Influência da exposição de herbicidas em duas espécies de anfíbios anuros nativas do sul do Brasil

Abstract

The consumption of pesticides, especially herbicides, has increased at alarming values in Brazil and worldwide. Glyphosate, 2,4-D, and atrazine are among the three most commercialized herbicides in Brazil and have already been detected in surface and groundwater. Among the vertebrates that are most negatively impacted by pesticides are amphibians. About 40% of amphibian species are under threat of extinction, besides, these animals are considered bioindicators and sentinels of environmental contamination. Thus, amphibians are good models for ecotoxicological studies, because they present some physical characteristics such as permeable skin, eggs without shell, exposed embryogenesis, free-living aquatic larvae, and dependence on terrestrial and aquatic environments. The species Boana faber (Anura: Hylidae) and Leptodactylus latrans (Anura: Leptodactylidae) are widely distributed species in South America and can occur in water springs near agroecosystems and consequently come into contact with pesticides. The present study evaluated the chronic effects of the mixture of 2.4 D and glyphosate in tadpoles of B. faber and L. latrans, and the effects of glyphosate and atrazine in B. faber. Chronic trials lasted 168 hours (7 days). Tadpoles were subjected to environmentally relevant concentrations and allowed by the legislation in force in the area of species distribution. From morphological and behavioral analyses, it was found that the mixture of 2,4-D + glyphosate caused damage to the mouth and intestine, changes in length and mass, and changes in the swimming activity of both species studied. Individual and combined exposure of atrazine and glyphosate in B. faber tadpoles caused damage to the mouth and intestine, changes in length and mass, and did not cause changes in swimming activity. The three herbicides showed to have genotoxic potential. In the micronucleus assay, micronuclei (MNs) and other erythrocytic nuclear abnormalities (ENAs) were inducing in tadpoles exposed to mixture 2,4-D + glyphosate and atrazine and glyphosate (individual and in a mixture). The risk analysis using two indicators (TER and CHQ), indicated a high ecological risk for B. faber and L. latrans exposed to the relevant concentrations of glyphosate + 2,4-D, which demonstrates that the allowed limit of these herbicides in the environment should be re-evaluated for non-target species. The two amphibian species have proven to be useful bioindicators and we suggest that tadpoles of different species can be used to determine the environmental impacts of pesticides on aquatic ecosystems.