ACUTE TOXICITY OF LAMDA-CYHALOTHRIN AND THE HISTOLOGICAL CHANGES OF GILL AND LIVER TISSUES OF TILAPIA Oreochromis niloticus

Cyhalothrin is one of the synthetic pyrethroid pesticide which is commonly used to kill pests like aphids, Colorado beetles, thrips, Coleoptera larvae and adults in agricultural crops such as cereals, cotton, potatoes, vegetables etc. Since fishes have poor ability to metabolize and eliminate such xenobiotics as compared to those of higher vertebrates, these pesticides become relatively more toxic to fish species as compared to that of mammals and birds.

To investigate the acute toxicity of pesticide, lambda cyhalothrin on Tilapia (Oreochromis Niloticus), 96 hours Lethal Concentration 50 (96 hrs LC₅₀) was determined and histological changes in gill and liver tissues was also examined. For the acute toxicity experiment, the fishes were exposed to different concentrations 0, 0.75, 1.5, 3, 6 and 12 ppb and the mortality rate of fishes in each concentration was recorded and fed in the probit software.

The results showed that maximum mortality was observed in higher concentrations (6 and 12 ppb) and minimum mortality was found at 0.75 ppb. The LC₅₀ value for the cyhalothrin pesticide on tilapia was found at 2.26ppb. The histological changes such as gill lesions, necrosis, curling of secondary gill lamellae, hyperplasia and clubbed tips of secondary gill lamellae were observed in gill tissues. In the liver tissues, changes such as irregular shape of nucleus, melano macrophage aggregation, hepatolysis and vaccuole formation were observed. This toxicity study concludes that cyhalothrin pesticide is highly toxic to tilapia even at low concentration of 2.26 ppb. Thus the usage of the pesticide should be restricted to have a healthy ecology and minimal use is recommended.