Chrondrichthyes Flashcards
What belongs to this group of Cartilaginous Fish?
Elasomobranchs and Holocephali.
What organism belongs to the Holocephail?
Chimaeras / ratfish.
Give an overview of the Ratfish?
Evolved from common ancestor of elasmobranchs, single gill opening, deep marine fish, whip like tail, cartilaginous skeleton, bottom feeders, large flat plates for feeding.
What are the three different lineages of sharks/rays?
Squaloid, Galeoid and Batoidea (skates and rays)
What defines the Squaloid sharks?
No anal fin e.g. Dogfish.
What defines the Galeoid shark?
Have an anal fin e.g. Great white, hammerhead, whale shark
What features are common of the Elasmobranch body plan?
Fusiform body or torso-ventrally depressed, Heteroceral (symmetrical) caudal fin (tail), lateral line, ventral mouth.
How are Elasmobranchs negatively buoyant?
No swim bladder, must keep swimming to stop sinking and must keep mouth open whilst swimming to create a flow of oxygenated water over the gills, oily livers can aid buoyancy.
What movement do each of the Elasmobranch fins control?
Paired fins (pelvic and pectoral) control pitch (up/down), Caudal fin control yaw (thirst forward, gives lift) and Dorsal/anal fins control roll.
What is unique about the external surfaces of sharks?
Their skin is covered by placoid scales (with an outer surface of vitro dentine) which make them highly streamlined.
What senses allow predatory sharks to detect prey?
Chemoreception; sensitive olfactory system, special adaption for vision in poor light, mechanoreception and electroreception (detection of electrical charges coming off prey).
What features do sharks and ray have for electroreception?
Ampullea of Lorenzini are modified hair cells of the lateral line.
Why are Hammerhead shark’s head shaped so?
To spread the distance between electro receptors.
What experiments prove that sharks use electroreception?
Electrical insulation over prey = no attack, chopped bait = no electrical cues and displaced olfactory cue, live electrodes = accurate attacks.
What is unique about shark teeth?
Single tooth is backed by replacement tooth, continue to replace teeth throughout life.
