Hábitos alimentares e relações morfológicas de espécies de Loricariidae (Actinopterygii: Siluriformes) da região da Volta Grande do rio Xingu, Pará, Brasil

Abstract

The relationship between morphological attributes and foraging habits was analyzed in 13 species of Loricariidae from Volta Grande do Xingu. We investigated the degree of similarity of morphological characteristics related to obtaining and processing food; and whether the composition of the species' diet is associated with the morphological features. Field collections were carried out between the years 2012 and 2013, including the receding water (July) and low water (September, October, and November) periods in the Volta Grande do Xingu region. The fish capture was carried out throughout direct search, through diving sessions, gillnets, and nets. A total of 185 individuals were used for morphological and diet analysis. 21 morphological attributes associated with food capture and assimilation were selected and analyzed by ordering methods, (Principal coordinate analysis (PCoA) and grouping (Cluster)), which allowed the visualization of morphological patterns between the species of the subfamilies Hypoptopomatinae, Hypostominae and Loricariinae. The analysis of the species diet indicated a broad diet spectrum, with 33 types of alimentary items identified. The Alimentary Importance Index (IAi) was used to identify the main alimentary items for each species, and according to the results, the species were classified into five trophic categories: detritivore, algivore, carnivore, omnivore, and xylophage. The non-metric multidimensional scaling (nMDS) and Cluster identified different trophic patterns and the use of alimentary resources by the species. The correlations between morphology and diet were tested by the Mantel test and a correlation was found between them, indicating that the morphological patterns are related to the feeding habits of the analyzed species, meaning that, the more different the morphologies, the more distinct the diets. Overall, our results show that the diversity of identified alimentary items demonstrated that diet among loricariids can be quite distinct, the importance of rapids environments for the trophic dynamics of these species and that the morphological variety of the digestive tract among species of Loricariidae may have allowed the success in the exploration of different food resources.