The Lift Produced by the Heterocercal Tails of Selachii
نویسنده
چکیده
Selachians have no swimbladders, and are denser than the water in which they live. When swimming horizontally, they must therefore exert a force against gravity. It is generally accepted that in the case of the sharks and dogfish upward forces are generated by the passage of the pectoral fins through the water at a positive angle of attack, and by the action of the heterocercal tail. Harris (1936, 1938) demonstrated the lift produced by the pectoral fins in wind-tunnel experiments with a cast of Muslelus. The lift produced by the heterocercal tail has been demonstrated qualitatively in experiments with models by Grove & Newell (1936) and by Affleck (1950). This paper reports experiments in which actual tails, not models, were used. The lift produced by them at various speeds of transverse movement was determined. The results are used in a quantitative discussion of the equilibrium of sharks swimming horizontally.
منابع مشابه
Teleost fishes typically possess a homocercal caudal fin with a symmetrical morphology in which the dorsal and ventral lobes
a symmetrical morphology in which the dorsal and ventral lobes of the tail fin are the same size and project posteriorly beyond the axis of the vertebral column. In contrast, most elasmobranch fishes and some primitive actinopterygian fishes possess a heterocercal caudal fin with an asymmetrical morphology in which the ventral lobe of the fin is smaller than the dorsal lobe and the vertebral co...
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