COMB JELLY

PHYLUM Ctenophora

CiROUP 6: PRIMITIVE ANIMALS

Comb jellies are among the many tiny animals that form plankton-a floating mass that drifts through the sea. Unlike many planktonic

animals, comb jellies are predators that prey on their fellow travelers.

SIZE Length: From 0.15 in.-3 ft., depending on the species.

BREEDING Mating: Each individual ejects both eggs and sperm into the water for external fertilization. Breeding season: Species vary. Sea gooseberry, late summer.

LIFESTYLE Habit: Move through the surface of ocean waters as part of zoo­plankton. Solitary or move in groups to increase the chances of fertilization. Diet: Floating marine animals that are also part of zooplankton.

RELATED SPECIES Comb jellies are classed in a phy­lum of their own, containing about 100 species in 5 orders. Their struc­ture is similar to that of jellyfishes and sea anemones.

Range of comb jellies.

DISTRIBUTION Comb jellies are found in all seas and oceans. They inhabit wa­ter of any temperature, from tropical to extremely cold.

CONSERVATION Comb jellies are rarely seen and rarely caught. They have no commercial value and are not threatened by humans.

CROSS SECTION OF THE SEA GOOSEBERRY

Tentacles: Have numerous filaments covered in adhesive cells. As they trail through the water, they trap prey and pass it to the mouth.

Comb rows: Total of 8. Each consisting of plates made up of thou­sands of upright cilia (small hairs) that move in a wavelike motion to propel a comb jelly through the water. Indi­vidual plates move in­dependently, controlled by the nervous system.

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Sense organ: Has a statocyst (balanc­ing organ) , which lets a comb jelly sense which part of its body is pointing upward

and if it has bumped into anything.

Digestive canals: Transport nutrients from the stomach to every part of a comb jelly's body, especially the comb rows.

Stomach: Lies at the center of a comb jelly's body.

Gullet: Takes food from the mouth to the stomach.

Mouth: Sucks in food brought to it by the tentacles. Waste is expelled through the mouth.

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Comb jellies are barely more substantial than

the water in which they float. These ghostly bags

of translucent jelly are bathed in flickering rainbows

of light that are reflected from the rippling comb rows

along their flanks. Comb jellies exist in a fascinating array

of unusual shapes, and they vary in size from just a

fraction of an inch to as much as three feet long.

~ HABITS Comb jellies are part of zooplank­ton-the floating cloud of ani­mals that drifts in the ocean's surface waters. Most plankton­ic animals feed on microscopic floating plants, but comb jellies prey on other zooplankton.

Although they tend to drift with the current, comb jellies can swim to a limited extent. Some swim like jellyfishes, con­tracting their bodies to force water out and propel them­selves forward. But a typical comb jelly propels itself through water with tiny plates arranged in rows along its body. Each

plate is formed from a line of cilia (small mobile hairs) joined together. A row of plates resem­bles a comb, which is how the animals got their name.

Some comb jellies produce light. Others reflect and scatter light as they move, generating flashes of color. The colors ripple up the comb rows in an irides­cent wave as the combs flick over one at a time, starting from the back. If a comb jelly bumps into something, a sensory organ reverses the wave, and the ani­mal backs slowly away, glitter­ing with light.

~ STRUCTURE Comb jellies are some of the strangest creatures in the sea, with transparent bodies that glow with light. Some look like light bulbs floating in the water; others resemble inflated plastic bags. But no matter what they look like, all comb jellies have the same basic structure.

A comb jelly's body consists of a thick layer of jellylike matter between two thin layers of cells. The body is spherical in many species. In the middle of the

Left: A comb jelly's long tentacles sweep through the water, catching small creatures.

DID YOU KNOW? • Many comb jellies glow in the dark. The light is gener­ated in the linings of the di­gestive canals through an efficient chemical reaction that produces no heat. • Small comb jellies such as sea gooseberries may drift ashore and become stranded in rock pools at low tide.

body is a central stomach. Radi­ating out from the stomach is a system of canals leading to the mouth on the body's underside.

The entrance to the mouth is often fringed with tentacles or fleshy lobes that help gather prey. Some comb jellies have huge stomachs and can engulf prey almost as large as them­selves. In other species the cavi­ty is reduced to a long gullet, and the animal resembles a solid sphere of jelly.

Right: The sea-cucumber-like Beroe cucumis sucks in its prey straight through its mouth.

• Some species no longer live in plankton. They creep along the seabed, searching for prey. • At a comb jelly's upper end there is a balancing organ called a statocyst. If this or­gan is damaged, a comb jelly becomes completely disoriented.

Comb jellies are hermaphrodites -possessing both male and fe­male sex organs. The sex organs are located beside the digestive canals. In the breeding season, a comb jelly produces eggs and sperm. After moving through the stomach and gullet into the mouth, the eggs and sperm are ejected into the sea.

~ FOOD &: FEEDING The sea gooseberry is one of the most common comb jellies in northern waters. It looks like a transparent gooseberry, except for its "fishing lines," which are two long tentacles trailing from its sides. Each tentacle is fringed with sticky filaments that trap floating animals. After making a catch, the sea gooseberry reels in the tentacle, retracts it into a deep pit, and passes the prey to its mouth.

Other comb jellies catch prey

Left: As light is reflected from the rippling combs, a beautiful range of colors appears.

Spawning is triggered by the presence of other comb jellies, so some of the eggs are likely to be fertilized by sperm from other individuals. The fertilized eggs develop into tiny replicas of their parents and feed on mi­croscopic marine organisms. The young can reproduce im­mediately after hatching.

in different ways. The Beroe cu­cumis catches its victims directly in its mouth and sucks them into its body, while the closely related B. gracilis uses this tech­nique to feed exclusively on sea gooseberries.

Prey is broken down inside a comb jelly, and the fragments are passed along a network of canals for further digestion. The canals deliver the nutrients to every part of a comb jelly's body, especially the comb rows. In this way, the canals take the place of blood vessels that do the same job in more complex animals.

EDIBLE SEA URCHIN

ORDER Echinoidea

FAMILY Echinidae

GENUS fit SPECIES Echinus esculentus

The edible sea urchin grazes in the Atlantic and the North Sea the way a sheep grazes in a field. It strips plants and

animals from the rocks with its powerful gnawing teeth.

SIZE Diameter: Up to 7 in.

BREEDING Breeding season: Spring. Mating: Eggs and sperm released into water for external fertilization. Larvae: Free-floating, planktonic.

LIFESTYLE Habit: lives and feeds on the sea­bed in rocky areas. Diet: Marine algae, plants, and an­imals such as sea mats and sea firs that encrust underwater rocks. lifespan: About 10 years.

RELATED SPECIES Many short-spined sea urchin spe­cies are found in rocky areas of the North Atlantic, including the green sea urchin, Psammechinus miliaris. Long-spined sea urchins are more typical of tropical seas.

Range of the edible sea urchin.

DISTRIBUTION The edible sea urchin is found below the low tidemark on the rocky coasts of northwestern Europe, from Norway and Iceland to Portugal.

