ContentsContentsIntroducing Wonders of the Sea 9

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Life in the Sea 10

The World of Plankton 12

Sponges, Anemones and Jellyfish 14

The World of Mollusks 16

Life on a Sandy Beach 18

Squid and Octopuses 20

Crustaceans 22

Sea Stars, Urchins and Worms 24

Life on a Rocky Shore 26

Rays and Sawfish 28

Sharks 30

The World of Eels 32

Life on a Coral Reef 34

Prickly and Poisonous 36

Pacific Salmon 38

Silvery Schooling Fish 40

Life in a Mangrove 42

Deep-sea Fish 44

Fast-swimming Fish 46

Seahorses and Shrimpfish 48

Life at a Deep-sea Vent 50

The World of Flatfish 52

Wonders of the Deep 54

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Glossary of Key Words 56

Index 57

Wonders of the SeaWonders

of the Sea

INTRODUCING

There is more sea than land on ourplanet and it is home to many amazing

creatures. Along the beach there aremollusks and crabs. Out at sea live spiny

lobsters, creatures with eight long arms and fish with wings.

Life began in the salty seas millions of years ago. All the layers of the oceans are inhabited, even

the deepest, darkest parts that are out of our reach.There may be mysterious creatures down there

that we have yet to find.

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The World of Plankton

WONDERS OF THE SEA

The World of PlanktonBillions of microscopic plants and

animals drift in the surface waters of the seas and oceans. They are calledplankton. These plants and animals are very important for underwater lifebecause they begin the food chain in thesea. Plant plankton are eaten by animalplankton, which in turn are eaten bylarger sea creatures. Many sea animalsdepend on tiny plankton for their food.

Small fish haslarge eyes to keep a lookout forpredators

Young fish feeds on otheranimal planktonSea gooseberries,

a type of animalplankton

Crab larva, or young crab

ANIMAL PLANKTONSome sea creatures, including crabs,some fish and sea gooseberries, beginlife in the sea as animal plankton. These larvae, or young, look verydifferent from the adult animals. Other creatures, such as copepods, stay as plankton all their lives.

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Fish larva, a type of animal plankton

Jellyfish larva, a typeof animal plankton

AMAZING FACTS★ Some kinds of dinoflagellates,tiny plant plankton, give off light.If a boat or swimming creaturedisturbs the surface of the sea atnight, the dinoflagellates glow andsparkle in the dark.

THE WORLD OF PLANKTON

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F I N D O U T MOR ETHE HUMAN BODY: Cells

INSECTS AND SPIDERS: Crustaceans

MICROSCOPIC LIFECollect some sea water in abucket or glass jar. It may bepossible to see planktonclumped together as colouredpatches in the water with anaked eye. For a closer view,place a few drops of the wateron a plate and look through a microscope.

Long antennae, orfeelers, help the copepodprobe for food

Dinoflagellates glow in the dark

Copepod, a tiny crustacean

Using a microscopeto see plankton

PLANT PLANKTONEach plant plankton is made up of only one cell. Millions of tons of new plant plankton grow everyyear. They are called the grass of thesea because so many animals feed onthem. Plant plankton use sunlight tomake their own food.

EAT OR BE EATENAnimal plankton, such as arrowworms, eat smaller animals orplant plankton. Most things thatlive in the sea will become foodfor something else. Arrow worm

Single-celled plantplankton floattogether in a chain

Plantplankton

The World of Mollusks

WONDERS OF THE SEA

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The World of MollusksBeaches are littered with empty

shells. Many of these were once thehomes of soft-bodied sea creatures,called mollusks, which include clams,oysters, mussels and sea snails. Overtime, these mollusks use a chalkysubstance found in sea water to buildtheir shells, which help to protectthem from enemies. Sea slugs, squidand octopuses are also mollusks, butthey do not have shells.

