Effects of Cypermethrin on Opercular movements, Oxygen Consumption and Histopathology of Gills in Oreochromis niloticus (Linnaeus 1758).

Cypermethrin, a synthetic pyrethroid, has been found to contaminate water bodies adjacent to agricultural lands and is reported to be moderately toxic to the organisms living therein. This study examined the effects of cypermethrin on respiratory biomarkers in Oreochromis niloticus at four sub-lethal concentrations, including a control (0.0, 0.3, 0.6, and 1.0 µg/L) over 96 h. The actual concentrations were analytically confirmed through GC-ECD, with an average recovery rate of 93±0.21%. Cypermethrin-exposed O. niloticus showed higher mean opercular movement rates and oxygen consumption than the control group. It was observed that when the concentration of cypermethrin in the aquatic medium increased, so did the impacts on respiratory rates and oxygen uptake. Both opercular movements and oxygen consumption of O. niloticus showed a strong positive correlation with cypermethrin concentration at all exposure periods. Histological examination of the gills revealed that there were effects of 96 h cypermethrin exposure on gill epithelia. In conclusion, cypermethrin can cause respiratory abnormalities in fish at environmentally relevant concentrations.