops.

Brown seaweeds  43

000 Rockpooling.indd 43

15/04/2019 12:40

Cuvie Laminaria hyperborea

Size 350cm

This common kelp is found on rocky shores all around the UK. It is brown and very similar in appearance to Oarweed but with a stiff, rough-textured stipe which is circular in cross section and often coated with red algae. The holdfast is branched and the frond is divided into long straps. It may be found on the very lowest part of the shore on an extreme spring tide. The stipes, which taper towards the end, may be seen standing erect in shallow water with the frond hanging from them.

Sugar Kelp Saccharina latissima

Size 150cm

This distinctive kelp is found on rocky shores all around the UK. It is golden to brown in colour with a single long frond, short stipe and a small, branched holdfast. The tapering frond does not have a midrib and has a crumpled, almost frilly appearance. The white powder that collects on dried fronds gives sugar kelp its name. This seaweed can be found on the lower shore, often in mixed kelp beds, and in rockpools.

44  Seaweeds

000 Rockpooling.indd 44

15/04/2019 12:40

Dabberlocks Alaria esculenta

Size 150cm

This colder water species is widespread in the UK but absent from the Channel coast and south-east of England. It is dark brown with a single, long wavy frond which has a thick midrib. In older plants the frond may wear away leaving just the midrib. It has a branched, claw-like holdfast and short cylindrical stipe from which a cluster of leaf-like reproductive structures emerges in mature plants. It can be found on the lowest part of the shore, especially on the vertical sides of rocks in very wave-exposed locations.

Wakame Undaria pinnatifida

Size 300cm

This invasive non-native seaweed which was first recorded in the UK in 1994 has been found at scattered locations around the country but mainly on the south coast. It is mostly recorded from estuaries and harbours but in some places has spread to the open coast. The frond is dark brown with a prominent midrib. Either side of the midrib, the frond is divided into fingers. The small, branched holdfast may attach to small rocks or pebbles in sheltered locations. The lowest part of the flattened stipe develops a series of distinctive folds reminiscent of an Elizabethan ruff. Look for this seaweed especially on sheltered coasts on the lower shore and on man-made structures.

Brown seaweeds  45

000 Rockpooling.indd 45

15/04/2019 12:40

Mermaid’s Tresses Chorda filum

Size 700cm

This tall seaweed is found all around the UK and cannot be mistaken for anything else. The very long, thin, brown strands are unbranched, giving it the alternative name of Bootlace Weed. They are slimy to the touch and covered with a fringe of fine hairs which can be seen when the seaweed is submerged. It is found in rockpools and on the lower shore on sheltered coasts where it attaches to the seabed or smaller stones via a small disc-shaped holdfast.

Oysterthief Colpomenia peregrina Size 7cm

This bulbous seaweed is most common on the south and western coasts of the UK. It is golden in colour with a papery texture and resembles a small balloon. The hollow globe can become torn and deflated as it ages. The name Oysterthief comes from the fact that plants attached to molluscs or small stones can trap air inside when exposed at low tide and then float away with their anchor when the tide returns. A native to the Pacific, this seaweed was not recorded in the UK until the early 1900s. It can be found in rockpools and on short algal turf on the middle to lower shore.

46  Seaweeds

000 Rockpooling.indd 46

15/04/2019 12:40

Leathesia marina

Size 5cm

While this seaweed is found all around the UK it is more common on south and west coasts. It is yellow or golden in colour and forms shiny, irregular balls growing on short algal turf, in particular on Corallina fronds. Unlike Oysterthief, the balls are solid and gelatinous when small but become hollow and more irregular in shape with age. It can be found in pools and amongst short algal turf on the middle and lower shore.

Peacock’s Tail Padina pavonica

Size 10cm

This rare seaweed is limited in the UK to a handful of locations on the south and south-west coasts of England and Wales, where it is at the northern edge of its range. Despite its name it is creamy-brown in colour and the frond forms a fan shape with bands of white, calcium carbonate which give it a coarse texture. It grows in shallow, silty rockpools on the middle or lower shore, usually in open patches with little other algal growth.

Brown seaweeds  47

000 Rockpooling.indd 47

15/04/2019 12:40

Beanweed Scytosiphon lomentaria

Size 20cm

This light brown seaweed is found all around the UK. It forms long, thin, hollow tubes which are constricted at intervals, giving the appearance of an irregular string of sausages. It tends to grow in clusters in rockpools on the middle to lower shore.

Sea Flax Weed Halopteris scoparia

Size 15cm

This bushy brown seaweed is limited in the UK to the south and south west coasts of England and Wales. It produces dense tufts of fine fronds which feel coarse to the touch and can resemble shaving brushes, hence its alternative name of Shaving Brush Seaweed. It can be found in lower shore rockpools, especially where sand is present.

48  Seaweeds

000 Rockpooling.indd 48

15/04/2019 12:40

Hairy Sand Weed Cladostephus spongiosus

Size 25cm

This common seaweed is found all around the UK. It is brown with thin, branched fronds, each covered in short filaments, which give them the appearance and texture of pipe cleaners. It grows in rockpools and amongst red algae on the middle and lower shore.

Forkweed Dictyota dichotoma

Size 15cm

This seaweed is found all around the UK and can be abundant. It is mid to pale brown with a flattened, forked frond and the tips are divided and blunt ended. The fronds are delicate and smooth to the touch and can display blue iridescence in sunny conditions. It can be found in low shore rockpools.

Brown seaweeds  49

000 Rockpooling.indd 49

15/04/2019 12:40

Red seaweeds This is the largest group of seaweeds (Rhodophyta) and there is wide variation in both colour and form, from encrusting patches to fine and feathery or tough and leathery fronds. Colour varies from pale pink to deep purple, depending on the level of red pigment, phycoerythrin, they contain. On the seashore the red algae tend to be limited to the lower parts of the shore or rockpools as they are not as tolerant of desiccation. Microscopic examination is often necessary for the identification of red algae, although those included here are identifiable in the field.

Irish Moss Chondrus crispus

Size 20cm

Also known as Carragheen, this very common seaweed is found all around the UK. The colour is dark red when fresh but is often bleached and may exhibit yellow tips, or may turn yellow or green when exposed to strong sunlight. The frond is flattened and fan shaped, forking at intervals along its length and the tips are divided. It can display iridescence when underwater. However, this species shows great variability in form depending on the level of wave exposure. It can be found on rocks and in pools on the middle and lower shore.

50  Seaweeds

000 Rockpooling.indd 50

15/04/2019 12:40

CARRAGEENAN Irish Moss contains carrageenan, an extract which has been used in foods and medicine since the early 19th century. Carrageenan has a number of useful properties, including as a gelling agent, making it a vegetarian alternative to gelatine. It is also used as an emulsifier, thickener or stabiliser in toothpaste, shampoo and paint and in food products such as non-dairy milks and ice-cream. It can also be used to clarify beer.

False Irish Moss Mastocarpus stellatus

Size 10cm

This seaweed is found all around the UK but is more abundant on the west coast. It is similar in colour and form to Irish Moss, being dark red or purple when fresh. However, the frond differs in that it has thickened edges which are often curled inwards, forming a channel. Mature plants also have reproductive bodies on the fronds which resemble small pips, hence the alternative name of Grape Pip Seaweed. It feels rough and thick to the touch, unlike the smooth Irish Moss. It prefers wave-exposed coasts although it is not limited to these, and may be found on rocks and in pools on the middle and lower shore.

Red seaweeds  51

000 Rockpooling.indd 51

15/04/2019 12:40

Pepper Dulse Osmundea pinnatifida

Size 15cm

This is a common seashore seaweed all around the UK. Although it is a red alga and can be dark red in colour, it loses this colour when exposed to strong sunlight, and fades to brown or bright yellow. The fronds are fleshy in texture and flattened, branching off alternately on either side of the main stem, becoming shorter towards the tip to give a fern-like appearance. At low tide this seaweed can produce a peppery tang to the air and has been used, dried and powdered, as a condiment, hence its English name. It can be very conspicuous, forming a short turf covering the rock in the middle and lower shore.

Dulse Palmaria palmata

Size 50cm

This leafy seaweed is widespread around the UK except on the east coast. The thin, flattened frond is dark red but may be crimson in sunlight. The texture is smooth and surprisingly tough and it often has small growths or fronds sprouting from the margins, giving it a ragged appearance. It can be found attached to rocks and in pools on the lower shore and is often found attached to the stipe of Cuvie (see page 44).

52  Seaweeds

000 Rockpooling.indd 52

15/04/2019 12:40

SEAWEED SHAKING Seaweed shaking is a great way to discover tiny animals living in algae that normally go unnoticed. It can introduce you to a whole hidden world on the seashore. What you need A bucket of seawater A white tray ● A sieve (a plastic kitchen sieve is fine) ● A magnifier ●

What to do

activity

●

1. Find a small, seaweed-covered rock. 2. Hold it, seaweed down, in the bucket and shake vigorously to loosen hidden animals. 3. Replace the rock exactly as you found it. 4. Pour the contents of the bucket through the sieve. 5. Tap or rinse the sieve contents into the white tray and top up with clean seawater. 6. Now examine your catch, giving it time to settle. Look for tiny sea snails, nudibranchs, sea spiders, skeleton shrimps and other minute crustaceans. 7. Finally, return your catch to the original rock.

2

4

5

6

53

000 Rockpooling.indd 53

15/04/2019 12:40

Red Rags Dilsea carnosa

Size 50cm

This large red seaweed is widespread around the UK but more common in the south. The colour is dark red and the broad, flat, leathery frond is roughly teardrop shaped in outline, although it is often torn and ragged, arising from a very short, thin stipe. Unlike Dulse, it has no outgrowths on the frond margins. It is found on the lower shore attached to rocks and often amongst kelp.

Purple Laver Porphyra spp.

Size 20cm

There are several species in this group which have the same general characteristics. As a group, this treacherously slippery seaweed is abundant all around the UK. The frond is burgundy or purple and the shape varies between species, from broad sheets to narrow strips. It is always thin, filmy and translucent, although surprisingly tough. When wet it is shiny and membranous but when dry it feels papery to the touch. In winter it carpets upper shore rocks. At other times it can be found on the middle and lower shore attached to rocks. It is the main ingredient of the famous Welsh laver bread.

54  Seaweeds

000 Rockpooling.indd 54

15/04/2019 12:40

Coral Weed Corallina officinalis

Size 10cm

This common seaweed is found all around the UK. It is pale to deep pink, often with white tips to the fronds, although it can be bleached to pale pink or yellow in strong sunlight. The fronds are made of articulated, calcified segments, like the bones of a skeleton, giving the seaweed a coarse, chalky texture. It is commonly found lining middle and lower shore rockpools and beneath larger brown seaweeds.

Jania rubens

Size 2.5cm

This small, pale pink, pompom-shaped seaweed is not common but occurs all around the UK except for the east coast. The fronds are calcified, giving it a coarse texture, and on close inspection the frond is seen to be composed of segments. The tips can bleach to white in strong sunlight. It resembles a much smaller, finer Coral Weed and can be found attached to other algae in middle and lower shore rockpools.

Red seaweeds  55

000 Rockpooling.indd 55

15/04/2019 12:40

Pink Paint Weed Lithophyllum incrustans

Size 10cm

This encrusting coralline alga is widespread around the UK apart from the east coast of England. It is one of a number of very similar species that are difficult to distinguish. It grows as a smooth, pink, calcified crust on rock, looking like paint. Patches spread outwards as they grow and where they meet other patches, fold up to form raised ridges. This species can become bleached white, especially around the edges of shallow pools. It is found on the middle and lower shore, in rockpools and beneath blankets of wrack. It also grows on stones and shells, sometimes completely coating small pebbles in a pink crust.

Pink Plates Mesophyllum lichenoides

Size 2cm

This calcified alga is restricted to the west and south-west coasts in the UK. It is pink and forms thin, undulating plates, giving it a crunchy, brittle texture. The colour can fade to yellow in strong sunlight. It grows on Coral Weed (page 55) and is found on the lower shore as a short turf or in rockpools.

56  Seaweeds

000 Rockpooling.indd 56

15/04/2019 12:40

Red Sea Pine Halopithys incurva

Size 20cm

This tough red seaweed is mostly restricted to the south coast of England and the Channel Islands. It is very dark red with a bushy structure and is often encrusted with other species such as spiral worms, purse sponges and encrusting sponges. The tips of the branches and fleshy fronds curve inwards. It can be locally common and is found on the lower shore on bedrock and in rockpools.

Banded Pincer Weeds Ceramium spp.

Size 25cm

This group of very closely related algae are difficult to tell apart without microscopic examination but can be found all around the UK. They are red or reddish-brown with fine, filamentous fronds. Under magnification the fronds appear banded and the two prongs at the tip resemble a pincer. This seaweed can be found on the lower shore often attached to other algae, especially Codium spp., wracks and kelps.

Red seaweeds  57

000 Rockpooling.indd 57

15/04/2019 12:41

Bunny Ears Lomentaria articulata

Size 10cm

This red seaweed is widespread all around the UK. It is dark red with a smooth, shiny surface. The fronds are fleshy and segmented, giving the appearance of a string of elongated beads. New branches emerge where the frond is constricted between segments, giving the seaweed a bushy shape. It can be found on the middle and lower shore, on the shady sides of rocks and beneath other algae, and in rockpools.

Bonnemaison’s Hook Weed Bonnemaisonia hamifera

Size 15cm

This non-native seaweed originating from the Pacific Ocean is found on south and west coasts of the UK and the east coast of Scotland and Northern Ireland. It is crimson to dark red and is soft and feathery in appearance with distinctive curved hooks on some of the branches. The hooks enable it to snag on other seaweeds where it can grow as an epiphyte. It can be found on the lower shore amongst other algae and in rockpools.

58  Seaweeds

000 Rockpooling.indd 58

15/04/2019 12:41

Harpoon Weed Asparagopsis armata

Size 25cm

This non-native, invasive seaweed can be found in two very different forms. It has been found on southern and western coasts and can be locally abundant. The fronds of the sexual form are soft, tufted and red to pale red in colour, although often bleached yellow or buff in shallow water. It has distinctive harpoon-shaped outgrowths which provide its English name. These are barbed and enable drifting specimens of the alga to snag on other seaweeds, where it then grows. The asexual form is also red but often bleached yellow and is called the Falkenbergia phase (below left) as it was once believed to be a separate species. This has the appearance of small fluffy balls which grow on other algae and often break loose and float. Both forms can be found in lower shore rockpools amongst other algae.

Red seaweeds  59

000 Rockpooling.indd 59

15/04/2019 12:41

Dumont’s Tubular Weed Dumontia contorta

Size 23cm

This stringy red seaweed is common and widespread in the UK. It is reddish-brown and consists of long, slimy tubes which are twisted and irregularly branched. It is sometimes called Elastic Band Weed as the fronds are stretchy, and is found in rockpools on the middle and lower shore.

Sand Binder Rhodothamniella floridula

Size 3cm

This seaweed is widespread around the UK. It is pinkish-red and appears as a dense carpet on rocks. As the name indicates, the fine filaments trap sand grains from the water creating a spongy cushion over the rock’s surface. It is found covering low bedrock and boulders adjacent to sandy gullies on the middle to lower shore.

60  Seaweeds

000 Rockpooling.indd 60

15/04/2019 12:41

Vertebrata lanosa

Size 10cm

This epiphytic red alga is found all around the UK. It is a small, dark red, filamentous seaweed which grows in tufts on Egg Wrack (page 37). It forms a secure attachment by penetrating the fronds of its host and can form a dense covering. It is found on the middle shore where Egg Wrack occurs and can occasionally be found on other wracks.

Devil’s Tongue Weed Grateloupia turuturu

Size 100cm

This non-native seaweed from the Pacific is not widespread, although it may be underrecorded. It has been found on the south and south-west coasts of England, the Channel Islands, and west coasts of Wales and Scotland, mostly around harbours and estuaries. It is bright red to brownish-red in colour, consisting of twisted, elongated ‘tongues’ which are flattened and feel slimy to the touch. It can be found in lower shore rockpools on sheltered coasts.

