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Ch. 8 Acoelommorpha, Platyzoa, and Mesozoa

Ch. 8 Acoelommorpha, Platyzoa, and Mesozoa. Flatworms. Gastrotrichs. Gnathiferans. Mesozoa. Phylum Acoelomorpha ( “ without hollow form ” ). Phylum Platyhelminthes ( “ flat worm ” ). Phylum Gastrotricha( “ hairy belly ” ). Phylum Gnathostomulida ( “ jaw mouth ” ).

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Ch. 8 Acoelommorpha, Platyzoa, and Mesozoa

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  1. Ch. 8 Acoelommorpha, Platyzoa, and Mesozoa Flatworms Gastrotrichs Gnathiferans Mesozoa

  2. Phylum Acoelomorpha (“without hollow form”) Phylum Platyhelminthes (“flat worm”) Phylum Gastrotricha(“hairy belly”) Phylum Gnathostomulida (“jaw mouth”) Phylum Micrognathozoa(“small jawed animal”) triploblastic Clade Platyzoa lophotrochozoans Clade Gnathifera (“jaw bearing”) Phylum Rotifera (“wheel bearing”) Clade Syndermata Phylum Acanthocephala (“spine head”) Phylum Mesozoa (“middle animal”)

  3. endoderm parenchyma Triploblastic Mesoderm (muscle layer) ectoderm bilateral cephalized Acoelomate Phyla  organ-system level of organization

  4. Ph. Acoelomorpha (“without hollow form”) • most are free living • incomplete gut • no ganglia • hermaphroditic • no circulatory, respiratory, excretory system

  5. Ph. Platyhelminthes (“flat worm”) Class Turbellaria (planarians) Class Trematoda (digenetic flukes) Class Monogenea (monogenetic flukes) Class Cestoda (tapeworms) • parasitic or free living • incomplete gut • flame cells • hermaphroditic • no circulatory system

  6. Digestive, Nervous, Reproductive, and Excretory Systems protonephridia

  7. Nervous System Ladder-like Nerve Cord

  8. Class Turbellaria ocelli auricles

  9. Branched gut pharynx

  10. Free Swimming Marine Turbellarians

  11. Class Trematoda Parasitic flukes Structurally similar to the more complex turbularians Adapations for parasitic lifestyle • glands • attachment structures • high reproductive rate • tegument

  12. Subclass Digenea complex (indirect) life cycle: first host (intermediate host) = mollusc final host (definitive host) = vertebrate Great diversity in host location • digestive tract • circulatory system • urinary tract • reproductive tract

  13. Clonorchis Life Cycle

  14. Schistosoma Life Cycle

  15. Class Cestoda • scolex • strobila (chain of proglottids) • mouth & gut absent • reproductive system repeated in each proglottid • parasitic • complex (indirect) life cycle with 1 or more intermediate hosts

  16. Cestode Life Cycle evaginated cysticercus invaginated cysticercus smallintestine cysts in meat gravid proglottid shelled larvae (in feces)

  17. developing cysticercus

  18. scolex

  19. Phylum Gastrotricha “belly hairs” gastric gland pharynx male gonads ovary intestine pedal gland

  20. Phylum Gnathostomulida “jaw mouth”

  21. Phylum Micrognathozoa “tiny jawed animals”

  22. Phylum Rotifera (“wheel bearers”)

  23. Typical Rotifer Life Cycle environmental stimulus meiosis 2N female 1N egg 1N male 1N egg 2N egg (amictic) 2N egg 1N sperm fertilization environmental stimulus 2N female (amictic) 2N resting egg parthenogenesis sexual reproduction

  24. Phylum Acanthocephala “spine head” proboscis with hooks & spines intestinal parasites

  25. Acanth Reproduction

  26. Phylum Mesozoa “middle animals”

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