Platyhelminthes

1. Platyhelminthes Flat worms

2. Coelom-(Body cavity)fluid-filled space in a multicellular organism

3. Acoelomate • have no body cavity at all. • Semi-solid tissues between the gut and body wall hold their organs in place. • Psuedocoelomate •  (“false cavity”) • which is a fully functional body cavity. • Tissue only partly lines the fluid filled body cavity of these animals. • organs are held in place loosely, they are not as well organized • Coelomate • (eucoelomates — "true coelom") • have a fluid filled body cavity • complete lining called peritoneum  • organs are attached to each other so that they can be suspended in a particular order but still move freely within the cavity.

4. Aceolomate Animals

5. General Characteristics • Protostome • Tripoblastic- three germ layers • Ectoderm • Mesoderm • Endoderm • Bilateral symmetry • Simplest animal to have bilateral symmetry • Dorsoventrally flattened • Large surface to volume ratio • Organ level of organization

6. General Characteristics cont. • ~12,200 species • Mostly marine • Some freshwater • Some parasitic • Some terrestrial • Size • >1mm to 10 m long • Locomotion • Creeping • Swimming • passive

7. Tegument and Musculature • Rhabdites- excrete protective mucous (toxic) • Parenchyma- fills space between muscles • Muscle fibers • Longitudinal muscles • Animal shortens • Circular muscles • Animal lengthens • Diagonal muscles • Animal flexes

8. Nutrition and Digestion • Incomplete digestive system • Mouth • Pharynx • Intestine • Intracellular digestion • No anus (the mouth also functions for excretion) • Parasitic flatworms have no digestive system

9. Excretion and Osmoregulation • Protonephridia (osmoregulatory organs) • Eliminates waste and excess water • secrete ammonia (nitrogen release) • Nitrogen is a byproduct of breaking down proteins • Flame cells • Cup shaped flagellated cells • Create negative pressure to pull liquids in

11. What’s in pee?Is it urine, uric acid, or ammonia? • It depends on your environment • Low H20= uric acid • Medium H20 = urine • H20 • urea • Salt • Sugar • High H20 • ammonia

12. Nervous System • Central nervous system • Cerebral/neural ganglia (mild cephalization) • Longitudinal nerve cords

13. Sense Organs • Ocelli • Light-sensitive eyespots • Tactile and chemoreceptive cells • More abundant on the auricles of planarians and mouth regions of other flatworms

14. Phylum Platyhelminthes • Consists of four classes • Turbellaria • Planarians • Trematoda • Internal flukes • Monogeneans • External flukes • Cestoda • tapeworms

15. Reproduction and Regeneration • Asexual • Fission- Transverse binary • Sexual • Monoecious • Self fertilization usually avoided • Exchange sperm keep eggs

16. PhlyumPlatyhelminthes: Class Turbellaria • Planarians • Free-living worms • Marine • Terrestrial • Freshwater • > 5mm to 50 cm • Dual gland system • Adhesive glands • Release glands

17. Parasitic life cycles • Hosts • Single vs. multiple • Multiple hosts • Definitive • Sexually reproductive stage • Intermediate • Asexually reproducing stage • Parasitic adaptations • Syncytialtegument/ extraepidermal layer • Loss of centralized nervous system • Decreased digestive and excretory systems

18. Problems of a parasitic existence • Reproduce within the definitive host • Get fertilized eggs out of the host • Contact a new and appropriate host • Obtain entrance into the host • Locate the appropriate environment within the host • Maintain position within the host • Withstand an often anaerobic environment • Avoid digestion or attack by the hosts immune system • Avoid killing the host, at least until reproduction is completed

19. Class Trematoda • Flukes (Asian liver fluke Clonorchissinensis) • Parasitic • External / internal • Body form • Similar to turbellarians • Leaf-like • Well developed gutand reproductive system • Penetration glands • Suckers and hooks

20. Trematoda Lifecycles • Complex lifecycles with up to four different hosts and several larval types • Definitive host • Mammals • Reptiles • Birds • Intermediate host • Arthropods • Gastropods • Fish

22. Fluke body plan

23. Trematode Stages • Adult – fluke in liver, bile ducts, respiratory tract, blood • Miracidium – ciliated, swimming larvae • Sporocyst – asexually reproductive stage producing redia (within sporocyst) • Redia – 2nd asexual phase producing cercaria • Cercaria – free swimming larval form • Metacercaria – encysted cercaria

24. Fluke transmission • Asian Liver flukes (30 million) • Eating raw or undercooked fish /shellfish • Blood flukes (200 million) • Wading in infected water • Lung flukes • Eating raw or undercooked fish/ shellfish • Intestinal flukes (10 million) • Eating unwashed aquatic vegetation • Sheep liver fluke • Eating unwashed aquatic vegetation

25. Blood Flukes:Schistosoma japonicum & Schistosoma mansoni

27. Schistosome Dermatitis (swimmer’s itch)

28. Class Cestoda • Tapeworms • Two hosts • Definitive host- carnivore • intestines • Intermediate host- herbivore • Encyst in muscle

29. Cestode body plan • Long and flat • Attach via scolex • Proglottids develop from base of scolex • Proglottids mature reproductively • Proglottids are shed in feces or crawl from anal opening

30. Taenia saginata Life Cycle- Human/Beef Tapeworm

31. Videos • http://www.youtube.com/watch?v=6V6Nck-lna4&list=PLA41FC25F77702A2A

32. Taenia solium – Human/Pork Tapeworm

33. Cestode Organs • Each proglottid matures as an egg sack

34. Host Specificity • Hydatid Cysts • Encystment of larva in definitive rather than intermediate host • Cysticercosis • Taeniasolium and T. saginata

35. Hydatid Cysts in Human Heart

36. Hydatid Cysts in Human Brain

37. http://www.youtube.com/watch?v=sVo6ARYhtd4&list=PLA41FC25F77702A2Ahttp://www.youtube.com/watch?v=sVo6ARYhtd4&list=PLA41FC25F77702A2A