Figure 1

Differentiating gonad of Atlantic cod, presumptive female. Transverse plastic section (2 μm) stained with Toluidine blue/Borax solution. a) and a’) formation of an ovarian cavity in a 16 mm TL juvenile. a): scale bar represents 100 μm; a’): scale bar represents 15 μm); b) gonad with an ovarian cavity in a 18 mm TL juvenile; c) ovary in a 30 mm TL juvenile. SB – swim bladder; In – intestine; BW – body wall; gc – germ cell. The stippled line identifies the ventral part of the swimming bladder in a). Arrows indicate primordial germ cells; arrowheads in c) indicate mitotic figures.