Assimetria flutuante e anomalias como ferramentas de medição de impactos ambientais em girinos de Pithecopus ayeaye Lutz, 1966 (Amphibia, Anura: Phyllomedusidae)

Abstract

Developmental instability (DI) is the inability of an organism to follow its predetermined developmental trajectory and can be perceived through phenotypic changes resulting from random perturbations. Information on ID can be obtained by analyzing fluctuating asymmetry (FA) — differences between the right and left sides of bilateral morphological structures, caused by random processes during development. FA levels may increase as environmental conditions become unfavorable. In addition, the analysis of anomalies in organisms can also provide information about the quality of the environment in which they developed, since their rates can increase when organisms experience stressors. Pithecopus ayeaye is an endemic species of highland regions of southeastern Brazil, along the states of Minas Gerais and São Paulo. The species breeds mainly in temporary streams in campos rupestres, whose conservation is threatened due to human activities. Considering the disturbances that affect the species' environment, we evaluated how different levels of environmental quality, represented by indicators of water quality and human occupation of the environment, reflect differences in symmetry and the presence of anomalies in the larvae. We collected tadpoles and water samples from different populations throughout the species' range. We obtained the physicochemical characterization of the drainages and indices of anthropic use of the soil. We measured eight bilateral morphological traits in individuals for the assessment of FA and anomalies. Correlations between environmental variables and morphological deviations were verified using generalized linear models (GLMs). Environmental factors such as lower turbidity, alkalinity and greater distance from preserved areas were correlated with higher levels of FA in P. ayeaye tadpoles. Meanwhile, lower temperatures, higher anthropic land use within 500 meters and higher concentration of total phosphorus were associated with a higher anomaly score. We observed that populations from more disturbed environments showed an increase in the levels of both morphological deviations, providing robust and complementary measures of environmental quality. Based on the evidence presented here, we point to P. ayeaye as a possible bioindicator species of temporary streams of campos rupestres, which are extremely important for the maintenance of biodiversity and water security in the Cerrado.