Avaliação dos efeitos letais e subletais dos inseticidas cipermetrina e fipronil em girinos de Physalaemus gracilis (Anura: Leptodactylidae)

Abstract

Agrochemicals are transferred and transported in the environment in several ways and can cross different environmental compartments, reaching the soil and especially water. The presence of pesticides in the environment can have deleterious effects on non-target organisms, such as amphibians, altering population dynamics and disrupting communities. Declines in the amphibian population due to the presence of pesticides have been recorded worldwide and threaten the development of species and their function within the ecosystem. In this study, the lethal and sublethal effects of two commercial formulations of insecticides widely used in agriculture were evaluated: cypermethrin and fipronil for Physalaemus gracilis. The acute assay lasted 96 hours and the chronic assay lasted 7 days. In the chronic trial, effects of environmentally relevant concentrations of these insecticides (μg.L-1) were evaluated on P. gracilis. Cypermethrin showed LC50;96h of 273.41 μg.L-1 for P. gracilis, indicating high acute toxicity for the species. In the chronic study, cypermethrin caused an increase in mortality reaching more than 50% of tadpoles at a concentration of 20 μg.L-1. It also caused an increase in the frequency of micronuclei and nuclear erythrocyte abnormalities, reaching 20% of the total cells evaluated at the highest concentration (20 μg.L-1). The risk of cypermethrin to P. gracilis was high, indicating that concentrations already recorded in nature may have serious short- and long-term effects on the species. Acute toxicity effects were not observed for fipronil. Fipronil did not cause changes in swimming activity and malformations in the mouth. However, it caused significant malformations in the gut. In the micronucleus test and nuclear abnormalities, fipronil also caused an increase in the presence of micronuclei and nuclear erythrocyte abnormalities, showing that it has genotoxic potential for P. gracilis. Despite this, the commercial formulation evaluated for fipronil presented a low chronic risk for P. gracilis. At the end of this study, amphibians proved to be useful bioindicators and we suggest that tadpoles of different species can be used to determine the environmental impacts of agrochemicals on aquatic ecosystems.