Biometric variations and oxidative stress responses in juvenile Clarias gariepinus exposed to Termex®

Abstract

The current study investigated the effects of termite insecticide, Termex^® (imidacloprid 35.50% SC), on biometric variations and oxidative stress biomarkers in Clarias gariepinus. Fish were exposed to 4.00 and 6.00 μg l^–1 sublethal Termex^® concentrations in 2017. The gill and liver tissues were sampled on days 7, 14, 21 and 28 and the results indicated that hepatosomatic index (HSI) decreased significantly when compared with the control on days 14, 21 and 28. The condition factor (CF) and viscera-somatic index (VSI) also decreased during the study period. The decrease was greater at 6.00 μg l^–1 Termex^® concentration on days 21 and 28 for CF and days 14 to 28 for VSI, respectively. The lipid peroxidation (LPO) in both tissues was highest in the 6.00 μg l⁻¹ Termex^® and increased with the duration. There was significant decrease (p < 0.05) in superoxide dismutase and glutathione peroxidase values, but significant increase in catalase activity in both tissues. The values of glutathione reductase in both tissues were comparable to the control, except on days 21 and 28 in the liver. There was negative correlation between the LPO in tissues and the HSI, CF and VSI values. The use of Termex^® in the environment should be monitored to safeguard the health of aquatic organisms.

Keywords: antioxidant enzymes, environmental pollution, freshwater ecosystems, insecticides