FLATWORMS

Belong to the KINDGOM ANIMALIA

PHYLUM PLATYHELMINTHES

Characteristics

1.Three germ layers (endoderm,

ectoderm, mesoderm)

2.Bilateral symmetry

3.Cephalization (has a head)

COELOM = fluid filled body cavity

Acoelomates = without coelom

FORM AND FUNCTIONFEEDING

Free-living - carnivores or scavengers; they have a digestive cavity, mouth and pharynx

Parasites – feed on blood, tissues or pieces of cells from within a HOST

Most do not have a

complete digestive system

because they absorb

material directly from host

Respiration, Circulation, and

Excretion1.Thin bodies allow for materials to diffuse

(respiration, excretion, etc)

2.Flame Cell – specialized cells that remove

excess water

Ganglia – group of nerve cells that

control the body (like a brain)

Response

Eyespot – group

of cells that can

detect light (like

an eye)

Movement

Flatworms move in 2 ways

1.Cilia helps them glide through the

water

2.Muscle cells help them twist and turn

Reproduction

Sexual Reproduction – most flatworms

are hermaphrodites (have both male

and female sex organs)

Asexual Reproduction by fission –

flatworms can split in two and

regenerate

Groups of Flatworms

CLASS TURBELLARIA

- free living flatworms

- live in fresh or marine

water

- ex. Planarian

Dugesia lives in

freshwater, mostly a

scavenger but can also

feed on protists

Planarians are hermaphrodites

They can also regenerate body parts and will sometimes split in half to reproduce (FISSION)

ANATOMY OF A PLANARIAN

Brain (ganglia) - planarian can process

information about their environment

Pharynx - used for suckling food in (the

mouth is at the end of the pharynx)

Eyespot - simple eye, can detect light

Flame cells - located along the lateral

edges, used for excretion

Intestine - digestion (does not have an anus)

●Class Trematoda = parasitic

flatworms

●a.k.a “flukes” live in mouth, skin, or

gills of hostPrimary host = the host in

which a parasite

reproduces sexually

Intermediate host = the

host in which asexual

reproduction occurs

Schistosoma mansoni - multiple host:

Primary host = human

Intermediate host = snail

Causes Schistosomiasis -in humans; decays

lungs liver, spleen, or intestines, occurs in tropical

areas with poor sanitation/sewage.

Class Cestoda =tapeworms

Long, flat, parasitic

Live in intestines

Scolex = a structure that contains suckers

and/or hooks

Proglottids = body segments of the

tapeworm

Each mature proglottid is a

hermaphrodite

Testes produce sperm, fertilize the

eggs to produce a zygote

Zygotes are

passed out

through the

feces.

Sometimes, a dormant, protective cyst is

formed in the intermediate host muscles

****This is why you should never eat

incompletely cooked meat.