1. Acoelomates Phylum Platyhelminthes Phylum Nemertea Phylum Gnathostomulida

2. Taxonomy

3. Acoelomate Phyla Platyhelminthes –Flat worms Nemertea –Ribbon worms Gnathostomulida –Jaw worms

4. Why bilateral symmetry? Movement toward prey or host –Cephalization –Directional sense organs Chemoreceptors Ocelli (light sensing eyespots) Rheoreceptors (sense water currents)

5. Acoelomates Key Features Three germ layers –Ectoderm, endoderm, mesoderm –Mesoderm forms muscle and mesenchyme Organ-system level of organization –Cephalization –Excretory system –Some have circulatory and one-way alimentary canal

6. Acoelomates Body Plan

7. Phylum Platyhelminthes Specialized Cells –Rhabdites - secrete mucous sheath –Tegument - outer covering of syncytial cells –Flame cells – Osmoregulation –Some have endolecithal egg cells – yolk contained within egg cell

8. Platyhelminthes Cross Section

9. Tegument Syncytium –Apical cell membrane missing

10. Flame Cell Osmoregulation –Beating flagella creates negative pressure to draw fluid into chamber –Water is directed through channels then through an external pore

11. Major Classes of Platyhelminthes Class Turbellaria –Planaria – free living Class Trematoda –Liver flukes – endoparasites Class Monogenea –Fish ectoparasites Class Cestoda –Tape worms – endoparasites

12. Class Turbellaria Key Features –Ladder like nervous system –Eye spots (Ocelli) –Auricles - chemoreceptors –Free living flatworms –Muscular and ciliary movement –Carnivorous

13. Planarian Body Plan

14. Class Trematoda Similar in structure to Turbellaria Special adaptation for endoparasitic life style –Cyst glands –Suckers and hooks for griping host Digenetic – complex life cycle with multiple hosts

15. Liver Fluke

16. Liver Damage Caused By Flukes Scar tissue Blocked bile ducts

17. Flukes in Liver Section

18. Fasciolopsis - Anterior End

19. Schistosoma mansoni Blood fluke Male and female are dioecious

20. Schistosoma cercaria

21. Class Cestoda Tapeworms - endoparasites Key Features –Lack a digestive system –Composed of reproductive units called proglottids –Adult tegument covered in microvilli-like projections – increases surface area, non-ciliated

22. Tapeworm New proglottids are added just behind the scolex

23. Tapeworm Tegument Microvilli help with food adsorption Sensory cells – no other sense organs

24. Mature Proglottid Reproductive unit Mature proglottids are either shed or produce shelled embryos Each proglottid has both male and female organs

25. Tape Worm Life Cycle

26. Taenia solium Pork tapeworm

27. Taenia Cyst in Muscle

28. Phylum Nemertea Ribbon worms –Ciliated epidermis –Locomotion – gliding over slime track and muscular contraction –Complete digestive tract – mouth and anus –Extracellular digestion –Proboscis to capture prey

29. Amphiporus