Publication Date:
2017-07-06
Description:
Fossil coelacanths, and their only living representative Latimeria chalumnae, possess a small, supplementary epicaudal fin of unknown function at the tip of the large tail. Movements of this fin were analyzed on film sequences taken with submersibles in the fish's natural habitat off Grande Comore, Indian Ocean. Epicaudal fin beats were not coordinated with strokes of paired and unpaired lobed fins, and the epicaudal fin did not move continuously. When in action, successive fin beats were performed more-or-less rhythmically but varied considerably in duration. Epicaudal fin beats occurred mainly in three different situations: during curve swimming, with slow forward motion of the body; during narrow turns on a point without significant forward motion of the body; and during station holding without forward, backward, or sideward motion of the body. In the latter case, the fin regularly stood still at maximum deflexion for several seconds. In turns and curves, epicaudal fin beats appeared to have a locomotory function, whereas during hovering, with standstills of the fin at maximum deflexion, beats presumably have a sensory function. The lateral-line canal extends to the very tip of the epicaudal lobe. If the lobe is held laterally at an angle to a local current parallel to the main body axis or to a current resulting from backward motions, water displacement in front of the lobe could be detected by the lateral line on the lobe.
Type:
Article
,
PeerReviewed
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