Flatworms

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Flatworms

  1. 1. Acoelomate Worms <ul><li>Phylum Platyhelminthes </li></ul><ul><li>Phylum Nemertea </li></ul><ul><li>Phylum Gnathostomulida </li></ul>
  2. 2. Bodies <ul><li>Acoeolomate </li></ul><ul><li>Bilateral Symmetry </li></ul><ul><li>Triploblastic </li></ul>
  3. 3. Platyhelminthes : the classes <ul><li>1. Turbellaria (flatworms) </li></ul><ul><ul><li>Polyphyletic </li></ul></ul><ul><ul><li>Remaining are monophyletic ( Neodermata ) </li></ul></ul><ul><li>2. Trematoda (flukes) </li></ul><ul><li>3. Monogenea </li></ul><ul><li>4. Cestoda (tapeworms) </li></ul>
  4. 4. Form and Function <ul><li>Cillliated epidermis (Turbellaria, larvae) </li></ul><ul><li>Basement layer containing rhabdite producing cells (mucous sheath) </li></ul><ul><li>Dual-gland adhesive organs (turbellarians) </li></ul><ul><ul><li>2 Viscid gland cells </li></ul></ul><ul><ul><li>1 Releasing gland cell </li></ul></ul><ul><ul><li>1 Anchor cell </li></ul></ul><ul><li>Muscle fibers </li></ul><ul><li>Parenchyma cells (solid mesoderm) </li></ul><ul><li>Ciliated, syncytial epidermis (some) = multiple nuclei - no separation </li></ul><ul><li>Tegument (epidermis) so </li></ul><ul><li>… Taxon, Neodermata (Trematodes, Monogenea & Cestodes) </li></ul><ul><li>Free living </li></ul><ul><li>Parasitic </li></ul>
  5. 5. Energy Aquisition <ul><li>Mouth, pharynx & intestine (except cestodes) </li></ul><ul><li>Intestine usually branches (gastrovascular cavity) </li></ul><ul><li>Most Turbellarians are carnivorous (detect prey by chemoreception ) </li></ul><ul><li>Trematodes, Monogenea and Cestodes are parasites (body fluids & cellular debris) </li></ul><ul><li>Extracellular digestion ( proteolytic enzymes) </li></ul><ul><li>Intracellular digestion by phagocytosis </li></ul>
  6. 6. Excretion & Osmoregulation <ul><li>Protonephridia with… Flame cells which are cilliated to drive fluid through tubes </li></ul><ul><li>Primarily osmoregulation (absent in marine species of turbellaria) </li></ul><ul><li>Some ammonia excretion (nitrogenous waste)… most by diffusion </li></ul>
  7. 7. Nervous System <ul><li>Subepidermal nerve plexus (primative) </li></ul><ul><li>Brain (mass of ganglion cells) </li></ul><ul><li>Nerve cords </li></ul><ul><li>Differentiation into </li></ul><ul><ul><li>Motor </li></ul></ul><ul><ul><li>Association </li></ul></ul><ul><ul><li>sensory </li></ul></ul><ul><li>5 sense organs (at least in Turbellaria) </li></ul><ul><ul><li>Tactile </li></ul></ul><ul><ul><li>Chemoreception </li></ul></ul><ul><ul><li>Rheoceptors (H 2 O flow) </li></ul></ul><ul><ul><li>Statocysts </li></ul></ul><ul><ul><li>Ocelli </li></ul></ul>
  8. 8. Turbellaria <ul><li>Polyphiletic (p. 302) </li></ul><ul><li>Simple life cycles </li></ul><ul><li>.5 to 50cm </li></ul><ul><li>Midventral mouth or proboscis (planaria) </li></ul><ul><ul><li>Not at anterior (head) end </li></ul></ul><ul><li>Muscular waves & or ciliary locomotion </li></ul><ul><li>Gut varies from none to highly branched (correlates with size) </li></ul><ul><li>Order Acoela (primative) only mouth, no gastrovascular cavity! </li></ul><ul><li>Amazing regenerative abilities- planaria developmental studies </li></ul>
  9. 9. Reproduction <ul><li>Turbellarians (e.g.. Planaria) </li></ul><ul><ul><li>Fission </li></ul></ul><ul><ul><li>Monoecious cross fertilization </li></ul></ul><ul><ul><li>Genital pore, Seminal receptacle & cirrus </li></ul></ul><ul><ul><li>Endolecithal (yolk) and ectolecithal (no yolk) </li></ul></ul><ul><ul><li>Cocoon attached to substrate </li></ul></ul><ul><ul><li>Embryos emerge as juveniles (similar to adults) </li></ul></ul>
  10. 10. Class Trematoda (flukes) <ul><li>Parasitic </li></ul><ul><li>Vertebrate host and invertebrate Intermediate host </li></ul><ul><li>Leaf-like </li></ul><ul><li>Suckers (two) & or hooks </li></ul><ul><li>Well developed </li></ul><ul><ul><li>alimentary canal </li></ul></ul><ul><ul><li>Nervous system </li></ul></ul><ul><ul><li>Excretory system </li></ul></ul><ul><ul><li>Reproductive system </li></ul></ul><ul><li>Subclass Digenea </li></ul><ul><ul><li>Molusc intermediate </li></ul></ul><ul><ul><li>Human definative host </li></ul></ul><ul><ul><li>Pass via excretia to H 2 O </li></ul></ul><ul><ul><li>Infect many tracts </li></ul></ul><ul><ul><ul><li>Digestive </li></ul></ul></ul><ul><ul><ul><li>Respiratory </li></ul></ul></ul><ul><ul><ul><li>Urinary </li></ul></ul></ul><ul><ul><ul><li>reproductive </li></ul></ul></ul><ul><ul><ul><li>Circulatory system </li></ul></ul></ul>
