Barilius bendelisis, one of the principal hill stream fish routinely experiences up to 5-6 °C of diurnal and 18-20°C of annual habitat temperature variations. The role of molecular chaperones like HSPs in enabling adjustment to these two temporally distinct patterns of thermal stress is still less explored. 2-D Gel Electrophoretic brain profile of different laboratory acclimatized populations according to seasonal and daily temperature variations, showed induction of different classes of Heat

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... ock proteins with different endogenous levels and variation in onset temperatures as well. Low molecular weight HSPs appear to play an important role in fluctuating temperatures while the larger weight chaperones (HSP70, 90) in chronic high temperatures. Further, individuals acclimatized to Summer-like temperature exhibited higher endogenous levels of HSPs as compared to winter-acclimatized individuals. The HSP induction temperature in winter-acclimatized fishes was around 20°C whereas the first appearance of HSPs in summer caught as well as 'winter caught-summer acclimatized' individuals was 30-32°C; an overall shift of 10-12°C that could well occur on a seasonal basis. These findings provide first molecular insight into survival strategy of a major hill stream teleost, Barilius bendelisis and suggest that variation in constitutive expression of HSPs plays significant role in imparting tolerance against thermal stress.