Thursday 1 March 2012

BRANCHIOSTOMA-FINS AND FOLDS

Branchiostoma bears three fins dorsal, caudal and ventral. The dorsal fins runs as a low, mid-dorsal fold along the entire length of trunk. It is contianuous behind with a much broader caudal fin around the tail. The ventral fin runs mid-ventrally from caudal fin upto atriopore. It is slightly wider than the dorsal fin. Fin rays are lacking in the caudal fin.The structure of fins and fin-ray boxes is different from that in fishes. Paired fins are absent.The are two hollow membranous metapleural folds.The two folds are connected by a horizontal fold of body wall, called epipleur, which forms the floor of the body.

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