CONSERVATION Collecting of the edible sea urchin for its tasty roe and decora­tive skeleton is a threat to some populations, but the species in general is not endangered.

STRUCTURE OF A SEA URCHIN

Anus: Opening through which the sea urchin dis­poses of waste.

Intestine ~~-=~~~2i

has a sucker on the end to enable the sea urchin to move around.

Gills

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Entrance to water-vascular system: Mechanism that pow­ers the tube feet by pumping fluid into them.

"Tooth" the sea urchin's underside so it can graze on algae and animals encrusting rocks.

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Genital opening: Where eggs and sperm are released.

Attached to roe, which has eggs and sperm.

Test: Strong shell-like skele­

ton bristling with moving,

sharp-pointed spines and oth­

er defensive systems.

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A sea urchin has a similar body pattern to a starfish,

with five equal sections that radiate from its center.

This primitive animal does not have eyes or a brain. Its

shell, which is called a test, bristles with very sharp,

moving spines. The edible sea urchin is known for its

roe, or sex organs, which are considered a delicacy.

~ HABITS Between a sea urchin's spines, there are many hollow tenta­cles called tube feet. Each ends in a small sucker. By pumping water into its tube feet, a sea urchin can move them and "walk" across the seabed.

Each tube foot has its own fluid reservoir fed by canals in the animal's body. Muscles in the canal walls push fluid into the tube feet to extend them, while muscles in the tube feet control direction.

Sharp spines protect a sea ur­chin from large predators such as fish . But they do not prevent the tiny sea creatures that drift

in currents from settling on the sea urchin's hard external sur­faces . Whether these creatures are parasites or simply "hitch­hikers," the sea urchin must get rid of them.

Many sea urchins have pin­cerlike defense organs on short, movable stalks between the spine bases. Most of these or­gans have three jaws that can grip tiny creatures and remove them . But some have glands that can inject a strong venom into an enemy such as a spiny starfish, which might insert its arms between the spines of a sea urchin to rip it apart.

~ FOOD &: FEEDING Protruding from the mouth on the underside of a sea urchin is a set of five "teeth" for grind­ing. These teeth are linked to­gether in a cagelike structure inside the mouth that is called Aristotle's lantern. When the cage is pushed down and out of the mouth, the teeth close together. But when the cage is raised, the teeth open.

While the sea urchin creeps along the seabed, it constantly works its jaws, scraping off the plants and animals that encrust

Left: The edible sea urchin lives be­low the low tidemark, moving on its many tube feet.

I DID YOU KNOW? • Many species of sea urchin grind small depressions into coastal rocks, where they stay when they are resting. • The word urchin is derived from a French name for the hedgehog, another animal protected by a coat of spines.

the rocks. If there are many sea urchins that are active in the same area, they may seem to keep the rocks bare of life. Yet they rarely run out of food be­cause the currents constantly sweep in new algae and larvae, which settle on the rocks and provide a fresh crop.

A sea urchin may travel sev­eral miles in order to find rich feeding grounds. But if food is plentiful, it spends its entire life in one area and goes over the same ground again and again.

Right: As it "walks" along the sea­bed, the edible sea urchin grazes on algae and barnacles.

• A sea urchin may cover itself with seaweed and other de­bris, probably as camouflage. • Seals and sea otters often eat young sea urchins, which have soft spines. But these mammals avoid older, sharp­spined sea urchins.

Left: Suckers on tiny tube feet surround a sea urchin's mouth. These enable the ani­malto climb vertical rock faces and even to cling upside down.

In spring, male and female sea urchins release sperm and eggs into the water, and the currents bring the sperm and eggs to­gether. Vast numbers of eggs are produced because so many are wasted. The few that are fertilized develop into micro­scopic larvae, which drift with plankton. Many are eaten by fish, sea anemones, and other marine creatures. Those that survive may travel far before they settle on the seabed to change into adult sea urchins.

Left: When the tide goes out, a sea urchin may be left high and dry on a rock.

MOON JELLYFISH

CLASS Scyphozoa

ORDER Semaeostomeae

GROUP 6: PRIMITIVE ANIMALS FAMILY Ulmaridae Aurelia aurita

The moon jellyfish inspires panic in swimmers, and its stinging cells may produce a mild rash in humans. Its main victims, however,

are the tiny animals it filters from coastal waters.

CHARACTERISTICS

Medusa diameter: Up to 18 in.

Ephyra diameter: Less than ~ in.

Coloration: Almost transparent,

except for 4 purple horseshoe­

shaped reproductive organs.

BREEDING

Mating: By external fertilization.

No. of eggs: Many thousands.

LIFESTYLE

Habit: Polyp is static, attached to

a rock. Medusa swims in schools

around coastal waters.

Diet: A variety of planktonic ani­

mals, such as oyster and barnacle

larvae and small worms.

RELATED SPECIES

The moon jellyfish is one of about

200 species in the class Scyphozoa,

which is divided into 5 orders. Oth­

er species include the lion's mane,

Cyanea capillata, which can deliver

a powerful sting.

Range of the moon jellyfish.

DISTRIBUTION

The moon jellyfish is found in shallow coastal waters in most

parts of the world. It is common around rocky shores.

CONSERVATION

The moon jellyfish is plentiful throughout its range. But in

some places it is adversely affected by pollution.

lIFECYCLE OF TH E MOON JELLYFISH

4. Medusa: The familiar adult form, with 4 horseshoe-shaped sex organs visi-ble through its bell. The mouth is beneath the bell and extends into 4 fleshy lobes. The rim of the bell has short, stinging tentacles.

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1. Planula: The tiny first development

from the fertilized egg. The fine hairs on its

surface propel it from the medusa's mouth. It remains near the mouth

lobes until big enough to swim.

2. Polyp: Has tentacles that let it trap food . It grows, attached to a rock or seaweed, until grooves appear along its body.

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3. Ephyra: Disklike form that detaches

itself from the tip of the polyp. Several

bud off from each polyp, and each de­

velops into a medusa.

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Found in coastal waters all over the world, the moon

jellyfish is one of the most common species of jellyfish. It is

named for the circular, almost transparent shape of the

adult form. The adult is also very easily identified by the

four horseshoe-shaped reproductive organs that are

located in the center of the jellyfish 5 body. The color

of these organs can range from lilac to a rich purple.

~ HABITAT The moon jellyfish lives near the

surface in coastal waters world­

wide. The bell-shaped adult, or

medusa form, is frequently seen

swimming in schools. It moves

inshore at breeding time, to

~ DEFEN SES The adult moon jellyfish looks

defenseless, but it is covered

with several kinds of protective

stinging cells that can stun and

paralyze victims.

A poison-injecting cell, or ne­matocyst has a small hair on the

outside that acts like a trigger. If

an animal brushes against it, a

areas with rocks and seaweed.

The polyp, the other common­

ly seen form of this species, looks

like a small plant and is attached

to rocks or seaweed. It feeds by

catching prey in its tentacles.

coiled thin tube shoots out of

the cell and punctures the ani­

mal's skin. The end of the tube

then bursts inside the animal's

body and pumps out poison,

deterring an attacker or paralyz­

ing prey. Other cells hook into

the jellyfish's victim and help to

entangle it.

