Comparative assessment of acute toxicity and histological changes in liver of African catfish Clarias gariepinus exposed to cotton insecticides

This study investigated the acute toxicity in Clarias gariepinus to insecticides currently used in Benin cotton fields, including Thalis 112 EC (Emamectin benzoate 48 g L⁻¹, Acetamiprid 64 g L⁻¹), Vizir C 92 EC (Cypermethrin 72 g L⁻¹, Abamectin 20 g L⁻¹), Pyrinex Quick 212 EC (Deltamethrin 12 g L⁻¹, Chlorpyrifos 200 g L⁻¹) and Pyro FTE 472 EC (Cypermethrin 72 g L⁻¹, Chlorpyrifos 400 g L⁻¹) with emphasis on liver histopathological effects. A set of 180 juveniles of C. gariepinus (5.21 ± 3.22 g) was exposed for 96 h to increasing concentrations of each pesticide. The values of 96-hLC₅₀ were 4.778, 0.002, 0.004, and 0.012 µL L⁻¹ for Thalis, Vizir, Pyrinex, and Pyro, respectively, indicating that Vizir, Pyrinex, and Pyro were very highly toxic to C. gariepinus juveniles. During the experiments, the morphological and behavioral responses (discoloration, hyperactivity, lethargy, etc.) were observed in exposed fish, hypothesizing the neurotoxicity of these pesticides. Histopathological alterations observed in liver of contaminated fish were regressive changes, such as necrosis, vacuolation, bleeding, nuclear degeneration, hepatocytes degeneration, sinusoids dilatation, etc. Vizir induced the highest histological alteration indices while the lowest were induced by Thalis, confirming the highest toxicity of Vizir. These results indicate that acute concentrations of these insecticidal molecules have destructive effects on the liver of C. gariepinus.