Aspectos da Biologia Alimentar de Potamotrygon leopoldi Castex & Castello, 1970 (Chondrichthyes: Potamotrygonidae) na Região do Médio Rio Xingu, Pará

Abstract

Potamotrygon leopoldi is a species of freshwater ray belonging to the Potamotrygonidae family. This species has a high value in the ornamental fish market and is endemic to the Xingu River basin. The present study is pioneer and represents a contribution to the knowledge of the feeding biology of this species. Samples were collected in the middle Xingu River in 2003, 2004 and 2005. Stomachs (n = 144) were analyzed and items were identified to the lowest possible taxonomic category, with the vast majority identified to the family level. Analyses included: Relative Frequency of Occurrence (% FO), Numerical Percentage (%N), Percent by Weight (%P), and Relative Importance Index (IRI and %IRI). The levels of repletion and digestion were also observed. The results indicated that these rays had replenishment level 1 (73.4%) and food items with digestion degree varying between 2 (47.6%) and 5 (51.4%). The results of all analyses indicated a gastropod species of the family Thiaridae as the predominant food item (%IRI 94.4). Other items (fish, insects, and crabs) were also observed, but in much lower proportions. Many fragments of plant tissue were also found and were probably accidentally ingested by sucking. The data indicate that this species is adapted to durophagia and should be considered a specialist malacophagist.