~ FOOD &: FEEDING As a young medusa, less than

an inch wide, the moon jelly­

fish is an active hunter. It preys

on small fish as well as crusta­

ceans, catching its victims with

its mouth lobes.

When it grows wider than an

inch, however, the moon jelly­

fish stops hunting and simply

floats on the current, waiting

for prey to drift into its path. As it moves, tiny planktonic ani­

mals stick to the mucus on its

body, especially under the bell .

Left: A fringe of tentacles on the edge of the bell helps the moon jellyfish remain upright.

DID YOU KNOW? • The moon jellyfish is 96 per­cent water. Even its skeleton is

made of water. The fluid-filled

canals that carry food and re­

move waste help to keep the

shape of the bell.

• The moon jellyfish is able to

survive in both very cold and

very warm waters. The lowest

temperature in which it can

Paralyzed by stinging cells in

the skin of the jellyfish, the prey

is swept over the surface of the

bell to its edge by cilia (mobile

tiny hairs). The jellyfish's four

long mouth lobes pick up the

prey and transport it, by way of

the mouth, into the stomach,

where it is slowly digested. Be­

cause the moon jellyfish is al­

most transparent, it is possible

to see the digested food mov­

ing through the body along tu­

bular purple canals.

Right: The horseshoe-shaped sex organs can be clearly seen from above or below.

live is 32° F. The warmest tem­

perature is 88° F.

• Although the moon jellyfish is a marine animal, it can also

be found in the mixed salt

and fresh water of an estuary.

The jellyfish's bell is very shal­

low in this somewhat salty wa­

ter and much deeper in very

salty water.

~ NATUREWATCH The moon jellyfish usually in­

habits shallow coastal waters,

at temperatures from 48° to

66° F. You may be able to spot

a school of adults by looking

over the side of a boat. At the

end of summer many may be

stranded on beaches at low

~ LlFECYClE The moon jellyfish changes its

form several times during a life­

time. A jellyfish is either female

or male, with the horseshoe­

shaped sex organs producing

eggs or sperm. When the male

releases sperm into his stomach,

they float into the sea. When

the female releases eggs into

her stomach, they remain there.

The sperm then drift into the fe­

male's mouth and fertilize the

eggs in her stomach.

Each fertilized egg develops

Left: The moon jellyfish spends one phase of its development rooted to a rock.

tide. Their stinging cells may

cause a rash if touched.

The lion's mane is a related

species found on both coasts

of North America. The world's

largest jellyfish, it can reach

eight feet in diameter, but

most are three feet across.

into a planula, or larva. The plan­

ula is covered with cilia that pro­

pel it from the mouth into the

shelter of the mouth lobes. It

then grows until large enough

to swim into the sea, then set­

tles on a rock or seaweed. The

planula changes into a polyp,

which has tentacles and feeds

like an anemone. As it grows,

grooves appear around its body.

These deepen until the polyp

looks like a pile of frilly saucers.

The top "saucer" develops buds

and becomes an eight-lobed

larva, or ephyra. This grows in­

to the adult medusa form.

COQUINA CLAM

CLASS Bivalvia

ORDER Veneroidea

GROUP 6: PRIMITIVE ANIMALS FAMILY Donacidae

.... GENUS fit SPECIES ~ Donax variabilis

The coquina clam is also known as the butterfly shell. It comes in an incredible variety of colors and patterns and is easy to find on sandy beaches, so it is a favorite with shell collectors.

'"------.;~KEY FACTS

SIZE

Length: /:1-% in.

BREEDING

Mating: Both eggs and sperm are re­

leased into the water, where they are

cross-fertilized .

Sexual maturity: 1 year.

Spawning season: From spring to

summer.

No. of eggs: 20,000-50,000.

LIFESTYLE

Habit: Lives in loose colonies in the

sand at the low-tide line.

Diet: Small edible particles filtered

from seawater.

RELATED SPECIES

The family Donacidae contains about

50 species and is found worldwide in

warm temperate and tropical seas. A

close relative on the Pacific coast is

the bean clam, Donax gouldii.

Range of the coquina clam.

DISTRIBUTION

Found along sandy ocean beaches from New York south to

Texas and northern Mexico.

CONSERVATION

The coquina clam is a wide-ranging species and appears to be

lin no danger at present. But, like all marine animals, it is vulner­

able to pollution.

FEATURES OF THE COQUINA CLAM

Feeding: When filtering food particles, the coquina often emerg es from the sand with its siphons extended.

"Foot": The muscular lower por­tion of the body is used to dig in the sand.

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Siphons: Whet) it feeds, the coquina draws water containing food particles throug'h one siphon and expels the water and any wastes through the other.

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The coquina clam prefers the turbulent sand at the edge

of breaking waves, where it lives in closely packed groups

of hundreds or thousands. In any single group you can

find all the variations in color and pattern that give

this little mollusk its scientific name-variabilis.

~ HABITS The small coquina clam can be

found on sandy beaches. It is

especially abundant at the low­

tide line and a few yards above

it. It rarely occurs much farther

out in coastal waters.

When a wave breaks, lifting

the loose sand, the colorful co­

quina is washed out onto the

shore and must quickly burrow

out of sight. After anchoring it­

self, it upends and digs down.

Most of the time the coquina

lives about one inch below the

surface of the sand . But when

the tide withdraws, it burrows

deeper for protection . It then rests until the water returns.

The coquina clam is generally

found in a group that contains

hundreds or even thousands of

individuals. But there may be

long stretches of empty beach

separating these loose colonies.

The coquinas often suddenly

abandon one spot in favor of

another, although there is no

apparent reason for this .

~ BREEDING At the start of the breeding sea-

son, the coquina clam releases

eggs and sperm into the water,

where fertilization takes place.

The members of a colony syn­

chronize their release of eggs

and sperm, so as many eggs as

possible are fertilized .

The eggs quickly hatch into

swimming trochophore larvae.

The trochophore soon changes

into a veliger larva, a tiny crea­

ture that already shows the ru­

diments of the adult's shell. The

rr\d NATUREWATCH If you walk along the beach at

the point where the waves are

breaking, you may see a large

number of coquinas. The ac­

tion of the waves exposes the

~ FOOD & FEEDING Like most bivalves, the coquina

clam is a filter-feeder. It draws

seawater in through one of its

two siphons, filters out the fine

particles of food, and then ex­

hales the water through its oth­

er siphon. Once inside.the coquina, the

food particles are picked up by

the mucus on the surface of the

clam's gills and are then slowly

carried forward to the mouth.

In nutrient-rich water, a contin­

uous stream of particles flows

over the coquina's gills and in­

to its mouth.

Left: The coquina clam 5 siphons have muscles in their walls so they can be contracted or extended.

Above right: After a storm, huge numbers of coquina clams are some­times found lying on the beach.

veliger floats freely among the

plankton, gathering microscop­

ic particles of food.

The veliger drifts for several

weeks, and it may travel many

miles from the place where it

hatched. Eventually the larva

settles into the sand and trans­

forms itself into a miniature of

the adult coquina.

