Sex Determination in the Near Threatened Guadalupe Fur Seal: Molecular Markers and Their Potential Applications

Abstract

The determination of sex by simple observation is often difficult in marine mammals, even in sex-ually dimorphic species. Moreover, there is often the practical necessity to determine sex in sam-ples that have been collected without handling or observing the subjects. In these cases, a molecu-lar assay for sex determination is required. We adapted an assay that targets the zinc-finger re-gion and is based on a single primer pair, to the Guadalupe fur seal, a near threatened species that has a very limited breeding range. First, we validated the assay with a sample of pups in which we determined the sex by direct observation during handling; second, we compared it to a more re-cent assay, based on two different primer pairs and, finally, we evaluated the effect of DNA quan-tity on its reliability. The assay that we tested produced excellent results and was more reliable than the other one based on two primers. Reliable results were also obtained when only remarka-bly small quantities of DNA were amplified. These results show the potential use of this molecular assay in case of non-invasive sampling, an overly common situation when dealing with species of problematic conservation status.