Feeding aspects of Knodus heteresthes (Characiformes, Characidae) in igarapé of the Nove Machado river basin, Rondônia, Brazil

Abstract

In this study, we describe the feeding habit of Knodus heteresthes in an Amazonian igarapé and explore the hypothesis that variations in diet are due to alternation of seasons and ontogenetic development. Most specimens collected were small-sized (< 30 mm). We observed that the species eats a wide variety of items, ranging from vegetal material, such as algae, seeds, and leaves, and animal material, such as arachnids, bryozoans, and terrestrial and aquatic insects at various life stages, suggesting an omnivorous diet with a significant consumption of allochthon insects. Items of allochthon origin were more representative than autochthon items for young (?2 = 70.4; p < 0.05) and adults individuals (?2 = 60.6; p < 0.05), in both seasons (rainy, ?2 = 53.0; p < 0.05; dry, ?2 = 77.0; p < 0.05), and they accounted for over 70% of the species’ diet in all samples, indicating some degree of specialization. Such specialization, in turn, can be related to the high abundances found by the species, which possibly show a good ability to allocate energy to growth, in the case of young individuals, and reproduction, in the case of adults, making it a dominant species in preserved igarapés.