A study of the sublethal effect of pesticide curacron 50 EC on estuarine catfish Mystus Gulio (Hamilton)

Abstract

Pesticides are stable compounds and they enter the aquatic ecosystem through the agricultural run off. The evaluation of nature and degree of harmful effects produced by toxic substances in the aquatic organisms are evaluated by toxicity tests. Fish were exposed to different concentrations of Curacron and data obtained was subjected to determine 96 hrs LC50. The fish in lethal media were found restless and disturbed. Erratic, imbalanced swimming activity, surfacing activity and increased opercular movements were observed, which could be related to the anoxic conditions. Fish in sublethal concentration were found under mild stress. The present study deals with some haematological alterations in blood of Mystus gulio in response to pesticide Curacron administration. The fish responded with significant decrease in the levels of hemoglobin. Data on the anomalies induced by pesticide exposure for the 30th day in the blood parameters of Mystus gulio reveal that erythrocyte count and Hb% decreases by more than 25 to 38% respectively causing anaemia. Number of RBC decreased while WBC increased in the treated fish. MCV, MCHC, MCH values were also altered in the treated fish. Protein content was more reduced due to the exposure in chronic stage. The biochemical contents in the present study show a gradual decrease in protein, glycogen and lipid content quantitatively with effect of different concentrations of the pesticide The present study investigated pesticide effects on gill morphology, liver, kidney and intestine of Mystus gulio exposed to sublethal Curacron concentration for 30th day. Gills of Mystus gulio exposed to different concentrations during 30th day presented a higher occurrence of histopathological lesions such as epithelial lifting, hyperplasia and lamellar aneurism. The liver tissues of pesticide treated fishes showed Sinusoids, which are irregularly distributed between the polygonal hepatocytes. There are often swollen with glycogen or neutral fat.