Notes on the occurrence and gender-based morphological aspects of Potamotrygon motoro (Elasmobranchii: Potamotrygonidae) in the complex of the Viana lake system- Maranhão, Brazil

The Brazilian Amazonian coast, extending from Amapá to Maranhão states, is drained by a series of small to medium sized rivers of the Amazon basin. The Pindaré-Mearim is an isolated basin formed by the junction of the Pindaré and Mearim rivers at its lower portion. Along the Pindaré and Mearim rivers there is a single reported species of freshwater stingray identified as Potamotrygon motoro. Although specimens have been deposited in research institutions, most of these specimens have been captured on the Amazon basin and its direct tributaries or along the Panará-Paraguay river basin. Hence, there is a severe lack of information on the P. motoro of the Pindaré- Mearim river basin. Here we present new data regarding P. motoro general morphology, emphasizing the color variation, sexual dimorphism and notes on its biological aspects.