Relationship between diet and pharyngeal jaw morphology of Crenicichla species (Cichliformes: Cichlidae) in streams from Uruguay and Jacuí basins, Southern Brazil

Abstract

Cichlidae have a magnificent ecological versatility that provides the species to explore many trophic niches, and behavioural biology. This versatility was achieved by modifications in the cranial and pharyngeal apparatus of cichlids. Accordingly, we aim to examine the relationships between pharyngeal morphology and diet of three species of the genus Crenicichla. We analysed the stomach contents and the morphology (through the geometric morphometric and teeth types) of their lower pharyngeal jaws (LPJ). We tested the hypothesis that LPJ morphology predicts the diet of Crenicichla species in streams. Our results indicated that the diet and the patterns of pharyngeal jaws were different among the species of Crenicichla, mainly the posterior process of the LPJ, the region of muscle insertion of LPJs with the neurocranium and the curvature of LPJ. Variation among the lower pharyngeal jaw shapes was shown to be directly associated with the use of food resources. Crenicichla species had a carnivorous diet based on fish and invertebrates (Aegla and aquatic insects). Higher fish consumption was observed in species with elongated lateral process in the LPJ and larger numbers of teeth, mainly recurved and conical unicuspid and bicuspid teeth (C. scottii and C. lepidota). On the other hand, higher consumption of Aegla was associated with a robust LPJ and molariform teeth (C. punctata). The total number of teeth was positively correlated with higher fish consumption. In addition, our results point to the need for investigations about spatial-temporal variations in Crenicichla diets to understand this group’s success in several freshwater environments.