Fig. 12

Overview of key genes and potential pathways that bipotential gonads develop to either testis and ovary development in C. maculata. In females, the expression levels of Foxl2 and Cyp19a1a began to increase at 20 dpf. In males, the expression levels of Sox11a, Dmrt1 and Sox9b began to increase at 20, 30, and 30 dpf, respectively. The ovarian cavity and efferent duct anlage were first observed at 25 dpf and 35 dpf in female and male gonads, respectively. Therefore, the periods of 20–25 dpf or earlier and 30–35 dpf or earlier were the morphological ovarian and testicular differentiation, respectively. Sycp3 and Spo11 exhibited a sharp increase from 30 to 90 dpf in female gonads, combining the first observation of primary oocytes at 40 dpf, it is inferred that molecular ovarian differentiation occurs at 40–60 dpf. In contrast, Sycp3 and Spo11 sharply increased from 60 to 90 dpf, with the first observation of secondary spermatocytes at 90 dpf, indicating that 60–90 dpf may be the key time window for molecular testicular differentiation. In general, it is hypothesized the fate of undifferentiated primordial gonads in C. maculata might be determined by the antagonistic action of the Sox11a–Dmrt1–Sox9b and Foxl2/Cyp19a1a pathways. Dashed arrows with direction indicate regulatory interactions between genes, and T-shaped arrows represent antagonistic relationships