Morfologia do trato digestivo em peixes da família Characidae em um rio não perene do semiárido brasileiro

Abstract

Non-perennial rivers and streams (NPRS) are highly dynamic ecosystems characterized by seasonal changes in hydrological regimes that modify environmental conditions and influence morphophysiological traits of aquatic populations. These variations may act as selective pressures, promoting adaptive responses in aquatic organisms. In this context, this study evaluated the influence of hydrological seasonality on the morphology of pyloric caeca, finger-like appendages located at the junction between the stomach and intestine that increase the surface area available for digestion and nutrient absorption, in four Characidae species (Serrapinnus piaba, Serrapinnus heterodon, Compsura heterura, and Phenacogaster calverti) from the Cruxati River, located in the Brazilian semiarid region. The data were obtained from the database of the Laboratory of Aquatic Ecosystem Ecology (LEEA) and included specimens collected in 2015. Diet composition between hydrological phases was evaluated using Permutational Multivariate Analysis of Variance (PERMANOVA) and Non-metric Multidimensional Scaling (NMDS). Differences in the number and area of pyloric caeca between hydrological phases (pool and flowing-water phases) and among species were assessed using the Wilcoxon test, Kruskal–Wallis test, and Dunn's post hoc test. Individuals collected during the pool phase exhibited a significantly higher number of pyloric caeca than those collected during the flowing-water phase, whereas pyloric caeca area did not differ significantly between hydrological phases. Among species, the number of pyloric caeca showed little variation, while pyloric caeca area differed significantly. These findings indicate that pyloric caeca morphology varies among the studied Characidae species and may respond to environmental changes associated with river intermittence.