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FISHES

FISHES. Fishes. All fishes retain four (4) primitive characters: Streamlined body Vertical tail fin Gills for gas exchange Lateral line system, No ears. Fishes. Three traditional vertebrate classes that remain aquatic. Class Bony Fishes Class Cartilaginous Fishes

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FISHES

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  1. FISHES Fishes.ppt

  2. Fishes • All fishes retain four (4) primitive characters: • Streamlined body • Vertical tail fin • Gills for gas exchange • Lateral line system, • No ears Fishes.ppt

  3. Fishes • Three traditional vertebrate classes that remain aquatic. • Class Bony Fishes • Class Cartilaginous Fishes • Class Jawless Fishes • All three classes well adapted to aquatic environment. Fishes.ppt

  4. Class Bony Fishes • Also called “Ray-finned Fishes” • ~30,000 species. • Majority of living vertebrate species. • Bony skeleton, well developed skull • Fins supported by cartilage or bony “rays” and minute scales (=lepidotrichia) • paired fins: • pectoral, pelvic • median fins: • dorsal, anal, caudal Fishes.ppt

  5. Bony Fishes • Fins • paired fins: • pectoral, pelvic • median fins: • dorsal, anal, caudal Fishes.ppt

  6. Bony Fishes • Bony dermal scales • covered by thin epidermis • NOT homologous to reptilian scales. • Operculum covers gills; one gill slit each side. Fishes.ppt

  7. Bony Fishes • Lungs, often modified to swim bladder. • Examples: • sturgeons • gars • catfish • trout • bass • Northern pike • American eel • note paired fins, jaw, operculum Fishes.ppt

  8. Class Cartilaginous Fishes • 400 - 600 spp. • Skeleton of cartilage, bone lost. • Fossil placoderms and jawless fishes had bone tissue, prob. ancestral to both Cartilaginous & Bony fishes. Fishes.ppt

  9. Class Cartilaginous Fishes • Cartilaginous skull poorly developed, esp. dorsal to brain • Fins supported by cartilage or horn-like rays Fishes.ppt

  10. Cartilaginous Fishes • No ribs. • No lungs or swim bladder. • Separate gill slits, usually 5 • Placoid scales, • tiny, tooth-like • Enlarged at edge of mouth  teeth • Homologous to teeth in all other vertebrates. Fishes.ppt

  11. Cartilaginous Fishes • Sharks, • Rays • specialized flattened sharks • “wings” are pectoral fins Fishes.ppt

  12. Development of Jaws • All animals studied so far are “Jawed Vertebrates” • Jaws developed from gill arch, • Allowed diverse diet Fishes.ppt

  13. Class Jawless Fishes • Survivors of earliest vertebrates • No jaws, • can not close mouth • No scales • No paired fins, only median caudal fin (continues dorsal & ventral to anus) • Single median nostril on top of head • Circular gill slits • 7 or 12 pairs on sides of pharynx. Fishes.ppt

  14. Jawless Fishes • Hagfishes • tentacles around mouth • predators on worms, mollusks • scavengers • 20 spp. in 4 genera • Lampreys • circular mouth, no tentacles • filter feeders, or • external parasites of bony fishes • 30 spp. in 10 genera Fishes.ppt

  15. Jawless Fishes • Life cycle of sea lamprey • Adult parasitic, feeding stage • Adults swim into small freshwater streams to breed • Larvae live in sediment as filter feeders up to seven years • Metamorphosis, migration to lake or sea to become parasitic adults Fishes.ppt

  16. Jawless Fishes • Sea lamprey in the Great Lakes • Lake Ontario since end of last Ice Age, prevented from entering upper lakes • Welland canal • Sea lamprey devastated commercial fishing • Control Fishes.ppt

  17. Overview of where we have been • All animals studied to date belong to: • Phylum Chordata • notochord • dorsal nerve cord • pharyngeal arches/clefts • bear gills in fishes, • modified to other structures in terrestrial animals • postanal tail Fishes.ppt

  18. Review • Subphylum Vertebrata • Notochord reduced, replaced by bony or cartilaginous vertebrae • Some notochord tissue usually remains • Pharyngeal arches bear gills • or developed into other organs: hyoid bone, larynx • Liver • Pancreas Fishes.ppt

  19. Review • Subphylum Vertebrata • 7 traditional Classes: • Jawless fishes • Cartilaginous fishes • Bony fishes • Amphibians • Reptiles • Birds • Mammals Fishes.ppt

  20. Invertebrate Chordates • Two more subphyla of Chordata, lack distinguishing characters of Vertebrates: • Subphylum Urochordata • tunicates, sea squirts • Subphylum Cephalochordata • lancelets, amphioxus Fishes.ppt

  21. Subphylum Urochordata • Adult is sessile filter-feeder • Larva shows all characters of Phylum Chordata Fishes.ppt

  22. Subphylum Cephalochordata • Adult and larva show characters of Phylum Chordata • Live in holes in sandy or muddy bottoms • Ciliated pharynx pulls in water • Filtered water exits atriopore • Food directed to intestine , feces disposed through anus Fishes.ppt

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