Biochemical and haematological changes following malathion treatment in the freshwater catfish Heteropneustes fossilis (Bloch)

Abstract

Male specimens of H. fossilis were exposed to a concentration of 8 mg litre⁻¹ of malathion in their aquarium water for 16 days during the early post-spawning phase. Its effects on glycogen of liver, testes and muscle, glucose and free fatty acids (FFA) in plasma, spleeno-somatic index (SSI), red blood corpuscle (RBC) and haemoglobin (Hb) were examined. Reduced levels of liver and muscle glycogen, associated with increasing plasma glucose, were noticed after 4 and 8 days of treatment but, after 16 days, a recovery was observed. Testicular glycogen did not respond to malathion exposure. Plasma FFA was also unchanged for 4 and 8 days of treatment but a higher level was recorded after 16 days' exposure. RBC and Hb were reduced following the 4-day exposure; however, no apparent change in their level was observed after 8 and 16 days' exposure. The SSI was also reduced during the 4- and 8-day treatments but 16 days' exposure caused the level to return to normal. Thus, this study demonstrates that, after prolonged exposure, H. fossilis develops a tolerance and partially recovers from the stress condition. In the initial stages carbohydrate was used as an energy source to meet the stress situation, while, in the later phase of exposure, FFA served as the major source of energy.