Toxicity of the chlorpyrifos-based pesticide Termifos®: effects on behaviour and biochemical and haematological parameters of African catfishClarias gariepinus

The present study, conducted in 2012, determined the toxicity of the chlorpyrifos-based pesticide Termifos® and its effects on behaviour and biochemical and haematological parameters in juvenile African catfish Clarias gariepinus. The 96 h LC50, estimated by probit analysis in a semi-static bioassay experiment, was 0.861 mg l-1. Fish were exposed to two sublethal concentrations, one-fifth LC50 = c. 172 µg l-1 and one-tenth LC50 = c. 86 µg l-1, and blood was sampled at 5, 10 and 15 d post-exposure. Fish exposed to 172 µg l-1 Termifos showed significantly lower red blood cell count and haematocrit values, and both sublethal concentrations significantly lowered the white blood cell count. The haemoglobin level did not change significantly at either dosage. Mean corpuscular haemoglobin, mean corpuscular volume and mean corpuscular haemoglobin concentration values were significantly elevated, compared to the control specimens. Glucose concentration showed an ascending trend and a positive correlation with Termifos concentration, whereas protein concentration declined and was negatively correlated with pesticide concentration. Following exposure to the pesticide, the fish showed remarkable behavioural abnormalities including erratic swimming movements, hyperactivity, faster opercular movement, surfacing to gulp air, secretion of copious mucus and loss of balance. Chlorpyrifos should be applied with caution in the environment, especially near water bodies, to avoid the possible ecotoxicological risks associated with its use.