Red seaweeds  61

000 Rockpooling.indd 61

15/04/2019 12:41

Clawed Fork Weed Furcellaria lumbricalis

Size 30cm

This red seaweed is common and widespread around the UK. The smooth fronds, which taper at the tips, are dark red but can fade to brown and yellow in strong sunlight. The cylindrical fronds fork at intervals, giving the seaweed a bushy shape. It is very similar in appearance to Discoid Fork Weed (below), although the holdfast is branched or claw-like in this species. It can be found in middle to lower shore rockpools.

Discoid Fork Weed Polyides rotunda

Size 20cm

This red seaweed is common and widespread around the UK. The smooth, cylindrical fronds, which taper at the tips, are dark red but can sometimes fade to brown or yellow. The fronds fork at intervals, giving the seaweed a bushy shape. It is very similar in appearance to Clawed Fork Weed (above), although the holdfast is disc-shaped in this species. It can be found in pools on the lower shore.

62  Seaweeds

000 Rockpooling.indd 62

15/04/2019 12:41

SEAWEED PRESSING Seaweed pressing is a great activity to do after a visit to the beach. You can make stunning pictures or build up your own personal catalogue of the different species, complete with memories of where and when you collected them. What you need ●

shallow tray nappy liner or absorbent, reusable cleaning cloth

newspapers sheet of plain paper ● fine paint brush ● ●

What to do

activity

●

1. Pour a little tap water into your tray – enough to cover the bottom. Then slide your sheet of paper into the water so the water covers it. 2. After rinsing your seaweed, arrange it on top of the paper in the water. Use the fine paintbrush to arrange the fronds so they don’t clump together. 3. Gently slide the paper out of the water. As the paper emerges, the seaweed should stick to it, but you need to be slow and careful. 4. Now place your paper on a few sheets of newspaper. 5. Place a nappy liner or reusable cleaning cloth on top of the seaweed to stop the newspaper sticking to it. Cover with another layer of newspaper. 6. Put the whole lot underneath a pile of heavy books and leave somewhere to dry out.

1

2

3

4

5

6

Tips Only take loose, fresh seaweed. Do not detach living seaweed from the shore. Replace the wet newspaper with dry every day or two to prevent mould. After a few days your seaweed should be dry and pressed, and ready to frame or add to your catalogue. Don’t forget to add a note to say what it is and where and when you collected it.

  63

000 Rockpooling.indd 63

15/04/2019 12:41

Lichen

000 Rockpooling.indd 64

15/04/2019 12:41

A

lichen is actually a combination of a fungus and a photosynthesising organism, generally an alga or blue-green alga. The structure of the lichen is formed from fungal filaments which house the algal cells. Lichens are generally low-growing, often forming crusts on rocks, and are abundant along the coast, although only a handful are found in the intertidal zone. They are notoriously difficult to identify without microscopic examination.

Black Lichen Lichina pygmaea

Size forms extensive patches

This tufted lichen is common and widespread on rocky seashores around the UK. It is matt black in colour and forms patches of dense tufts up to 1cm in height. At low tide it feels dry and crispy, although when wet it is fleshy. It provides habitat for a host of tiny animals, most notably the bivalve mollusc, Lasaea adansoni (page 228) and the isopod, Campecopea hirsuta (page 155). This lichen can be found attached to rocky outcrops and boulders on the upper and middle shore, often in association with barnacles. A similar species, Lichina confinis (opposite), is restricted to the high water mark and splash zone. It is more compact, only growing to a height of 0.5cm.

Lichens  65

000 Rockpooling.indd 65

15/04/2019 12:41

Verrucaria mucosa

Size up to 30cm wide

This encrusting marine lichen is common on rocky seashores all around the UK. It forms bottle green to dark green patches, with a paler ring around the edge, on smooth intertidal rock. It is gelatinous and slippery when wet and can be found on the upper and middle shore.

66  Lichens

000 Rockpooling.indd 66

15/04/2019 12:41

Tar Lichen Verrucaria maura

Size forms extensive sheets

This encrusting marine lichen is common and widespread on rocky shores in the UK. It forms matt black patches or sheets and can be mistaken for dried tar, hence its name. On close inspection, the surface appears cracked. It can be found on the upper shore from above the high water mark down to the barnacle zone.

Collemopsidium foveolatum

Size forms very small patches

This small, inconspicuous marine lichen forms a crust on limpet and barnacle shells and causes pitting and erosion of the shells over time. It appears as scattered, tiny dark spots. It can be found by examining limpets and barnacles on the upper and middle shore with a magnifier.

Lichens  67

000 Rockpooling.indd 67

15/04/2019 12:41

Sponges

000 Rockpooling.indd 68

15/04/2019 12:41

S

ponges are simple animals, having no specialised tissues or organs. They come in a wide variety of colours and forms, from flat, encrusting sheets on rocks to bulbous masses and branching structures. They are not mobile and remain attached to a firm substrate. Their internal structure is designed to create a flow of water through the body, from which food particles are filtered out. Tiny pores on the surface, called ostia, create an entrance to allow water in and this is moved through the various canals and cavities on the interior by the beating of tiny, whip-like appendages or choanocytes, finally exiting the sponge through larger pores called oscula. Many sponges contain spicules, which are hard parts forming a kind of skeleton to support the structure of the sponge. The shape and structure of the spicules are often used to identify species. However, some sponges can be identified from their outward appearance. While sponges form a large group (the phylum Porifera), there are a few living on rocky seashores that can be fairly easily identified in the field.

Breadcrumb Sponge Halichondria panacea

Size up to 15cm but may be more

This common encrusting sponge is found on rocky seashores all around the UK. Colour is olive green or buff with obvious, large oscula which are sometimes slightly raised above the flat surface of the sponge. The green coloration comes from an alga which lives within the sponge in sunlit, shallow-water areas. The buff-coloured varieties lack this and are normally found in deeper or more shaded areas. The name comes from the granular texture, said to resemble breadcrumbs. It can be found on the lower shore beneath overhangs, in gullies and among seaweed holdfasts.

Sponges  69

000 Rockpooling.indd 69

15/04/2019 12:41

Hymeniacidon perlevis

Size 15cm

This common intertidal sponge is widespread around the UK. It is deep orange to redorange in colour with a very variable form. It forms irregular encrusting sheets with a rough texture, and the oscula are not always obvious. It can be found from the middle to the lower shore on bedrock, in crevices and overhangs and on kelp holdfasts.

Oscarella sp.

Size 30cm

This encrusting sponge is widespread around the UK. It forms thin orange or pale yellow bubbly sheets which have a slimy, gelatinous texture. Look for it beneath rocks on the lower shore. The species name is under review.

70  Sponges

000 Rockpooling.indd 70

15/04/2019 12:41

Blue Encrusting Sponge Terpios gelatinosus

Size 5cm

This encrusting sponge is found on south and west coasts in the UK. The colour of this sponge is actually orange-yellow but it appears blue as a result of the symbiotic algae within. It is soft and smooth in texture with no obvious oscula. Look for this sponge on the underside of boulders on the lower shore.

Goosebump Sponge Dysidea fragilis

Size 15cm

This encrusting sponge is widespread around the UK. It is dirty white, with a pimply texture and prominent oscula. It often forms small, cushion-like mounds. Look for it on sheltered shores beneath lower shore rocks.

Sponges  71

000 Rockpooling.indd 71

15/04/2019 12:41

Black Tar Sponge Dercitus bucklandi

Size up to 15cm or more.

This encrusting sponge is recorded from south and west coasts in the UK. It is identified by its black colour and stretched appearance, resembling a sheet of thin rubber. The surface appears smooth with irregular patches of oscula. It is found in crevices and beneath rocks on the lower shore.

White Lace Sponge Clathrina coriacea

Size 30cm

This encrusting sponge is widespread around the UK. It is dirty white, with sheets formed by a latticework of thin tubes. It can be found beneath rocks, often fusing rocks and shells together and forming quite large patches.

72  Sponges

000 Rockpooling.indd 72

15/04/2019 12:41

Spiky Lace Sponge Leucosolenia spp. Size 2cm

Species within this genus are impossible to identify in the field and are grouped together here. They are widespread around the UK. The colour is white or grey and the sponge forms a cluster of upright pipes, each with an osculum at the end. Look for it attached to seaweed on the lower shore.

Compressed Purse Sponge Grantia compressa Size 2cm

This small sponge is widespread and common around the UK. It takes the form of a slightly flattened cream or grey vase-shaped bag with the osculum at the free end. The base is attached to rock or seaweed. It may be found singly or in groups, hanging from the roof of overhangs or on seaweeds in rockpools on the lower shore.

Purse Sponge Sycon ciliatum Size 3cm

This sponge is widespread around the UK. It is cream to pale brown and cylindrical, with a hairy texture and a frill of fine bristles around the osculum at the tip. It is normally solitary, although small groups can sometimes be found. The base of the sponge attaches to seaweed or stones on the lower shore.

Sponges  73

000 Rockpooling.indd 73

15/04/2019 12:41

Bryozoans

000 Rockpooling.indd 74

15/04/2019 12:41

S

ometimes called moss animals, these are colonial animals and very varied in appearance, from hard crusts to erect, gelatinous structures and plant-like colonies. They belong to the phylum Bryozoa. All are sessile, remaining firmly attached to the substrate. Each colony is made up of individual zooids, each housed in a box-like construction. Superficially these look like tiny anemones with a ring of tentacles circling the mouth. However, in bryozoans the tentacles have hair-like cilia to collect microscopic food, whereas anemones (page 87) and hydroids (page 79) have stinging tentacles. It can be difficult to distinguish hydroids from bryozoans outside the laboratory, as both groups are very varied in structure. Some seashore bryozoans require microscopic examination to identify species. Those included here should be identifiable in the field.

Sea Mat Membranipora membranacea

Size 7cm

This encrusting bryozoan is widespread around the UK. It forms smooth-edged white sheets with a lacy pattern on the fronds of kelp. Under a hand lens the regular pattern is seen to be made up of rectangular boxes, each housing an individual zooid. Look for it on kelp fronds on the lower shores. Left: Single Horned Bryozoan (page 76)

Bryozoans  75

000 Rockpooling.indd 75

15/04/2019 12:41

Hairy Sea Mat Electra pilosa

Size 5cm

This encrusting bryozoan is widespread and common around the UK. It forms white patches with sharply pointed fingers, reminiscent of frost patterns on a window. Under magnification the pattern is made up of oval boxes housing the individual zooids. It can be found encrusting red algae, especially Irish Moss and False Irish Moss, as well as other seaweeds, stones and shells. It can form a complete cylinder around an algal frond.

Single Horn Bryozoan Schizoporella unicornis

Size variable up to 15cm

This encrusting bryozoan is common all around the UK. The colour is white to pale pink or orange and the colony is made up of many individual zooids in flask-shaped structures. Look for it on the underside of middle to lower shore rocks and on kelp holdfasts. See photo on page 74.

76  Bryozoans

000 Rockpooling.indd 76

15/04/2019 12:41

Red Ripple Bryozoan Watersipora subatra

Size uncertain

This non-native bryozoan is currently recorded from the Channel coast of England, Channel Islands and Pembrokeshire, although it has the potential to expand its distribution in the UK. It is distinctive in appearance, forming reddish-orange sheets with black spots and often appearing to flow like volcanic larva over itself and other obstructions as it grows. Look for this species on the underside of rocks, especially in sheltered locations such as estuaries and harbours.

Amathia gracilis

Size 1.5mm (autozooid size)

This bryozoan is widespread around the UK although easily overlooked. It is pale to translucent in colour, forming a network of fine threads with clusters of vase-shaped autozooids arranged throughout. Look for it on the underside of rocks or on algae on the lower shore.

Bryozoans  77

000 Rockpooling.indd 77

15/04/2019 12:41

Cnidarians

000 Rockpooling.indd 78

15/04/2019 12:41

T

his large and varied group of animals includes the jellyfish, sea anemones, corals and hydroids. They generally have radial symmetry and a jelly-like body. The single opening or mouth is surrounded by stinging tentacles, the stinging mechanism being contained in special cells called nematocysts or cnidocytes which are unique to this group of animals (the phylum Cnidaria). Generally cnidarians have two very distinct life stages, the free-swimming medusa stage, most easily seen in the jellyfish, and the attached polyp stage, as seen in hydroids and sea anemones. The subgroup an animal falls within depends upon which stage is present and/or dominant. female medusa fertilised egg

male medusa

egg

sperm larva

medusa bud

attached larva

polyp forming

adult polyp

reproductive polyp

young hydroid colony Life cycle of the hydroid Obelia sp.

Hydroids Hydroids, also known as sea firs, are plant-like colonies made up of individual polyps attached together by a stolon that gives the colony its structure and attaches it to the seabed or algal host. Although superficially they look like seaweed, they can be distinguished by their pale, colourless tinge. Individual polyps perform different roles in the colony, such as feeding, reproduction and defence. The defence polyps are equipped with stinging cells called nematocysts, a unique feature of the phylum Cnidaria. This is a large and complex group (the class Hydrozoa) and can be difficult to identify to species level. Relatively few are found on the seashore.

Hydroids  79

000 Rockpooling.indd 79

15/04/2019 12:41

Kelp Fur Obelia geniculata

Size 5cm

This hydroid is common and widespread around the UK. It is whitish with a single stolon which has a zigzag structure. It can be found forming a fuzzy turf of uniform length on the fronds of kelp and wrack species on the lower shore.

Sea Oak Dynamena pumila

Size 5cm

This hydroid is common and widespread around the UK. It is pale buff in colour and can appear as single unbranched stems or longer branched colonies. The colonies have a serrated appearance, with polyps arranged in opposite pairs along the stem. Sea Oak can be found growing on wrack fronds, especially Serrated Wrack, on the middle and lower shore.

80  Cnidarians

000 Rockpooling.indd 80

15/04/2019 12:41

Hermit Crab Fur Hydractinia echinata

Size 0.5cm

This hydroid is widespread around the UK. The colonies are pale pink, white and brown and form a short turf on gastropod shells inhabited by hermit crabs, making the species relatively easy to identify. Look for it on the shells of hermit crabs, especially the larger Common Hermit Crab living in Common Whelk shells.

Oaten Pipe Hydroid Tubularia indivisa

Size 15cm

This distinctive hydroid is widespread around the UK. The long stem is brown with a pink or red hydranth at the tip with drooping white tentacles. It can be solitary, or colonial with a cluster of stems. It attaches to rocks and shells on the extreme low shore and in deep rockpools and gullies.

Hydroids  81

000 Rockpooling.indd 81

15/04/2019 12:41

Candelabrum cocksii

Size 12cm (when extended)

Although widespread around the UK, this solitary hydroid is more common in the south and west. The overall colour is a mottled reddish-brown, white and pink. Its habit of extending and contracting give it a worm-like appearance. However, closer inspection reveals a pale root-like structure which attaches it to the rock and a reddish-brown extendible body covered in tiny bulbous tentacles. The basal part may be decorated with round balls which are the reproductive structures. Look for it on the underside of lower shore rocks.

82  Cnidarians

000 Rockpooling.indd 82

15/04/2019 12:41

PHOTOGRAPHY ON THE SEASHORE – 1

What you need ●



activity

The seashore is probably one of the most challenging places for photography. It is a world of reflection and contrast, as well as being a hostile environment for sensitive equipment. However, rapid advances in compact camera and smartphone technology have made the instant capture of good quality images accessible to all, which is very useful when identifying species. Small, lightweight cameras also make it easier to photograph animals in hard-to-reach places such as overhangs and gulleys. Mobile phones have revolutionised the way we take and share images making it possible to take photos and videos of rarely seen species and behaviour.

A waterproof bag or case will keep your phone or camera safe, should you drop it in a rockpool or handle it with wet hands.

Tips for better photos ●

Rather than creating shade by getting too close to a small subject, try standing back a little to let the light in. You can always zoom in and crop the image later if necessary. ● Position yourself to avoid having your own reflection or shadow in the image. ● Some animals, such as sea squirts and fish, are shiny and reflective out of water. These are often best photographed submerged in shallow water. ● Animals such as seaslugs often contract when exposed to air, so place them in water to allow them to open up and show off their natural shape. What seemed like an insignificant blob on a rock can suddenly become a magnificent sea slug.

