Toxicidade de imidacloprido para colêmbolos folsomia candida: efeitos individuais e de misturas com fipronil ou clotianidina

Abstract

The contaminants are usually found as chemical mixtures in the terrestrial environment. However, little information is available about the joint effects of pesticides on soil organisms. The present study aimed to assess the toxicity of individual and binary mixtures of imidacloprid with fipronil or clothianidin on Folsomia candida. Reproduction and growth rates were assessed by ecotoxicological tests, to understand whether the individual and simultaneous (binary) presence of sublethal doses of fipronil (experiment 1) or clothianidin (experiment 2) can cause changes in the toxic potential of imidacloprid to F. candida. For the individual exposures, imidacloprid had EC50 values of 0.85 mg kg-1 and 0.76 mg kg-1 in 2 individual tests performed, whereas for fipronil and clothianidin the EC50 values were 0.80 and 0.10 mg kg-1, respectively. Mixture toxicity effects were assessed by using the Abbott and Additive Index (AI) method. For the reproduction endpoint, a synergistic effect was observed on binary mixtures of imidacloprid + fipronil (EC50 = 0.320 mg kg-1 of imidacloprid + 0.316 mg kg-1 of fipronil) and antagonistic effect for the binary mixtures of imidacloprid and clothianidin (EC50 =0.584 mg kg-1 of imidacloprid + 0.051 mg kg-1 of clothianidin). On the growth, both tests showed antagonistic effects of both mixtures were observed for the species, however, growth proved to be a less sensitive parameter, being used as a complementary endpoint to assess the adverse effects that the mixtures of contaminants can cause. Our findings demonstrate that the simultaneous presence of insecticides in the soil can lead to changes in the potential toxicity of imidacloprid to non-target organisms, demonstrating the need to include new assessment methodologies for regulating the use of pesticides in the country.