Sublethal effects of the herbicide thiobencarb on fecundity, histopathological and biochemical changes in the African catfish (Clarias gariepinus)

Abstract

Fish have been widely documented as useful bioindicator model for ecotoxicological studies because of their differential sensitivity to pollution. Thus, the present study was carried out to determine the sublethal effects of commercial herbicide thiobencarb (Saturn®, 50 EC) on the African catfish (Clarias gariepinus). Fish females were exposed to sublethal concentration of thiobencarb (½ LC50, 0.72 ppm) for 3, 9 and 15 days. Severe abnormality in swimming behavior was observed in fish groups exposed for 9 and 15 days. Biometric parameters, e.g. condition factor, gonadosomatic index and hepatosomatic index were analyzed. An adverse effects on the ovary and liver weights were observed. A significant decrease in absolute fecundity was remarked after exposure to thiobencarb at all three periods. Thiobencarb significantly decreased the activities of serum aspartate aminotransferase and alanine aminotransferase as well as protein and glucose levels. Histopathological changes in the liver architecture of fish exposed to thiobencarb were characterized by necrosis, changes in nuclear shape, formation of vacuoles and atrophy of hepatocytes. The ovary of fish exposed to thiobencarb showed atretic vitellogenic oocytes with increased size follicular cells, liquefaction of yolk globules as well as inflammatory cells infiltration. These results indicate that thiobencarb is toxic and has the potential to impair on the physiological activities in African catfish. The use of thiobencarb should be strongly controlled and carefully monitored to avoid the possible damage done to the environment.