Morphology of sagitta, lapillus and asteriscus of Patagonian Genidens barbus

Abstract

Otoliths are calcium carbonate structures, deposited as aragonite, located in the inner ear of bony fish. In recent years, they have become a useful tool for the determination of fish species, trophic content, age studies, and the identification of fish stocks. The objective of this work was to describe the morphology of the three pairs of otoliths of the marine catfish Genidens barbus of Patagonian distribution. Otoliths of specimens obtained at four sampling points in the Negro River were analyzed. It was observed that otoliths presented the general morphological pattern proposed for Siluriforms, where lapilli are the largest and most robust of the three. Lapillus presented a rounded shape, a pronounced elevation in the central position, a delimited sulcus, but not very evident, without evidence of a minor sulcus. The sagitta is claviform, with an elongated conical posterior region, dorsal wings that continue as lateral expansions called basal wings, and the presence of a fissure. The asteriscus has an ear shape, a median opening, a short pointed rostrum, a poorly developed anti-rostrum and a slightly curved acoustic fossa. In this work, sagitta and asteriscus otoliths were described for the first time for G. barbus, thus completing the description of the three pairs.