Interactions between diet, pharyngeal jaw and ontogeny in Cichlasoma portalegrense (Cichliformes: Cichlidae)

Abstract

Morphology plays a central role in determining diet. Knowledge of ecological and morphological relations between a species and its ecosystem is highly relevant. The aims of this study are to describe the diet and the lower pharyngeal jaw (LPJ) of Cichlasoma portalegrense and to test for the existence of ontogenetic and spatial patterns in its diet. Samplings took place in four sampling sites in Viamao, including two at the Refugio de Vida Silvestre Banhado dos Pachecos. Collected individuals were grouped in accordance with size categories and dissected. Food items were identified and quantified for each size category in each sampling site, according to the volumetric method, related to frequency of occurrence. Four linear measurements of the LPJ were carried out. The quantity and quality of their teeth were ascertained. Teeth arrangement was also analysed. Cichlasoma portalegrense is omnivorous with a tendency to carnivory and feeds on pelagic and benthic items from different origins. It shows neither ontogenetic patterns nor spatial variation in its diet. The species can feed on any possible food resource, thus being an advantage regarding the others. The LPJ has five types of teeth, is generalist without specializations, which is an adaptive advantage, since it is already adapted to selection pressures from different kinds of food. The shape of the LPJ and teeth distribution clearly show a same arrangement, regardless of fish size categories.