  83

000 Rockpooling.indd 83

15/04/2019 12:41

Stalked jellyfish This small group of marine animals (order Stauromedusae) belongs to the phylum Cnidaria, along with sea anemones and true jellyfish. They have an upward-facing umbrella-shaped bell fringed with eight arms, each tipped with a pompom of stinging tentacles. The animal attaches to algae or seagrass via a stalk with an adhesive sucker at the base. Stalked jellyfish can move to find a more suitable location by cartwheeling, using their tentacles and basal sucker. The stinging tentacles are used to catch small prey, which is then passed to the central mouth. Stalked jellyfish can be found in mid- and low-shore rockpools attached to algae. There are four commonly found species in the UK plus a fifth that is less common.

tentacles

arm

anchor

bell stalk

basal sucker

St John’s Jellyfish Calvadosia cruxmelitensis

Size across the bell 1.2cm

This stalked jellyfish is recorded from the south-west of England. It is pink or purple with a short stalk which is often hidden beneath the bell as this partially inverts, overhanging it. Inside the bell are numerous white spots, some forming a small Maltese cross shape in the centre, which gives rise to its alternative name of Maltese Cross Jellyfish.

84  Cnidarians

000 Rockpooling.indd 84

15/04/2019 12:41

Calvadosia campanulata

Size across the bell 3cm

This stalked jellyfish is widespread around the UK. It is variable in colour from green or brown to orange or red. The outer surface of the bell is warty in appearance and there are white spots on the inner surface. There are no oval-shaped anchors between the arms.

Craterolophus convolvulus

Size across the bell 2.5cm

This stalked jellyfish is widespread around the UK. Colour varies but is uniform with no spots and can be orange, brown or purple. It has short arms and a short stalk, from which an elongated vase-shaped bell emerges.

Stalked jellyfish  85

000 Rockpooling.indd 85

15/04/2019 12:41

Kaleidoscope Jellyfish Haliclystus spp.

Size across the bell 2.5cm

These stalked jellyfish are widespread around the UK. There are two very similar species in the genus, Haliclystus auricula and H. octoradiatus, and identification is difficult in the field. Both can be identified by the long stalk, equal in length to the umbrella, and a white, oval-shaped anchor on the webbing between each arm. H. octoradiatus also has scattered white spots on the umbrella, which H. auricula lacks.

Lucernaria quadricornis Size across the bell 7cm

There are few UK records for this stalked jellyfish, although it has been found on the Shetland Isles, Isles of Scilly and in south Cornwall. It has a distinctively shaped bell with the eight arms arranged in four pairs, giving it a square appearance.

86  Cnidarians

000 Rockpooling.indd 86

15/04/2019 12:42

Anemones and corals Sea anemones belong to the phylum Cnidaria and are solitary, soft-bodied animals. The cylindrical body or column has an opening at the top surrounded by rows of stinging tentacles. Although they can move position, anemones generally remain attached to a hard surface via a sucker at the base of the column. They are often brightly coloured and are sometimes called the flowers of the sea. In corals, the soft body is protected within a hard, calcareous skeleton.

Beadlet Anemone Actinia equina

Size 5cm

This is the most commonly found anemone in rockpools and on rocky shores all around the UK. Colour can vary between deep red, brown and green. It derives its name from the row of blue beads, called acrorhagi, circling the crown of the column. These contain stinging cells – nematocysts – and are used in territorial battles with other individuals. As with all anemones, the tentacles also contain nematocysts which fire automatically when touched by passing prey, injecting a paralysing toxin. Beadlet Anemones survive in the mid-shore on rocks where they are exposed to the air at low tide. They reduce their surface area by inverting their tentacles into the column, where they retain a reservoir of water, to avoid drying out. Look for these in rockpools or in the shade beneath seaweed, in crevices and gullies and under rocks. The lucky observer might witness these anemones giving birth. Unlike most anemones, they produce offspring through their mouth as fully formed miniatures which settle on the surrounding rock. Even closer observation might reveal one of their predators, the sea spider Pycnogonum littorale (page 170), which feeds on sea anemones.

Anemones and corals  87

000 Rockpooling.indd 87

15/04/2019 12:42

Strawberry Anemone Actinia fragacea

Size 12cm

This anemone is most common in the south-west, although it can be found in other parts of the UK. Once thought to be a variation of the Beadlet Anemone, the Strawberry Anemone gets its name from its crimson colour with small green spots which make it resemble a plump strawberry. It grows to a larger size than its close relative the Beadlet Anemone, is generally found lower on the shore and is less common. It also has a circle of blue beads around the crown of the column. Look for it in low shore rockpools, under rocks or at the base of rocky outcrops on sandy beaches. Unlike the Beadlet Anemone, it tends to be solitary and cannot fully retract its tentacles.

88  Cnidarians

000 Rockpooling.indd 88

15/04/2019 12:42

Snakelocks Anemone Anemonia viridis

Size 18cm

This anemone is found on south and west coasts in the UK and is easily identified by its long, sinuous tentacles for which it gets its common name. There are two colour variations: green tentacles with purple tips or a plain pinkish-grey. In a similar way to the algae hosted by tropical corals, the green coloration of this anemone is due to algae living inside which harness energy from sunlight. For this reason, the anemone prefers sunlit water to enable the algae to photosynthesise. However, as it is unable to fully retract its long tentacles it is usually found in low shore pools. The anemone also catches prey using its stinging tentacles, injecting a toxin to paralyse them before ingestion. Like the clown fish associated with tropical sea anemones, there are animals that live within the protective canopy of the Snakelocks Anemone’s stinging tentacles, although it is unlikely these ‘lodgers’ benefit their host. They include the Anemone Shrimp Periclimenes sagittifer (page 143) and Inachus sp. (page 148). Also look out for its common predator the Grey Sea Slug Aeolidia papillosa (page 214), which can look very similar to its prey, transferring the stinging cells from its meal into the long cerata on its back.

Anemones and corals  89

000 Rockpooling.indd 89

15/04/2019 12:42

NOCTURNAL LIGHT SHOW A number of rockpool sea anemones, including the Snakelocks Anemone, Gem Anemone, Strawberry Anemone and Red Speckled Anemone, exhibit fluorescence under ultraviolet light. This is produced by a protein in the animal’s cells which – it is believed – protects them from the intense ultraviolet rays they are exposed to in shallow water, acting like a natural sunblock. This can be observed during a nocturnal low-tide exploration by shining an ultraviolet torch or ‘black light’ into shallow pools.

caption

90  Cnidarians

000 Rockpooling.indd 90

15/04/2019 12:42

Gem Anemone Aulactinia verrucosa

Size 6cm

In the UK this is a fairly common sea anemone on the low shore in the south and west, although easily overlooked. They are often tucked into crevices in rows, sometimes partly covered in sand or silt. If disturbed, this anemone will fully retract its tentacles, revealing the small, pink, warty column forming a dome, with white stripes radiating down it. When open the short, pale tentacles are banded with white and may have a pinkish hue.

Red Speckled Anemone Anthopleura ballii

Size 10cm

This anemone appears to be restricted to south and west coasts in the UK. Colour is variable but a distinguishing feature is the column with its rows of warts, each tipped with a red spot. These warts are not adhesive and do not have pieces of gravel and shell stuck to them, as in other, similar species. Look for it on the middle or lower shore in holes and crevices and under boulders.

Anemones and corals  91

000 Rockpooling.indd 91

15/04/2019 12:42

Glaucus Pimplet Anthopleura thallia

Size 5cm

In the UK this anemone appears to be mostly restricted to the south-west of England and the Hebrides in Scotland. Colour is variable but a distinguishing feature is the warty column which usually has gravel sticking to it, although this tends to be buried in sand. Look for it on the mid to low shore of wave-exposed coasts, especially in the cracks and crevices of small, shallow rockpools where gravel and broken shell collect. It can also be found amongst mussels on these shores.

Dahlia Anemone Urticina felina

Size 20cm

This large anemone is commonly found all around the UK, especially on wave-exposed shores. It has short, stout tentacles which retract if disturbed and a thick, warty column which often has small pebbles and shell fragments stuck to it for camouflage when closed up. Colour is very vivid and most often in shades of red, purple, white and orange. Look for this anemone in rockpools on the lower shore emerging from crevices, in gullies or in groups carpeting the bottom of deep pools.

92  Cnidarians

000 Rockpooling.indd 92

15/04/2019 12:42

Daisy Anemone Cereus pedunculatus

Size 12cm

This anemone is fairly common in the UK, especially on south and west coasts. The long column is hidden, with its base attached to bedrock or pebbles buried in soft sediment, often in rock crevices, with just the brown and white-flecked crown of tentacles exposed. The tentacles are laid flat along the rock and if disturbed, the whole crown folds and retracts. Look for it under rocks where sediment collects. In some places it is associated with a small sea slug predator, Aeolidiella alderi (page 215).

Mud Sagartia Sagartia troglodytes

Size 12cm

This anemone is widespread around the UK. The column is hidden, with the base attached to bedrock or pebbles buried in soft sediment, often in rock crevices or old piddock holes, with just the crown of tentacles exposed at the surface. The crown is very variable in colour. The crown is often partially covered in a layer of fine sediment and will retract into the crevice if disturbed. Look for it in the bottom of rockpools where sand collects, around kelp holdfasts and under silty rocks.

Anemones and corals  93

000 Rockpooling.indd 93

15/04/2019 12:42

Elegant Anemone Sagartia elegans

Size 4cm

This common anemone is widespread around the UK and has a number of colour varieties. It is sometimes present in clusters of the same colour. There is an all-white variety, one with white tentacles and an orange disc, pink or orange tentacles with a variously coloured disc, or an orange and brown-patterned disc and tentacles. The upper part of the tall column has white spots and less obvious pores which produce white threads (acontia) for defence if disturbed. It is found under stones or overhangs in rockpools, usually with the base hidden in a hole or crevice.

Fairy Anemone Aiptasiogeton hyalinus

Size 1cm

This tiny anemone is rare in the UK, only found at a handful of sites in the south-west of England. It is translucent but can appear white overall, or have translucent pink or orange tentacles. The column is long and smooth with a small disc of tentacles which do not normally retract. Look for it on the lower shore in rock crevices and kelp holdfasts where, above water, it may appear as a tiny translucent blob.

94  Cnidarians

000 Rockpooling.indd 94

15/04/2019 12:42

Sandalled Anemone Actinothoe sphyrodeta

Size 5cm

This anemone is only occasionally found intertidally and likes shady places on the lower shore, where it attaches to flat rock. There are two colour varieties: all-white, or white tentacles with a yellow-orange disc, hence its alternative name, Fried Egg Anemone. It could be mistaken for Sagartia elegans (opposite), but has a short column with white stripes as opposed to spots, and has a fine dark line around the base of each tentacle. It is not normally found in holes or crevices.

Trumpet Anemone Aiptasia mutabilis

Size 15cm

This is a nationally scarce species found on south-west coasts in the UK. It has an overall brown colour with translucent white streaks radiating from the mouth, sometimes with a bluish tint. Its English name derives from the tall, trumpet-shaped column which gradually flares out towards the disc. It is found in rockpools, beneath stones and overhangs or among kelp holdfasts on the lowest part of the shore.

Anemones and corals  95

000 Rockpooling.indd 95

15/04/2019 12:42

Jewel Anemone Corynactis viridis

Size 2.5cm

Intertidally, this species is more common on south and west coasts in the UK. It is not a true anemone but is the only British member of the order Corallimorpharia, similar to a coral but without the hard skeleton. It is small, with a short, squat column and short tentacles, each tipped with a little knob or acrosphere. Colour varieties include bright yellow, emerald green, vivid pink and orange, normally in clusters or patches of the same colour. The acrospheres tend to be a contrasting colour to the disc and tentacles. Although it is more commonly seen by divers, look for it on a low spring tide in deep shade under overhangs in surge gullies on the lowest part of the shore.

Devonshire Cup Coral Caryophyllia smithii

Size 3cm

Intertidally, this coral is more commonly found on west and south-west coasts in the UK, where it is sometimes found on the lower shore in deep pools and shade. It is a solitary hard coral with a calcified cup-shaped skeleton containing the soft polyp. The skeleton or corallum is short and stout and the cup is divided around the edge by hard ridges or septa. The short translucent tentacles have a small white knob at the tip. Colour is shades of orange and yellow sometimes with a zigzag pattern in the centre. The tentacles can be fully withdrawn into the cup.

96  Cnidarians

000 Rockpooling.indd 96

15/04/2019 12:42

Scarlet and Gold Star Coral Balanophyllia regia

Size 2.5cm

In the UK, this cup coral is restricted to south-west coasts of England and Wales. It is usually found in small groups. It is brightly coloured, with translucent golden-yellow or orange tentacles and a deeper coloured, often red, centre. The tentacles are covered in tiny warts and do not have a knob at the tip. The spongy cup or corallum is more fragile than other British hard corals. It may be found on the extreme low shore in surge gullies and caves.

Dead Man’s Fingers Alcyonium digitatum

Size 15cm

While this species is common sublittorally all around the UK, it prefers areas with a strong water movement and can be found on the shore in surge gullies, dangling beneath overhangs. This is a type of colonial soft coral in the form of fleshy, irregular lobes, often finger-shaped, covered with tiny translucent polyps. The colony can be white or orange, coloured. When the polyps are actively feeding below water the colony appears furry, but when closed or dormant, during autumn and winter, the fingers appear smooth.

Anemones and corals  97

000 Rockpooling.indd 97

15/04/2019 12:42

Worms

001 Rockpooling.indd 98

15/04/2019 14:12

Bristle worms The bristle worms are a large class of worms called Polychaeta. Their bodies are segmented, and each of these segments have a pair of fleshy flaps called parapodia. The parapodia bear bundles of bristles or chaetae which give this varied group of animals its name. The parapodia differ between species, depending on the lifestyle of the worm, they are most obvious in the free-living worms where they are adapted to form paddles which can be used for swimming or moving across the seabed.

Keelworms Keelworms (in the family Serpulidae) are commonly found all around the UK. They live inside a hard, white, calcareous tube which is cemented to rock. A crown of feeding tentacles are extended from the open end of the tube when submerged but these are withdrawn and the opening plugged with an operculum when exposed at low tide. The tube has one or more ridges running along its length, which help with identification of species. There are three species that may be found on the lower shore attached to rocks, pebbles and shells.

Spirobranchus lamarcki

Size 25mm

This keelworm can be identified by the three ridges running along the upper surface of the tube, the central one ending in a spine protruding above the opening. This is the species most commonly found on the seashore. Spirobranchus triqueter looks very similar, but with a single ridge running along the tube, and is most commonly found sublittorally.

Worms  99

001 Rockpooling.indd 99

15/04/2019 14:12

Serpula vermicularis

Size 70mm

This distinctive keelworm has a pink-tinged tube and on the seashore it tends to be solitary, although sublittorally, in sheltered locations it can form dense aggregations and reef-like structures. Intertidally it is most commonly found in the south-west, where it attaches to rocks, stones and bivalve shells.

Spiral worms Spiral worms (Spirorbidae) are commonly found intertidally all around the UK and can be abundant. There are several similar species, each living inside a hard, white, calcified spiral tube. Each species tends to be associated with a particular substrate. They can be difficult to identify to species without magnification. A crown of feeding tentacles is extended from the open end of the tube when feeding.

Spirorbis (Spirorbis) spirorbis Size 4mm

This spiral worm is one of the most commonly found in the UK. It has a smooth, white tube which opens in a clockwise direction. It mainly attaches to wracks, especially Serrated Wrack (page 36) where it can be abundant to the point of restricting photosynthesis. Look for it on these algae on the middle and lower shore.

100  Worms

001 Rockpooling.indd 100

15/04/2019 14:12

Spirorbis (Spirorbis) corallinae Size 1mm

This worm is similar in appearance to Spirorbis (Spirorbis) spirorbis (opposite), with a smooth tube opening in a clockwise direction. It is mainly found attached to Coral Weed (page 55) in rockpools and on the lower shore.

