THE ANNUAL REPRODUCTIVE-CYCLE AND LUNAR S PAWNING RHYTHMS OF THE PURPLE SEA-URCHIN ANTHOCIDARIS-CRASSISPINA

The annual reproductive cycle and lunar spawning rhythms in the spawni ng season of the purple sea urchin A. crassispina, which lives in Mera Bay of South Izu in Shizuoka, were examined by the successive change of the gonad index and histological observation of the gonad. The foll owing is the annual reproductive cycle of the purple sea urchin; the g onad become to develop from January to May, the spawning season to be from June to August, and the gonadal growing action to degenerate from September to December. Moreover, it was suggested that this cycle is closely related to the annual change of the sea water temperature. As the population of this species spawned several times every full moon p eriod in the spawning season, they were thought to have lunar spawning rhythm that spawns once each the lunar period. It was suggested that the gonad in the spawning season could recover for the next spawning i n about a week.