Toxicity Of Atrazine (herbicide) To Juveniles Of The African Catfish Clarias Gariepinus (brchell 1822)

In the present study, juveniles of Clarias gariepinus were exposed to the herbicideatrazine in order to determine the herbicide‟s toxicity to the species at both acute andsub-lethal exposures.Fish were exposed to acute concentrations of 9, 10, 11, 12 and13mg/L of atrazine, as well as sub-lethal doses of 0.59, 1.19 and 2.38mg/L of atrazine.Both experiments had a control that served as a reference point. Effects of the herbicidewere measured using behavioural, haematological, biochemical, histopathological aswell as growth indices (as suggested by previous authors). Results of the acute toxicitytest showed that atrazine was toxic to the species in a dose-dependent manner. The LC50value of atrazine established for the species was 11.89mg/L. Most importantly, atrazineinduced hyperactivity at acute levels of exposure. Significant (p<0.05) haematologicalchanges observed at both acute and sub-lethal exposures included anaemia,leukocytosis, proteinaemia, haemoglobinaemia, neutrophilia as well as lymphocytosis.Acute and sub-lethal concentrations of atrazine also induced an increase in thegeneration of reactive oxygen species. Histopathological changes observed in the gillsincluded attenuation and clubbing at the tips of the primary lamellae, gradualdegeneration of the primary lamellae, total dislocation of the primary lamellae from itsposition as well as mild congestion in the cartilage. Changes in the liver of exposed fishincluded perivascular cuffing around the central vein, mild congestion of the sinusoids, pyknosis of the nuclei, mild necrotic damage, congestion of the central vein as well asmild coagulative necrosis. Atrazine also had effect on the growth parameters (weightgain, percentage live weight gain and specific growth rate) as well as nutrient utilizationparameters (feed conversion efficicency, feeed conversion ratio, gross feed conversionefficiency and nitrogen metabolism) although some of these effects were notstatistically significant (p>0.05). The study revealed that atrazine was moderately toxic to C. gariepinus juveniles and affected the behaviour, haematology, biochemistry,histology as well as growth of the fish. Hence, use of the herbicide should be withcaution especially near water bodies.

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