Toxicity of the Herbicide Roundup Original DI® in Tadpoles of Physalaemus erikae and Physalaemus cicada (Anura: Leptodactylidae).

Abstract

Brazil is one of the largest consumers of herbicides in the world, and glyphosate-based herbicides (e.g., Roundup^®) are commonly applied in cropland. Among vertebrates, amphibians are especially susceptible to contamination due to their strong association with freshwater environments. However, our knowledge of how these herbicides affect amphibians is still scarce, mainly regarding the impacts of commercial formulations. In this study, we experimentally evaluated the effects of Roundup Original DI^®, a glyphosate-based herbicide, on tadpoles of Physalaemus cicada and Physalaemus erikae. Spawnings were collected in south and southern Bahia, transported to the laboratory, and kept until the tadpoles reached developmental stage 25. Tadpoles were acclimated for 24 h and subsequently exposed to increasing herbicide concentrations at acute and chronic levels to assess survival, lethal concentration (LC50 96 h), and morphological and ontogenetic responses. Contamination significantly decreased the survival of tadpoles of both species and affected the development of tadpoles of P. erikae. The estimated lethal concentration (LC50) after 96 h for Physalaemus cicada was 5.52 mg a.i./L, and Physalaemus erikae was 3.40 mg a.i./L. Also, at chronic concentrations, morphological changes were observed in the tadpoles of P. erikae, with the changes being mainly in the tadpoles' tail and body shapes. Therefore, Roundup Original DI^® is considered moderately toxic to both species. Our results extend the knowledge regarding the action of pesticides mainly for species of the genus Physalaemus, which is the best-known genus for glyphosate based-herbicide toxicity.