Effects of acute exposure to cotton insecticide thalis 112 EC (emamectin benzoate 48 g.l<i>-1</i> and acetamiprid 64 g.l^-1) in African catfish <i>Clarias gariepinus</i> embryos

Abstract

Thalis 112 EC, a binary insecticide based on Emamectin benzoate (48 g.L-1) and Acetamiprid (64 g.L-1), is widely used in agriculture in Benin, to control cotton pests including Helicoverpa armigera. In order to assess the impact of acute concentrations of this binary on the development of  eggs/embryos of the African catfish Clarias gariepinus, an experiment was conducted in the laboratory. The fertilized eggs of C. gariepinus (n 100)  were exposed to six concentrations of Thalis (T0: 0.0; T1: 10.0; T2: 60.0; T3: 110.0; T4: 160.0 and T5: 210.0 ppm), each in three replicates. The  arithmetic method of Karber was used to calculate LC50 values. The 24h-LC50 and 48h-LC50 values of Thalis for eggs/embryos were 124.09 and  117.58 ppm, respectively. High Thalis concentrations significantly increased eggs/ embryos mortality and decreased hatching success (p<0.05,  Dunnett’s test). Rates of various physical deformities such as short-tail and lordosis, and the abnormalities such as black pigmentation on yolk sac,  intense lethargy, etc., also climbed with increasing Thalis concentrations (p<0.05, Dunnett’s test). The findings from the current study showed that  Thalis exerts adverse effects on embryo development of C. gariepinus. They constitute an alert on the toxic effect of chemical pesticides used in  Benin on the first developmental stages of fish inhabiting aquatic ecosystems.