Objective This study aims to explore the histological characteristics of early gonadal differentiation and development of Siniperca scherzeri, enrich the reproductive biology data of this species, and provide a theoretical basis for mono-sex breeding.

Method Artificial breeding S. scherzeri aged 2 to 62 days post-hatching (dph) were taken as the research objects,and 15 individuals were sampled every 5 days. Gonadal tissue sections were prepared by paraffin embedding sectioning and hematoxylin and eosin (H.E) staining techniques. These sections were observed, photographed and measured by Olympus FX380 microscope and CaseViewer2.4 software.

Results The primitive gonads of S. scherzeri had already formed at 7 dph, distributed in pairs on the coelomic membrane between the mesonephric ducts and the intestines.In male S. scherzeri, the spermaduct anlage and primary spermatocytes were observed at 17 dph and 27 dph respectively, marking the beginning of anatomical and cytological differentiation of the testis. The testis of S. scherzeri belonged to lobular structure,and its development process was relatively rapid: it was in stage I at 17 to 27 dph, entered stage II at 32 dph, reached stage III at 37 dph, and developed to stage IV at 62 dph. In female S. scherzeri,the ovarian cavity and primary oocytes were observed at 22 dph and 32 dph respectively, marking the beginning of anatomical and cytological differentiation of the ovary. Ovarian development was comparatively slower: remaining at stage I from 22 to 42 dph, and progressing to stage II from 47 to 62 dph.

Conclusion Under natural water temperature conditions, primitive gonads of S. scherzeri had been formed within one week after hatching.The anatomical differentiation of the gonads preceded the cytological differentiation, and the testis differentiation and development were significantly earlier and faster than that of the ovary. The critical period for anatomical differentiation of the gonads was between 7 and 22 dph. By 62 dph, the testis had developed to stage IV, while the ovary had only developed to stage II. This study clarifies the key timeline and histological characteristics of early gonadal differentiation in S. scherzeri, providing a theoretical foundation for its mono-sex breeding practices. In this study, the key time nodes and development characteristics of gonadal differentiation in the early stage of artificial breeding of S. scherzeri were preliminarily clarified, which can provided some theoretical basis for the practice of single-sex breeding of this fish. This study initially clarified the key timeline and histological development characteristics in the early gonadal differentiation of artificial breeding of S. scherzeri, which could provide a theoretical foundation for the development of mono-sex breeding of S. scherzeri.