Purple sea snail hangs from its bubbleraft, waiting for food

European whelk, a typical gastropod

Warty venusclam, a typicalbivalve

DOUBLE OR SINGLE SHELLSSome mollusks, such as clams andscallops, have two shells, joinedtogether by a hinge. They are calledbivalves. Others, such as snails andwhelks, have only one shell. They are called gastropods.

FLOATING ON BUBBLESThe purple sea snail lives near thesurface of the sea. It cannot swim, so to stay afloat it makes a “raft”from hundreds of bubbles it hasblown and stuck together. If it isseparated from its raft, the snailsinks to the seabed and dies.

“CLAPPING” SCALLOPSScallops can move fast whenescaping from enemies, such assea stars. They open their shells to draw water in, then clap themtogether to squirt it out again.This shoots them backwardthrough the water, out of reach.

Bubbles are madefrom slime produced in the snail’s body

Whelk hunts other creatures to eat

Siphons, or tubes,for filtering foodfrom the water

Muscular “foot” helps mollusks move

Scallop closing the two halves of its shell

Jet of watershoots scallopbackward

HOW A PEARL GROWS

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Purple seasnail clingingto bubbles

Opened oystershell, with pearl

As sea snail grows,it builds extra sections onto its curved shell

F I N D O U T MOR EINSECTS AND SPIDERS: Mollusks

THE MARVELS OF SCIENCE: Floating

1An irritating pieceof grit or sand gets

stuck inside anoyster’s shell.

2To protect its softbody, the oyster

covers the grit withmother-of-pearl(nacre) from thelining of its shell.

3After a year ormore, a smooth,

round pearl hasformed inside theoyster, and there is nolonger any irritation.

AMAZING FACTS★ The biggest shell of allbelongs to the giant clam.Some clam shells aremore than 1 m (3 ft)wide and weigh a quarter of aton.

Sea snail eatssmall sea animals,such as jellyfish

Giant clam and diver

THE WORLD OF MOLLUSKS

WONDERS OF THE SEA

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Life on a

Sandy Beach

Life on a

Sandy Beach

Red ribbon wormgrows up to 15 cm (6 in) long

Sandmason wormcollects food in itstentacles

Empty cockle shellwashed up on thebeach at high tide

Sea stars, orstarfish, feed on mollusks

Channel wrack seaweed

Lesser sand eels

SPINY DIGGERThe heart urchin is a type of sea urchin. It uses its strong, broad spines to diginto the sand in search of food. It feedson tiny pieces of plant and animal food.

SHORE-LIVING CRABSCrabs belong to a group of hard-shelledcreatures called crustaceans. Some crabslive in deep water, but others live onsandy shores, where they search formollusks and other food. If in danger,the crabs burrow into the sand. When inits burrow, the masked, or helmet, crabcan breathe through a long tube madefrom its antennae.

Every day, the sea risesand falls along the shore.These changing tides can causeproblems for creatures of theseashore. At low tide, theyneed a damp place to hide sothey will not dry out. When thetide comes in, animals have totake shelter so they do not getswept away by the waves.

A sandy beach may look empty, butplenty of creatures live just below thesurface of the sand. These includeworms, mollusks, crabs and evenburrowing fish. When the tide goes out,lesser sand eels dig themselves into thesand. They stay in their damp burrowsuntil the sea floods in again.

Masked, or helmet, crab

Lugwormin its burrow

BEACHCOMBINGThe tide washes up many fascinating thingsonto the beach. Look for mollusk shells,the egg cases of sharks and rays,called mermaids’ purses and deadcrabs. Remember – only emptyshells should be collected.

F I N D O U T MOR EBIRDS: Shore birds

PLANET EARTH: Tides

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Tellin clam hastwo siphons, or tubes,for breathing andfiltering food

Peacock worm

Ribbon worm

Ragworm with segmented body

Sand gaper,a clam

Razor shell,shaped like an old-fashioned razor

Sea mouse,a type of worm

Common whelksearches the shorefor food

LIFE ON A SANDY BEACH

BURROWING WORMSRibbon worms, ragworms andlugworms all burrow into the sand.Lugworms leave little coils of sand,called casts, on the beach at one endof their U-shaped burrows. Peacockworms live in tubes made of grains ofsand stuck together with slimy mucus.