Right: Although the coquina clam hides itself in the sand when the tide is out, it readily emerges from its burrow when the tide comes in.

clams for a few seconds. Since

they rarely burrow more than

an inch or so in the sand and

the sand is usually loose, they

are easy to collect.

DID YOU KNOW? • Fossil coquina shells form a compacted rock that is called

coqu ina stone. It is used as a building material in Florida,

Bermuda, and several tropical

countries. The stone is easy to

cut into blocks, and it hardens

with age.

• The coquina clam does not see its own or other coquinas'

bright colors because it lacks

eyes. The reason for the spe-

cies' colors, which range from

white or yellow to pink or pur­

ple, is unknown.

• Shell collectors must bathe coquinas in mineral oil to pre­

serve their colors. Otherwise

the colors gradually fade be­

cause the natural oils in the

clams' shells are destroyed by

contact with the air.

• A very tasty chowder can be

made from coquina clams. -.J

MILLIPEDE

PHYLUM Arthropoda

.. SUPERCLASS "11IIIIIIII Myriapoda

CLASS Dip/opoda

The name millipede comes from the Latin words for "thousands of feet, " but these animals rarely have more than 200 legs. There are

nearly 8,000 millipede species, found almost everywhere in the world.

CHARACTERISTICS Length: .08-11 in. Coloration: Some are darkly colored to provide camouflage. Others are bright or luminous to warn off predators.

BREEDING Mating season: Spring and sum­mer in North American species. No. of eggs: 10-300, depending on the species. Hatching period: From 2 days to several weeks. Eggs may overwin­ter in temperate climates.

LIFESTYLE Habit: Usually active by night. Diet: Mostly leaves, fruit, and simi­lar plant matter. lifespan: 1-7 years.

RELATED SPECIES: There are about 8,000 millipede species in the class Dip/opoda,

which is divided into 7 orders.

Range of millipedes.

DISTRIBUTION Millipedes are found almost all over the world. Although some millipedes live in temperate climates, they are most common in tropical zones.

CONSERVATION

There are no population figures for many individual millipede species. Destruction of the Amazon rainforest may threaten many species.

FEATURES OF SOME MILLIPEDES

Defense: The pill milli-pede has jointed back plates, so it can curl up into a ball when threatened.

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Snakelike millipedes: May grow to 10 inches long. The tough, smooth cuticle has at least 40 segments, enabling the body to bend when moving. Most seg­ments have 2 pairs of legs.

Antennae: Short; one on either side

of head. They have sensory hairs for

feeling and senso­ry cells for tasting

and smelling.

Pill millipedes: With their shorter, more rounded bodies, these species can burrow in the soil. Found in all types of habitat. Often mistaken for sowbugs.

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Because they have certain superficial similarities/

millipedes and centipedes are often grouped together

in the superc/ass Myriapoda. But these two animals

have very different habits. Centipedes eat flesh and are

relatively fast and aggressive. Most millipedes/ on the

other hand/ are slow, plant-eating creatures.

~ HABITAT A millipede must live in moist, damp surroundings because its hard, protective cuticle (out­er skin) lacks a waxy coating and, as a result, is likely to dry out. Millipedes are frequently found in woods and gardens, living underneath stones, in a tree's bark, or buried deep in piles of moss or rotting leaves.

Various species of millipede have adapted their particular body shapes to their habitats. Burrowing millipedes have

smooth, cylindrical bodies and rounded heads, while species that hide in crevices, such as the blue-keeled millipede, have flattened bodies.

Some millipede species are considered pests because they may damage the root systems of plants. One species of julid millipede, found in Australia, infests houses, living in cellars and damp carpets.

Right: Tropical millipede species tend to be the brightest in color.

~ DEFENSES Millipedes are preyed upon by hedgehogs, birds, spiders, and centipedes. To compensate for their lack of speed, they have developed a variety of defenses. Some are camouflaged by their brown or black coloring, but those with red, orange, or yel-

~ BREEDING Both male and female millipedes have their reproductive organs on their undersides. The male winds around the female, hold­ing onto her while he deposits sperm inside her.

The female lays the fertilized eggs in tiny holes in the ground. She may coil around the eggs

Left: A male millipede transfers sperm to a female by using a pair of modified legs.

DID YOU KNOW? • The most legs ever counted on an individual millipede is 710, but most species have fewer than 200 legs. • Millipedes are not able to close their spiracles (breathing tubes). As a result, they are in danger of being drowned by

low coloring protect themselves by secreting a toxic or repellent fluid from special glands.

The setae (barbs) projecting from a millipede's body are a further protection, making it unpalatable to anything that attempts to eat it.

for a time before covering them with grass and other debris. The hatching time varies from a few days to weeks.

The young have only three pairs of legs and six body seg­ments. They molt several times, adding legs and body segments until they reach the adult form.

Right: Some millipede species can protect themselves by curling up into a ball.

even an extremely light rain. • When hunting, flesh-eating rock millipedes can move at speeds of up to three inches a second-almost twice as fast as most other species. • Millipedes are sometimes called diplopods.

I [ ~:;Ia NATUREWATCH Many species of millipede are The easiest way to find mil-common in North America. lipedes is to set a trap. Fill a Because they need shade and flower pot with damp straw moisture, they are active at or shredded newspaper and night and are usually discov- leave it in a shady spot. Af-ered only if their daytime hid- ter a few days you may find ing place is disturbed . some millipedes living in it.

~ FOOD &: FEEDING Most millipedes feed on decay­ing leaves, fruits, and similar vegetable matter. The food is steadily absorbed as it passes through a tube from the mouth to the anus.

Millipedes usually have simple mouthparts, but some tropical species, known as sucking mil­lipedes, have mouths that form into pointed tubes. The animal can then pierce plant cells and suck out the contents.

Several burrowing pill milli-

pedes have a special adaptation for life in the soil. They eat soil, in much the same way as earth­worms do, digesting the veg­etable matter it contains.

Rock millipedes have adapted to life in the desert. These flesh eaters have fearsome jaws and prey on worms and insects. To cope with dry conditions, the animal hunts mostly in the cool nights and has a waxy cuticle and special sacs at the base of its legs to gather morning dew.

PINK CONCH

ORDER Mesogastropoda

FAMILY Strombidae

GROUP 6: PRIMITIVE ANIMALS .... GENUS &: SPECIES

"11IIIIIIII Strombus gigas

The pink conch is famed for its lovely shell that has a pale, gracefully curving lip. The animal that lives inside this beautiful covering can be

quite active and sometimes even leaps out of harm sway.

SIZES

Shell length: ~-1 ft.

Weight: Can be over 4 lb.

BREEDING

Sexual maturity: 3 months.

Mating: Any time between

February and October.

Gestation: Several weeks.

No. of young: Female lays be­

tween 180,000 and 460,000 eggs.

LIFESTYLE

Habit: Day-active adults and night­

active young.

Diet: Mainly algae.

Lifespan: 10-25 years.

