Exposure to heavy metals causes histopathological changes and alters antioxidant enzymes in fresh water fish (Oreochromis niloticus)

Expansion in technology, development in industries and extensive applications of synthetic chemical have become major regulatory issues toward the public health, wildlife and aquatic ecosystems. Therefore, the monitoring and investigation of environmental contaminants in order to mitigate the adverse impacts is crucial to safe the public health and aquatic wildlife. The present study describes the deleterious effects of heavy metals at low levels in fresh water fish. A total of 120 fish of same age and body mass were arbitrarily distributed and allocated into eight groups (A-H). Group A was run parallel to other groups and maintained as control group. Collected data was analyzed by using Tukey’s Test. Results indicated various clinical ailments including erratic swimming and jerking movement. Microscopic observation of gills, liver and brain tissues showed different histopathological changes in fish exposed to various heavy metals. The antioxidant enzymes activities were increased or decreased in a concentration and enzyme dependent manner. Exposure of treatments showed significant increase in peroxidase and glutathione-s-transferase but decreased catalase and superoxide dismutase activity at higher exposure to heavy metals. Regarding overall toxicity, nickel was least sensitive towards the fish, but tertiary metal mixture was more toxic to fish (Oreochromis niloticus) followed by binary mixture. In conclusion, results of our study suggested that the exposure to different heavy metals even at low concentrations poses serious concern towards their potential danger to the survival and growth of fish and induces deleterious effects in gills, brain and liver tissues.