Discriminating Scleromystax barbatus (Siluriformes: Callichthyidae) populations from Atlantic Rainforest streams employing otolith shape

Abstract This study assessed the lapillus otolith shapes of males and females of Scleromystax barbatus from southern and southeastern regions in the Atlantic Rainforest biome employing Fourier and Wavelet descriptors. The utricular otoliths of S. barbatus are ovoid, with the gibbus maculae occupying almost all the ventral portion, similar to most Callichthyidae species. Otoliths of males and females of S. barbatus from the southeastern studied region are more elongated in the anterior-posterior direction and present larger sulcus and gibbus maculae, with heterogeneous borders. We found no sexual-based dimorphism in otolith shape within regions, however regional differences were registered and attributed to variations in fish life history mediated by differences in environmental factors (e.g., climatic conditions) between the southern and southeastern regions in the Atlantic Rainforest biome. Additional studies are suggested to investigate the influence of genetic effects and their environmental interactions to better understand how these factors are related with otolith shape and influence the discrimination among S. barbatus populations.