Respostas morfológicas, comportamentais e celulares de girinos de physalaemus cuvieri expostos a água do interior e entorno do Parque Natural Municipal de Sertão

Abstract

Amphibians are known to be bioindicators due to their sensitivity to environmental impacts. Physalaemus cuvieri, a small frog with wide geographical distribution in South America, has been studied to understand environmental toxicity and disturbances. The objective of this study was to evaluate morphological, behavioral, and cellular responses in P. cuvieri tadpoles exposed to waters from preserved environments within the Municipal Natural Park of Sertão (PNMS) and altered environments in the surrounding agricultural area. Water samples were collected from two ponds in each environment, transported to the laboratory, and analyzed for physical-chemical parameters and pesticides. P. cuvieri egg clutches were collected at Federal University of Fronteira Sul (UFFS) and reared until Gosner stage 25. Microcosms were set up with water and plants from the ponds, stones, and 20 tadpoles each, in triplicate. The assay lasted 21 days, with periodic monitoring of pH, temperature, oxygen, and ammonia. Survival parameters were analyzed; length and mass were measured; Body Mass Index (BMI) and Scaled Mass Index (SMI) were calculated; behavioral tests were conducted; and nuclear abnormalities in erythrocytes were assessed. Physical-chemical parameters varied little, except in PA1 (higher BOD and COD) and PA2 (more phosphorus and nitrate). Nine pesticides were detected in the surrounding area and five within the park, notably the herbicide 2,4-D (higher concentration inside) and atrazine. No mortality or malformations occurred in tadpoles. However, tadpoles from inside the park exhibited greater mass, length, BMI, and SMI. In the aversive test, tadpoles from the surrounding area spent more time in the risk zone. In the predation test, they showed greater exploration of the area, less time at the edges, and more time in the center, indicating altered risk perception. Tadpoles from the surrounding area also had more nuclear abnormalities—such as micronuclei and lobed, notched, and budded nuclei. Waters from the surrounding area caused more alterations, likely associated with pesticide mixtures. The mixture of pollutants intensified effects more than isolated compounds. Even waters from inside PNMS showed impacts, demonstrating that not even protected areas are free from contamination.