HISTOLOGICAL ALTERATIONS IN SOME ORGANS OF OREOCHROMIS NILOTICUS EXPOSED TO METALAXYL FUNGICIDE

ABSTRACT Fungicides enter aquatic ecosystems as a result of the intensive and poorly regulated usage causing harmful effects on fish population and behaviour of aquatic organisms. This study is aimed at evaluating the histopathological alterations in Oreochromis niloticus exposed to acute toxicity of Metalaxyl fungicide. Two hundred and fifty (250) healthy and active O. niloticus juveniles of both sexes were acelimatized for two weeks (14 days) prior to the commencement of the experiment. Fish were batch weighed (10 fish) and distributed into a set of 18 rectangular plastic tanks (75x45x45 cm) each filled with 30L of unchlorinated water. The range-finding tests (400, 500, 600, 700 and 800 ml) for Metalaxyl were carried-out to determine the definitive test (500, 600, 700, 800 and 900 ml). The behavioral pattern and mortality of the test in each tank was monitored. At the end of the experiment (96hr), sample was collected for histological analysis. The acute toxicity 96hr [p-[Lso was 7.41ml. Histological alterations observed in the Gills include Congestion of the secondary lamellae, Necrosis, Epithelial degeneration, Curling of secondary lamellae and Epithelial degeneration. Diffuse vacuolation, Granular degeneration and Diffuse atrophy of hepatocytes were observed in Livers. Vacuolation in dermis and more spaces in between epidermal tissues were observed in Skins. Histopathological changes observed in aforementioned organs of O. niloticus exposed to acute dose of Metalaxyl shows its detrimental effect on the cellular integrity of these organs. Hence, there should be strict and monitory control of the use of Metalaxyl to prevent harmful contact on feral and cultured fish.