Anatomical description of the Cortés damselfish Stegastes rectifraenum (Perciformes: Pomacentridae). Key structures for omnivore feeding

Abstract

Pomacentridae is one of the most abundant fish families in coral and rocky reefs of tropical and temperate waters. Stegastes rectifraenum (Gill, 1862), as other members of the genus, is territorial and actively farm algae on its territory, helping in the regulation of the algal community structure and the reef productivity. It is endemic and one of the most abundant species along the Mexican Pacific coast. Even with its strong relationship with algae, this species is omnivorous. In this analysis, we present the first complete anatomical description of a species of Pomacentridae, focusing in one research question: which structures allow S. rectifraenum to have an omnivorous diet? Through the analysis of the skeletal, muscular and digestive systems, the anatomy of the species was described. The complex anatomy of S. rectifraenum shows a set of characters previously described for grazers (mandibular muscles), herbivorous (mandibular teeth), omnivorous with preference for algae (general skull osteology) and zooplanktivorous species (intestine shape and pharyngeal teeth). According to our results, S. rectifraenum is a grazer, omnivorous with preference for algae. Finally, the key character that facilitates S. rectifraenum access to a wider range of resources is the shape of the pharyngeal teeth, which can effectively grind, fasten and tear.