RELATED SPECIES

The genus Strombus includes sever­

al other species, such as the West

Indian fighting conch, S. pugilis, the hawk-wing conch, S. raninus, and the rooster-tail conch, S. gal­lus, which has a graceful "tail" to

its shell.

Range of the pink conch.

DISTRIBUTION

The pink conch is found in the warm, clear waters of the Gulf of

Mexico, the Caribbean, and the West Indies.

CONSERVATION

The population is threatened by commercial exploitation, but

the pink conch is not considered an endangered species.

FEATURES OF THE PINK CONCH

Shell: Continually built up with secretions first from glands in the conch's back and later from the edges of its mantle, or cape. Very old specimens have very thick-lipped and encrusted shells. Older conchs grow • wing-like extensions on their shells. The / conch's exterior tubercles (projections) may be blunt or sharp and spiny. The I shell is pink or orange on the inside and dull brown on the outside.

Eyes: Mounted on the tips of long stalks that protrude from the head . The conch usually keeps one eye extended and the other tucked in close to the shell's lip.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A. 0160200841 PACKET 84

Unlike many of its more docile relatives, the pink conch is an

alert creature that often becomes aggressive. If it is disturbed

from its leisurely grazing, it may thrash around wildly with

its muscular foot. Near the end of the foot, a jagged, clawlike

projection called the operculum acts as a trapdoor closing

the animal inside the shell. The pink conch can also use its

operculum to inflict nasty wounds on an attacking predator.

~ HABITAT The pink conch flourishes in the warm, clear waters of the West Indies. The adult settles near the coast at depths of 1 to 65 feet. It also lives near coral reefs and is­lands and on submerged banks between the reefs and shore.

Immature pink conchs have a

~ FOOD &: FEEDING The pink conch feeds by day. It grazes on algae that grows on submerged blades of turtle and eel grass. First the conch secretes a sticky mucus that helps trans­fer the food from its mouth to its stomach. It then scrapes the

more adventurous existence. They are swept out to sea, hun­dreds of miles from their birth­place. Up to two months may pass before they drop to the seabed to finish growing. Only a few individuals survive this dangerous journey.

algae off the grass with its radu­la, a tonguelike band with rows of inward-curving teeth. A flexi­ble, rodlike organ winds in the mucus ribbon from the mouth, drawing the food into the ani­mal's stomach cavity.

~ BREEDING The pink conch mates almost year-round . The female lays a mass of eggs in sand or turtle grass beds. The egg mass is a coiled tube about two to three inches long. It may hold nearly half a million eggs. The eggs hatch in three days.

The creamy white larva has a paper-thin shell. Called a veliger, it can swim at once. Its heart is visible through its flesh and be­gins to beat a day after the veli­ger hatches. Soon the veliger

Left: The curved clawlike opercu­lum projects from the underside of the pink conch's foot.

DID YOU KNOW? • The pink conch is at times host to a small cardinal fish known as the conch fish. This species hides inside the man­tle of the conch for protection. As many as five cardinal fish have been found within a sin­gle conch. • Before they acquired metal, Carib Indians used the lip of

grows delicate wings that help it move through the water. It feeds on planktonic plants.

After a two-month voyage on the open sea, the conch comes to rest on the seabed. Its other organs now finish developing. The conch is still only about an inch long, and its shell is very thin. It is active only at night un­til the shell hardens enough to withstand the attacks of such enemies as hermit crabs, lob­sters, and eagle rays.

Right: The large, empty shells of dead pink conchs often wash up on Caribbean beaches.

conch shells to make knives, chisels, and even ax heads. • In Greek mythology the Tri­tons used trumpets made out of empty conchlike shells. The pink conch has at times been used in "shell orchestras." Al­though it has a musical repu­tation, a conch shell does not usually have a pleasing sound.

~ PINK CONCH &: MAN For centuries, Caribbean people have prized the flesh of the pink conch. They wade into shallow turtle grass beds to pick it up, or they hook it with a pole into a boat. Where conchs are abun­dant, a two-person crew can gather 500 to 600 a day.

Conch flesh also makes good fishing bait, so conchs have de-

~ BEHAVIOR Although the pink conch may appear to be unaware of its sur­roundings, it is always watching for predators. It can see better than most other gastropods, or single-shelled mollusks.

While grazing, the conch rests its right eye in a shallow dip in the lip of its shell that is called the stromboid notch. The other eye watches from the tip of a longer stalk nestled in another dip. If an enemy approaches, the animal retreats into its shell .

Left: If overturned by currents, the pink conch can push the operculum against its shell to right itself.

clined near fishing ports in the Florida Keys, Jamaica, and the Bahamas. In a few harbors, piles of discarded shells are so high that they are a hazard to ships.

In other places the pink conch is collected for its beautiful shell . Artists once made cameos from it. Today the shell is widely sold to tourists as a souvenir.

It then holds its hard operculum against the narrow opening and shuts out the aggressor.

The conch is very mobile. It has a muscular foot, which is long and narrow with a high arch. Attached to the back of the foot is the operculum. This curved claw is a good weapon and allows the conch its unique form of locomotion. By sinking the claw into the sand and ex­tending its body, the conch can move over the seabed in a series of jumps. If threatened, it rapid­ly moves to safety, covering half its own length with each jump.

GREAT POND SNAIL

ORDER Gastropoda

FAMILY Lymnaeidae

GROUP 6: PRIMITIVE ANIMALS ... GENUS &: SPECIES ~ Lymnaea stagnalis

The great pond snail is related to the common garden snail but lives in fresh water, where it grazes on the organic

debris that most other animals ignore.

SIZES Shell length: 1 ~-2 in. Shell width: ~-1 in .

LIFESTYLE Habit: Solitary; lives in still or slow-flowing waters. Diet: Organic debris and algae scraped off submerged surfaces; also some live prey. Lifespan: 2-3 years.

BREEDING Breeding season: Whenever water is warm enough in spring or summer. Mating: Hermaphrodite, but 2 individuals cross-fertilize. Eggs: About 500 per batch, laid in jelly and glued to submerged ob­jects. Young hatch fully formed.

RELATED SPECIES Other pulmonate water snails in­clude the wandering snail and the great ramshorn, an aquarium fa­vorite with a flat-coiled shell.

FEATURES OF A FRESHWATE

Ramshorn snail: This lung-breather is related to the great pond snail but is much smaller. It is common in still water, where it may be seen riding on the shell of its larger relative.

Foot: Lacks an operculum (plate) . This is one way of distinguishing a lung-breathing snail, such as this species, from a gill-breather. The

. latter uses its op­erculum to seal the shell after withdrawing inside.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

Range of the great pond snail.

DISTRIBUTION Still and slow-flowing fresh water in chalk- or limestone-rich areas throughout Europe, east across southern Asia as far as northwestern India. Also occurs in northwestern Africa.

CONSERVATION Although not directly threatened, the great pond snail has suf­fered from the drainage and pollution of wetlands throughout its range.

Sense or­gans. Flat­

tened on the sides and

triangular in shape. In con­

trast many oth­er snail species

have thread­like tentacles.

