Reproduction of the tropic al corallim orpharian Rhodactis ( = Oiscosoma) indosinensis Carlgren 1943, was studied for two years (1988-1990) in shallow waters off Wanglitung, southern Taiwan. Rhodactis indosinensis occurred gregariously, and formed three large aggregations in the study site. R. indosinensis is gonochoristic. Oogenesis takes about nine months, while spermatogenes is three months. Mature eggs are large (maximum diameter 850 µm). Both sperm and eggs matured in May and spawning occurred between May and June. Three modes of asexual reproduction, i.e., longitudinal fission, inverse budding, and two-mouth fission, were recorded; the latter two have not been reported previously for anthozoans. Longitudinal fission is the dominant mode and occurs with high frequency durin g summer in polyps greater than 50 mm in oral disc diameter. Inverse budding is the second most common mode, occu ring in the period between winter and spring in polyps from 30 to 60 mm in oral disc diameter. Twomouth fission occurs only occasionally. Asexual reproduction occurred earlier in the aggregation located near the shore , and the frequency of asexual reproduction was higher when water temperature increased, suggesting that environ mental factors (e.g., temperature) affect the onset of asexual reprodu ction in R. indosinensis.
Reproductive periodicity, Gametogenesis
