BIOL 3114 Lecture Notes - Lecture 5: Gill Slit, Pharyngeal Arch, Clasper
20 Oct 2016
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Document Summary
Cartilaginous fishes: chimeras, sharks, rays, skates: skeleton is only cartilage. Lipid-filled liver: heterocercal tail, placoid scales, claspers on males. Earliest forms some evidence of bone. Amphistylic jaw support palatoquadrate and hyoid arch. Species today occurred in jurassic and cretaceous. Two main lineages: holocephali chimeras and ratfishes. Cephalic clasper in males: neoselachii (elasmobranchi) sharks, skates, and rays. Sharks streamlined, gill slits on side of body. Skates and rays expanded pectoral fins. Some parasitic (e. g. , cookie-cutter sharks) on large fish and whales. First gill slit modified to form spiracle. Hyostyly enlarged hyomandibular cartilage attaches to side of cranium and posterior of palatoquadrate. Protrusion of upper jaw away from cranium. May be crepuscular or feed at depths where there"s little light lots of rods in retina and tapetum lucidum: allows animals to see in the dark, reflective crystals. Electroreception neuromast organs, ampullae of lorenzini concentrated on rostrum jelly-filled pores with canal to surface of skin and single layer of electroreceptor cells at base.
