A study of the correlation between the feeding habits and the structure of the hind brain in the South Indian cyprinoid fishes

Abstract

That the hind brain of fishes shows a high degree of structural variation in different forms has long been known to zoologists. Owen (1866) has stated “The primary division of the brain which consists of the medulla oblongata with the cerebellum and other less constant appendages in fishes is called “epencephalon”; it is relatively larger, occupies a greater portion of the cranium, and is more complex and diversified in this than any of the higher classes of Vertebrata.” The important lobes of the medulla oblongata are the vagal and the facial lobes, which are the terminal centres for the nerve fibres of the vagal and the facial nerves respectively. The size of these lobes depends upon the extent to which their nerve fibres supply the taste buds. Herrick (1928) has pointed out that the taste buds in the pharynx are supplied by the IX and X nerves and those on the snout and the outer surface of the skin are supplied by the VII nerve. The fact that the variation in the structure of the medulla oblongata depends on the distribution of the taste buds had led Evans (1931-32) to a very instructive work on the comparative study of the brains in the British Cyprinoids in relation to their feeding habits. It is endeavoured to point out in this paper certain structural variations in the hind brain of some of the South Indian Cyprinoids in relation to their feeding habits (Cyprinidæ includes Cobitidæ also). Material The fishes have been collected from all the big tanks in the Mysore State, especially from the Marikanive tank (water area 34 square miles) and Sulekere (40 miles in circumference).