Childrens Illustrated Encyclopedia

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ALL THE WONDERFUL sHELLs you find

on the seashore were once the homes

of soft-bodied sea creatures. These

creatures are commonly known as

shellfish, although they are not fish

at all, but mollusks, like slugs and

snails. There are thousands of

different kinds of shellfish living

in the sea, including mussels,

oysters, and clams. Many, such

as the winkle, have small,

delicate shells; others, such

as the queen conch, have big,

heavy shells. The shell itself is like

a house, built by the shellfish. As it

feeds, the shellfish extracts calcium carbonate from the

water. This mineral is used by the shellfish to build up

layers of shell, little by little. As the creature grows bigger,

its shell grows bigger too. some shellfish live in a single,

coiled shell; others, known as bivalves, have a hinged

shell with two sides that open and close for feeding.

HOW sHELLs gROW

shellfish hatch as larvae from eggs, and

then develop shells. Creatures with single

coiled shells, such as this triton, grow by

adding layers of shell-building material

(calcium carbonate) to the open end.

Hinged-shell creatures, such as

cockles, add calcium carbonate to

the rounded edges, in the form

of coils called growth rings.

COCkLE sHELL

The ridged cockle

buries itself in

sand and feeds

when the tide

comes in.

sCALLOp

The scallop is

able to swim

by “flapping”

its two valves.

By snapping

the two sides shut, it can shoot through the

water to escape from a predator.

pEARL

We value oyster pearls highly

because of their white, shiny

appearance, but other kinds of

shellfish make pearls too. The Caribbean conch

makes pink pearls, and some shellfish make

orange ones. The pearl shown here is a “blister

pearl” on a black-lipped oyster shell.

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Pearl comes free,

removing the

irritation.

Eggs

Larva has a

smooth shell.

Foot

Young shells are tiny

and have few coils. Growth rings are slowly added to the open end.

Inside a cockle

Hinge

Mother-of-pearl

(nacre) forms

over grit.

Tiny piece of

grit irritates

oyster.

HiNgED sHELLs

The two sides of a hinged

shell (bivalve) are held

together by a tough

ligament. powerful

muscles keep the valves

closed for protection.

The valves open slightly

to allow the creature

to breathe and feed.

Growth rings on

adult triton shell

How a pearl is made

if a piece of grit gets lodged in an oyster’s

shell, the oyster covers it with mother-of-

pearl (nacre), a substance lining its shell.

Inside a scallop

MUssEL

The mussel

is a common

bivalve on many

seashores.

Siphons for

breathing

Gills filter food

from the water.

Find out more

Animals

Animal senses

ecology and food webs

Ocean wildlife

seashore wildlife

iNsiDE A sHELL

The pearly nautilus

has a shell with many

chambers. As it grows,

the animal shuts off more

chambers by building a

“wall” and lives only

in the last chamber.

NAUTiLUs

This predator and scavenger hunts

at night. it lives in the indian and

pacific oceans and has more than

30 tentacles for catching prey.

Head

Tentacles

Shells and shellfish

ARgONAUT

The paper nautilus is

a type of octopus that

makes a thin shell to

keep its eggs in. it is also

known as the argonaut,

after the sailors of greek

legend, because people

believed they used its

papery shell as a boat.

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