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Fish Digestive System Variations

Dive into the diverse digestive systems of fish, from mouth structures to intestinal adaptations. Explore how diet influences mouth and pharynx anatomy, and learn about the unique features like gill rakers and pyloric caeca. Discover the specialized feeding mechanisms of species like the paddlefish and grass carp. Find out about the circulatory system in fish and the pathways through the heart and major vessels.

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Fish Digestive System Variations

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  1. Digestive System

  2. Digestive System - basic plan • Mouth (toothed jaws, oral valves) • Oral cavity (vomerine, palatine teeth, tongue w/ teeth) • Pharynx (pharyngeal tooth pads, gill arches/rakers) • Esophagus (gullet) • Stomach

  3. Digestive System - basic plan • Pylorus (pyloric valve, pyloric caeca) • Small intestine (ducts bring in bile, pancreatic secretions) • Large intestine/cloaca • Anus

  4. Variation based on diet, lifestyle

  5. Mouth & Oral Cavity

  6. Teeth in Jaws • Food generally swallowed whole • Teeth used for capture, not chewing

  7. Pharynx - gill rakers

  8. Gill rakers • Gill rakers on anterior side of each gill arch - prevent escape of prey • Gill filaments on posterior side of each gill arch

  9. Size and shape of rakers depend on types of foods eaten

  10. Short, blunt gill rakers • Large prey

  11. Long, fine gill rakers • Particle or suspension feeder

  12. Developmental changes • Gill rakers can change in form as fish develops

  13. Paddlefish - suspension feeder • Long, fine gill rakers to strain plankton from water column

  14. Zooplankton’s view!

  15. Pharyngeal teeth

  16. Pharyngeal Teeth • Variety of teeth in the same general region • Derived from gill arches

  17. Feeding

  18. Pharyngeal teeth • Aid oral teeth in holding “prey”, directing them into esophagus • Modified for crushing, grinding, shearing of foods

  19. Pharyngeal Teeth • Present in many herbivores that eat plants, algae, and/or phytoplankton • E.g., Grass carp

  20. Esophagus & stomach • Structure varies with diet • Simple tube to blind-sac, elastic pouch

  21. Pylorus • Pyloric valve controls release of stomach contents • Ray-finned fishes peculiar among vertebrates • Possess numerous pyloric caeca - digestive/secretory glands Pyloric caeca

  22. Intestines

  23. Carnivore intestines • Intestine usually very short in carnivores • Animal foods digested, absorbed easily

  24. Herbivore intestines • Intestine usually very long in herbivores, detritivores • Plant foods digested, absorbed slowly

  25. Chondrichthyes

  26. Shark digestive system

  27. Spiral valve in sharks Increases food passage time through intestine - improves absorption

  28. Typhlosole in lampreys • Flap of tissue extending • into lumen of intestine • increases surface area • for absorption • Disclaimer - this is a • picture of an earthworm, • not a lamprey

  29. Circulatory System • Fish have a single-loop circulatory system

  30. Typical pathway Heart to gills to body, back to heart

  31. Major vessels run along (ventral to) vertebral column Branches to organs, muscles (segmental)

  32. Heart • Fish have a 2-chambered heart

  33. Lungfish Circulatory System • Lungfish have added features

  34. Lungfish Circulatory System

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