Fig. 5
Gonad development at 25 dpf in the control (cyp19a1a+/−; fish A–F) and mutant (cyp19a1a−/−; fish G–L). The GFP intensity in the gonads (boxed in the photo) started to diverge in the control (A–C vs. D–F) but not the mutant fish (G–L), suggesting the start of gonadal differentiation. Two groups of fish could be distinguished by histological analysis. One group had well-developed EPOs (asterisks) in the gonads (fish A–C) in the control and (G–I) in the mutant) and the other contained mostly undifferentiated germ cells (fish D–F) in the control and (J–L) in the mutant. The EPOs in the control fish (A–C) were generally larger with stronger GFP signal than those in the mutant fish (G–I). Numerous meiotic germ cells (arrowheads) were present in the gonads of both control and mutant fish. The dark-stained condensed apoptotic germ cells (arrows) were often observed at this stage, indicating the process of juvenile ovary-testis transformation.