Shell: A hardened secretion of calcium. The snail obtains

THE SNAIL'S EGGS

The snail lays about 500 eggs in each batch, embedding them in a mass of jelly to guard them from predatory fish.

calcium from the hard water Within the jelly, each egg embryo in which it lives. develops into a perfect miniature

replica of the snail. It may take about a year to reach maturity.

PRINTED IN U.S.A. 0160200801 PACKET 80

Unlike most other aquatic mollusks, the great pond snail

breathes air instead of absorbing oxygen from the water.

It is therefore able to colonize stagnant ponds that contain

little oxygen but that have plenty of nutritious, decaying

plant and animal life. As a result, the great pond snail

can thrive in the most unpromising places, with little

competition from other, more oxygen-hungry animals.

~HABITS Most aquatic mollusks have gills that take oxygen from the wa­ter. But just like the land snails that it is related to, the great pond snail is a pulmonate: it has a lung cavity laced with minute blood vessels that absorb oxy­gen from the air.

This lung system is somewhat of a disadvantage because the snail may need to surface every 15 minutes or so to draw in a lungful of air. But since it does not rely on oxygen dissolved in water, it can colonize stagnant,

deoxygenated pools with plen­ty of food and little competition from other animals. In such wa­ters the great pond snail often hangs from the surface, gliding on its long, slimy foot.

In an oxygen-rich pond, the snail breathes by carrying an air bubble in its lung, into which oxygen diffuses from the sur­rounding water. This enables the snail to live on the pond bed, where food is abundant.

Right: The great pond snail will feed on dead or dying animals.

~ BREEDING The great pond snail is a herma-phrodite, possessing both male and female sex organs. Never­theless, it always mates with an­other snail, each fertilizing the other. The snail lays its eggs in batches of approximately 500, which it glues in a sticky band of jelly to the underside of a sub­merged leaf.

Within each egg the snail em­bryo develops as a tiny replica of its parents, complete with

Left: Although great pond snails can produce both eggs and sperm, they mate with other adults.

Right: A thick and gelatinous cas­ing prevents fish from eating the snail's tiny eggs.

DID YOU KNOW? • The closely related dwarf pond snail lives in wet pas­tures. It is a notorious host of liver fluke parasites, which in­fect cattle and sheep. • The pond snail's shell is usu­ally sinistral (left-handed) but is occasionally dextral (right­handed). Hold a shell upright by its ends-if the opening

shell. It is fully formed and inde­pendent when it hatches. The newborn snails move away im­mediately but are so vulnerable that few survive to maturity.

Right: Even though it breathes out of the water, the great pond snail rarely travels on land.

lies to the right of the central axis, it is dextral. Sinistral shells open to the left. • Water snails are beneficial in garden ponds and aquari­ums because they help clean up debris. But the snails breed so quickly that they take over unless they are kept in check by natural predators.

.-

[ ':nh'~ NATUREWATCH The great pond snail lives on- in aquariums, where it scrapes Iy in hard water, which pro- algae off the glass. The snail vides the calcium it needs to also creeps across the surface, build its shell. As long as it has hanging from the tension on calcium, the snail can survive the top of the water. Touch it almost anywhere, from ponds gently and it will drop to the to slow-flowing rivers. bottom like a stone, having

L--_T_h_is_s_n_ai_1 a_l_so_d_o_e_s_v_e_ry_w_ e_II __ ejected the air from its lung. J

~ FOOD &: FEEDING In any pond or lake submerged plants, stones, and mud are cov­ered with decaying plant and animal remains, microscopic al­gae, and tiny animals. The great pond snail feeds on this materi­al, scraping it up with its radula, a rasping tongue.

Made of chitin the horny ma­terial that also forms insect skel­etons, the radula resembles a coarse-toothed file. It is always growing: as the front teeth wear down, sharp back teeth move forward to replace them. Some

flesh-eating snails use their rad­ulae to scrape through the shells of prey. But the great pond snail uses its radula more like a scour­ing pad, to clean algae off rocks.

This snail also feeds on other animals' eggs and larvae and attacks small fish and newts, es­pecially dying ones. As the snail eats it grows, adding to its shell at the lip. When conditions are bad, as in winter, growth stops. Such interruptions appear as lines on the shell, giving a visible record of an adult's life history.

RAZOR CLAM

... PHYLUM ~ Mollusca

... CLASS ~ Bivalvia

GROUP 6: PRIMITIVE ANIMALS FAMILY Solenidae

GENERA Ensis, Solen, Siliqua, etc.

Razor clams are familiar mollusks that are often found on sandy beaches. But the empty shells on the beach do not reveal

how these animals have adapted to shore life.

KEY FACTS

SIZES

Length: Up to 10 in.

Width: Up to 1 in .

LIFESTYLE

Habit: Stays in one place, burrow­

ing into beach sand.

Diet: Food particles that are fil­

tered from seawater.

lifespan: Up to 10 years.

BREEDING

Breeding season: Spring.

Eggs: Huge numbers released into

water along with sperm and fertil­

ized externally.

Larvae: Planktonic, drifting to new

sites to settle.

RELATED SPECIES

Of the 100 or so species in the

family Solenidae, 13 are found in

North America. These include the

Atlantic razor clam, Siliqua cos to to; the Pacific razor clam, S. patula;

and the rosy jackknife clam, Solen rosaceus.

Range of razor clams.

DISTRIBUTION

Razor clams are found in shallow coastal waters in all temper­

ate and tropical seas.

CONSERVATION

like all beach-dwelling animals, razor clams are vulnerable to

shore pollution. Because they live near the tide line, they are

not greatly affected by the summer crowds that swarm over

many beaches.

THREE SPECIES OF RAZOR CLAM

Curved razor clam

Pod razor clam

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

Grooves: As a razor clam

grows to full size, distinct

ridges appear on its shell -one for

each year of the clam's life.

ligament mus­cle: Holds the 2 halves of the shell together. Even when the animal is dead, the shell remains hinged by this strong muscle.

PRINTED IN U.S.A.

Siphon tubes: One draws wa­ter in, while the

other expels water, with

the waste it carries.

Gills: Absorb oxygen from the

water drawn in through the

siphon .

Foot: Very strong. Pulls the body down

into the sand.

0160200871 PACKET 87

When they are alive, razor clams are invisible inhabitants

of sandy beaches that survive by taking in seawater and

filtering it for morsels of food. These primitive animals are

burrowers. They are equipped with powerful muscles

and streamlined shells that enable them to disappear

underneath dense, wet sand in the blink of an eye.

~ HABITS A razor clam spends most of its

life buried in the sand below the

low tidemark, out of sight of its

enemies. When the tide is in, it

generally lies vertically with the

top end of its shell just project­

ing out of the sand. Two short,

snorkel-like siphon tubes pro­

trude to draw in water, which

contains all the food and oxy­

gen the animal needs.

A razor clam rarely moves. But

if a very low tide exposes its bur-

row, it withdraws as much as

a foot and a half below the sur­

face and waits for the next tide.

If suddenly threatened, a razor

clam can move extremely fast. It

thrusts its long, muscular foot

deep into the sand, inflating the

foot with blood to anchor it. The

razor clam then pulls itself down.

