SEXUAL DIMORPHISM IN THE BIOMETRIC PARAMETERS OF THE FRESHWATER STINGRAY POTAMOTRYGON ORBIGNYI IN THE UATUMÃ RIVER, AMAZON REGION

The present study aimed to analyze the biometric parameters of male and female Potamotrygon orbignyi in the Uatumã River basin, Amazonas, Brazil. We sampled 38 individuals, including 20 males and 18 females, during the dry season in November 2022. Disc width, total length, and body weight were measured. Differences between sexes were evaluated using one-way analysis of variance, followed by Tukey’s test. Females exhibited significantly higher disc width, total length, and body weight than males, as well as greater variation in biometric measurements. These results indicate sexual dimorphism in P. orbignyi, possibly linked to greater female energetic investment in reproductive processes such as vitellogenesis and embryonic development. This study contributes to understanding the species' biology in the Uatumã River basin and expands knowledge of morphological patterns in Amazonian freshwater stingrays.