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Lecture 7

Lecture 7

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University of Guelph
ZOO 2090
Roy Danzmann

Lecure72010doc 2 Lungs to swim bladders pg 0.35.04 Oct 2010 Purpose of swim bladder 1. To maintain an air-filled space inside the body cavity of the fish Evolution of Swimming and evolution of lungs in primitive fishes 2. 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 Two types of swim bladders:pg 0.35.1 negatively buoyant (drop) 1. P Responseswim bladders are -500'-%'. to the stomach by a duct called the pneumatic do Generate forward motion with caudal finmove forward but sink as well Inflation: requires swallowing air at the surface and forcing it back through duct into bladder.ate lift with heterocercal fin (0.34pdf) Deflation: requires belching.t with pectoral fins isaLook at some fishes, fins and body shapesne depth only, positively buoyant at surface and then decline until depth reached. Result: can’t go very deeprms o 0.29pdf placoderms o 0.30pdf mid.Devonian o 0.32pdf Diversity of modern fishes o 0.33r.pdf diversity of bony fish homocercal caudal finhave achieved neutral buoyancy Inflation: by secretion into the bladder from blood stream via the gas gland Deflation: by reabsorption via the Ovale or oval window LUNGDisadvantage: can’t rise fast as physostomes as the bladder would burst. How was this done? How doesyhdeoclstsmientlofdeswork?bladder (organ for buoyancy regulation) derived from lungs The gas gland excretes lactic acid and produces carbon dioxide. The resulting acidity causes the hemoglobin of the blood to lose its oxygen (Root effect), which mya) then diffuses partly into the gas bladder. The blood flowing back to the body firstw in oxygen enters a rete mirabile where virtually all the carbon dioxide and oxygen produced insure for the development of lungs the gas gland diffuses back to the arteries supplying the gas gland. Design : counter- current multiplier.arose early as a method of improving gas exchange in water, rather than moving Elsewhere, into landlar structure known as the oval window (ovale), the bladder is in contact with blood and the oxygen can diffuse back. Together with oxygen other gasses are salted out in the gas bladder that accounts for the high pressures of other gasses as well. Advantages of ne
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