The effort may send a spout of

water three feet or more into

the air. In seconds the animal is

out of reach of predators.

DID YOU KNOW? • In Ireland and Orkney, peo­

ple catch razor clams for food,

forcing them to the surface by

pouring salt in their siphon

tubes. Anglers sometimes use

them as bait for cod and bass.

I • A razor clam is able to live in

muddy sand that contains no

~ BREEDING Razor clams rely on currents to

bring about the fertilization of

their eggs and to disperse their

young. All razor clams in one

area spawn at about the same

time in early spring, producing

very large numbers of eggs and

sperm. These mingle, and those

that fuse together grow into lar­

vae that float with plankton.

The larvae are vulnerable to

fish, sea anemones, and filter­

feeding mollusks that consume

plankton. Surviving larvae may

drift a long way before settling

on a sandy beach and develop­

ing into adults.

Left: Cold weather may kill razor clams, leaving their empty shells scattered on the shore.

Right: A razor clam's two siphon tubes are occasionally exposed at low tide.

oxygen, breathing through its

siphon tube. The bacteria that

blacken the sand also turn the

razor clam black.

• Razor clams have extremely

sharp edges and are named I

for their resemblance to old-

fashioned razors.

[ :J NATUREWATCH You are unlikely to see a live

razor clam on the beach since

it burrows down if a low tide

exposes it. You may see one

feeding at the water's edge,

ejecting a fountain of waste

water. If you attempt to ex-

~ FOOD &: FEEDING The shallow coastal waters teem

with food particles, from decay­

ing fragments of dead animals

and plants to floating eggs and

larvae. All a razor clam has to do

is strain a meal out of the water.

The animal draws water into

its body through one of its two

siphon tubes. It forces the water

through a sievelike gill network.

Left: A razor clam's long shape and muscular foot enable it to bur­row easily in sand.

tract it, it will dig down, some­

times spouting water as it goes.

Empty shells are very easy to

find higher up on the beach.

Notice the growth rings and J the strong, supple ligament

that hinges the two halves.

The blood-flushed gills absorb

oxygen from the water and get

rid of carbon dioxide. The gills'

cilia (minute, hairlike structures)

trap food particles, smothering

them with mucus. This food is

carried on a sticky conveyor belt

to the stomach.

After digesting any edible ma­

terial, a razor clam expels shell

fragments, silt, and other debris

back into the sea through its

second siphon.

EUROPEAN LOBSTER ___ .....;G;;.;.R~O;.....;U;..;..P....;6;..;...: PRIMITIVE ANIMALS

PHYLUM Crustacea

CLASS Malacostraca

~ ORDER '11IIIIIIII Oecapoda

~ GENUS & SPECIES ~ Homarus vulgaris

Protected by its hard shell, the European lobster scavenges on the seabed. It uses its large, powerful claws to crush the shells of dead crustaceans, including other lobsters.

KEY FACTS

SIZES

Length: Up to 20 in.

Weight: Normally up to 10 lb. In

unusual cases, may weigh as much

as 151b.

BREEDING

Sexual maturity: 5-6 years.

Breeding season: Summer.

No. of eggs: Up to 150,000. Gestation period: 9-1 2 months.

LIFESTYLE

Habit: Solitary; active at night.

Diet: Dead crabs, snails, and other

crustaceans. Also some live prey,

including fish.

Lifespan: Up to 20 years.

RELATED SPECIES

Close relatives include the north­

ern lobster, Homarus american us, found in the Atlantic off the coasts

of Canada and New England, and

the rock lobster, Palinurus interrup­tus, of the Pacific Coast.

Range of the European lobster.

DISTRIBUTION

The European lobster is found in the coastal waters of most of

Europe and North and West Africa, including the Atlantic Ocean,

Mediterranean Sea, and North Sea.

CONSERVATION

A popular delicacy, the European lobster is trapped in large

numbers for food. Although it is not as common as it once

was, it does not seem to be in danger.

FEATURES .OF THE EUROPEAN LOBSTER

Structure: The body has 19 parts, each covered by a section of shell. The shell is thin and soft where the parts join, enabling the lobster to bend and move.

Sensors: The legs, antennae, and shell are covered with millions of tiny, hair­like sensors. These detect chemicals in the water and help the lobster find food .

• limbs: Of the 5 jointed pairs, 4 are used for walking. The large fifth pair (the pin­cers) are used to kill and handle food.

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The European lobster is one of the largest

of the world's 35,000 species of crustaceans. It is

certainly the biggest crustacean found in Europe.

Because of its rich and tasty flesh, this lobster has been

hunted for many centuries. Yet it is still found living

in substantial numbers throughout most of the coastal

waters of Europe as well as North and West Africa.

~ CHARACTERISTICS By day the European lobster hides in a cave or crevice on the seabed, with only its long an­tennae and powerful claws pro­truding. If it cannot find shelter, it digs a burrow under a rock.

At night the lobster emerges to forage on the seabed. It walks slowly on four pairs of legs and holds out its front claws to bal­ance its heavy tail. If danger threatens, it flicks its tail under its body and drives itself back­ward through the water to safety.

The lobster's heavy shell acts as armor against attack. But it has a major disadvantage--

once the shell hardens, it does not stretch. The only way the lobster can grow is to burst out of its shell, discard it, and devel­op a new one.

By the time the lobster starts to feel pinched, it has already grown a soft, new shell inside the old one. At the right mo­ment it retreats to a safe place and draws water into its body, pumping itself up to pry the old shell apart. The pressure splits the shell along a special line of weakness. The lobster then crawls out and waits for the new shell to harden .

~ BREEDING The female lobster first mates in the summer when she is five or six years old. She initially pro­duces a few thousand eggs, but in later years she may lay up to 150,000. After the eggs are fer­tilized by the male, the female does not release them into the water. Instead, she carries them with her, clasped under her tail.

The eggs take 9 to 12 months to hatch, depending on the wa­ter temperature. The shrimplike larvae that emerge look very dif-

Left: When first exposed, the new shell is soft, leaving the lobster vul­nerable to attack.

DID YOU KNOW? • There are fossilized remains of lobsters dating from 200 million years ago. • If one of a lobster's limbs is seized, it may snap off to en­able the lobster to get away. Another limb eventually grows to replace it. • The lobster's compound eyes are made up of hundreds of

ferent from their parents. For about three weeks, the larvae live near the surface of the wa­ter, feeding on floating microor­ganisms and drifting with the currents to new areas.

At this stage many larvae are eaten by plankton-feeding fish. The survivors settle on the sea­bed, where they molt (shed their coverings) several times while developing into small adults. They grow slowly and steadily for the rest of their lives.

Right: To avoid predatory fish, the lobster retreats into its shelter, with its claws held out in defense.

tiny mirrors that reflect light onto receptor cells to form an image. • When a lobster sheds its shell, it often eats some of the old shell to recycle the materials in it. • The male European lobster is called the cock, and the fe­male is called the hen.

r ~ .;.~ NATUREWATCH The European lobster is abun­dant off the Atlantic coasts of westem Europe. It rarely comes ashore, but may get caught in a tidal pool. Usually, however, lobsters live well below the low tidemark. The best way to see a live lobster is to watch lob-

~ FOOD &: FEEDING Despite the fierce look of its pin­cers (claws), the European lob­ster is primarily a scavenger. It creeps across the seabed at night, testing the water with its long antennae and sniffing its way toward decomposing flesh.