  11. 11. Trematoda contd. <ul><li>Fluke life cycle </li></ul><ul><ul><li>Egg </li></ul></ul><ul><ul><li>Miracidium (free swimming larva) penetrates first invertebrate host </li></ul></ul><ul><ul><li>Sporocyst forms in host ( asexual repro) </li></ul></ul><ul><ul><li>Rediae from sporocyst which also reproduce asexually to create.. </li></ul></ul><ul><ul><li>Cercariae which emerge from the intermediate host to become.. </li></ul></ul><ul><ul><li>Metacercariae which infect another intermediate or final vertebrate host and mature, usually after ingestion </li></ul></ul><ul><ul><li>Eg. Chinese liver fluke (monoecious) </li></ul></ul><ul><ul><li>Multiplication </li></ul></ul><ul><ul><li>1 miracidium to 250,000 cercariae!!! </li></ul></ul>
  12. 12. Other Digenea <ul><li>Schistosoma (blood flukes) </li></ul><ul><ul><li>Sexual dimorphism (dioecious) </li></ul></ul><ul><ul><ul><li>Male larger than female </li></ul></ul></ul><ul><ul><li>Snail </li></ul></ul><ul><ul><li>Human </li></ul></ul><ul><ul><li>200 - 300 million people infected globally </li></ul></ul><ul><ul><li>Multiple organ infection </li></ul></ul><ul><ul><li>Sometimes fatal </li></ul></ul><ul><ul><li>No rediae intermediate </li></ul></ul><ul><ul><li>Cirrhosis of the liver (eggs) </li></ul></ul><ul><ul><li>Image </li></ul></ul><ul><li>Lung Flukes </li></ul><ul><ul><li>Snails </li></ul></ul><ul><ul><li>Crabs and crayfish </li></ul></ul><ul><ul><li>Vertebrates (humans) </li></ul></ul><ul><li>Leucochloridium paradoxum </li></ul><ul><ul><li>snails and birds </li></ul></ul><ul><ul><li>sporocyst </li></ul></ul><ul><li>Be careful what you drink & eat! </li></ul>
  13. 13. Monogenea <ul><li>One form (one host therefore one form) </li></ul><ul><ul><li>Oncomiracidium larva (free swimming) </li></ul></ul><ul><ul><li>Opisthaptor (attachment organ) </li></ul></ul><ul><li>Related to Cestoda? </li></ul><ul><li>Most external parasites (ectoparasites) of fishes </li></ul><ul><li>Some internal </li></ul><ul><ul><li>Bladders of frogs and turtles </li></ul></ul>
  14. 14. Class Cestoda <ul><li>Tapeworm </li></ul><ul><ul><li>Taenia saginatus (beef) </li></ul></ul><ul><ul><li>Taenia solium (pork) </li></ul></ul><ul><ul><ul><li>Cysticercosis (ingestion of eggs or proglottids) </li></ul></ul></ul><ul><li>Form </li></ul><ul><ul><li>Scolex </li></ul></ul><ul><ul><li>Germinative zone </li></ul></ul><ul><ul><li>Proglottids (Strobila chain) </li></ul></ul><ul><ul><li>Microthrix (tegument) </li></ul></ul><ul><ul><li>Gutless wonders! </li></ul></ul><ul><li>Life Cycle </li></ul><ul><ul><li>Self fertilization (or not) </li></ul></ul><ul><ul><li>Gravid proglottid </li></ul></ul><ul><ul><li>Shelled larvae </li></ul></ul><ul><ul><li>Consumed by intermediate </li></ul></ul><ul><ul><li>Muscle cysts </li></ul></ul><ul><ul><li>Bladder cysts (invaginated cysticercus) </li></ul></ul><ul><ul><li>Uncooked meat </li></ul></ul><ul><ul><li>Definitive host consumes intermediate host </li></ul></ul>
  15. 15. Phylum Nemertea ribbon worms <ul><li>Proboscis worms </li></ul><ul><li>Several cm in length to several meters (60) </li></ul><ul><li>900 species </li></ul><ul><li>Body similar to tubellarians </li></ul><ul><ul><li>Cilliated epidermis </li></ul></ul><ul><ul><li>Flame cells like flatworms </li></ul></ul><ul><ul><li>anus present (means a complete digestive system ) </li></ul></ul><ul><ul><li>Circulatory system (vessels) </li></ul></ul><ul><li>Primarily marine </li></ul><ul><li>Glide or move by muscular contraction </li></ul><ul><li>Prey on invertebrates </li></ul><ul><li>Proboscis (stylet) </li></ul><ul><li>Reproduction varied </li></ul><ul><ul><li>Fragmentation </li></ul></ul><ul><ul><li>Mostly Dioecious; some Monoecious </li></ul></ul><ul><ul><li>External or Internal fertiliazation </li></ul></ul><ul><ul><li>Some ovoviviporous </li></ul></ul>
  16. 16. Phylum Gnathostomulida jaw worms <ul><li>Wormlike </li></ul><ul><li>Less than 2mm long! </li></ul><ul><li>Marine sediments shallow to deep </li></ul><ul><li>Glide or swim </li></ul><ul><li>Sensory cillia </li></ul><ul><li>Hermaphroditic </li></ul><ul><li>G-V cavity </li></ul><ul><li>Respiration by diffusion </li></ul><ul><li>Tolerate low O 2 </li></ul><ul><li>Pharynx with lateral jaws to scrape fungi and bacteria </li></ul>

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