Food assimilation of a neotropical riverine detritivorous fish, Prochilodus lineatus, studied by fatty acid composition (Pisces, Curimatidae)

Food assimilation by the detritivorous fish Prochilodus lineatus, throughout a life cycle, was studied by means of fatty acid analysis. Fish length ranged from 2.7 to 55 cm and weight from 2 to 2670 g. Samples for fatty acid determination were taken from the mesenteric deposit in adults and from the whole fish in juveniles. Phyto and zooplankton, and superficial mud were also studied. Samples were taken from the principal channel of the Parana River and lentic environments in its alluvial plain (60 degrees 29'W and 31 degrees 40'S). Fatty acids in the smaller fish (2.8-3.8 cm) indicated the assimilation of zoo and phytoplankton. Longer P. lineatus have a fat-deficient diet, particularly in polyunsaturated acids. At different stages of life, P. lineatus is adapted to different sources of food. When young, it eats zoo- and phytoplankton, becomes gradually detritivorous and has a series of adaptations of the digestive tract (morphological and histological) to enable it to assimilate detritus.