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  1. 1. COMPARATIVEVERTEBRATE ANATOMYAgnatha and Chondrichthyes
  2. 2. Agnathans and Chondrichthyes *
  3. 3. Agnathans Agnathans = Group that includes the jawless vertebrates with a fossil record extending back over 500 million years that is represented today by the living hagfishes and lampreys.
  4. 4. AgnathansHagfish “Myxine” (Myxiniformes) HagfishLamprey “Petromyzon” (Petromyzontiformes)*Both possess aCyclostome (round Lampreymouth).
  5. 5. Hagfishes There are 45 living species. Possess integumentary glands that secrete mucus for protection. (Gives them the common name “Slime Hags”.) Similar to amphioxus, tunicates, and echinoderms because they lack jaws, paired appendages, and bone. Lack vertebrae.*
  6. 6. Hagfishes, Cont. Remain Isosmotic with sea water. Are Serially Hermaphroditic (are male when newly matured but become female). [Other organisms may start as female and become male.] Oviparous reproduction.
  7. 7. Lampreys There are approximately 40 living species. Feed by attaching the buccal funnel with keratinized “teeth” to prey and secreting an anticoagulant onto the tissue. Most species are Anadromous. (Reside in the ocean as adults and return to rivers to spawn).
  8. 8. Lampreys, Cont. Some species remain in fresh water their entire lives. Adults die after spawning. Eggs hatch into Ammocoete larvae. Larvae are filter feeders that trap food in a mucus-like secretion which comes from the subpharyngeal gland.
  9. 9. Extinct Jawless Vertebrates There are many groups of extinct jawless vertebrates according to fossil records. Many of these species possessed body scales, shields, or plates. Also, many species possessed “acellular” bone, which differs from typical vertebrate bone by lacking enclosed cells.
  10. 10. Gnathostomes Gnathostomata = All of the jawed vertebrates. Also possess: - Paired Nostrils - Five Gill Slits - Articulated Gill Arches - Two Sets of Paired Appendages - Three Semicircular Ducts in the Ears
  11. 11. Gnathosomtes, Cont. Considered the dominant vertebrates. Include: - Placoderms (plate; skin) (heavily armored) [Extinct.] - Chondrichthyes (cartilaginous fishes) - Etc. (every other vertebrate group)[Group of Placoderms and Chondrichthyestogether is called Elasmobranchiomorphi.]
  12. 12. Evolution of Jaws
  13. 13. Chondrichthyes Chondrichthyes = The cartilaginous fishes, including the sharks, skates, rays, and chimaeras. - Elasmobranchii includes the sharks, skates, and rays. - Holocephili includes the chimaeras.
  14. 14. Chondrichthyes, Cont. Chimaera (Ghost Shark) *From Wikipedia
  15. 15. Chondrichthyes, Cont. There are approximately 800 living species. Lack true bone and dermal plates although the cartilage is calcified. Possess Placoid Scales that may be remnants of body armor. May be Oviparous, Ovoviparous, or Viviparous.
  16. 16. Chondrichthyes, Cont. Fertilization of eggs is internal and males possess Claspers to facilitate copulation. Lack swim bladders, but produce lipids in the liver to increase bouyancy. Possess electroreceptors called Ampullae of Lorenzini to locate prey.
  17. 17. Chondrichthyes, Cont. Differences in Holocephali: - Scales are mostly absent. - Upper jaw is firmly attached to the cranium. - Gills are covered by a flap called an Operculum.
  18. 18. Evolution of the Fishes
  19. 19. Conclusions The following trends occurred in the evolution of vertebrate lineages. – Vertebral Column – Jaws – Paired Appendages (fins) – Respiration by Gills