Earthworm avoidance behavior to antimicrobial sulfadiazine on tropical artificial soil

Veterinary pharmaceuticals can reach the soil via animal excretions and cause impacts on aquatic and terrestrial ecosystems. In this work, we employed a standardized avoidance behavior test to assess the sublethal effects of antimicrobial sulfadiazine on the earthworm Eisenia andrei. Cultivation of red worms was based on an alternative substrate made of mostly household vegetable wastes and dry leaves. The bioassays were performed with tropical artificial soil spiked with the tests substance at five different concentrations ranging from 0.01 to 100 mg sulfadiazine kg-1. The outcome resulted in avoidance response of 30% (maximum) and a nonlinear concentration-response curve, differing from classical pollutant responses and correlating with those asymmetric responses over the environment caused by some rare xenobiotics. Avoidance tests were validated with reference substance, resulting in an EC50-48h of 819 mg boric acid kg-1 (628-1066 mg boric acid kg-1 95% confidence interval). We concluded that the avoidance test with E. andrei is useful as a standardized tool for a rapid ecotoxicological screening of soil.