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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.
© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A.
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.
0160200651 PACKET 65
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
© MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM
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.
0160200811 PACKET 81
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.
©M CMXCVI IMP BV/IMP INC. WILDLIFE FACT FILETM
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.
US P 6001 12076 PACKET 76
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.
C9 MCMXCII IMP BV/IMP INC WILDLIFE FACT FILETM PRINTED IN U.S.A.
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.
0160200941 PACKET 94
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.
©MCMXCIV IMP BV/IMP INC WILDLIFE FACT FILETM
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.
PRINTED IN U.S.A. US P 6001 12067 PACKET 67
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.
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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.
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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.
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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
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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.