Genetic sex identification and the potential sex determination system in the yellow drum (Nibea albiflora)

Sex-specific markers have important implications in genetic improvements of economical traits in aquacultured fish. Yellow drum (Nibea albiflora) is a commercially important fish species distributed in China, Southern Japan and Korea, exhibiting a sex-dependent dimorphic growth pattern where females grow much faster than males. Yet its sex determination mechanism was unclear and sex-specific markers were missing. In this study, a 45 bp deletion within the first intron of Dmrt1 was detected only in males through comparative analysis between males and females. Two pairs of primers (male-specific primers MS-F/R and male and female shared-primers MFS-F/R) were designed to efficiently distinguish the genetic sex of the yellow drum. Importantly, genotyping the deletion in large cohorts of both artificially bred and wild yellow drum confirmed its male-specific property. Our results showed that this male-specific genetic marker could be used to establish a simple and reproducible method for genetic sex identification. Furthermore, the fact in which males are heterozygotes and females are homozygotes of the marker indicates that yellow drum adopted the male heterogametic XX/XY sex determination system.