Effects of ultraviolet photooxidation of cypermethrin on the activities of phosphatases and digestive enzymes, and intestinal histopathology in African catfish, Clarias gariepinus (Burchell, 1822).

The possibility of ultraviolet (UV) photooxidation of cypermethrin generating more toxic intermediates or isomers demands that studies that look at the effects of cypermethrin and UV irradiation under a coexposure scenario be carried out. In this study, juvenile African catfish (Clarias gariepinus) were exposed to 50 µg/L cypermethrin, 100 µg/L cypermethrin, UV, 50 µg/L cypermethrin + UV or 100 µg/L cypermethrin + UV, in a static renewal for 3 weeks. The control fish were maintained in uncontaminated water, and not exposed to UV radiation. After the exposure duration, the fish were killed, and the activities of acid phosphatase, alkaline phosphatase, amylase, protease, and lipase were determined in the liver or intestinal homogenates. Also, the histopathology of some sections of the intestine was performed. The results showed that the activities of the enzymes decreased significantly following exposure to cypermethrin while there was no change in the activities of the enzymes due to UV irradiation alone. The histopathological analyses indicated that exposure to cypermethrin caused alterations in the histoarchitecture of the fish such as severe erosion of the mucosa layer, faded lamina propria, and disintegration of the muscle layer. The exposure of fish to both cypermethrin and UV irradiation caused significant decrease in the activities of the enzymes. This could be an indication that UV irradiation has the tendency to potentiate cypermethrin‐induced toxicity in fish. Research Highlights: The exposure of C. gariepinus to cypermethrin caused significant decrease in the activities of important metabolic enzymes, and altered the histoarchitecture of the intestine. UV exposure potentiated cypermethrin‐induced toxic effects in the fish. [ABSTRACT FROM AUTHOR]