Chapter 14 - Flatworms

What major change occurs starting in this chapter?

Animals are triploblastic (three germ layers).

What symmetry do most triploblastic animals have?

Bilateral symmetry.

What are the two major bilaterian divisions?

Protostomes and Deuterostomes.

In protostomes, what does the blastopore become?

Mouth.

What body cavity types appear in triploblasts?

Acoelomate, pseudocoelomate, coelomate.

Are Acoelomorphs true flatworms?

No.

What is the body symmetry of Acoelomorphs?

Bilateral.

Do Acoelomorphs have a complete gut?

No (absent or incomplete).

Do Acoelomorphs have respiratory or excretory systems?

No.

What is the reproduction type of Acoelomorphs?

Asexual fragmentation and monoecious sexual reproduction.

Are flatworms acoelomate or coelomate?

Acoelomate.

What type of symmetry do flatworms have?

Bilateral.

Do flatworms have a complete digestive system?

No (usually blind-ended).

What is a protonephridium?

Excretory/osmoregulatory organ.

What special cell is in protonephridia?

Flame cell.

What do flame cells do?

Use flagella to draw fluid through filtering structure.

What type of digestion do flatworms have?

Both extracellular and intracellular.

Do parasitic flatworms usually have a digestive system?

Often no; rely on host.

Do flatworms have longitudinal nerve cords?

Yes.

What are ocelli?

Light-sensitive eyespots.

Compared to cnidarians, are flatworm senses more developed?

Yes.

Are Turbellaria mostly free living or parasitic?

Mostly free living.

How do Turbellaria move?

Cilia + muscles.

Are Trematodes parasitic?

Yes (all).

Do Trematodes usually have complex life cycles?

Yes.

What are intermediate and definitive hosts?

Hosts where larval and adult stages occur.

What is a miracidium?

Free-swimming larval stage.

What is a cercaria?

Larval stage that leaves snail host.

What is a metacercaria?

Encysted juvenile stage.

What is an example of a human blood fluke?

Schistosoma.

How do Schistosoma infect humans?

Cercariae penetrate skin.

Are Monogeneans parasitic?

Yes (usually fish gills).

Is the life cycle of Monogeneans simple or complex?

Direct life cycle.

What is an oncomiracidium?

Ciliated larva.

What structure attaches Monogeneans to their host?

Opisthaptor (hooks).

What is the scolex of a tapeworm?

Hooked attachment head.

What are proglottids?

Reproductive body segments.

What is the strobila?

Chain of proglottids.

Do tapeworms have a digestive system?

No.

How do tapeworms absorb nutrients?

Across body surface (microtriches).

Can tapeworms self-fertilize?

Yes.

What are mesozoans?

Tiny parasitic organisms with ~20-30 cells.

Are mesozoans parasites?

Yes.

What is unique to Nemerteans?

Eversible proboscis.

What special body cavity do Nemerteans have?

Rhynchocoel (true coelomic cavity).

Do Nemerteans have a complete digestive system?

Yes.

Do Nemerteans have a circulatory system?

Yes (blood vascular system).

Do Nemerteans have a respiratory system?

No.

What larval form do Nemerteans have?

Pilidium larva.