1. Phylum: Platyhelminthes
“flatworms”
Examples: tapeworms, flukes, planarians

2. Traits
Flattened, worm-like body

3. Traits
Bilateral symmetry

4. Traits
Cephalized – have a distinct head end with a concentration of sensory nerves and brain

5. Traits
Ladder-like nervous system

6. Traits
3 cell layers

7. Traits
Blind sac digestive system

8. Types Planarians – free living flatworms
Tapeworms – segmented parasitic flatworms
Flukes – non segmented parasitic flatworms

9. Planarian structure Ectoderm (epidermis) – outside layer of cells
Endoderm – inside layer of cells
Mesoderm – the middle layer of cells

10. Mesoderm
Advantage – allows for the development of complex internal organs
Disadvantage – since not every cell is in contact with the water, getting oxygen and getting rid of wastes is a problem

11. Planarian structure
Eyespot – detects light but can’t see shapes and images

12. Planarian structure
Flame cells – excretory structures, collect nitrogenous wastes and force them out of the body through a series of tubes

13. Planarian structure
Digestive system – blind sac, branches a lot so no cell is very far from food

14. Movement
Can glide on ventral cilia or use muscles to swim

15. Reproduction
Asexual – by regeneration or binary fission

16. Binary Fission

17. Reproduction
Sexual – hermaphrodites, must exchange sperm (mate) with another worm

18. Tapeworms
Segmented parasitic flatworms

19. Advantages of parasitism
Food is readily available
don’t waste energy through movement
protected from the environment

20. Disadvantages of parasitism
If the host dies, they die
Must get offspring to another host
Must produce a lot of offspring

21. Tapeworm Structure
Scolex – head of a tapeworm

22. Tapeworm Structure
Hooks and suckers – attach the tapeworm to the host’s intestinal wall

23. Tapeworm Structure
Neck – pinches off proglottids

24. Tapeworm Structure
Proglottids – reproductive segments of a tapeworm

25. Tapeworm Structure
Cuticle – non cellular outside layer that keeps them from being digested from the host’s enzymes

26. Tapeworm Infestations

27. Symptoms Weight loss and fatigue
Final diagnosis is from a stool sample

29. Cure
Easy
Since they live in the intestines, the medicine goes directly to them, then they are eliminated with the feces

30. Life Cycle
Adults live in the human intestines, mate, eggs leave with the feces
A pig ingests food or water contaminated with the eggs
Eventually lodge and form cysts in pig’s muscle
A human eats poorly cooked pork and it starts all over again

31. BEEF TAPEWORM LIFE CYCLE
5. Uncooked meat in consumed
1. eggs released
3. eggs eaten
4. larvae migrate to muscle & form cysts
2. eggs on grass

32. Cysts in contaminated pork

33. Prevention
Cook meat well
Good sewage systems

34. Flukes
Non segmented parasitic flatworms

35. Flukes
Endoparasites – live inside the body

36. Cure?
Very difficult
Since they live in liver, medicine doesn’t go directly to them
If you do kill them, the body can’t eliminate them easily

37. Sheep liver fluke Live in a sheep’s liver
Can clog the bile duct and possibly kill the sheep

38. Alternation of hosts
Need at least 2 separate hosts to complete its life cycle

39. Life cycle
Adults live inside the sheep’s liver, mate, eggs leave with feces
Hatch into larvae which enter snails, reproduce asexually
Leave snails and form cysts on grass which is eaten by the sheep and start over

41. Prevention
Spray and kill the snails

42. Chinese liver fluke
Infest the liver of humans

43. Life cycle
Adults live in the human liver, mate, eggs leave with feces which is used to fertilize fields
Flood irrigation washes them into rivers, hatch into larvae which enter snails, reproduce asexually
Leave snails and enter fish which are eaten raw by humans and start over

45. Prevention Cook the fish Use other fertilizers
Other irrigation methods