ZOOL 403 Lecture Notes - Lecture 10: Fish Scale, Tiger Shark, Branchial Arch
9 May 2020
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Chondrichthyes : cartilaginous skeleton- prismatic calcified cartilage, pelvic claspers (penises, open gill slits (uncovered, placoid scales (next slides) Skeleton: prismatic calcified cartilage (web: cartilage that is mineralised, not as solid sheets, but as tiny prisms) tesserae (t) of a portion of a gill arch. Tesserae at the top are oriented in lateral view; those below show their exposed outer surfaces. Hyomandibula allows the downward movement of the jaws. Holocephali: single gill-opening, gill arches beneath braincase. E. g. - spotted ratfish, hydrolagus colliei: chimaeras live in deep ocean floors, with few at depths shallower than 200m, have elongated soft bodies with a bulky head, single gill-opening, lengthy tail in some species. In some species, the snout is modified into an elongated sensory organ. E. g. - some has long nose for olfactory senses- to detect preys in deep water and also approaching predators. Specialized sensory receptors in chimaeras: shortnose chimaera, longnose chimaera, plownose chimaera.
