Effect of Steroids on Gonadal Growth and Gametogenesis in the Juvenile Red Sea Urchin Pseudocentrotus depressus.

Red sea urchins, 10 months old, were fed for 30 days on a casein-based diet containing progesterone, androstenedione, testosterone, estrone, or estradiol-17{beta}. The mean gonad indices of male animals in the androstenedione-and the estrone-treated groups were significantly higher than those in the control group, suggesting that these steroids promote gonadal growth in male animals. Histological observations indicated that spermatogenesis in the estrone-treated group was also promoted compared to that in the control group. In contrast, female urchins were not obviously affected by the steroid-treated diets, probably because yearling female P. depressus are not otherwise ready to carry out gametogenesis. We conclude that androstenedione, estrone, and possibly their derivatives, are involved in the reproduction of male P. depressus.