[Rapid determination of sex in Myocastor coypus embryos in the first stage of gestation]

Utility and Applicability of a Universal Set of Primers in Identifying the Sex of South and Southeast Asian Mammals

Sex identification of individuals is an important task in wildlife forensics as well as in conservation biology. It helps scientists understand population sex ratios with respect to maintaining genetic diversity, managing inbreeding depression and preventing the demographic consequences of sex-biased poaching. The literature on the use of mammalian molecular sex markers indicates that the success of accurate sex identification is variable across species. Very little is known about the effectiveness of such markers on the mammals of South and Southeast Asia. Therefore, we selected and tested three sets of universal primers for low-cost gel-based sex identification of mammals. We amplified different sets of markers-SRY (157 bp) and 12S rRNA (384 bp); Y-53-SRY (225 bp) and ZFX/ZFY (P1/P2; 445); SRY (157 bp) and 12S rRNA (151 bp)-to be used with different types (tissue, hair and skin) of samples from 20 mammalian species. All three sets of primers amplified the sex-specific fragment in a range of samples from hair to tissue. With an increasing number of field studies using non-invasively collected samples, this proposed low-cost gel- based method of molecular sexing may be applied in various aspects of the ecology and biology of South and Southeast Asian mammals, their conservation and forensics. We suggest that at least two sets of primers be used for any biological samples to avoid ambiguity.

Cortisol advantage of neighbouring the opposite sex in utero

Population sex ratios naturally fluctuate around equality. It is argued that the production of an equal number of male and female offspring by individual parents should be favoured by selection, if all costs and benefits are equal. Theoretically, an even sex ratio should yield the highest probability for a fetus to be adjacent to a fetus of the opposite sex in utero. This may cause developmental costs or benefits that have been overlooked. We examined the physiological and developmental parameters associated with in utero sex ratios in the nutria (Myocastor coypus), an invasive wildlife species with a strong reproductive output. Using hair testing, we found that litters with even sex ratios had the highest average cortisol levels. Fetuses neighbouring the opposite sex exhibited longer trunks than those neighbouring the same sex, which might imply better lung development. Our results are the first, to our knowledge, to link intra-utero sex ratios and fetal cortisol and suggest that fetal cortisol might be a mechanism by which even sex ratios are maintained via developmental advantages.

A minimally invasive method for gender determination in the prehensile-tailed porcupine (Coendou prehensilis)

Prehensile-tailed porcupines (Coendou prehensilis), like other rodents, lack external sexual traits, making it difficult to non-invasively determine their gender. By exploiting genetic differences between the X and the Y chromosome, we developed a simple genetic test to determine the gender of Coendous from shed quills. We Sanger sequenced a short portion (195 bp) of the zinc finger protein gene of known male (XY) Coendous to identify positions that are polymorphic between the X and Y chromosomes at this locus. By directly sequencing this fragment, we were able to correctly determine (confirmed via anatomical sexing) the gender of male and female Coendous by the presences or absence of polymorphisms in the resulting chromatograms. This assay is simple, quick and is applicable to other porcupine species.