ABSTRACT
The olfactory epithelium of two closely related species of snowtrout— Schizothoraichthys progastus McClelland and Schizothorax richardsonii Gray (Subfamily: Schizothoracinae. family-Cyprinidae, Teleostei), from a perennial glacier-fed river Mandakini of Garhwal hills was studied by employing transmission electron microscopic method The olfactory lamella comprises two epithelia—anterior and posterior, with a stroma sandwiched in between. Both are strartified. The anterior one is thicker than posterior. In Schizothoraichithys progastus, the sensory part of epithelium has two types of receptor cells—ciliated receptor cells and rod cells whilst in Schizothorax richardsonii, there arc three types of receptor cells—ciliated receptor cells, microvillous receptor cells and rod cells in addition to sustentacular cells, basal cells and mucous cells. While inhabiting similar hillstream habitat, the differential ecological niches, feeding habits etc., account for the presence of different receptor cell types in these species, It implies the possible diversification at cellular and physiological levels so as to minimize the competition by using varied olfactory cues.