摘要：Cypermethrin a potent insecticidal pyrethroid and a major pollutant present in agricultural and domestic wash out waterthat enter aquatic food chain and have toxic effect on aquatic organisms. Fish are considered as a tool to assess theenvironmental quality by studying the effect of pollutants on its physiological function and most importantly itssurvival. In the present study the fish tilapia Oreochromis mossambicus was taken as an experimental animal to studythe toxic effect of cypermethrin at different concentrations and time of exposure up to 192 hours. The lethalconcentration LC50 was calculated by arithmetic logic method and found to be 0.04 ppm at 96 hours. The histologicalalterations on the gills were observed and recorded at different time intervals up to 192 hours. The gills showedsignificant alterations in structure and histology at the sublethal concentrations and thereby reduction in the oxygendiffusion capacity leading to distress in breathing in the fish. The findings were significant as the toxic effect ofcypermethrin was found to increase with time of exposure suggesting its deleterious effect on aquatic organisms notonly directly but also by bio accumulations.
