Abstract
THE mode of swimming of the sunfish (Mola), which I have had many opportunities of observing at close quarters, is unusual, perhaps unique, but easy to comprehend as compared with that of other fishes. The long dorsal and ventral fins are stiffened on their anterior and flexible on their posterior edges, like the wings of insects. The action of great masses of muscle at their bases causes them to strike the water laterally, first to the right and then to the left, the two fins striking simultaneously towards the same side like wings, but in a horizontal instead of a vertical direction (Fig. 1, B). Owing to the differences of flexibility over the surfaces of the fins, their planes are twisted in the act of striking so as to give a forward thrust (Fig. 1, C). Of course, since they strike sideways, there is also a lateral thrust, but this is correlated with the flattened shape of the body, which, acting like the keel of a sailing boat, resists lateral displacement.
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DAMANT, G. Locomotion of the Sunfish. Nature 116, 543 (1925). https://doi.org/10.1038/116543b0
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DOI: https://doi.org/10.1038/116543b0
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