REPRODUCTION AND CYCLE OF GONADAL DEVELOPMENT IN THE MEDITERRANEAN GORGONIAN PARAMURICEA-CLAVATA

Paramuricea clavata (Risso, 1826) is a typical gorgonian species of sublittoral communities found on rocky substrates in the Mediterranean Sea. The reproductive biology of this species was studied from 1990 to 1992 off the Medes Islands (northwestern Mediterranean). P. clavata is dioecious. The sex ratio was 1:1. Oogenesis lasted 13 and 18 mo, beginning between February and July and culminating in the release of 13 (SD = 2.2) mature eggs per polyp during the summer (June to July) of the following year. Maximum egg diameter varied between 400 and 500 mu m. Male gonads appeared in January and ripened in a much shorter time, 6 to 7 mo. Maximum spermary diameter ranged from 500 to 750 mu m. Male gonadal volume per polyp was larger than female gonadal volume. P. clavata is a perennial, iteroparous species. Reproduction was synchronous each year. Over the 3 yr study period spawning took place during 2 discrete week-long periods in June and July. Spawning occurred at the end of May coinciding with increasing water temperature and correlated with the lunar cycle wherein spawning also occurred 3 to 6 d after the full moon or the new moon. Spawned eggs adhered, through the action of a mucous coating, to the outer surfaces of the female colonies. Embryonic development in P. clavata was relatively uncommon. Embryogeny (total and equal cleavage) and final maturation of the planulae took place among the polyps. On leaving the surface of the colonies, larvae immediately settled on the surrounding substrate. Asexual reproduction was negligible and the maintenance of the population is based on sexual reproduction.