Histopathological Effects Of Cypermethrin On Juvenile Nile Tilapia (Oreochromis Niloticus)

Abstract

Agrochemicals affect fish by interfering with their reproduction, behaviours and reducing their growth with evidence of tissue damage, which may lead to their mortality. Fish are particularly sensitive to a wide variety of agrochemicals and their environment may become toxic due to deliberate discharge of chemicals into waterways and even from approved agricultural practices. The acute toxicity of cypermethrin (an insecticide) was investigated with emphasis on its histopathological effects. Oreochromis Niloticus (Nile Tilapia) juvenile were exposed to 0, 0.02, 0.9, 3, 9 and 31mg/l of cypermethrin. The lethal concentration (LC50) value of cypermethrin was 0.019mg/l for 96h of exposure. Cypermethrin concentration corresponding to the 96-h LC50 values for juvenile tilapia was
used to study the effects of cypermethrin exposure with emphasis on histopathological changes of gills, livers, kidney 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 varies with the concentration of the toxicant and this indicate that mortality increased with increase in concentration. Cypermethrin is highly toxic
to juvenile fish.

Keywords: Oreochromis Niloticus, cypermethrin, acute toxicity test, histopathology.

African Journal of Livestock Extension Vol. 5 2007: pp. 1-13