Spirorbis (Spirorbis) tridentatus Size 3mm

This worm has a clockwise opening tube which is smooth but with distinct ridges running along the length. It is found on rocks and in crevices on the lower shore.

Janua heterostropha Size 2mm

This spiral worm is very widespread and common in the UK. It has a slightly off-white ridged shell, and the tube spirals in an anti-clockwise direction. It is possibly the most common spiral worm, as it attaches to a wide range of substrate, including rocks, shells, seaweed and crabs on all parts of the shore, both in and out of rockpools.

Bristle worms  101

001 Rockpooling.indd 101

15/04/2019 14:12

Honeycomb worms Belonging to the family Sabellariidae, these worms build a tube from sand grains glued together by mucus and may aggregate in large numbers, forming reef-like structures.

Honeycomb Worm Sabellaria alveolata

Size 200mm (tube length)

In the UK this worm is most common in the south-west of England but can be found in suitable habitat around most of the country. Individual worms build a tube from coarse sand and shell fragments, and large aggregations of these are built up to form a cushion-like mound which resembles a honeycomb. The colour of the tubes varies with the colour of sand available, but is often golden orange. Where colonies join together they can form reef structures measuring several metres across. On some beaches these structures can dominate the lower shore and be seen from some distance. However, in other areas these worms appear as individual tubes attached directly to the bedrock and are less conspicuous. The tubes are quite brittle to the touch and easily damaged if walked on. At high tide the worms extend their feeding apparatus into the water to filter feed, retreating back into the tube at low tide. They require a fair amount of water movement, so tend to be found on more exposed coastlines where there is rock to attach to but also a supply of the required size of sand grains.

102  Worms

001 Rockpooling.indd 102

15/04/2019 14:12

Ross Worm Sabellaria spinulosa

Size 30mm (worm length)

This tube-building worm has been recorded all around the UK. Like the Honeycomb Worm, it builds a hard tube by cementing sand grains and shell fragments together. Tubes are attached to rock, normally individually on the seashore, although sublittorally they can occasionally aggregate and form low-lying reefs. The tubes vary in colour depending on the sand available. They can be hard to spot, on the underside of rocks or in rock crevices, as they blend in with the sediment. Look for them on the lower shore.

Fan worms Fan worms (included in the family Sabellidae) build a protective tube into which they can withdraw if threatened. To feed they extend a circle or crown of feathery tentacles into the water column and filter feed. Eye spots on the tentacles warn of danger, and retreat into the tube is instantaneous. The tube may be fully or only partially buried in sediment and may extend above the surface to hold the crown higher in the water column.

Bristle worms  103

001 Rockpooling.indd 103

15/04/2019 14:12

Twin Fan Worm Bispira volutacornis

Above: when withdrawn, the tubes have a distinctive pinched top

Size 100mm

While this worm is found in various locations around the UK, it is most common in the south-west of England. The grey, leathery tube is built out of mud and silt grains. The crown or fan of feathery feeding tentacles emerges from the tube but withdraws instantly if threatened. The crown is white or cream in colour and forms two circles side by side, hence the name. Although it is mainly subtidal, it can be found in deep rockpools on the lower shore or in shallow water alongside rocky ledges.

Peacock Worm Sabella pavonina Size 270mm

This tube-dwelling worm is found all around the UK. The grey, flexible tube is formed of fine mud particles glued together by mucus and projects up to 10cm above the surface of the sediment in which it is anchored. A colourful crown of feathery tentacles extends from the tube to filter feed at high tide. At low tide on the lower shore the tentacles retract, leaving just the tube on view. The crown is banded and variable in colour with red, brown or purple. This animal can be found on sheltered shores where mud is present, for example in harbours and estuaries.

104  Worms

001 Rockpooling.indd 104

15/04/2019 14:13

Branchiomma bombyx

Size 45mm

This worm is widespread around the UK. It lives inside a brown, papery tube attached to the underside of stones, shells or in rock crevices and kelp holdfasts. The crown of tentacles is banded brown or red and may be seen if the animal is submerged. Look for it beneath rocks on the lower shore.

Terebellid worms Belonging to the family Terebellidae, these worms usually live within a tube built of sand grains, although others live in burrows in the sediment. Their numerous feeding tentacles or palps are long, thin and flexible and are extended from the tube to collect detritus from the seabed.

Sand Mason Lanice conchilega Size 200mm

This distinctive worm is found on coasts all around the UK. The tube, built of sand grains, forms a branching structure resembling a tree with the lower part buried in sediment. When submerged, the long feeding palps extend through and out of the branches to collect food from the seabed. If exposed, the tentacles retract into the tube for safety. Whilst most common on sandy shores where they can be abundant, they are also found in rockpools where sand is present.

Bristle worms  105

001 Rockpooling.indd 105

15/04/2019 14:13

Strawberry Worm Eupolymnia nebulosa Size 150mm

This worm is widespread around the UK, although not common on the seashore. The orangey-red body is covered in white spots, giving the animal its English name, with a mass of long, white or pale feeding tentacles at the head end. It lives within a thin, slimy tube and can be found beneath rocks on the lower shore.

Cirratulus cirratus Size 100mm

This worm is widespread around the UK. Colour varies from orangey to yellow or very pale. The body is cylindrical with two tufts of long, sinuous feeding palps behind the rounded head and shorter, tentacle-like gills arranged along the length of the body. It lives hidden in soft sediment under rocks on the lower shore with just the writhing mass of feeding palps visible.

Cirriformia tentaculata Size 200mm

This worm is widespread around the UK and more common in the south of England. It is similar in appearance to Cirratulus cirratus but grows larger with a pointed head and more numerous feeding palps. Look for the mass of red feeding tentacles under silty lower shore rocks and in crevices.

106  Worms

001 Rockpooling.indd 106

15/04/2019 14:13

Terebella lapidaria Size 90mm

This red worm is found in south and south-west England where it can be locally common. It is found wedged in crevices from where it extends its feeding palps. It may be revealed on the lower shore when loose slabs of rock break away.

Thelepus cincinnatus Size 200mm

This worm is widespread all around the UK. The body is pale yellowy-orange or brown, with a mass of pale orange tentacles and a cluster of bright red gills at the head. The body segments are welldefined, giving the worm a distinctive ridged appearance. It can be found beneath lower shore rocks, sometimes within a long, sand-encrusted tube, although often without it.

Amphitritides gracilis Size 120mm

This worm is found on south and west coasts in the UK. It is pale yellow to white, with red gills which give the front section of the animal a reddish tinge. A mass of long, pale, sinuous feeding palps are visible at the head. The worm tends to coil up when disturbed. It can be found on the lower shore in silty rock crevices.

Bristle worms  107

001 Rockpooling.indd 107

15/04/2019 14:13

Flabelligera affinis

Size 60mm

This worm is widespread but uncommon in the UK. It has an almost transparent body through which the internal structure can be seen. The appendages appear bristly. It lives in a mucus tube on the underside of rocks but can easily be overlooked as it is covered in sand and silt. It can also be found amongst the spines of sea urchins such as the Green Sea Urchin (page 243).

Polydora ciliata

Size 25mm

These worms are widespread in the UK where there is a suitable type of rock. However, the traces of their burrows are more easily spotted than the worm itself. They favour limestone and chalk but can also burrow into other types of soft rock, mudstone and shells. Within the burrow they build a tube from mud particles, in which they live. Underwater they extend a pair of long feeding palps from their burrow. These can be seen waving around in shallow pools and depressions in the rock from high to low shore.

108  Worms

001 Rockpooling.indd 108

15/04/2019 14:13

Malacoceros vulgaris

Size 160mm

In the UK this worm is found on south and west coasts. It is orange or red, with many fine appendages along its sides. Look for it on the lower shore under stones in muddy sand.

Ragworms and paddleworms Ragworms (Nereididae) and paddleworms (Phyllodocidae) have a long segmented body, each segment with a pair of parapodia or paddles for locomotion. They are mobile, active animals which emerge to scavenge for food. Some undergo changes in body structure during breeding, producing epitoke worms (page 110) which can swarm in surface waters at specific phases of the lunar cycle.

Perinereis cultrifera

Size 250mm

This large, active ragworm is widespread around the UK. It is greenish-brown, with an obvious red line along its back which is its blood vessel. At low tide it can be found on the lower shore beneath undisturbed boulders, in crevices and in kelp holdfasts.

Bristle worms  109

001 Rockpooling.indd 109

15/04/2019 14:13

EPITOKE WORMS Many types of ragworm undergo significant changes to their morphology during breeding. The body separates into the front section which retains the normal organs while the posterior section develops for reproduction and grows a head. It will be either male or female at this stage. At a particular time of the lunar cycle this rear end breaks away from the rest of the worm and swims to the surface where it releases its eggs or sperm. These epitoke worms can often be witnessed in high numbers at night at the sea’s surface, looking like fat worms. The front end of the worm may then regenerate a new posterior section.

Estuary Ragworm Hediste diversicolor Size 120mm

This large ragworm is common and widespread around the UK, where it is found in estuaries, harbours and other sheltered brackish water sites. Its colour varies from greenish-yellow to orangebrown with an obvious red line along its back, which is its blood vessel. It does not have an epitoke stage but instead, males release sperm near the eggcontaining burrows of females. It lives in a burrow excavated in mud or muddy sand but can be found beneath stones adjacent to the burrow.

110  Worms

001 Rockpooling.indd 110

15/04/2019 14:13

Greenleaf Worm Eulalia viridis

Size 100mm

This bright green paddleworm is common and widespread on rocky shores around the UK. It is active during the daytime, when it can be found crawling around among barnacles and mussels, feeding on damaged individuals. It is also sometimes found in kelp holdfasts and in crevices. The green jelly egg masses found attached to seaweed in the spring are widely believed to be produced by this worm, although this has not been scientifically confirmed. There is some question about whether the worms found in the UK are actually a very closely related but separate species, E. clavigera.

Pterocirrus macroceros

Size 80mm

In the UK, this carnivorous paddleworm is found on south and south-west coasts of England. It is pale in colour but can vary from buff, yellow or pink to green and is flattened in outline. The paddles lining the sides of the body are large and ornate, even leafy in appearance. Look for it on the lower shore in silt-filled crevices and under stones.

Bristle worms  111

001 Rockpooling.indd 111

15/04/2019 14:13

Eunicid worms Although these worms look superficially like paddleworms, they are in a separate group (Eunicidae).

Marphysa sanguinea Size 500mm

This active and mobile worm is widespread in the UK and is found in a variety of habitats. Colour varies and can be pink, orange or grey but with a distinctive iridescence and a fringe of red gills along most of the body. On the seashore they can be found beneath lower shore rocks and in crevices where they live in burrows lined with mucus.

Lysidice ninetta

Size 50mm

This active worm is found in the south and south-west in the UK. It is orange-brown in colour with a cylindrical body. The blunt, pale head is distinctive and bears three short tentacles. It can be found on the lower shore beneath silty rocks and in crevices.

112  Worms

001 Rockpooling.indd 112

15/04/2019 14:13

Lugworms Lugworms Arenicolidae

Size 200mm

The cast of the lugworm is a familiar sight on sandy beaches at low tide. These worms live inside a U- or J-shaped burrow, ingesting sand, digesting the organic material and leaving the mineral part of the sand for excretion. The waste is squeezed out of one end of the burrow, forming the coiled cast that we see. Casts can also be seen on rocky shores, in sandy pools and between stones. Arenicolides branchialis and Arenicolides ecaudata (below) form finer casts and burrow into sediment under rocks and in crevices. Unlike in the more familiar lugworms (Arenicola marina) used by anglers, the frilly red gills of these two species extend to the tip of the tail.

Bristle worms  113

001 Rockpooling.indd 113

15/04/2019 14:13

Scaleworms Scaleworms have two rows of overlapping scales or thin plates covering all or part of their back. The scales are delicate and easily dislodged and lost if the worm is handled, so special care should be taken. Scaleworms tend to be shorter and wider than many bristle worms. They are active animals feeding on detritus, carrion and tiny prey.

Alentia gelatinosa

Size 90mm

This worm is widespread around the coast of the UK. It is a large scaleworm with a smooth, shiny appearance. The overlapping scales are large with a bare strip between the two rows, which reveals brown and white banding. The scales cover the full length of the body. Look for this worm beneath mid to low shore rocks.

Lepidonotus clava

Size 35mm

This scaleworm is widespread in the UK but most common on south and west coasts. It has a bristly appearance and is more robust than other species. The round scales do not overlap across the back, leaving a bare strip down the middle of the two rows and around the head. The scales are mottled brown, usually with a paler patch on each. It can be found beneath low shore rocks.

114  Worms

001 Rockpooling.indd 114

15/04/2019 14:13

Harmothoe extenuata

Size 70mm

This scaleworm is widespread around the UK. The overlapping, kidney-shaped scales do not extend all the way along the worm, leaving the posterior section bare. There is also a bare strip along the middle. The scales vary in colour but are often orangey brown or grey. It can be found beneath lower shore rocks.

Harmothoe impar

Size 25mm

This scaleworm is widespread around the UK. The overlapping, kidney-shaped scales extend all the way along the body and overlap along the midline. The scales are brown, often with a yellow spot, and covered in small tubercles. It can be found beneath middle and lower shore rocks. In spring these scaleworms pair up to breed.

Bristle worms  115

001 Rockpooling.indd 115

15/04/2019 14:13

Sthenelais boa

Size 200mm

This large scaleworm is widespread around the UK. At first glance it might be mistaken for a ragworm-type animal but close inspection reveals the scales, which overlap to completely cover the back. Colour is variable but may be brown, orange or yellow. It tends to roll into a spiral when disturbed. It prefers shores with some sand, mud or gravel and can be found beneath embedded stones on the middle to lower shore.

Bamboo worms Bamboo worms Maldanidae

Size up to 160mm

This group of worms are very difficult to identify to species but are distinctive from other worms and can be found on rocky seashores. They get their English name from the pale rings and constrictions at intervals along the length of the body, like a bamboo cane. Overall colour tends to be reddish-brown. They can be found beneath embedded rocks on the lower shore, where they live in a maze of lined galleries or horizontal burrows.

116  Worms

001 Rockpooling.indd 116

15/04/2019 14:13

Flatworms Flatworms (Platyhelminthes) have a soft, flattened body and glide along by using microscopic hairs, cilia, on the underside. They can change their shape becoming shorter and wide or longer and narrow. They are mostly carnivorous, feeding on carrion and small slow-moving, or sessile, animals such as sea squirts. Although there is a variety of seashore flatworms to be found in the UK, very few are easily identified in the field. These animals are extremely thin and easily damaged if handled, although they may be carefully rinsed off a rock into a white tray if necessary for viewing.

Candy Striped Flatworm Prostheceraeus vittatus Size 50mm

This distinctive flatworm is widespread around the coasts of the UK. It is pale yellow, cream or white with thin dark stripes. The sides of the animal are wavy and it has a distinctive head end with a pair of tentacles, which can lead to it being mistaken for a sea slug. It can be found in rockpools and beneath stones on the lower shore, where it feeds on sea squirts. It is worth looking among clusters of Light Bulb Sea Squirts for this animal (page 250).

Leptoplana tremellaris Size 25mm

This flatworm is widespread around the UK but easily overlooked. It is a translucent pale brown or buff, and if viewed against a dark background, white patches may be seen. The body is wider at the head end, tapering towards the rear. It is extremely thin and easily damaged if handled. Look for it on the underside of stones, where it feeds on sponges and sea squirts, or amongst seaweed. Alternatively, use the seaweed-shaking technique (page 53).

Flatworms  117

001 Rockpooling.indd 117

15/04/2019 14:13

Procerodes littoralis

Size 7mm

This easily overlooked flatworm is widespread on seashores all around the UK. It is elongated, pale brown with paler markings on the head, which also bears two small projections or tentacles. There may also be a paler band down the middle. It can be found in the upper and middle shore under rocks, especially where there is freshwater input.