Dead and dying animals pro­vide easy food, but sometimes the European lobster attacks live prey, such as mollusks, crabs, and fish . It may even eat anoth­er lobster.

To facilitate feeding, each of

Left: The lobster's formidable pin­cers are its main weapons for at­tack and defense.

ster boats being unloaded. A live lobster is not red-its

shell turns red only when it is cooked. It is important not to handle a live lobster of any kind because, even when it is out of water, it can hurt a per­son with its pincers.

the lobster's two massive front pincers is adapted for different tasks. The larger left pincer has several substantial teeth and is used to crush shell or bone. The smaller, more finely toothed claw seizes prey and functions like shears, cutting flesh into man­ageable chunks.

The lobster's mouthparts con­sist of a pair of jawlike mandi­bles and three pairs of maxillipeds,

highly modified limbs that shred food into tiny pieces for swal­lowing. The food is ground up even more in the lobster's giz­zard for easy digestion.

SEA SLUG

PHYLUM Mollusca

CLASS Gastropoda

,. ORDER "'IIIIIIII Nudibranchia

Sea slugs are among the most beautiful of all invertebrates. But these dazzling marine creatures have much in common with the

drab, slimy terrestrial species that badly damage gardens.

SIZE

Length: Up to 1 ft.

BREEDING

Mating: Sea slugs cross-fertilize

in shallow water.

Breeding season: Usually summer.

No. of eggs: Tens or hundreds

of thousands, embedded in rib­

bons of jelly.

LIFESTYLE

Habit: Some adults can swim;

others glide across the seabed.

Larvae drift on currents.

Diet: Some species eat flesh such

as sponges, jellyfish, and anemones.

Others eat various seaweeds.

lifespan: 1-2 years.

RELATED SPECIES

The sea butterflies, Thecosomata and Gymnosomata; sea hares,

Anaspidea; and bubble shells,

Cepha/aspidea, are among the

many varied species of sea slugs.

FEATURES OF SEA SLUGS

Skin: Often covered with warts and brightly colored to camouflage the slug or warn off predators.

'" ~ ." . .. Cerata: Branched outgrowths. Often numerous, they cover the slug to give it a furry appearance. Contain branches of the intestine and store defen­sive stinging cells near the tips to fire at an attacker.

© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM

Range of sea slugs.

DISTRIBUTION

The many species of sea slug are found throughout the seas

and oceans of the world, generally in relatively shallow water.

CONSERVATION

Although sea slugs are threatened by pollution and marine de­

velopment, they are not exploited by humans. Sea slugs repro­

duce in such quantities that numbers remain constant.

Dorid sea slug

PRINTED IN U.S.A.

Gills: A ring of 9 or more retractable plumes around the anus. The animal breathes through its gills.

Tentacles: Usually 2 or more pairs,

known as rhinopores. They pick up chemical

signals emitted by nearby prey.

0160200621 PACKET 62

Most species of sea slug can perform a remarkable

trick. They can feed on toxic animals and take in their

poison cells. In this way sea slugs are able to repel their

own enemies by using the weapons of other creatures.

Sea slugs also keep predators away with acid and

with dazzling displays of glowing color.

~ CHARACTERISTICS Sea slugs look like underwater flowers, but they are essentially similar to their garden slug rel­atives. Both have lost the shells that characterize other mol­lusks. Both are gastropods, a word that means "stomach foot" and refers to the slimy soles of garden slugs.

Some sea slugs glide like gar­den slugs over seaweed and rocks. Others are agile swim­mers, propelled by muscular flaps on their flanks. Still oth­ers live on the water's surface, hanging upside down from it.

While garden slugs breathe air through a simple lung, sea

Right: Some sea slug species may mimic both the color and form of certain seaweeds.

slugs get oxygen from the wa­ter. Some species absorb oxy­gen straight through their skin. Others breathe through feath­ery gills that sprout from their bodies. This is the origin of their scientific name, Nudibranchia, meaning "exposed gills."

Right: A sea slug's jaws consist of two plates that rub together to crush prey.

~ BREEDING Like most mollusks, sea slugs possess both male and female sex organs. Most species cross­fertilize, migrating to shallow waters in summer to exchange sperm and lay eggs. The eggs are produced in vast quantities -300,000 at a time-and em­bedded in a long ribbon of jelly.

The young hatch as tiny veli­ger larvae, which float among

Left: Disruptive coloring breaks up a sea slug's shape, making it less visible to predators.

DID YOU KNOW? • The soft bodies of some sea slugs are reinforced with needles of calcium carbonate that act like skeletons. Other mollusks use calcium carbon­ate to build their shells.

• The floating sea slug, Glau­cus atlanticus, attacks the Por-

the microscopic plants and ani­mals known as plankton. Each larva has two winglike lobes of tissue covered with tiny, beat­ing hairs called cilia that drive it through the water and trap food. After drifting for several weeks, the larva absorbs its "wings" and sinks to the bot­tom, where it changes into a miniature adult sea slug.

Right: Sea slugs congregate to mate in summer, when they exchange eggs and sperm cells.

tuguese man-of-war, immune to the poison that paralyzes other creatures in seconds.

• One group of sea slugs has broad, winglike lobes on each side. Since they use these to "fly" through the water, they are known as sea butterflies.

l SPECIAL ADAPTATION

Some sea slugs feed on corals that harbor tiny plants, which use sunlight to convert water and carbon dioxide into food . When a slug eats the coral, it also ingests these plants, keep­ing them alive and transfer-

~ DEFENSES Some sea slug species, known as aeolids, have long, brightly colored projections called cera­to. The tips of these cerata are loaded with stinging cells. When fired at an attacker, the stinging cells enter the body through the skin pores. A sea slug does not generate these cells. They origi­nate in toxic corals, hydroids, and anemones. When a slug

~ FOOD &: FEEDING Some sea slugs eat plants, some attack animals (including other sea slugs), and some scavenge for debris and bacteria. Most sea slugs graze on the mats of animals and plants that encrust submerged rocks.

The mouthparts of different

ring them to its long, flat cer­ata (see Defenses below). The slug turns its cerata to catch the sunlight, so t hat the plants can manufacture food . The slug then absorbs most of this

food into its own system. ---1

preys on these creatures, it di­gests the body tissues but saves the stinging cells in working or­der. The cells accumulate in the tips of the cerata, where they are stored for defense.

Other sea slug species defend themselves by squirting acid at attackers. The dazzling colors of many sea slugs also act as a de­fense, warning off predators.

sea slug species vary. Many spe­cies remove prey from a rock using a filelike, toothed tongue called a radula. Other species have bladelike teeth for cutting softer prey. Still others lack teeth and have mouths that can suck out creatures like barnacles.