Histological characteristics of gonadal development of Holothuria scabra from Hainan Island

The characteristics of gonadal development of Holothuria scabra from Hainan Island were investigated by histological obser- vation. Results show that gonadal development of H. scabra from Hainan Island were divided into five stages: recovery stage (Ⅰ) , growing stage (Ⅱ) , mature stage (Ⅲ) , partly spawned stage (Ⅳ) and spent stage (Ⅴ) . The characteristics of testis development are as follows: at StageⅠ, a few spermatogonias and spermatocytes started to grow along the germinal epithelium and the germ tube wall was the thickest. At Stage Ⅱ, the germinal epithelium became thinner and the longitudinal folds extended into the lumen. At Stage Ⅲ, lumens packed densely with mature spermatozoas, while at Stage Ⅳ, the germinal epithelium recovered into the original folding morphology. At StageⅤ, a few of relic spermatozoa remained in the lumen. The characteristics of ovary development are as follows: at StageⅠ, oogonias and previtellogenic oocytes started to grow along the germinal epithelium. At Stage Ⅱ, central lumen contained numbers of vitellogenic oocytes, surrounded by oogonias and previtellogenic oocytes. At StageⅢ, the lumen densely packed with vitellogenic oocytes. At Stage Ⅳ, the previtellogenic oocytes re-presented in germinal epithelium, and some nutritional phago-