Fecampia erythrocephala (cocoon)

Size cocoon 10mm

This flatworm is found in the south and west of England and Wales. As an adult it is a parasite of crabs, particularly shore crabs, where it lives within the body cavity. To breed, it leaves its host and creates a hard cocoon into which it deposits its eggs. The white cocoon is cemented along its length to the underside of mid-shore rocks. Although these look similar to a seaweed fly maggot, they are hard to the touch.

118  Worms

001 Rockpooling.indd 118

15/04/2019 14:13

Ribbon worms Ribbon worms (Nemertea) are unsegmented, smooth-bodied and tend to be very long and thin, hence the name ribbon worm. The body is highly extendable but fragile, and should be handled with care to avoid breaking. They are carnivorous predators, catching and feeding on crustaceans, molluscs and other worms, although some are scavengers. Most species are very difficult to identify, but there are a couple of distinctive intertidal species included here.

Bootlace Worm Lineus longissimus

Size up to 10m, exceptionally up to 30m

This worm is widespread around the UK. It is the longest ribbon worm and one of the longest animals in the world. It is shiny and dark brown, slightly paler at the tip of the head and with paler longitudinal lines which are sometimes visible, although it often appears black with an iridescent purple tinge. It tends to lie coiled in a tangled mass under rocks on the lower shore, is slimy to the touch and gives off mucus when disturbed. It may also sometimes be seen in rock crevices or among kelp holdfasts, but should not be removed as it is easily broken.

Ribbon worms  119

001 Rockpooling.indd 119

15/04/2019 14:13

Lineus viridis

Size 80mm

Records for this species in the UK are patchy, but it is present on Atlantic and south-west coasts. It is smooth-bodied with a crinkly appearance and triangular head. Overall colour is green and this can vary from dark green or olive to very pale. It lives beneath middle to low shore rocks with mud or silt. It may be found by using the seaweed-shaking technique (page 53) with small rocks. It is a voracious predator and will eat small animals kept with it in a tray or bucket.

Spoon worms Spoon worms (Echiura) are worm-like animals, although there is some debate about how closely related they are to annelid worms. They are unsegmented with a body divided into two distinctive parts: a fat, pointed, cylindrical trunk at the rear and a flattened, extendable proboscis which is curled to form a groove.

Gaertner's Spoon Worm Thalassema thalassemum Size 70mm

This spoon worm is the only one of its group found on rocky seashores in the UK. Here it is mostly restricted to southwest coasts. While the trunk lies hidden in crevices, the proboscis extends to collect detritus, which it gathers from the sediment by producing a sticky mucus string. The trunk varies from pink, orange, yellow or blue, while the proboscis tends to be orange or cream. It can be found tucked into crevices and cracks in low shore rocks.

120  Worms

001 Rockpooling.indd 120

15/04/2019 14:13

The spoon worm Thalassema thalassemum

Peanut worms Peanut worms (Sipuncula) are worm-like animals, although there is some debate about how closely related they are to annelid worms. They are unsegmented and when contracted, loosely resemble a peanut, hence their English name. The cylindrical body is wider at the rear but tapers to form a nipple shape at the end, while the front section, called the introvert, is narrower and can be drawn in.

Golfingia elongata

Size 150mm

This peanut worm is one of the few in this group that is easily identified, and is widespread around the UK. It is pale pink or orange in colour. When the introvert is extended, a cluster of tentacles is visible at the end. The animal can be found beneath rocks and burrows in soft sediment where this is present.

Peanut worms  121

001 Rockpooling.indd 121

15/04/2019 14:13

Crustaceans

001 Rockpooling.indd 122

15/04/2019 14:13

Crabs Moulting Crabs have a hard outer casing, the exoskeleton, which acts like a suit of armour. This does not stretch or grow, so as the crab grows it needs to periodically moult its shell. It does this through a process called ecdysis, whereby the crab produces chemicals to separate the exoskeleton from the underlying tissue. Finally, it swells its body and bursts open a seam at the back of the carapace, climbing out and leaving the empty moult behind. The moult looks just like a dead crab, complete with carapace, legs and eyes. It feels light and can be opened at the back with a fingernail. By contrast, a dead crab will feel heavy and smell strongly. The freshly moulted crab is around 20% larger than its moult, with a soft, flexible skin. During the moulting process and immediately afterwards, it is at its most vulnerable and will hide away in a crevice or beneath rocks. Sometimes you can find a moult in a rockpool, which may indicate a soft crab hiding nearby. Crabs undergoing this process are referred to as ‘peeler crabs’.

Mating

A freshly moulted crab and moult

A female crab is only able to mate when freshly moulted. As she prepares to moult, she releases pheromones which attract males. A male crab finding such a female may hold on to her, carrying her beneath him until she has moulted, ensuring he is present at the right moment. Crabs mate abdomen to abdomen as he fertilises her eggs, which she then carries beneath her. The egg mass can vary in colour between bright orange or yellow to pale or dark brown, depending on species and how well developed the eggs are. male

female

The abdomen, tucked underneath, differs between male and female crabs, being broader in females in order to carry the egg cluster.

Crabs  123

001 Rockpooling.indd 123

15/04/2019 14:13

A female crab and eggs

Crab larvae at various stages of development

The female keeps the eggs clean and aerates them until the larvae hatch and join the other plankton in the water column. Here they feed and develop through a number of larval stages until they settle as tiny, recognisable juvenile crabs on the seabed.

Limb regeneration Moulting gives crabs the opportunity to regrow lost limbs. The new limb starts to regrow beneath the exoskeleton but remains hidden until the moult, at which time the new limb is revealed. Crabs can sometimes be found with a half-grown claw which at the next moult may have regenerated to normal size. However, regeneration of limbs uses a lot of energy and if the loss of legs or claws restricts the crab’s ability to find enough food, it may be fatal.

Epiphytes Crabs can occasionally be found encrusted by epiphytes. Once a crab has finished grow­ ing and moulting, a variety of animals may attach to its shell, such as barnacles and keel worms. Even tiny Blue Mussels have been found living in the eye sockets of Shore Crabs.

124  Crustaceans

001 Rockpooling.indd 124

15/04/2019 14:13

Shore Crab Carcinus maenas

Size carapace 80mm

This is the most widespread crab in the UK, found in most shallow-water habitats. Although colour can vary, Shore Crabs are mostly green, while older individuals can be brown with orange or yellow underneath and around their joints. Juveniles exhibit a range of colours and patterns which help camouflage them in various habitats (below). The roughly heartshaped shell has five teeth either side of the eyes and three rounded lobes between the eyes. As this is not a ‘swimming crab’, the rear legs are not flattened. Shore Crabs are found in the middle to upper shore, often beneath rocks, in rockpools and beneath wrack. Often, females can be found carrying their cluster of eggs tucked against their underside (see opposite). When the eggs are newly produced they are bright orange, changing to brown as they develop and grow. Occasionally both male and female crabs can be infected with the parasitic barnacle, Sacculina carcini, which appears in the same place as an egg-cluster but is smooth and creamy-coloured in appearance (page 169). Male Shore Crabs are often found carrying a female beneath them in readiness for mating (page 123).

A juvenile Shore Crab

Crabs  125

001 Rockpooling.indd 125

15/04/2019 14:13

Velvet Swimming Crab Necora puber

Size carapace 100mm

This crab is widespread around the UK and can be locally common. The red eyes and purple striped legs of the Velvet Swimming Crab make it unmistakable. Along with its belligerent nature, awarding it the alternative name of Devil Crab, its behaviour makes it unmistakable as well. This crab will often rear up on flattened hind legs to snap at probing fingers with its sharp claws. The English name refers to a velvety covering of fine hairs coating its carapace and the crab's ability to swim away in short bursts if threatened, using its flattened back legs as paddles. It is found on the middle to lower shore, often beneath rocks, in rockpools and beneath seaweed. Like the Shore Crab, male Velvet Swimming Crabs are often found holding onto a female in readiness for mating.

126  Crustaceans

001 Rockpooling.indd 126

15/04/2019 14:13

Edible Crab Cancer pagurus

Size carapace 250mm

This is a common crab, commercially fished all around the UK. Its orange-brown, ovalshaped shell has a distinctive ‘pie-crust’ edge, the large claws have black tips, and all the walking legs are pointed. Very small juveniles can be white. This robust crab uses its powerful claws and legs to grip onto rocks and algae or wedge itself into a crevice, making it difficult to remove. If you do pick it up it will curl up its legs and play dead. It is found on the middle to lower shore, often beneath rocks and in rockpools.

Hairy Crab Pilumnus hirtellus

Size carapace 15mm

This crab is widespread around the UK and can be locally common. It is a small, deepbodied crab with an overall hairy appearance. The bristly hairs that cover its legs and carapace trap sediment and help camouflage the crab beneath seashore rocks and boulders. Its claws are relatively chunky with brown tips and one is noticeably larger than the other. It is found on the middle to lower shore, often beneath rocks.

Crabs  127

001 Rockpooling.indd 127

15/04/2019 14:13

Long-legged Spider Crab Macropodia sp.

Size carapace 20mm

There are two common species of Long-legged Spider Crab, Macropodia rostrata and M. deflexa, which are both widespread around the UK. With a small body and very long spindly legs which they decorate with algae, they sport excellent camouflage and are easily overlooked. The algal camouflage obscures the features, making it difficult to identify them to species level. The easiest way to find this crab in a rockpool is to gently run your fingers or a small net through the seaweed, or shake seaweed into a tray of water.

Inachus sp.

Size carapace 20mm

There are two common species, Inachus dorsettensis and I. phalangium, which are both widespread around the UK. These small-bodied crabs have long legs, although they are slightly thicker and shorter than those of Macropodia sp. Inachus crabs cover themselves with sponges for camouflage and this makes it difficult to identify them to species level. They are normally found on rocks in silty habitats, frequently hiding beneath the tentacles of the Snakelocks Anemone, Anemonia viridis (page 89).

128  Crustaceans

001 Rockpooling.indd 128

15/04/2019 14:13

ECO-CRABBING Eco-crabbing is a harmless alternative to the traditional pastime of catching crabs using a crab line with hooks, which can damage small rockpool fish attracted to the bait. These types of line require constant replacement of the bait, as it is quickly taken. Crab lines with a net bag attached in place of hooks are now widely available in seaside shops. What you need ● ●

A crab line with a net bag A large, robust bucket A fishing net

●

Bait – leftover or out-of-date meat or fish can be frozen and stored for future use. Do not use limpets or other seashore animals

What to do 1. 2. 3. 4. 5.

Fill your bucket almost to the top with cold seawater. Bait the net bag and lower it into a rockpool, keeping hold of the frame. Be patient and quiet while you wait for crabs to investigate. When a crab holds onto the bag, gently lift the line out of the water. Hold the net beneath the crab and carefully transfer it to your bucket.

Looking after your catch and the environment ● ● ● ●

activity

●

No more than three similar-sized crabs per large bucket. If they fight you will need to remove them. Regularly refresh the bucket with cool seawater to maintain oxygen levels. Examine your catch and return to where they were caught as soon as possible. Leave no kit or litter behind.

129

001 Rockpooling.indd 129

15/04/2019 14:14

Common Spider Crab Maja brachydactyla

Size carapace 200mm

This large crab is more common along south-west and west coasts in the UK. It is often highly decorated with algae. If a clump of seaweed in a rockpool suddenly starts walking, this is probably a Common Spider Crab. It has an orange coloured, teardrop-shaped carapace covered in spiny tubercles with spines around the edge, as well as long legs and small, tweezer-like claws. Look for it in lower shore rockpools where it may be out in the open, confident in its camouflage.

DECORATOR CRABS Spider crabs decorate the hard shell covering their body and legs with seaweed, sponges, hydroids, and other marine growth as a way of camouflaging themselves. The Common Spider Crab snips lengths of algae and ‘plants’ them on its shell, where they can continue to photosynthesise and grow. Tiny hooks between the spines on its shell hold the algae in place. When the crab moults its shell it is very quick to redecorate. Younger crabs tend to have the most elaborate decoration whereas larger, older crabs can have almost bare shells with just the odd barnacle living on them.

130  Crustaceans

001 Rockpooling.indd 130

15/04/2019 14:14

Furrowed Crab Xantho hydrophilus

Size carapace 30mm

Also known as Montagu's Crab, it is common on west and south-west coasts in the UK. A robust, chunky-looking crab, with large, powerful claws, a sculptured carapace and tiny, beady eyes. It looks, and is, belligerent and will hold its claws wide open if threatened. It has a vice-like grip and its claws cannot be prized apart once it has grabbed hold. For this reason, care should be taken when handling this crab. The behaviour and habitat is similar to that of Edible Crabs, hiding beneath boulders and wedged into crevices on the middle and lower shore.

Risso’s Crab Xantho pilipes

Size carapace 30mm

This crab is common on west and south-west coasts in the UK. It is very similar in behaviour and appearance to the Furrowed Crab but has a distinctive fringe of hairs around its legs and carapace. The colour appears to be more varied in Risso’s Crabs, which can have a mottled appearance. The two species can often be found together.

Crabs  131

001 Rockpooling.indd 131

15/04/2019 14:14

Four-horned Spider Crab Pisa tetraodon

Size carapace 40mm

This crab is widespread around the UK although, as it decorates its shell with algae as a means of camouflage, it is usually spotted by accident whilst investigating dense seaweed as it is rarely found out in the open. The male’s much longer claws distinguish it from the female. The crab has four distinct ‘horns’ between the eyes, although these may be well hidden beneath its algal covering. At first glance it can look like a very young Common Spider Crab, but the rear legs are noticeably shorter.

Xaiva biguttata

Size carapace 23mm

This small crab is rare in the UK, only known from a handful of sites in the south-west. However, it bears a close resemblance to the Shore Crab and Toothed Pirimela so may have been under-recorded. The colour is variable but it may have a pale green tinge and purple claws. The small eyes are close together with a single lobe in between, and five carapace teeth either side of the eyes, the first of which is broad and flattened. Look for it where sand is present on the middle to lower shore, where it may be buried.

132  Crustaceans

001 Rockpooling.indd 132

15/04/2019 14:14

Toothed Pirimela Pirimela denticulata

Size carapace 15mm

This very small crab is widespread all around the UK and could easily be confused with a very young Shore Crab. However, its carapace is more diamond-shaped and the teeth along the edge are pronounced. It is enormously variable in colour, which enables it to blend in with its habitat. It is easily overlooked but can normally be found buried in sand at the bottom of rockpools.

Crabs  133

001 Rockpooling.indd 133

15/04/2019 14:14

Brush-clawed Shore Crab Hemigrapsus takanoi

Size carapace 28mm

This non-native crab arrived in the UK in 2014, probably brought to Europe from the Pacific Ocean as larvae in ships’ ballast water. It looks similar to the Asian Shore Crab, green to orange-brown with a square carapace and banded legs. However, the three teeth either side of the carapace are less pronounced and there are often dark spots on the claws. The distinctive hairy growth around the male’s claws gives this crab its English name. It lives in muddy, sheltered habitats in estuaries and sheltered locations, beneath rocks.

Asian Shore Crab Hemigrapsus sanguineus

Asian Shore Crab with its fresh moult

Size carapace 34mm

This non-native crab arrived in the UK in 2000, and is thought to have been brought to Europe from the Pacific Ocean as larvae in ships’ ballast water. It is recognised by its mottled green, brown or purple square-shaped carapace and banded legs. There are three distinct teeth on the edge of the carapace either side of the eyes. Although it is not widespread, it has potential to extend its UK range. Look for it under boulders on rocky shores from the upper shore down.

134  Crustaceans

001 Rockpooling.indd 134

15/04/2019 14:14

Broad-clawed Porcelain Crab Porcellana platycheles

Size carapace 15mm

This common crab is widespread around the UK. It is small and flattened in shape but the most noticeable feature is the pair of broad claws which give it its English name. Porcelain crabs are not true crabs but are more closely related to squat lobsters, having only three pairs of walking legs and a pair of long antennae. The upper side of this species is covered in very fine hairs which trap silt, giving it a muddy appearance, while its underside is white. Broad-clawed Porcelain Crabs can appear in large numbers and will retreat rapidly to find cover if their boulder is turned over. Look for them on the underside of rocks and boulders on the middle and lower shore.

