Energy Conservation Strategies in an Indian Air-Breathing Catfish, Heteropneustes Fossilis, in Conditions of Hypoxia

Low oxygen concentration is a common feature occurring in a wide range of aquatic systems and in varied ranges depending upon temporal frequency, seasonality and persistence of a place. There have always been naturally occurring low oxygen condition in freshwaters of tropical countries like India. Moreover, anthropogenic activities, related primarily to organic and nutrient enrichment, have led to increase in hypoxia and anoxia both in fresh and in marine system. The fishes in a tropical country like India are quite frequently exposed to this. Aquatic organisms which are frequently exposed to hypoxia show adaptations at all the three levels, namely behavioural, morphological and physiological. To assess the effect of hypoxia at physiological level, change in anaerobic and aerobic enzyme activities and protein profiling in selected tissues of air-breathing catfish, Heteropneustes fossilis , was undertaken. Fish were exposed to experimentally provoked hypoxia for different durations and were killed to study the effect of hypoxia on selected enzymes activities in heart, liver, brain and muscle. Significant changes were recorded. The observations indicated that different tissues respond differently to the stress of hypoxia and the enzyme activity responds in a tissue-specific manner.