ABSTRACT.The Present research studies the acute sub lethal toxicity of potassium cyanide (KCN) in the fresh water, Clarias gariepinus and the effects on its behaviour and the Na + -K + ATPase enzyme activity. Acute toxicity of potassium cyanide (free cyanide) to the freshwater fish was studied using static bioassay method over a period of 96 h. Different concentrations of the toxicant (KCN) were used and LC 50 value was found to be 361µg/L. Behavioural changes when exposed to lethal concentration of KCN showed increased feed intake, cannibalism, irregular swimming activity, rapid jerk movement, aggressiveness, loss of balance, opercula movement, surface behaviour, loss of equilibrium, change in body colour and convulsion. The effect of potassium on the Na + -K + ATPase of various physiological tissues which includes the gill, liver, muscles and intestinal over duration 0f 12 h-35 days were also studied. Cyanide intoxication resulted in marked changes in ATPase, shown by significant decrease in the enzyme activities. The result shows that ATPase enzyme together could be employed as a sensitive and useful biomarkers for cyanide pollution while the behavioural changes could be an early signal of toxicity.

The Present research studies the acute sub lethal toxicity of potassium cyanide (KCN) in the fresh water, Clarias gariepinus and the effects on its behaviour and the Na+ - K+ ATPase enzyme activity. Acute toxicity of potassium cyanide (free cyanide) to the freshwater fish was studied using static bioassay method over a period of 96 h. Different concentrations of the toxicant (KCN) were used and LC50 value was found to be 361μg/L. Behavioural changes when exposed to lethal concentration of KCN showed increased feed intake, cannibalism, irregular swimming activity, rapid jerk movement, aggressiveness, loss of balance, opercula movement, surface behaviour, loss of equilibrium, change in body colour and convulsion. The effect of potassium on the Na+ - K+ ATPase of various physiological tissues which includes the gill, liver, muscles and intestinal over duration 0f 12 h-35 days were also studied. Cyanide intoxication resulted in marked changes in ATPase, shown by significant decrease in the enzyme activities. The result shows that ATPase enzyme together could be employed as a sensitive and useful biomarkers for cyanide pollution while the behavioural changes could be an early signal of toxicity.