TOXIC EFFECTS OF GLYPHOSATE ON THE BEHAVIOUR, HAEMATOLOGY, HISTOPATHOLOGY AND GROWTH OF THE AFRICAN CATFISH, Clarias gariepinus (Burchell, 1822) JUVENILES

Abstract

ABSTRACT Fish are particularly sensitive to a wide variety of agrochemicals including glyphosate herbicide that may arise from not only deliberate discharge of these chemicals into waterways but also from approved agricultural practices. The toxic effects of glyphosate on Clarias gariepinus juveniles of mean weight 10.05 ± 1.50 g and mean length of 10.75 ± 1.80 cm were investigated for a period of 12 weeks. The concentrations of the toxicant were prepared as 0.00 (control), 39.02, 78.04, 156.09, 312.19 and 624.39 mg/L with replicates each for the acute effects of glyphosate for mortality rate and behavioural responses for 96 period hours. Behavioural, haematological, histopatological, growth and physico-chemical analysis were carried out based on standard experimental procedures. Percentage treatments from LC50 were determined as follows: 00 (control), 23, 38, 53, 68 and 83 mg/L, respectively using the LC50 of the toxicant which was 151.36 mg/L. The physical and behavioural changes of the exposed fishes occurred as the concentration increased; restlessness, uncoordinated movement, air gasping, discolouration of the skin and eventual death. The haematological study indicated a significant reduction in White Blood Cells (WBC) and Packed cell Volume (PCV) counts with increased concentrations of the toxicant. In the liver, the enlargement of the hepatocytes was related to the concentration and duration of exposure resulting in large vacuoles in the hepatocytes with pyknotic nuclei. Focal necrosis was also observed in the hepatocytes. The skin showed few atrophying mucous cells, dense inflammatory cells, necrotic epidermis. The weight and length growth occur more in the lower concentrations. The physico-chemical parameters were dose and duration dependent. From this research it was evident that glyphosate had deleterious effects on the fish exposed. Therefore, their use near fish farm or in areas close to aquatic environment should be discouraged or minimized.