Platyhelminthes- flatworms

first one that has…

organs!

triploblastic

has three germ layers- ectoderm, mesoderm, and endoderm

protonephridia

“primitive kidney” composed of flame cells, removes waste, regulates osmosis

flame cell

flat worm nervous system

cephalization- concentration of nervous tissue at anterior

flat worm digestive system

gastrovascular cavity, only one opening

snail predation

inside out throat, injecting venom

renerative

can be cut up and regenerate, 20% stem cells

trematoda example

blood fluke

cestoda example

tapeworms

trematode life cycle

1. Eggs: Immature eggs are passed in the stool of the definitive host. 

2. The eggs hatch into ciliated larvae

3. The larvea infect a first intermediate host, usually a snail, and develop into a sac-like structure called a sporocyst. 

4. The sporocyst asexually produces cercariae, which leave the snail. 

5. The cercariae encyst on aquatic plants or invertebrates. 

6. Adult: When a vertebrate eats the second intermediate host, the metacercariae excyst and develop into adult flukes in the vertebrate's intestine

cestoda life cycle

1. Eggs 

   • Tapeworms pass eggs in their feces

   • Eggs are ingested by an intermediate host, such as a pig or cow

2. Larvae

   • Eggs hatch into larvae in the intermediate host's digestive system 

   • Larvae burrow into the intermediate host's blood or lymphatic vessels 

   • Larvae develop into cysticerci, or cyst-like larvae, in the intermediate host's muscles 

3. Adults 

   • The definitive host eats undercooked meat from the intermediate host

   • The cysticerci release baby worms in the definitive host's intestine

   • The baby worms attach to the intestine and develop into adult tapeworms