In situ works on ecotoxicology in amphibians: current state of the art

Abstract

Amphibians play a fundamental role in the functioning of ecosystems, mainly in the nutrient cycle, energy flow, and pest control. This group has a massive population decline, with approximately 41% of all species at risk, highlighting pesticide pollution as one of the main threats to the loss of anuran biodiversity. This occurs since amphibians have an epidermis with high permeability and a biphasic life cycle, where they use both the aquatic and terrestrial environments, allowing exposure and making them susceptible to chemical agents released into the environment. This makes amphibians a model group in ecotoxicological studies. However, due to the greater control of experimental conditions, the vast majority of studies are carried out in the laboratory, thus maintaining a gap in knowledge about the effects of pesticides on amphibians in natural environments. Under natural conditions, where environmental variables are not controlled, experiments must relate all the dynamics of the interaction of substances existing in the environment, and their influences on organisms. To evaluate the studies already performed under natural conditions, a bibliographic survey was carried out through a search with the Web of Science and SCOPUS databases, considering articles published in the last twenty years, using the terms 'field experimentation' or 'in situ study', associated with 'tadpole' and 'agrochemical' or 'pesticide', using a descriptive methodology. Twenty-one abstracts were pre-selected, they were further evaluated and the methodologies were checked to ensure only the analysis of experiments conducted in the field conditions. Thus, ten works were selected for the construction of the review. The works selected used native amphibian species, considered generalists, present in the study region, and were carried out in environments intended for agricultural cultivation with control groups in preserved locations. In these works, different methodologies were used, such as intentional spraying of water bodies, quantification of pesticides in the study sites, and verification of changes caused by the environment on tadpoles. The main evaluations were based on the survival and morphological changes of the tadpoles and, in some cases, on cytological and biochemical assays.