Utilização do detrito por espécies de peixes amazônicas: assimilação diferencial e partilha de recurso

Abstract

The coexistence of sympatric and congeners species that explore the same resource could be explained by the variation in the food habit and the morphological and physiological characteristics between them. Detritus is one of the resources consumed by fish, it is composed of partially decomposed organic matter of plant and animal tissue, and also microorganisms and mineral. Although abundant, few species have specialized in consuming the detritus, but in the Amazon region the detritivorous species account for about 50% of the total fish biomass, and their high abundances are represented mainly by species of the family Curimatidae. Because they occupy the same trophic niche, it is crucial that these species adapt and develop strategies that allow them to inhabit the same environment. Thus, the objective of this work was to investigate variations in the morphological, physiological and ecological characteristics that allow the coexistence of curimatids in a floodplain in Central Amazonia. The results showed that adaptations in the digestive tract and structures associated with feeding allow the species to consume the detritus efficiently and confirm that there are differences in the consumption and assimilation of food between species. Species of Potamorhina ingest smaller agglomerate of detritus, while of Psectrogaster ingest larger agglomerate. Potamorhina latior assimilates detritus items more easily digestible, which reflects in a shorter intestine with less area of nutrient absorption area. Psectrogaster rutiloides consumes a more diversified detritus, composed of larger amounts of starch and lipids. Differences were also observed in the amount of food ingested and the time of foraging among the species. In addition, it was found that adverse hydrological events associated with intra and/or interspecific relationships of predation, density and competition may be promoting a population control of the curimatids, but that, nevertheless, this group presents a high proportion, when compared to the other groups, confirming that the detritivorous occupy an important and representative part of the ichthyofauna in amazonian aquatic environments.