Chronic toxicity of hexavalent chromium affects the morphology and behaviour of Ctenopharyngodon idellus (Cuvier and Valenciennes)

Chromium is one of the most common elements in the earth’s crust and is used in more than 50 different industries. The discharge from these industries pollute the waters and affects the biota. In the present study, the 96 h LC50 of Cr (VI) was determined for Ctenopharyngodon idellus and was 53.08 mg/L. chronic toxicity of Cr on the morphology and behaviour of fish was assessed on exposing the fish to sublethal concentrations for 45 days. Acetylcholinesterase activity was also examined. Cr toxicity altered the morphology of the fish with cryptic colouration, loss of scales and a thick coating of mucous on the body. Fish displayed mild hyperactivity, loss of balance, erratic swimming and lethargy; followed by a decrease in fin and opercular movements. The activity of acetylcholinesterase also witnessed modification, thus confirming the behavioural changes. It can be concluded that chromium is toxic to C. idellus even at sublethal levels and affects its normal survival in the polluted waters.