UNDERGROUND MOLLUSKSMany clams and other mollusks hide justbeneath the sandy surface. When the tidecomes in, they push up a tube, take inwater, and feed on tiny scraps of foodthey filter from the water. One clam, therazor shell, can burrow into the sandfaster than a person can dig.

Look out for seashells andegg cases on the beach

Heart urchinhas long feedingtubes

Cockle feedson plankton

Lugworm castat one end of its burrow

Animal life on asandy seashore

Squid and Octopuses

WONDERS OF THE SEA

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Squid and OctopusesSquid, octopuses and cuttlefish

are mollusks, but they do not have shellsto protect their soft, bag-shaped bodies. All have eight long arms, but squid and cuttlefish also have a pair oftentacles, which they use forcatching prey. Octopuses haveexcellent eyesight and largebrains. They are believed tobe the most intelligent of all invertebrate animals.

Octopus reacts fastwhen attacked and escapesbehind an inky “smokescreen”

Funnel directs a squirt of water to jet the octopus backward

INK SQUIRTERSOctopuses squirt out thick clouds ofbrown or black ink to confuse theirenemies. This gives them time to make a quick getaway. The ink comes from aspecial sac, or bag, in the octopus’s body.Squid and cuttlefish produce ink, too.

SPEEDY SQUIDSquid often travel in groupscalled schools. Squid can swim,in short bursts, at speeds of upto 32 km/h (20 mph). Water is taken into the body, thensquirted out through a tubenear the neck. This forces the squid through the water.

School of squid Two rows of suckers lineeach arm

Sea Stars, Urchinsand Worms

Sea Stars, Urchinsand Worms

WONDERS OF THE SEA

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Spiny sea stars and sea urchins belong to a group calledechinoderms. Their prickly spinesprotect them from enemies. Theyhave hundreds of feet like tinytubes, which they use to crawl overthe seabed. Many types of wormsalso live in the sea. Some are goodswimmers but others spend theirlives in burrows.

Large mouthlies under the centre of the body

SEEING STARSA sea star, or starfish, has a centralbody, with five or more arms aroundit. If an arm is damaged, the sea stargrows a new one within a few weeks.Sea stars eat mollusks and corals.

Sea star squeezes its stomach inside the shell and digests the clam’s flesh

AMAZING FACTS★ Some sea stars have eyeson the ends of their arms.

★ The sunflower star is one of the biggest of all sea stars. It measures about 132 cm (52 in) from tip to tip.

Sea star preyingon a clam

SEA STARS, URCHINS AND WORMS

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STICKY DEFENSEThe sea cucumber is not a plant – it isrelated to sea stars and sea urchins. Itdefends itself by shooting out a streamof sticky threads. While the attackeruntangles itself, the sea cucumbermoves away on its tube feet.

Sea mouse

Fire worm

Fan wormsanchored to seabed

Sharp spines with suckers andpincers among them

Long, strong armswrap around clam

Suckers on the endof tiny tube feet force the clam shell open

Sucker

Spine

SPINY SHELLSSea urchins have hard, round shellscovered in sharp, poisonous spines.They use their spines as weapons forself-defense. Some also use them forburrowing into the sand. The suckersand pincers are used for seizing prey.

SEA-LIVING WORMSSea worms have many differentlifestyles. Fan worms wavetheir feathery tentacles to trapfood. The fire worm is anactive hunter, covered withstinging bristles. The hairysea mouse hides in mudor sand on the seabed.

Sea cucumber clingsto stones with itstiny suckers

PincerSea urchin

Clam trapped by sea star

Tentacles

Stingingbristles

Body coveredwith fine hair

Prickly spines

F I N D O U T MOR ETHE HUMAN BODY: Stomach

INSECTS AND SPIDERS: Worms