BIOL 3114 Lecture Notes - Lecture 4: Rete Mirabile, Swim Bladder, Neutral Buoyancy
20 Oct 2016
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Document Summary
Characteristics of aquatic environments- box 4-1 in textbook. >800 times as dense as air: provides support. 18 times as viscous as air: need streamlined shape. Low o2 content: 10-50 ml o2/l compared to 209 ml/l in air. High heat capacity and conductivity: temperatures more stable than in air, ++/-- (advantages and disadvantages) Higher electrical conductivity: detection, communication, weaponry. Gills: unidirectional water flow across gills, most osteichthyes (bony fishes), some chondrichthyes (sharks) Buccal pumping- contraction of buccal and opercular muscles. Also called branchial muscles: most chondrichthyes and some open ocean osteichthyes (e. g. , mackerel, tuna) Ram ventilation- swim with mouth open to force water across gills. Secondary lamellae: thin, delicate ridges of epithelial tissue. Countercurrent exchange: direction of blood flow in capillaries of secondary lamellae is opposite to direction of h2o flow across the gill. Lungs and accessory respiratory structures: gulping air into buccal cavity, vascularized lips, labyrinth chambers in head (gouramis, bettas, vascularized intestines, lungs- outpocketing of anterior surface of gut.
