Childrens Illustrated Encyclopedia

Earthworm

there are more than 3,000 kinds

of earthworms. these long-bodied

animals help to keep the soil healthy.

as the earthworms push their way

along, they take in soil at the head

end, digesting nutrients in the soil

particles. the undigested remains

that come out at the rear end form a

worm cast. By burrowing in the earth, worms

mix the soil layers, and their burrows allow

air and water to soak downward, generally

increasing the fertility of the soil.

InsIdE an Earthworm

although earthworms are annelids, with a body

divided into many similar segments, not all the

segments are the same. a digestive tube runs along

the worm’s body. the main nerves come together at the

head end of the body to form a simple brain. the blood

vessels in the worm’s body sometimes form five pairs of hearts.

Tapeworms grow by adding segments

immediately behind the scolex (head).

Each segment contains a full set of

reproductive organs. The largest segments

at the end of the tapeworm contain eggs

and are shed with the faeces.

tapEworm

this worm is a parasitic, segmented flatworm that

lives in the digestive systems of various animals.

a cat, for example, becomes infected when it eats a

mouse that has eaten a plant coated with tapeworm

eggs. the eggs hatch into larvae inside the mouse

and then develop into tapeworms once inside

the cat. when waste matter passes out of

the cat, tapeworm eggs also pass out.

pond worms

Even a small pond contains many worms, such

as leeches and bloodworms. most leeches have 33

body segments. they suck the blood or fluids of

other animals, including mammals and fish. the

leech can swim by flapping its body,

which has a sucker at each end.

Bloodworms, or tubifex

worms, show deep

red blood through

their thin skin.

sEashorE

Worms

ragworms are

active predators

that seize prey such

as smaller worms.

their name comes

from the flaps along

the body that make

the animal look like a

strip of torn rag. Large

ragworms can bite through

human skin and draw blood.

Lugworms live in U-shaped

burrows and feed on organic

material such as micro-organisms

and detritus present in the sediment.

577

wE dEsCrIBE manY long, slender, soft, legless creatures as worms.

there are thousands of different kinds, ranging from the tiny

hookworm to the much larger bootlace worm. the word worm

is a fairly general term, and there are a number of distinct groups.

annelids, or segmented worms, include leeches, earthworms, and

ragworms. nematodes, or roundworms, have long tubelike bodies

without segments. there are at least 20,000 kinds of roundworms.

some, including hookworms, cause serious diseases in humans such

as river blindness and elephantiasis. Flatworms, or platyhelminths,

make up a third group. there are more than 29,000 kinds,

and they include the parasitic flukes and tapeworms

that infest sheep, pigs, and other animals.

Ragworm lives

in sand and

under rocks.

Entire body may be more than 30 ft (9 m) long.

Proglottis (single

segment)

Scolex (pin-

sized head)

has hooks

and suckers.

Worm’s tiny bristles

grip the soil

particles.

Lugworm eats

sand at head end.

Tubifex

(bloodworm)

Upper main

blood vessel

Intestine

Hearts

Mouth

Medicinal

leech

Reproductive organs Main nerve

BLoodworm taILs

pond-dwelling

bloodworms, or tubifex

worms, wave their rear

ends in the water to

gather oxygen. their

heads are buried in the

mud, taking in nutrients.

WORMS

Undigested

sediment passes

through the gut and

is expelled from the

body, producing the

characteristic casts

seen on the surface.

Find out more

animals

medicine, history of

soil

Fat part

of body is

called the

saddle.

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