Cytochemical features of olfactory receptor cells in benthic and pelagic Sculpins (Cottoidei) from Lake Baikal

Abstract

Electron and laser confocal microscopy were used to analyze the adaptive cytochemical features of the olfactory epithelium in three genetically close deep-water Cottoidei species endemic to Lake Baikal ? golomyanka (Baikal oilfish) Comephorus baicalensis, longfin Baikal sculpin Cottocomephorus inermis and fat sculpin Batrachocottus nikolskii ? whose foraging strategies are realized under different hydrostatic pressure regimes. Hypobaric hypoxia that developed in B. nikolskii (a deep-water benthic species) upon delivery to the surface caused distinct destructive changes in cells of the olfactory epithelium. In C. baicalensis and C. inermis, whose foraging behavior involves daily vertical migrations between deep and shallow layers, these cells are characterized by a significantly higher structural and functional stability than in deep-water B. nikolskii. The results of morphological study and quantitative analysis of functionally active mitochondria in cells of the olfactory epithelium of closely related deep-water fish species with different modes of life provide evidence that tolerance of the olfactory apparatus to hypobaric hypoxia is different in pelagic and benthic species. These results help elucidate the mechanisms responsible for the consistent functioning of the olfactory system in animals evolutionarily adapted to extreme environmental factors, and provide theoretical and practical implications in different fields of biology, neurology and extreme medicine.