Stingrays of the Potamotrygonidae family are a singular group of Neotropical ichthyofauna. Although ancient reports exist about the group, there are still many questions that need to be clarified, such as the biology of the species that occur in the Paraná-Paraguay River system. In the present work, the diet of Potamotrygon falkneri and Potamotrygon motoro, captured in the Upper Paraná River, downstream from the Engenheiro Souza Dias Hydroelectric Power Station (UHE Jupiá), was analyzed. Both species showed a diversified diet, consisting of 14 food items, including Mollusca, Crustacea, Insecta and fish, with the predominance in diversity and abundance of aquatic insects. Only one individual of each species ingested fish. Potamotrygon motoro consumed mainly Ephemeroptera, while P. falkneri consumed mainly Mollusca, Hemiptera and Trichoptera. The data apparently indicate a more specialized diet for P. motoro, consuming more Ephemeroptera (Baetidae), and a more generalized diet for P. falkneri. The analysis of individuals captured in three microhabitats that differ in function of the substrate type and presence of marginal vegetation, suggests differences in the food items consumed.
diet; rays; resource partitioning; microhabitat