Acute Toxicity of Cypermethrin on Nile tilapia Fry

The present study aimed to evaluate the acute toxicity effect of cypermethrin contaminated aquatic ecosystems by using a 30 days post-hatching fry of Nile tilapia as a test model. The control and six test experiments, each comprising 10 animals, were repeated three times and evaluated with the static test method. The lethal concentrations at 50 % (LC50) and 70 % (LC70) for 96 h were determined using the probit analysis. Behavioural and histological changes were observed in fish exposed with cypermethrin at both 96 h LC50 and 96 h LC70. The values of 96 h LC50 and 96 h LC70 were estimated at 32.496 and 40.311 ppb, respectively. The affected fish exhibited the loss of equilibrium with erratic and darting swimming movements, hyperactivity, secretion of mucous and increasing rate of opercula activity. Severity of histopathological lesions were related to concentration levels and exposure times. The histological changes of gill tissues included the swelling of epithelial cells and the fusion of secondary lamella. An enlargement of sinusoids, pyknotic nuclei, vacuole formation and degeneration in hepatic parenchyma were observed in liver. The degeneration of glomerulus combining with oedema of renal tubule was also noticed in kidney. No alter lesion was seen on skin tissue. The results in the present study suggest that low levels of cypermethrin in the aquatic environment may alter adverse effect on growth and development in Nile tilapia.