Histological Characterization and Comparative Transcriptomic Analysis of Gonads During Early Sex Differentiation in the Northern Snakehead ( <i>Channa argus</i> )

ABSTRACT The northern snakehead ( Channa argus ) is an economically important aquaculture species in China. It exhibits significant sexual dimorphism in growth, with males growing significantly faster than females, making all‐male breeding a highly valuable strategy for aquaculture productivity. However, the critical window and precise timeline of its early sexual differentiation remain unclear. To address these questions, we conducted a histological examination of gonads across 12 developmental stages spanning from undifferentiated gonads to differentiated ovaries and testes of C. argus . The results indicated that histological sex differentiation, ovarian cavity formation, and efferent duct primordium formation were initiated at 17, 19, and 21 days post‐fertilization (dph), respectively. Subsequently, we performed comparative transcriptomic analyses at four key developmental time points: 10 dph (gonadal primordium), 17 dph (predifferentiation), 40 dph (differentiated gonads at Stage II), and 100 dph (differentiated gonads at Stage III) and identified a series of sex‐biased genes, including female‐biased ( cyp19a1a , foxl2 , figla , and id2 ) and male‐biased ( dmrt1 , amh , gsdf , and wt1 ) factors. Functional enrichment analysis revealed that these genes were significantly involved in TGF‐β signaling, Wnt signaling, and steroid hormone synthesis pathways. Furthermore, protein–protein interaction analysis identified several hub genes (e.g., dmrt1 , amh , wt1 , foxl2 , and figla ) central to the regulatory network. Collectively, our study clarifies the early sex differentiation timeline in C. argus and uncovers the dynamic expression profiles of key genes, revealing a critical time window (17–21 dph) for potential hormonal or environmental sex manipulation and laying a foundation for future sex‐control breeding in aquaculture.