Ch. 10

Platyhelminthes

(flatworms)

Characteristics

• 1mm to 25 meters long

• Flat bodies

• Simple organ systems

• 4 classes

Characteristics

• Reproduction-

sexually or asexually.

Planaria use fission.

Tapeworms form

chains

Myxozoa

Arthropoda Annelida

Mollusca

Lophophorates

Hemichordata

Chordata

Other

pseudocoelomates

Nematoda

Porifera

Ctenophora

CnidariaPlacozoa

Platyhelminthes

Nemertea

Ciliophora

Sarcomastigophora

Microspora

Apicomplexa

Mesozoa

Echinodermata

CrustaceaChelicerata

Uniramia

Protochordates

Class Turbellaria• Ex: Planaria

• Free living. Some in

fresh and some salt

water. Beating cilia

create turbulence in

water.

• Predators &

scavengers.

Carnivores.

• Food gets sucked into

intestine. Waste goes

back out through

pharynx.

Turbellaria

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Sense Organs

• Auricles- look like

earlobes. Have

chemoreceptors for

food location.

• Ocelli- light sensitive

eyespots

Class Monogenea• Ex: Flukes

• Single Host- eggs

hatch, then attach.

• External parasites

(mainly on fish, some

frogs, turtles)

• Usually don’t harm

host

Class Trematoda• Ex: Flukes

• Parasites of vertebrates (as adults)

• Complex life cycle-many intermediate stages.

• Usually “shelled eggs” leaves host in excrement & reaches water to develop further.

Class Cestoidea

• Ex: Tapeworms

• Parasites inside

vertebrate digestive

system.

• Lack mouth &

digestive tract.

Absorb nutrients

through body wall

(tegument).

Class Cestoidea

• Scolex- suckers &

hooks for attachment

to host intestine.

• Proglottids-

reproductive

segments (in a chain).

• Requires at least two

hosts.

Scolex

Proglottid

Uterus

Testes

Ovary

Yolk gland

Vas deferens

Seminal receptacle

Class Cestoidea

• Reproduction: new

proglottids form

behind scolex. Cross

fertilize. Shelled

embryos expelled

through uterine pore.

• OR, entire proglottid

breaks off.

Worm movies on Notebook