Abstract
Aquatic ecosystems in areas with intense mining activity are often subject to cyanide contamination; the present study was aimed to evaluate the harmful effects of sodium cyanide on histoarchitechtural aspect of spleen of freshwater fish Cyprinus carpio using an in vivo approach. The fishes were exposed to a sublethal concentration of 0.2 mg/L of sodium cyanide for duration of 10 and 20 days and were further allowed to undergo recovery for 14 days in a toxicant free medium. From the present investigation findings like occurrence of haemosiderin pigment, melanomacrophage centers, vacuolation and necrotic eosinophils were evident in all the fishes exposed to sodium cyanide. However, changes were more pronounced in fish subjected to 10 days of exposure, which was followed by 20 days of exposure and 14 days of recovery. The study revealed that there seemed to be the presence of homeostatic mechanism in fish that allows them to stabilize and overcome stress, which in present case is caused by sublethal concentration of sodium cyanide. Since the recovery phenomenon may be adaptive and even strategic, the present investigation also throws a light on adaptive behaviour of fish under stressful environments.

Key words: Histopathology, Melanomacrophage center, Recovery studies, Sodium cyanide, Spleen.