SEXUAL AND ASEXUAL REPRODUCTION OF THE TROPICAL CORALLIMORPHARIAN RHODACTIS (=DISCOSOMA) INDOSINENSIS (CNIDARIA, CARALLIMORPHARIA) IN TAIWAN

Sexual and asexual reproduction of the tropical corallimorpharian Rhod actis (=Discosoma) indosinensis (Cnidaria: Corallimorpharia) in Taiwan . Zoological Studies 34(1): 29-40. Reproduction of the tropical corall imorpharian Rhodactis (=Discosoma) indosinensis Carlgren 1943, was stu died for two years (1988-1990) in shallow waters off Wanglitung, south ern Taiwan. Rhodactis indosinensis occurred gregariously, and formed t hree large aggregations in the study site. R. indosinensis is gonochor istic. Oogenesis takes about nine months, white spermatogenesis three months. Mature eggs are large (maximum diameter 850 mu m). Both sperm and eggs matured in May and spawning occurred between May and June. Th ree modes of asexual reproduction, i.e., longitudinal fission, inverse budding, and two-mouth fission, were recorded; the latter two have no t been reported previously for anthozoans. Longitudinal fission is the dominant mode and occurs with high frequency during summer in polyps greater than 50 mm in oral disc diameter. Inverse budding is the secon d most common mode, occuring in the period between winter and spring i n polyps from 30 to 60 mm in oral disc diameter. Two-mouth fission occ urs only occasionally. Asexual reproduction occurred earlier in the ag gregation located near the shore, and the frequency of asexual reprodu ction was higher when water temperature increased, suggesting that env ironmental factors (e.g., temperature) affect the onset of asexual rep roduction in R. indosinensis.