A pioneering approach for non-invasive sex identification of Chinese sturgeon at early stage

Abstract

The Chinese sturgeon (Acipenser sinensis) is critically endangered in China. Owing to the lack of visible sexual dimorphism and effective DNA markers for sexing in this species, a novel non-invasive method for sex identification in Chinese sturgeons would be helpful for conservation management. The zona pellucida (ZP) gene and sex determining region Y-box 9 (Sox9) gene were considered as candidate genes involved in gonadal differentiation. Here, we first detected the differences in expression of the ZP3.2 and Sox9 genes in the gonads and ventral fins of 107 Chinese sturgeons aged 2, 3, 6, 7, and 9–11 years old, using quantitative real-time polymerase chain reaction (qRT-PCR) to develop non-invasive expression markers. The accuracy of the developed marker was confirmed using endoscopy in another 240 individuals in four different age groups (aged 5–8 years old).The expression levels of the ZP3.2 gene in the ovaries and ventral fins at different ages were significantly (p < 0.05; p < 0.05, respectively) higher than those in the counterparts of males. The expression levels of the Sox9 gene in the testes at different ages were significantly (p < 0.05) higher than those in the ovaries, whereas the expression levels of the Sox9 gene in the male ventral fins were low, similar to those observed in the female ventral fins. Furthermore, a sex identification accuracy of 78.33% to 86.66% for the ZP3.2 gene in the ventral fin was confirmed by conducting endoscopies on individuals of four different age groups.The differential expression of ZP3.2 in the ventral fins of female and male Chinese sturgeon can be used as an effective non-invasive sex indicator in individuals over 2 years of age. This work also provides a novel solution for non-invasive sex identification in other surgeon species.