Arulraj, J.S.; Pandurengan, P.; Arasan, S.; Gopalrajan, S., and Paulraj, J., 2019. Acute toxicity of Lamda-Cyhalothrin and the histopathological changes of gill and liver tissues of tilapia (Oreochromis niloticus). In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 235-238. Coconut Creek (Florida), ISSN 0749-0208.

Cyhalothrin is one of the synthetic pyrethroid pesticides commonly used to kill pests in agriculture fields. Fishes have a poor ability to metabolize and eliminate such xenobiotics. Hence, to investigate the acute toxicity of the pesticide, lambda-cyhalothrin on tilapia (Oreochromis niloticus), 96 hours lethal concentration 50 (96 h LC₅₀) was determined, and histological changes in gill and liver tissues were also examined. The fishes were exposed to different concentrations such as 0, 0.75, 1.5, 3, 6 and 12 ppb, and the mortality rate of fishes in each concentration was determined. The results showed that maximum mortality was observed in higher concentrations (6 and 12 ppb) whereas the minimum was found at 0.75 ppb level of cyhalothrin. The LC₅₀ value for the cyhalothrin pesticide on tilapia was found at 2.26 ppb. 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, the irregular shape of the nucleus, melanomacrophage aggregation, hepatolysis and vacuole formation were observed. This toxicity study revealed that cyhalothrin pesticide is highly toxic to tilapia even at a minimum concentration (2.26 ppb), and the responsible use of lambda-cyhalothrin in the agriculture field is recommended.