Long-clawed Porcelain Crab Pisidia longicornis

Size carapace 10mm

This crab is widespread around the UK. It is a tiny crab with a circular carapace, a pair of long antennae and two relatively long, thin claws. It is often found with the Broadclawed Porcelain Crab beneath middle and lower shore boulders but it lacks the other’s hairs and therefore has a cleaner appearance. As it retreats backwards it drags its long claws behind.

Crabs  135

001 Rockpooling.indd 135

15/04/2019 14:14

Hermit crabs Hermit crabs lack the hard carapace of true crabs although their legs are armoured. Instead, their soft body is hidden inside an empty sea snail shell which has to be swapped for progressively larger ones as they grow. Their soft abdomen hooks inside the spiral shell to help carry it around and they can also withdraw into the shell if it is large enough. Some have lodgers such as worms that live inside the shell with them or anemones that coat the outside and give added protection. As they will often retreat inside their shell when disturbed, it is best to view them in a bucket or tray, left for a while until they emerge.

Common Hermit Crab Pagurus bernhardus

Size carapace 30mm

In the UK, this is the most widespread and common of the hermit crabs and also the largest. It can be found in a wide range of sea snail shells from tiny periwinkle and topshells to large Common Whelk shells, although in rockpools they tend to be smaller specimens in small shells. If you see what looks like a snail zipping along, it is probably a hermit crab.

136  Crustaceans

001 Rockpooling.indd 136

15/04/2019 14:14

Pagurus cuanensis

Size carapace 15mm

This small hermit crab is found on south and west coasts in the UK. It looks different from the Common Hermit Crab as it is noticeably covered in bristly hairs and appears reddish in colour. It inhabits small intertidal sea snail shells such as those of Netted Dogwhelk and Sting Winkle and can be found in lower shore rockpools.

Anapagurus hyndmanni

Size carapace 10mm

This tiny hermit crab is widespread around the UK but easily overlooked because of its very small size. It is very pale in colour, the claws appearing white. It can be found in areas of the lower shore where sand and gravel collect in gullies and rockpools. Look for it in small snail shells such as Rissoa spp., Netted Dog Whelks and periwinkles.

Crabs  137

001 Rockpooling.indd 137

15/04/2019 14:14

St Pirans Crab Clibanarius erythropus

Size carapace 15mm

This small hermit crab is at the northern edge of its range on the south-west coast of England. Its coloration is very distinctive, having red legs and black-tipped claws which are of equal size. It also has black eyes with white spots, on the end of long, red eye stalks. On the seashore it can be found in shallow rockpools living inside the shells of small gastropods such as Dogwhelk, topshell and Sting Winkle.

RED-LEGGED SOLDIER Clibanarius erythropus, which translates from latin as ‘armoured soldier with red legs’, was thought to be lost from its mainland stronghold in south-west England following the Torrey Canyon oil spill on the Cornish coast in 1967. However its rediscovery during a public rock pool survey in 2016 resulted in a national competition to give this crab a common name. The winning name was St Piran’s Crab, St Piran being a hermit who survived being thrown into the sea tied to a millstone. He is also recognised as one of the patron saints of Cornwall. The story illustrates how rockpoolers can make important discoveries.

138  Crustaceans

001 Rockpooling.indd 138

15/04/2019 14:14

Lobsters, shrimps and prawns The crustaceans in this group tend to have an elongated body compared to crabs, comprising the carapace covering the head and thorax, and the abdomen tipped with a tail fan. The tail fan, or telson, can be flapped to enable the animal to escape backwards if threatened. The first pair of legs are modified as claws or pincers for feeding. The names shrimp and prawn are widely and randomly used for the small crustaceans in this group. For example, an alternative common name for the Snapping Prawn is Pistol Shrimp. This may be a result of the more familiar species in this group being traditionally caught as seafood and being given regional names by fishermen.

Common Lobster Homarus gammarus

Size 400mm

This species is widespread around the UK. This highly valuable, commercially caught animal is unmistakable because of its overall blue colour, pair of long red antennae and large claws; one used for crushing and the other for cutting its prey. Small adults and juveniles can occasionally be found in rockpools. The adults are normally found in deep pools and gullies, hiding in crevices, while the tiny juveniles, measuring from around 50mm in length, can very occasionally be found under boulders on the seashore.

Juvenile Common Lobster

Lobsters, shrimps and prawns  139

001 Rockpooling.indd 139

15/04/2019 14:14

Spiny Squat Lobster Galathea strigosa Juvenile Spiny Squat Lobster

Size 80mm

Although this animal is widespread around the UK it is not common in rockpools. It can occasionally be found on the extreme low shore hiding in crevices with its claws folded in front. It is bright red with striking blue banding, and its long, hairy claws are spiny. Juveniles can sometimes be found also with the distinctive squat lobster shape, but displaying bold bands on their claws and legs. Squat lobsters have a distinctive pair of long claws and long antennae, and they hold their tail tucked under. They only have three obvious pairs of walking legs plus a much-reduced pair at the rear.

Common Squat Lobster Galathea squamifera

Size 35mm

This species is widespread around the UK and is a common find in rockpools and on the seashore, where it hides on the underside of lower shore boulders, sometimes several together beneath one rock. They have an overall dark green colour but on close inspection have paler banding and blue markings. When disturbed they will frantically flap their tails to escape, even when out of water and upside down.

140  Crustaceans

001 Rockpooling.indd 140

15/04/2019 14:14

Snapping Prawn Alpheus macrocheles

Size 35mm

This is a rare species on the seashore, where it is found on the south coast of England. It is unmistakable, having a bright orange or yellow overall colour with one massive, thick claw. Snapping Prawns occupy water-filled fissures or hollows beneath rocks and large boulders. These hollows collect sediment in which the prawns excavate a tunnel. They are often found in pairs, usually guarding both entrances to the tunnel. The animals can sometimes be heard before they are seen, with audible clicks coming from underneath the boulders as the tide comes in. They are generally found beneath large rocks on the lower shore.

NOISY NEIGHBOURS The Snapping Prawn is a member of a group of animals, sometimes called Pistol Shrimps, which are mostly found in tropical waters. Many of them live commensally with gobies, which guard the entrance to, and inhabit, the burrows and tunnels that the shrimp excavates. The over-sized claw is used to create a shockwave of water to stun small animal prey and is also used in competition with others of their species or to proclaim the boundary of their territory. The claw works in a similar way to a gun, hence the name Pistol Shrimp. One section of the claw is cocked in position like the hammer on a gun and then released. This happens at a speed of around 62 miles an hour and fires a cavitation bubble through the water. As the bubble implodes at a temperature of 4,700°C, close to that of the sun’s surface, it forms a shock wave which is enough to stun small prey. The implosion of the bubble also generates noise and Pistol Shrimps are a major source of noise in the ocean, even interfering with sonar. For their size, these small animals are the loudest in the sea, producing sounds as loud as whales.

Lobsters, shrimps and prawns  141

001 Rockpooling.indd 141

15/04/2019 14:14

Hooded Prawn Athanas nitescens

Size 20mm

This small prawn is more commonly found on south and west coasts in the UK. The broad stripe down its back marks it out. Its colour is variable but the stripe is always pale. The claws are of equal size and chunkier than the thin pincers of Common Prawns, making it more lobster-like in shape. The carapace reaches forward, partly covering the eyes and giving it its English name. It is normally found in water beneath lower shore boulders and rocks.

Anemone Shrimp Periclimenes sagittifer

Size 30mm

In recent years this shrimp has extended its distribution to the south coast of England, whereas previously its most northerly record was from the Channel Islands. With violet leg bands and a lilac chevron on its back, this colourful shrimp would look at home on a tropical reef, indeed it has many tropical relatives. It lives within the stinging tentacles of the Snakelocks Anemone (page 89) to which it is immune, seemingly offering nothing in return for the protection. Hard to spot, it can be found by sweeping the tentacles aside.

142  Crustaceans

001 Rockpooling.indd 142

15/04/2019 14:14

Chameleon Prawn Hippolyte varians

Size 30mm

Although this is a common species all around the UK, it is rarely seen because of its cryptic coloration. The colour can be incredibly variable depending on where it is living, hence its English name. The rostrum between the eyes is long and straight and in line with the carapace. In rockpools it is found amongst seaweed, and depending on whether it is associated with red, brown or green algae it can be pink, brown, green, flecked or almost transparent. However, it may be found by gently sweeping a small net through seaweed on the middle to lower shore or shaking a weed-covered rock into a tray or bucket (see seaweed shaking on page 53).

Hippolyte leptocerus

Size 20mm

This rare prawn is restricted in the UK to south-west England. It is transparent with brown and pink markings. It has a hairy appearance as a result of the feathery tufts covering its body and antennae. Look for it amongst coralline algae in lower shore rockpools.

Lobsters, shrimps and prawns  143

001 Rockpooling.indd 143

15/04/2019 14:14

Eualus cranchii

Size 45mm

This prawn is found all around the UK. It has a short rostrum, unlike Common and Chameleon Prawns, and is semi-transparent with pink, yellow or brown mottling. Its profile is distinct, with an upward-curving head and pronounced eyes standing proud of the rostrum. This prawn can sometimes be found with Chameleon Prawns amongst weed in lower shore rockpools.

A PRAWN MANICURE Prawns are scavengers, feeding off carrion and leftovers from other animals. By doing this they provide a cleaning function but will also go as far as picking detritus from living animals. If you hold your hand still in a rockpool they will often give you a manicure, picking the dead skin and dirt from fingers and fingernails.

144  Crustaceans

001 Rockpooling.indd 144

15/04/2019 14:14

Common Prawn Palaemon serratus

Palaemon serratus

Size 100mm

This is a large prawn, although small juveniles are very common in rockpools in summer, and it is widespread all around the UK. It is one of the most familiar finds when rockpooling and is very active, coming out to investigate probing fingers but darting under cover if threatened. The transparent body and legs are decorated with brown and yellow bands. There are several similar-looking prawns which are distinguished by the shape and number of teeth on the rostrum. The Common Prawn has six or seven teeth on the top edge of the rostrum, which curves upwards. Palaemon elegans looks very similar to the Common Prawn but is slightly smaller, growing to 60mm in length, and its rostrum is straight rather than upturned, with eight or nine teeth along the top edge. Palaemon elegans

Lobsters, shrimps and prawns  145

001 Rockpooling.indd 145

15/04/2019 14:14

Brown Shrimp Crangon crangon

Crangon crangon

Size 80mm

This shrimp is common and widespread all around the UK. The Brown or Common Shrimp is distinguished from the Common Prawn by its flattened body, which enables it to bury itself beneath sand with just its eyes showing, whereas the prawn does not bury and has a more arched body. They also have much shorter, stouter and more discreet pincers. While the name may suggest this shrimp is brown, its colour can vary to match the colour of the sand where it lives. It emerges to feed and if threatened, can rapidly retreat beneath the surface. As shrimps require sand they can be found in middle and lower shore rockpools with a sandy floor. Philocheras fasciatus is similar in shape to the Brown Shrimp but is much smaller, only growing to 20mm, and with dark banding on a pale body. It can sometimes be found together with the Brown Shrimp but its coloration marks it out.

Philocheras fasciatus

146  Crustaceans

001 Rockpooling.indd 146

15/04/2019 14:14

Opossum shrimps This group (Mysidae) are small, generally transparent crustaceans, shrimp-like in appearance with long, thin bodies, long antennae and large, conspicuous eyes. They are free-swimming, often hanging in the water in a vertical position in shoals. The name opossum shrimp comes from the large brood pouch on the underside of females, like a marsupial pouch. A few species may be found sheltering beneath the seaweed fringing intertidal rockpools, although they are difficult to identify in the field.

Chameleon Shrimp Praunus flexuosus

Size 25mm

This opossum shrimp is widespread and abundant in the UK. Colour is variable from transparent to dark grey and it is bent when seen in profile. The stalked eyes are large and conspicuous. It may be confused with other species in the genus. Pushing a small aquarium net gently through rockpool seaweed is the best way to find it.

Lobsters, shrimps and prawns  147

001 Rockpooling.indd 147

15/04/2019 14:14

Isopods The isopods form a large group of crustaceans (Isopoda), most of which live in the sea, although a few have evolved to live on land, the most familiar being the woodlice. They have a flattened, segmented body, each segment having a pair of walking legs. The telson, at the rear, is generally used for swimming. The Sea Slater is the only rocky shore isopod adapted for terrestrial living.

Sea Slater Ligia oceanica

Size 30mm

This seashore woodlouse is common and widespread and is the UK’s largest terrestrial isopod. It is very active at night and on damp days, hiding away in crevices and beneath rocks on dry days. As an air-breathing animal it can only forage on the shore as the tide falls, retreating back up as the tide returns. It looks like a garden woodlouse but with a broad, flattened body and large antennae and is grey to olive green in colour. It is nocturnal, feeding on decaying seaweed, and the best time to see these animals in action is at night with a torch.

148  Crustaceans

001 Rockpooling.indd 148

15/04/2019 14:14

Idoteidae There are five species of Idotea which are widespread and commonly found in rockpools. They are fairly easy to distinguish by using a hand lens to examine their antennae and their posterior segment (pleotelson). These marine isopods have an elongated body, living and feeding on algae and matching their colour to the host species and as such, their colour and markings are extremely variable. They can often be seen on loose seaweed drifting in the shallows or by using the seaweed shaking technique (page 53). They can sometimes be found in abundance and mixed together. Two additional species of Idotea and two species of Stenosoma are more restricted in their distribution.

Idotea balthica Size 30mm

The pleotelson is squareended with a small projection in the centre.

Idotea emarginata Size 30mm

The pleotelson is broad with a notch in the centre.

Isopods  149

001 Rockpooling.indd 149

15/04/2019 14:14

Idotea pelagica Size 11mm

The pleotelson is smoothly rounded, with a subtle projection in the centre and short antennae. It is found amongst barnacles and fucoid algae.

Idotea neglecta Size 30mm

The pleotelson is rounded with a small projection in the centre.

Idotea granulosa Size 20mm

The pleotelson is elongated and tapered with a projection in the centre.

150  Crustaceans

001 Rockpooling.indd 150

15/04/2019 14:14

Idotea linearis Size 40mm

The body is narrow and elongated, with long antennae. The pleotelson has a shallow, curved notch. On rocky seashores it is mostly associated with sandy pools in the south-west of the UK.

Idotea chelipes Size 15mm

Green in colour, this idotea has a pleotelson similar in shape to I. granulosa, rounded with a projection. It is mostly restricted to brackish water, so may be found in estuaries and lagoons around the UK.

Stenosoma lancifer Size 22mm

Normally red in colour, the pleotelson curves outwards and then inwards to an elongated point. It is mostly associated with red algae. Distribution is mostly limited to the south-west in the UK.

Stenosoma acuminatum Size 25mm

Brown in colour, with a similar body shape to S. lancifer. It has an elongated pleotelson with a smoothly tapering point. It is mostly associated with the brown alga Sea Oak Halidrys siliquosa (page 38), mimicking the seaweed’s pods. Distribution is mostly limited to the south-west in the UK.

Isopods  151

001 Rockpooling.indd 151

15/04/2019 14:14

Janirid isopods Within this family of isopods (Janiridae), Jaera spp. have very small, oval, flattened bodies, resembling woodlice, while Janira spp. are identified by their small size, more elongated bodies, long antennae, and uropods.

Jaera sp.

Size 5mm

This is a common but easily overlooked isopod living on the underside of seashore rocks. There are several UK species that are very difficult to distinguish in the field because of their small size. Unlike Idoteidae, they look quite like woodlice, with oval bodies, long antennae and grey or brown coloration. A magnifier is useful for finding these animals as they hug the contours of the rock and stay still when disturbed.

Janira maculosa

Size10mm

This small isopod is widespread around the UK. It is similar in appearance to Jaera sp. but with very long antennae and a pair of forked appendages projecting from the rear. It is variable, often yellowish and mottled in colour with a pale band between the eyes. Look for it on the lower shore beneath silty rocks among sponges, sea squirts and bryozoans.

