Flatworms-Platyhelminthes Least complex worm No body cavity (acoelomate) No respiratory system No circulatory system ◦All cells close to environment

Flatworms Three Classes ◦Turbellerians (Planarian) ◦Cestoda (Tapeworms) ◦Trematoda (Flukes)

Turbellarians Symmetry –Bilateral Structure ◦shovel head ◦flat body

NERVOUS SYSTEM Mass of nerve cells [ganglia] form a simple brain Ladder-like arrangement throughout body Head sensitive to touch, smell, and taste Two eyespots sensitive to light

REPRODUCTION Reproduction  Asexual  If cut into pieces – each piece will grow into new organisms  Split themselves apart  Sexual  Produce both male and female sex cells (hermaphodidic)  Cannot fertilize itself  Lay eggs

COOL! Planaria Regeneration An injury divided the head of this planarian in half. The two halves regenerated their lost parts. Eventually, the planarian will split lengthwise into two new planarians.

DigestionExcretion

The Monsters Inside Me

Class Trematoda Parasitic flukes a) Liver flukes b) Schistomomes / intestinal flukes that suck blood c) use snails as an intermediate host sucker

uterus testis ovary FLUKE – flat/parasitic Monoecious / hermaphroditic Class Trematoda

suckers SEM image

Intestinal Schistosomiasis 16 yr. Old boy Abdomen accumulates fluid- a body immune response to eggs embedded in tissues

Intermediate host Definitive host Schistosomiasis

Tapeworm showing proglottids Mature proglottids

Tapeworm scolex (head ) light microscope hooks suckers Immature proglottids)

Tapeworm scolex and hooks SEM image I love you

Flea larva eats tapeworm eggs. Tapeworm larvae develop inside flea Worm grows in dog Dog eats infected flea Proglottids with eggs leave in wastes

Rotifer video 2:30 Rotifer 1:30 Rotifer feeding

Egg produced by adult exits in host in feces Host ingests eggs Hatch in host intestine Migrate to lungs as larva Molt in lungs Migrate to trachea, carried to stomach Adult stage in host intestine.

Eggs ingested by host Organism matures in host large intestine Adult lives in host large intestine Adult migrates to perianal region to lay eggs at night Host gets eggs on fingers

Eggs hatch in feces Develop into larva in the mud/soil Penetrate host skin through toes Enters circulatory system Migrates to lungs Matures and migrates to trachea Swallowed by host Adult stage in small intestine Eggs produced