Invasive molluscs in the diet of Pterodoras granulosus (Valenciennes, 1821) (Pisces, Doradidae) in the Upper Parana River floodplain, Brazil

Diet composition of Pterodoras granulosus was investigated from June 2004 to June 2005 in the Upper Parana River floodplain, following invasion by two mollusc species Corbicula fluminea and Limnoperna fortunei. Stomach and intestinal contents analysis showed spatial differences in the diet composition. In the Baia River, P. granulosus diet consisted mainly of C. fluminea, whereas plant items dominated in the Ivinheima River, and L. fortunei was the most important food in the Parana River. There was little selectivity in shell length consumed. In spite of C. fluminea being a larger mollusc, L. fortunei appears to be energetically more profitable because its shell is more fragile and is rapidly opened and digested. A considerable amount of closed shells of C. fluminea at the end of the digestive tract points to a possible role of P. granulosus as a mollusc disperser.