152  Crustaceans

001 Rockpooling.indd 152

15/04/2019 14:14

NOCTURNAL ROCKPOOLING Many seashore animals hide away in the daytime but are active during the hours of darkness. A spot of nocturnal rockpooling can reveal species and behaviour that you wouldn’t otherwise see. Crabs, Sea Slaters, bristletails and rockpool fish can be seen out in the open, while a UV torch will reveal the fluorescence of creatures such as sea anemones, cup corals and marine worms. Safety

What you need ● ● ● ● ● ●

activity

You are more at risk of slips, falls and becoming disorientated and lost in the dark, so extra safety measures should be taken when planning nocturnal rockpooling. We recommend visiting the beach in daylight to ensure familiarity with access, hazards and orientation. Check tide times and take a compass bearing to ensure you can find the exit point in the dark. Do not go alone and tell a third party where you are going.

A head torch (to keep your hands free for safety) A backup torch A lantern for placing at the back of the beach for orientation in the dark (unless there is already a house or street light) A UV torch (blacklight) A mobile phone for emergencies (even if coverage is poor) A compass

What to do

Use your torch to watch where you are walking as crabs, Sea Slaters and other mobile animals will be scurrying around on the shore. Shine your UV torch into rockpools to find ‘glow in the dark’ sea anemones and other creatures.

153

001 Rockpooling.indd 153

15/04/2019 14:14

Pill isopods These isopods in the family Sphaeromatidae tend to be squarer in shape and can roll into a ball when disturbed, hence the English name for this group, pill isopods. There are several species commonly found on rocky seashores and they need close examination of the telson and rear segments with a magnifier or sometimes a microscope to tell apart. Males and females are normally different in appearance with males having distinguishing spikes and bumps on the rear end, which females lack.

Dynamene bidentata

male

female

Size 8mm

Found in seashore crevices or rolled up inside the empty shells of barnacles. Males have two spikes projecting from the sixth segment. Restricted to the south and west in the UK.

Cymodoce truncata

male

female

Size10mm

Found around kelp holdfasts and loose algae or beneath seashore rocks. Males have hairs fringing the uropods at the rear. It appears to be restricted to the south-west in the UK.

154  Crustaceans

001 Rockpooling.indd 154

15/04/2019 14:14

Campecopea hirsuta

male

female

Size 4mm

Found in the intertidal lichen, Lichina sp., and in empty barnacle shells. This is one of the most easily identified pill isopods as males have a pair of large, curved uropods as well as a prominent spike projecting backwards from the sixth segment. In the UK it is restricted to the south and west of England and Wales.

Sphaeroma serratum

rolled

Size10mm

Found in rock crevices and beneath stones from the mid-shore down, where they are often seen in clusters. Close examination of the outer edge of the uropod will reveal that it is serrated. In the UK it is restricted to the south and west of England and Wales.

Isopods  155

001 Rockpooling.indd 155

15/04/2019 14:15

Munnidae Munna kroyeri Size 3mm

This tiny isopod appears to be restricted to the south and west of England and Wales but may be under-recorded due to its small size. It is insect-like in appearance with a squat body and long legs. The pleotelson curves upwards. Look for it under lower shore rocks or by using the seaweed shaking technique.

Gnathiidae Gnathia maxillaris juvenile

female

male

Size 5mm

This common isopod is found in the south and south-west of England and Wales. It has an interesting life history and can be found in various stages of development. The juveniles or pranzia often stand out because of the vivid coloration of their swollen body which can be blue, yellow or green. They can be found using the seaweed shaking technique or by close examination of rockpool fish which they parasitise. The pale coloured adults exhibit sexual dimorphism with the males and females looking very different. The male has a large square head with a pair of oversized mandibles. The female has a rounded, swollen body in which her eggs are brooded. The adults can be found in kelp holdfasts and in lower shore rock crevices often together in nests along with recently hatched young.

156  Crustaceans

001 Rockpooling.indd 156

15/04/2019 14:15

Tanaids This order (Tanaidacea) of small animals resemble isopods but have a pair of claws, which isopods lack. They are often overlooked as they live in burrows or tubes they build themselves, hidden in crevices or amongst barnacles and Lichina sp. or beneath undisturbed rocks. They can be found from the upper to lower shore in suitable habitat.

Apseudes talpa Size 8mm

Recorded from the south and west regions of the UK, this small crustacean has a square-shaped head with a triangular front section protruding to a point between the eyes. It is dirty white in colour with numerous spines fringing the rear section.

Apseudes latreillii Size 7mm

This tanaid appears to be widespread in the UK, having been recorded in the southwest and north-east. It is dirty white in colour and has a square head with a small spine projecting forwards between the eyes, but much less obvious than in A. talpa. The rear section has numerous short spines, less obvious than in A. talpa.

Tanais dulongii Size 7mm

Widespread and common around the UK, this small crustacean has a mottled brown coloration. It has a rounded head with the claws protruding forwards from underneath. On the rear section is a band of spines that gives it the appearance of wearing a fluffy tutu.

Tanaids  157

001 Rockpooling.indd 157

15/04/2019 14:15

Cumaceans Cumacea Size up to 10mm

This order of small crustaceans can only be identified to species level under microscopic examination. They are widespread and common around the UK and may be found when shaking seaweed samples. They have a red to brown colour and superficially resemble a tadpole with a head and body covered in a carapace and a long, tapering segmented rear section.

Nebaliidae Nebalia spp. Size 12mm

These small crustaceans are common and widespread around the UK. They are mostly translucent white with red eyes. They have a superficially shrimp-like appearance with a forked ‘tail’ and can be found beneath rocks, in rockpools and on seaweed holdfasts. They can become trapped on the surface film of water when a rock is lifted and can be seen floating there.

Ostracods Ostracoda Size 1mm

Also known as seed shrimps, these tiny animals are widespread around the UK, but easily overlooked. The different species cannot be identified without microscopic examination. They are a shrimp-like animal enclosed within an egg-shaped shell, with a slit through which the legs can protrude. You can find them by shaking seaweed in a tray. Any dislodged animals can be seen scooting around in the water.

158  Crustaceans

001 Rockpooling.indd 158

15/04/2019 14:15

Amphipods Amphipods (order Amphipoda) are small crustaceans, generally with a laterally flattened, segmented body which is divided into separate sections, although these are not easy to distinguish. Each segment has a pair of specialised legs and the body section they belong to determines their use. Those near the head are used for feeding and clasping (gnathopods), others are used for walking, swimming (pleopods) and burrowing. Generally, the body is curved with the rear end tucked under. In some species the male clasps the female and carries her around for a few days before they mate. Fertilised eggs develop into juveniles within the female’s brood chamber. Amphipods are found in a wide range of intertidal and subtidal habitats, often burrowing in the sediment, under stones or among seaweed. A small number live above the high tide mark on beaches and are more familiar as Sand Hoppers. This is a large group and species can be difficult to identify in the field. In some species, males and females may look different. The best way to find most of them is by using the seaweed shaking technique (page 53) and examining them in a white tray under magnification. Only the most easily recognised species have been included here.

Gammarus locusta

Size 35mm

This amphipod is widespread around the UK and may be abundant. It is brown with a greenish tinge and kidney-shaped eyes, and the top pair of antennae have a spur forking off. It can be found on the middle and lower shore under stones or seaweed and shuffles away on its side when disturbed.

Amphipods  159

001 Rockpooling.indd 159

15/04/2019 14:15

Mottled Tube-maker Jassa sp. Size 13mm

This tube-building amphipod is widespread around the UK. The most common species is Jassa falcata. It has variable red-brown mottling and large antennae. Males and females differ, the males having a large claw on their gnathopod. Look for it in its tubes on seaweed holdfasts in lower shore rockpools. It is most easily found by using the seaweed-shaking technique (page 53).

Dexamine spinosa Size 12mm

This amphipod is widespread around the UK. It is mottled red brown in colour with white flecks. It has pale eyes, long antennae and small, unobtrusive gnathopods. Close examination will reveal teeth running along the back. Look for it on the lower shore amongst seaweed holdfasts. It may be found by seaweed shaking.

Iphimedia nexa Size 6mm

This small amphipod is widespread around the UK. Colour is variable but generally it is pale in colour with yellow or orange markings. It is short and plump giving it an almost oval outline. The gnathopods are not obvious. Look for it on the lower shore among algae. It may be found by seaweed shaking.

160  Crustaceans

001 Rockpooling.indd 160

15/04/2019 14:15

Lysianassidae Size 10mm

This group of amphipods is widespread around the UK. The colour is pale yellow with white spots and the antennae are short. The gnathopods are not visible and the body is noticeably smooth. Look for this animal in rockpools on the lower shore amongst algae. It may be found by seaweed shaking.

Maera grossimana Size 10mm

This amphipod is found on south and west coasts in the UK. It is a translucent colour with a pink tinge. The gnathopods are large and obvious, with a mitten-like appearance, and the body is slender and smooth. Look for it beneath stones on the middle to lower shore.

Nototropis swammerdamei Size 10mm

This amphipod is widespread around the UK and can be common. It is pale and translucent with brown patches and large, kidney-shaped eyes. It has long antennae and small, unobtrusive gnathopods. Look for it on the lower shore among seaweed, especially where sand collects.

Amphipods  161

001 Rockpooling.indd 161

15/04/2019 14:15

Melita palmata Size 16mm

This species is widespread around the UK. It is a translucent buff in colour with brown markings. The antennae are long and the body slender. The gnathopods are large and angular in appearance. Look for it on the lower shore among silty stones.

Leucothoe spinicarpa Size 12mm

This amphipod is found on south and west coasts in the UK. It is translucent with a pink or red tinge, a smooth, slender body and short, stout antennae. The gnathopods are large and oval in shape. Look for it on the lower shore among algal holdfasts and inside sea squirts and sponges. It may be found by using the seaweed shaking technique (page 53).

Podocerus variegatus Size 4mm

This tiny amphipod is found on south and west coasts in the UK. The colour can be red, brown, purple and pink, often with the legs and antennae a different colour to the body. It has long legs in comparison to its body size and appears insect-like. The long, stout antennae almost look like a pair of legs. Look for it in lower shore rockpools among algae, especially Corallina sp.

162  Crustaceans

001 Rockpooling.indd 162

15/04/2019 14:15

Apohyale prevostii Size 8mm

This amphipod is widespread around the UK. Its colour is variable but often brown or greenish and may depend upon its habitat. The eyes are generally black. It is more closely related to the Sand Hoppers found on beach strandlines and it can hop surprising distances. It is found from the upper shore to the sublittoral but is commonly found amongst wracks on the middle and upper shore, and amongst Lichina sp. (page 65).

Skeleton shrimps Skeleton shrimps (Caprellidae) are a type of amphipod but look quite different to the normal amphipod shape. They are not laterally flattened, have elongated thin bodies with few legs and are generally found clinging to algae, sponges and hydroids. They tend to have large gnathopods at the front of the body and sparse, hooked legs at the rear for clinging to their host. They have a characteristic posture, appearing to sit upright, clinging with their rear legs and swaying in the water. They move in a looping fashion which is very characteristic.

Caprella acanthifera Size 20mm

This skeleton shrimp is frequently found intertidally on south and west coasts of the UK. It is very variable in colour, has hairless antennae and tubercles on the body. Females have a brood pouch on the underside and may appear broader than males. Look for it on algae, hydroids and bryozoans in rockpools on the lower shore. Seaweed shaking is a good way to find this animal.

Skeleton shrimps  163

001 Rockpooling.indd 163

15/04/2019 14:15

Barnacles Despite looking more akin to molluscs, with a cone-shaped shell, barnacles (Cirripedia) are actually a type of crustacean and therefore more closely related to crabs and shrimps. As larvae they drift among the plankton until they find a suitable place and settle on the seabed amongst adults of the same species, where they cement themselves, upside down, to the substrate and build a tough shell around themselves for protection. At this stage they are called spat. Plates at the top of the shell open and close to allow the feeding apparatus to extend into the water column, where they sieve food particles passing by. The feeding appendages, modified limbs, are covered in groups of fine hairs or cirri, hence the name Cirripedia, which means hairy feet. Barnacles also have the dubious honour of having the longest penis in relation to their size of any animal. This is needed to ensure they can reach their neighbours for breeding, being unable to move. Acorn barnacles are the most familiar barnacles and are found in abundance on the seashore attached to rocks. They can dominate intertidal rocks, completely covering the bedrock in places, but are often overlooked as their shells are closed up tightly to avoid dessication when exposed at low tide. Although they create a nuisance as fouling organisms on ships’ hulls and other artificial structures, they create a habitat for other species on the shore and also a food source for many marine animals.

carina shell plate

cirri eye mouth rostrum shell plate opercular plate.

base

Cross-section showing internal structure of an acorn barnacle

Acorn barnacles can be difficult to identify to species level, but the features to examine are the shape of the operculum and the number of plates making up the cone. Although the common seashore barnacles exhibit zonation, with some species extending higher up the shore than others, they can often overlap and be mixed together. Barnacles are more easily identified under a magnifier. Stalked barnacles have a different appearance and lifestyle, many attaching to floating objects in the open ocean and spending their lives drifting wherever the wind and currents take them. There are also types of barnacles that are parasites of other crustaceans and have evolved a completely different lifestyle.

164  Crustaceans

001 Rockpooling.indd 164

15/04/2019 14:15

carina

suture

opercular plates (paired)

lateral plates

rostrum

Semibalanus balanoides

operculum

Chthamalus montagui

Chthamalus stellatus

Shell plate arrangement in three common acorn barnacles

Northern Rock Barnacle Semibalanus balanoides

Size 15mm

This common barnacle is widespread around the UK although less common in the southwest. It is grey-white in colour, often whiter in younger individuals, with six shell plates around the edge and a diamond-shaped opercular opening. The rostral plate is broad and on close examination it can be seen to overlap the lateral plates. If not tightly closed it can be seen that the tissue lining the opercular plates is white or pinkish. Look for it on the middle shore.

Barnacles  165

001 Rockpooling.indd 165

15/04/2019 14:15

Montagu’s Stellate Barnacle Chthamalus montagui

Size 14mm

This common barnacle is found on south and west coasts in the UK. It is grey or buff, with six shell plates around the edge, although these are often eroded, making them difficult to count. The opercular opening is kite-shaped, with the suture three-quarters of the way up towards the apex of the kite. If not tightly closed, pale blue tissue can be seen lining the opercular plates. This barnacle is found on the high to middle shore.

Poli’s Stellate Barnacle Chthamalus stellatus

Size 14mm

This barnacle is found on south and west coasts in the UK. It is pale grey, with six shell plates around the edge, although these may be eroded and difficult to make out. The opercular opening is oval, with the suture roughly two-thirds of the way towards the apex of the oval. If not tightly closed, it can be seen that the tissue lining the opercular plates is blue with orange markings. This barnacle is found on the middle to lower shore.

166  Crustaceans

001 Rockpooling.indd 166

15/04/2019 14:15

New Zealand Barnacle Austrominius modestus

Size 10mm

This non-native barnacle, originating from New Zealand, was first recorded in the UK in 1946 and is now widespread around the UK. Younger individuals are pale grey but become slightly browner as they age. It is distinctive, having only four shell plates around the edge and a large, diamond-shaped opercular opening. This barnacle is found on all levels of the shore but is most common on the middle shore.

Volcano Barnacle Perforatus perforatus

Size 30mm

This large and distinctive barnacle is found in the UK on south and west coasts of England and Wales. It is purple with a tall, volcano-like shape. The six shell plates around the edge are often fused and have vertical ridges, and the opercular opening is relatively small. Look for it on the middle to lower shore, especially under shady overhangs.

Barnacles  167

001 Rockpooling.indd 167

15/04/2019 14:15

Wart Barnacle Verruca stroemia

Size 10mm

This small barnacle is widespread in the UK. It is pale grey in colour and irregular in form with four ridged shell plates around the edge giving it an asymmetrical shape. It is low in profile and the opercular opening is not central. Look for it on the lower shore on the underside of boulders, on shells and on seaweed holdfasts.

