ABSTRACT

Clarias gariepinus fry were exposed to sub lethal concentrations of atrazine in a semi-static renewal bioassay. The fry were exposed to environmentally relevant concentrations of atrazine (0.03, 0.3, 3.0, and 30.0µg/L). The control tank was dechlorinated water without atrazine. The effects of atrazine were measured using behavioural, histopathological and mortality as toxicity indices. Results of the toxicity test showed that atrazine was toxic to the species in a dose-dependent manner. Histopathological indices observed include disintegration of the nervous tissues, degeneration of the myocyte loss of gill cytoarchitecture, degeneration of dorsal cement gland and degeneration of the eye. Abnormal behavioural traits including erratic and fast swimming, discolouration, lethargy and hanging on to surface water were observed. Mortality of exposed fry during the bioassay was concentration and time-dependent across all the treatments with the highest mortality recorded in 30µg/L.The study revealed that atrazine was moderately toxic to C. gariepinusfry and affected the behaviour, histoarchitecture of vital organs as well as mortality of the fish. Hence, the use of atrazine should be with caution especially near water bodies.