Flatworms

Class Turbellaria (Planarians)

mostly free-living flatworms found in freshwater, saltwater, or moist land.

Class Trematoda

all parasitic flatworms, often with complex life cycles involving multiple hosts. These live inside the livers of animals

Class Cestoda (Tapeworms)

all parasitic and live in the intestines of vertebrates. They have a unique segmented body.

Acoelomate

The mesoderm completely fills the space between the ectoderm and endoderm. There's no fluid-filled cavity.

Pseudocoelomate

have a fluid-filled body cavity called a pseudocoelom. It's lined by mesoderm on the outside but not completely on the inside (the endoderm also forms part of its boundary)

Coelomate

have a true coelom, a fluid-filled body cavity that is completely lined by mesoderm. This provides space for organs, allows for greater movement and flexibility, and aids in internal transport.

Gastrovascular Cavity

branched digestive system where food is taken in and digested.

Proglottids

Repeating body segments that contain reproductive organs.

Phototaxis

move away from light.

Chemotaxis

detect chemicals in the water and move towards food sources (positive chemotaxis) or away from harmful substances (negative chemotaxis)

Thigmotaxis

prefer contact with surfaces and often move along them.

Monoecious

an individual animal has both male and female reproductive organs

Auricle

these are ear-like lobes on the sides of the head. They aren't for hearing like our ears, but are mainly used for detecting chemicals in the water

Pharynx:

This is a muscular tube that planarians (and some other flatworms) can extend from their belly side (ventral). It's like a feeding straw that they poke out to suck up food. It's connected to their gut.

Planarians exhibit basic forms of learning:

• Habituation

• Classical Conditioning

• Regeneration and “Memory Transfer”

Basic parts of Planarians (Turbellaria)

• Eyespots

• Auricle

• Pharynx

• Gastrovascular Cavity

• Nerve Cords

Basic parts of Liver Fluke (Trematoda)

• Oral Sucker:

• Ventral Sucker (Acetabulum)

• Digestive Tract

• Reproductive Organs

Ventral Sucker (Acetabulum)

Another sucker on the ventral side for stronger attachment to the host.

Digestive Tract

A branched gut with a mouth leading to a pharynx and then two blind-ended branches (caeca).

Basic parts of Tapeworm (Cestoda)

• Scolex

• Neck

• Proglottids

Scolex

The "head" region with hooks and suckers for attaching to the host's intestine.

reproductive organs

an organ which occupies the majority of the body space of the fluke

sporocyst and the cercaria

two intermediate larval stages in the life cycle of flukes

Young proglottids

are small and primarily contain developing reproductive organs.

Mature proglottids

have fully developed male and female reproductive organs and are actively producing fertilized eggs.

Gravid proglottids

are filled almost entirely with fertilized eggs, and the reproductive organs may start to degenerate. These are the segments that eventually detach and are passed out of the host.

Mesoderm

A true coelom is completely lined with