Balanus crenatus

Size 25mm

This barnacle is widespread around the UK but is not common on the seashore. It is pale grey in colour with six shell plates around the edge and a diamond-shaped opercular opening. The upper edge of the shell plates is toothed and the whole shell appears to lean to one side when seen in profile. The base of the shell is calcareous and leaves a scar or patch on the rock after the barnacle has been dislodged. Although this barnacle is mostly sublittoral, look for it on the lower shore attached to shells, stones and rock.

168  Crustaceans

001 Rockpooling.indd 168

15/04/2019 14:15

Atlantic Goose Barnacle Pollicipes pollicipes

Size 50mm

This is the only species of goose barnacle living intertidally in the UK, where it is rare and only recorded from Cornwall. It is attached to rock by a dark brown flexible, scaly stalk: the peduncle. At the end of the stalk is the main body: the capitulum, which is enclosed in a number of whitish plates of various sizes. The animal is very robust, having to withstand the full force of Atlantic storms. These barnacles have been recorded from a handful of sites in Cornwall on the lower shore in wave-exposed locations.

Parasitic Barnacle Sacculina carcini

Size 25mm

This barnacle is widespread around the UK, although not immediately recognisable as a barnacle. It infects crabs, especially the Shore Crab, Carcinus maenas, and appears as a cream, orange or brown, oval-shaped tumour that sits under the tail flap of both males and females, where the cluster of eggs would be held in females. However, unlike eggs, it is smooth and may pulsate. The parasite prevents the host from breeding or moulting. Look for this bizarre animal on the underside of Shore Crabs. There are other similar parasitic barnacles that infect specific crab species.

Barnacles  169

001 Rockpooling.indd 169

15/04/2019 14:15

Sea spiders These spider-like marine animals (Pycnogonida) are not directly related to true spiders but bear a very obvious resemblance to them, with their eight jointed legs and slender body. Some also have the habit of curling up their legs when disturbed. In addition to the walking legs they also have a abdomen pair of ovigerous legs which are short and used to carry the eggs. They are carnivorous, feeding on bryozoans, hydroids and sea anemones. They have two pairs ocular tubercle with eyes of feeding appendages on the head, the palps and the chelifores, although these are absent in some species. trunk Although they are easily palp overlooked, they can sometimes ovigerous legs be found intertidally in proboscis surprisingly large numbers by using the seaweed-shaking chelifore technique (page 53).

Pycnogonum litorale

Size body 20mm

This squat sea spider is widespread on rocky shores around the UK. It is buff or brown, with a stout body and short, thick legs, each with a claw-like appendage at the tip. The head lacks palps and chelifores, just having a cone-like proboscis, which it plunges into its sea anemone prey. Look for this animal beneath lower shore rocks where sea anemones occur.

170  Crustaceans

001 Rockpooling.indd 170

15/04/2019 14:15

Gangly Lancer Nymphon gracile

Size body 10mm

This slender sea spider is widespread on rocky shores around the UK. It is generally brown in colour, with very long, thin legs and a slim body. The ovigerous legs are short and curly and held beneath the body. The head bears both palps and chelifores and a long proboscis. This is one of the few sea spiders that can sometimes be seen freeswimming in rockpools. It can be found beneath rocks and amongst seaweed on the middle and lower shore, or by gently running a small aquarium net through seaweed or by using the seaweed shaking technique.

Endeis spinosa Size body 3mm

This slender sea spider is widespread on rocky shores around the UK. It generally has a pink or green tinge. At first glance it may resemble Nymphon gracile (above) but on closer examination it lacks the palps and chelifores on the head, and the legs bear spines which are absent in N. gracile. It may be found on the lower shore by using the seaweed shaking technique.

Sea spiders  171

001 Rockpooling.indd 171

15/04/2019 14:15

Achelia spp. Size body 2mm

The three species of this small sea spider are widespread and can be common on rocky shores around the UK, but are not distinguishable in the field. They are generally buff in colour, with a rounded body and short, stout legs. The head bares a pair of palps and a broad proboscis but no chelifores. They are often covered in silt when found. Look for them on the middle to lower shore by using the seaweed shaking technique.

Ammothea hilgendorfi

Size body 3mm

This non-native sea spider, which originated from the North Pacific, currently has a very limited UK distribution on the south coast of England. It was originally recorded in Southampton Water, Hampshire and has become abundant in Poole Harbour, Dorset. It may be present in other harbours and estuaries along the south coast, from where it may spread to the open coast. Its colour is variable, but there is noticeable banding on the legs, which are long and slender. It has a pair of palps alongside the proboscis but no obvious chelifores. Look for it in harbours and nearby sheltered shores beneath rocks on the middle to lower shore.

172  Crustaceans

001 Rockpooling.indd 172

15/04/2019 14:15

POOTERING ABOUT

What you need ● ●

A pooter – available online from ecological equipment suppliers A magnifying pot

What to do 1. Locate your minibeast and capture it using the pooter. 2. Examine and identify your minibeast in situ or carefully transfer it to a magnifying pot. 3. Release the animal when finished.

activity

A pooter is a small pot used to catch live invertebrates for closer examination and identification without having to handle them. It consists of a clear pot with a lid into which two tubes are inserted. The idea is to suck through one tube while holding the end of the other above a small fly or beetle. The air sucked out of the pot results in air being sucked in through the second tube, along with the target invertebrate. A fine mesh over the internal end of the sucking tube prevents you from inhaling the creatures.

173

001 Rockpooling.indd 173

15/04/2019 14:15

Insects

and other air-breathing arthropods

001 Rockpooling.indd 174

15/04/2019 14:15

I

nsects and other air-breathing arthropods are not generally associated with marine environments and yet a wide variety can be found on the seashore. While the adults of some flying insects can fly away when the tide comes in, many remain in situ, living under the water in air-filled crevices or as fully marine larvae living in pools. Some form of magnification is needed for finding and identifying many of the species included here.

Springtails and bristletails Springtails (Collembola) are related to insects but are wingless. Most live in soil and are thought to be the most abundant terrestrial animal on Earth. Bristletails (Archaeognatha) are considered to be primitive insects, although they do not have wings. They have three prominent bristles projecting from their rear.

Anurida maritima

Size 3mm

This tiny, wingless insect is widespread and abundant around the UK coast. The cylindrical body is grey-blue, with a pair of short antennae. It is unusual among springtails as it lacks the ability to spring and instead moves by crawling. These animals are normally seen rafting together in groups on the surface film of calm, upper shore rockpools, although they can also be found individually, walking on nearby rocks in search of food. They are important scavengers on the shore, normally feeding on dead molluscs and crustaceans.

HYDROPHOBIC Anurida maritima, although an air-breather, can survive on the upper shore, where it remains underwater for extended periods. Water-repellent hairs on the body trap air and keep the body surface dry. As the tide comes in, these animals retreat into crevices or amongst seaweed, breathing the film of air trapped by the hairs.

Springtails and bristletails  175

001 Rockpooling.indd 175

15/04/2019 14:15

Anuridella marina

Size 2mm

Although this springtail is widespread around the UK, it is not common. It is yellow, orange or white and is similar in appearance to Anurida maritima (page 175), with a cylindrical body and short antennae. Like A. maritima, it cannot spring. It can be found in silt-filled rock crevices on the middle shore.

Axelsonia littoralis

Size 2mm

This springtail is rare in the UK but may be overlooked. Superficially, it looks like Anurida maritima (page 175) and is the same, grey-blue colour. However on close inspection this animal has longer legs and antennae and, most importantly, it has the ability to spring. It does not raft on the surface of rockpools. Look for it beneath upper shore rocks.

176  Insects

001 Rockpooling.indd 176

15/04/2019 14:15

Sea Bristletail Petrobius maritimus

Size 15mm

This wingless insect is common around the coast of the UK, although less so on the east coast. It is grey, with a body tapering towards the rear, from which three long bristles emerge. It has a pair of long antennae on the head and is very fast moving, running and springing away if disturbed. It is found above the high water mark under damp boulders or in crevices but is more active and out in the open at night.

Beetles Beetles (Coleoptera) are a very large group of insects. Their forewings, called elytra, are hardened and used to cover and protect the rear pair of flying wings when not being used.

Aepopsis robinii

Beetles  177

001 Rockpooling.indd 177

15/04/2019 14:15

Aepopsis robinii Size 2mm

This tiny crevice beetle is found at scattered locations around the UK coast where there is suitable habitat. It is orange with long antennae and large mandibles. One of the identifying features of this beetle is the elytra, which do not cover the entire abdomen. Look for it on the middle to upper shore on the underside of boulders or in silt-filled crevices.

Aepus marinus Size 2mm

This crevice beetle, like Aepopsis robinii, is rare in the UK and lives in a similar habitat, although higher up the shore in the upper shore and splash zone. It looks almost identical, the distinguishing feature being the elytra, which cover the entire abdomen in this species. Look for it on the underside of boulders or in siltfilled crevices.

Marine Moss Beetle Ochthebius marinus Size 2mm

This seashore carabid beetle is rarely recorded around the UK but may be overlooked, due to its habitat and extremely small size. It is dark brown and under close inspection, longitudinal ridges can be seen on the elytra. On exposed coasts it can be abundant in splash zone rockpools which are isolated from the sea for extended periods. These often stagnant pools are extremely variable in salinity and temperature and are a harsh environment for most animals. Look for these tiny dark beetles around the shallow edges of these pools.

178  Insects

001 Rockpooling.indd 178

15/04/2019 14:15

Micralymma marinum Size 5mm

This is a seashore rove beetle which is rarely recorded in the UK but may be overlooked. It is black or dark brown, with short elytra which expose the elongated abdomen. It can be found in rock crevices or amongst algae on the middle shore of moderately exposed coasts.

Flies Flies (Diptera) are a group of insects which include the familiar houseflies as well as hoverflies, midges and craneflies. This group is one of the largest groups of insects found in the UK.

Barnacle Fly Aphrosylus celtiber

Size 6mm

Records for this fly are limited but it appears to inhabit barnacle-encrusted rocks on west and south-west coasts in the UK and can be locally common. The body is grey, with very long legs and a pair of silver palps at the front which reflect the light and appear to flash as they move. The animal tends to run in quick bursts rather than fly, although it is able to fly when necessary. As an adult it hunts small invertebrates such as springtails at low tide, while the larvae, which live underwater, feed on barnacles. Look for the fly on barnaclecovered rocks, where it can be seen dashing around and flashing its palps.

Flies  179

001 Rockpooling.indd 179

15/04/2019 14:15

Fucellia spp.

Size 6mm

There are three very similar species of this shore fly which cannot be separated in the field. They are recorded from scattered locations all around the UK coastline but are probably under-recorded. They are grey in colour and similar in appearance to a common house fly. They feed on dead animals and can be found from the middle shore up to the beach strandline.

Thalassomyia frauenfeldi

Size 3.5mm

This seashore midge is rarely recorded around the UK coast but is probably more common than records suggest. It is grey and resembles a mosquito, with very long legs and swept-back wings; however, it is a non-biting midge. It can be found on the middle and upper shore, frequently associated with green algae such as Sea Lettuce and Gutweed (pages 30–31). It can often be found in mating aggregations.

180  Insects

001 Rockpooling.indd 180

15/04/2019 14:15

Clunio marinus

Size 1.5mm

This non-biting midge and its larvae are common on seashores around the UK, although easily overlooked because of their size. Close examination will reveal that this fly has a dark body with pale legs and wings. It only lives for a few hours as an adult, during which time the males can be found in large numbers dashing around on algae-covered rocks looking for pupae that contain the wingless females. Having found one, the male peels back the casing and mates with the female before carrying her to a pool to lay her eggs. They both die before the tide comes back in. The larvae can be found by using the seaweed-shaking technique (page 53) as they live in silk tubes attached to algae, emerging to feed on the organic film coating their host’s surface. They provide an important food source for invertebrates on the seashore.

Marine Splash Midge Telmatogeton japonicas Size 4.5mm

This non-biting midge is a recent invasive non-native in the UK, where it is becoming increasingly common and widespread. It has very long legs, which it uses to run on vertical intertidal rocks or concrete structures, which it prefers. Its body is dark, with swept-back pale wings. Adults mate on wet, vertical surfaces anywhere in the intertidal zone and eggs are laid singly in crevices. The planktonic larvae build and settle into protective tubes stuck to the substrate.

Flies  181

001 Rockpooling.indd 181

15/04/2019 14:15

Shore Hoverfly Eristalinus aeneus

Size 12mm

This large, plump fly is not restricted to the coast but is likely to be found on the upper shore where suitable habitat occurs. The large eyes, covered in dark spots, are an identifying feature for this species. The adult can be found around stagnant upper shore or splash zone pools, where it lays its eggs. These hatch into larvae which are called Rattailed Maggots, and are easier to spot than the adult. They have a long tail which acts as a respiratory siphon, extending to the surface of the water.

Bugs Bugs (Hemiptera) are a group of insects with a straw-shaped mouth, which they use for piercing the plants or animals on which they feed. Their first pair of wings is also partly hardened, similar to the elytra on a beetle.

Aepophilus bonnairei Size 3.5mm

This virtually wingless insect is recorded from south-west coasts in England and in Wales, although it is probably under-recorded. It is the only true bug to be found living intertidally on rocky shores. It is brown with red eyes and a covering of golden hairs. The remnants of wings can be seen on the thorax. The fine hairs are water repellent and trap a thin layer of air around the body, enabling the animal to breathe when submerged. It is found in crevices or between layers of loose rock.

182  Insects

001 Rockpooling.indd 182

15/04/2019 14:15

Centipedes Centipedes (Chilopoda) are members of the Myriapod group, which have elongated segmented bodies with a pair of legs on each segment.

Hydroschendyla submarina Size 40mm

This seashore centipede is limited in distribution, currently recorded in south-west England and south Wales. It is red in colour and is the only centipede which lives in the intertidal zone. It can be found tucked into silt-filled rock crevices on the middle shore where it builds nests. While it is tolerant of salt water it is an airbreather, surviving at high tide on air trapped in its crevice home.

Arachnids This group (Arachnida) includes the familiar spiders, mites and scorpions. They are invertebrates with four pairs of legs, a body divided into two sections and a hard exoskeleton. They have no wings or antennae.

Neobisium maritimum

Size 3.2mm

In the UK this tiny pseudoscorpion is found on south and west coasts of England and Wales. The body is brown with a pair of long, red claws which give it the appearance of a scorpion, although it lacks a tail. It lives on the upper shore in silt-filled crevices, breathing on pockets of trapped air at high tide. In its hidden world it is the apex predator, preying on tiny springtails and other invertebrates.

Arachnids  183

001 Rockpooling.indd 183

15/04/2019 14:15

Neomolgus littoralis Size 3.5mm

This coastal snout mite appears to be widespread but is under-recorded. It is bright red in colour, with a soft body and elongated mouthparts used to attach to its prey, hence the name ‘snout mite’. It can be found running around on middle and upper shore rocks among barnacles and algae.

Cyrthydrolaelaps hirtus Size 1.4mm

Distribution of this species is unknown. It is bright orange, with a hard body. Its legs are hairy and this can be seen under magnification. It ranges throughout the intertidal zone but is commoner on the lower shore around crevices, on algae and open rocks.

Halotydeus hydrodromus Size 1.6mm

Distribution of this species is unknown. The soft body is dark with a pale orange line down the middle and bright orange legs. This fastmoving, predatory mite can be found amongst rocks, barnacles or algae on the upper shore, but is more common on the middle to lower shore.

184  Insects

001 Rockpooling.indd 184

15/04/2019 14:15

Hermannia pulchella Size 0.9mm

Distribution of this species is unknown. This tiny black mite is teardrop-shaped in outline with a hard, bulbous body. It has rows of longitudinal, raised bumps running along its abdomen. It can be found in the upper shore and splash zone, amongst Lichina spp. (page 65), where it can be abundant.

Ameronothrus marinus Size 0.7mm

Distribution of this species is unknown. This tiny black mite is flattened in shape with a hard body. It can be found in the upper shore amongst Lichina spp. (page 65) and down to the lower shore beneath stones and amongst barnacles and mussels.

Marine mites Halacaridae Size