STUDIES ON REPRODUCTION IN THE HERMAPHRODITIC SEA STAR, ASTERINA MINOR: THE FUNCTIONAL MALE GONADS, "OVOTESTES."

¹ Department of Biology, Tokyo Women's Medical College, 10 Kawada-cho, Shinjuku-ku, Tokyo 162, Japan

Development of gonads in the sea star, Asterina minor Hayashi was studied by light microscopy. In adults, two series of gonads are found in one interradial area. Each series consists of an ovary, supernumerary ovaries, and ovotestes with a regular alignment to the margin. In breeding season, the ovotestes have sperm and some small basophilic oocytes. After releasing sperm, the ovotestes are much reduced in size, but the small oocytes remain. After spawning, as no rapid increase of testicular tissue occurs, these gonads resemble supernumerary ovaries. In addition to the previously existing series of gonads, a few new ovotestes are formed in more marginal positions annually. During and after the spawning period, the germinal cells in the genital rachis increase in number, differentiate into ovotestes, and form a gonoduct and gonopore of their own.

Hermaphrodism in this species is maintained by the annual formation and maturation of ovotestes and by the annual maturation of oocytes in ovaries (cf. Fig. 1).