ZOO 2090 Lecture Notes - Lecture 7: Rete Mirabile, Neutral Buoyancy, Swim Bladder
3 Dec 2013
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Document Summary
Evolution of swimming and evolution of lungs in primitive fishes: to maintain an air-filled space inside the body cavity of the fish, vary the volume of gas to maintain neutral buoyancy. Primitive fishes faced a fundemental swimming problem. Their tissues were heavier than water, ~1. 3x, and their bodies were covered with heavy armor. Result:fish heavier than water negatively buoyant (drop) Response: physostome swim bladders are -500"-%". to the stomach by a duct called the pneumatic duct. Inflation: requires swallowing air at the surface and forcing it back through. Generate lift with heterocercal fin (0. 34pdf) duct into bladder. Look at some fishes, fins and body shapes. Disadvantage: fish are neutrally buoyant at one depth only, positively buoyant at surface and then decline until depth reached. Result: can"t go very deep: generate forward motion with caudal finmove forward but sink as well, 0. 28pdf ostracoderms, 0. 29pdf placoderms, 0. 30pdf mid. devonian, 0. 32pdf diversity of modern fishes, 0. 33r. pdf diversity of bony fish.
