FIGURE 1

FIGURE 1

Gonadal sex differentiation and oocyte staging in zebrafish. Adapted from Blokhina et al. (2021). At 13-days post fertilization (dpf) the gonad is considered bipotential (i.e., can develop as either a testis or an ovary) and is made up of pre-follicle and early follicle stages (referred to as stage IA and IB, respectively, based on staging in Selman et al., 1993) and includes cells in meiotic prophase I. Following Stage IA oocyte formation, testis transitioning occurs ∼20–30 dpf in roughly 50% of larvae. In this case, oocytes undergo apoptosis and spermatogenesis is initiated. In animals that differentiate as females, oocytes develop further, and Stage IA oocyte production continues through adulthood. (A) Hematoxylin and Eosin (H&E) stained section of 24 dpf gonad. Scale bar = 20 μm. (B) H&E section of adult ovary. Scale bar = 100 μm. (C) H&E section of adult testis. Scale bar = 20 μm.