Toxicity of glyphosate herbicide on Nile tilapia (Oreochromis niloticus) juvenile

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. In
the present study, the toxicity of glyphosate an herbicide was investigated with emphasis on histopathological
effects. Nile tilapias (Oreochromis niloticus) juvenile 15 ± 1.0 g were exposed to 0, 2, 9, 30, 97, 310 mg/l of
glyphosate. The lethal concentration (LC50) value of glyphosate was 1.05 mg/l for 96 h of exposure. Glyphosate
concentration corresponding to the 96 h LC50 values for juvenile tilapia was used to study the effects of glyphosate
exposure for 4 days in inducing histopathological changes of gills, livers, kidneys and brains. In the gills, filament
cell proliferation, lamellar fusion, lamellar cell hyperplasia, and epithelial lifting were observed. In the liver, there
was vacuolation of hepatocytes and necrosis. Kidney lesion consisted of hyaline droplets in the tubular epithelial
cells and pkynosis. The brain lesion also consisted of generalized neuronal degeneration and spongiosis. The
changes in these tissues occur predominantly in the 96 h exposure. Respiratory stress, erratic swimming and
instant death of fish were observed in exposed fish, which varied with the concentration of the toxicant and this
showed that mortality increased with increase in concentration. Glyphosate is highly toxic to Nile tilapias, which are
more susceptible to this herbicide; therefore their use near fish farm or in area close to aquatic environment should
be discouraged.