Fig. 1

Histological analysis of characteristic gonadal stages in tilapia ovary (XX) and testsis (XY). Panels indicate gonads sampled from fish at different days after hatch (dah) as follows: a and b at 5 dah, c and d at 20 dah, e and f at 30 dah, g and h at 40 dah, i and j at 90 dah, and k and l at 180 dah. OG, oogonia; SG, spermatogonia; OC, oocytes; CV, ovarian cavity; ST, spermatids; SC, spermatocytes