The identification of sex chromosomes is fundamental for exploring the mechanism and evolution of sex determination. Platichthys stellatus, a species exhibiting clear sexual dimorphism and homomorphic chromosome pairs, has received limited research concerning its sex determination mechanisms. Clarifying the sex chromosome of P. stellatus will enhance our understanding of sex chromosome evolution in Pleuronectiformes. This study employed whole-genome resequencing to investigate the sex chromosome and sex determination system in P. stellatus. Notably, Chr23 was identified as the sex chromosome in P. stellatus, with the sex-determining region (SDR) occupying 48.1% of the chromosome and featuring an XX/XY system. Sex chromosome turnover was observed within Pleuronectiformes, with P. stellatus, Verasper variegatus, and Hippoglossus hippoglossus sharing a common ancestral karyotype. No inversions were detected within the SDR of P. stellatus, although chromosomal rearrangements between sex chromosomes and autosomes were identified. Additionally, a sex-specific marker for P. stellatus was ascertained, enabling genetic sex identification, with significant implications for improving breeding programs and aquaculture practices.
性染色体的鉴定是探索性别决定机制以及进化的基础。星突江鲽展现出明显的性别二态性，并且具有同型染色体对。鉴于目前对星突江鲽性别决定机制的研究有限，确定其性染色体将促进鲽形目鱼类性染色体演化的理解。该研究使用全基因组重测序探究星突江鲽的性染色体和性别决定系统。显而易见，星突江鲽的性染色体为Chr23，性别决定区域占性染色体总长度的48.1%，并且性染色体类型为XX/XY。在鲽形目中，性染色体发生转换，星突江鲽、圆斑星鲽、大西洋庸鲽共享同一条性染色体祖先核型。在星突江鲽的性别决定区域内，没有检测到倒位事件。但性染色体与常染色体之间发生了重排。此外，一种星突江鲽性别特异性标记被确定，这一标记能够鉴定其遗传性别，这对指导星突江鲽繁殖策略的制定和推动水产养殖业的发展具有重要的意义。.
Keywords: Ancestral karyotype of Pleuronectiformes; Platichthys stellatus; Sex chromosome; Sex determination system; Sex-specific marker.