Toxicity study and the effect of organophosphate pesticide on the gill of <i>Oreochromis niloticus</i> (Linnaeus, 1758)

Abstract

The exposure of Oreochromis niloticus to perfekthion pesticide revealed the potential destructive impact of the toxicant on living systems using the gill as a parameter. Perfekthion which has dimethoate 400 g/L as the active agent is used in agricultural practices to eradicate pests and parasites to reduce pre and post-harvest losses. Bioassay treatment using perfekthion as the toxicant was administered to test fishes which were randomly selected. Ten (10) fishes were selected and placed all together in each of the treated chambers of 10 L capacity with the following concentrations; 2.8 mg/L, 5.6 mg/L, 11.2 mg/L , 22.4 mg/L , 44.8 mg/L and 0 mg/L which served as the control for the toxicity test. Histological analysis at the end of the 96-h acute test, showed huge damages inflicted on the test organisms. The impact increased as the concentration increased with the highest degree of gill lamellae degeneration in the 22.4 mg/L and 44.8 mg/L concentrations treatment chambers. Erosion of gill filaments were also seen at both concentrations. Lesions of gill tissues were also visible in the treatment medium with 11.2 mg/L concentration. Complete erosion of gill tissues was observed in the treatment with highest concentration of 44.8 mg/L of perfekthion. The gills of test fish exposed at treatments 2.8mg/l and 5.6 mg/L had no observable impact when compared with the control. From the overall inference, the study strongly recommends careful application of pesticides.Key words: Toxicity test, Organophosphate pesticides, Oreochromis niloticus, Bioassay, Gill histology, Dimethoate