author(s)
Manju V Raj, Sherin K and Sherly PS

abstract
Fish use olfaction, the capability of sensing smell for various physiological as well as psychological activities. The fore brain region of fish possess olfactory system that consists of olfactory tracts with olfactory bulbs or olfactory lobes. Olfaction, gustation, and vision are the three important senses used by fishes for feeding. Present study analyse histology of olfactory system of two fishes Carassius auratus and Botia striata, of the order Cypriniformes and finds its association with feeding behaviour. The histological combined with morphological, and statistical studies of olfactory systems of these two fishes shows variations depending on the nature of its feeding behaviour. Carassius auratus possess long olfactory tract with oval olfactory bulbs, while B. striata possess short olfactory tracts with lobes. In Carassius, the olfactory bulb possess glomerular, banded mitral and conspicuous granular cell layers whereas in B striata no such banded mitral cell layers are seen. This indicates the surface dwelling fish Carassius uses olfaction while Botia use olfaction as well as gustation for feeding purpose indicating the surface and bottom feeding nature of these two fishes. Statistical studies of this fishes shows significant differences between brain volume and olfactory lobe volume.