EFFECTS OF DITERPENES DERIVED FROM THE SOFT CORAL SINULARIA-FLEXIBILIS ON THE EGGS, SPERM AND EMBRYOS OF THE SCLERACTINIAN CORALS MONTIPORA-DIGITATA AND ACROPORA-TENUIS

Sinularia flexibilis Quoy and Gaimard, 1833 is a dominant soft coral o n many Indo-Pacific coral reefs, and has been found to release toxic c ompounds (diterpenes), which cause tissue necrosis and death in nearby scleractinian corals. This study investigates how S. flexibilis-deriv ed diterpenes inhibit the development of Acropora tenuis Dana, 1846 an d Montipora digitata Dana, 1846 eggs and larvae in vitro. Collection a nd experimental sites at Magnetic (146 degrees 49'E; 19 degrees 8'S) a nd Orpheus (146 degrees 28'E; 18 degrees 32'S) Islands, Queensland, Au stralia, were utilized during the spawning seasons of 1989-1992. Fresh ly spawned coral eggs were placed in solutions of three different terp enes, flexibilide, dihydroflexibilide and sinulariolide, at 5 and 10 p pm, before, during, and after fertilisation. The majority of eggs whic h were fertilised in the presence of the diterpenes lost their cellula r integrity and burst just a few hours after treatment. Terpenes were not toxic to unfertilised eggs, nor to 24 h-old embryos, although sper m ceased swimming activity after 1 h of treatment. The terpenes were n ot fatal to the sperm because fertilisation still occurred in their pr esence. The ability of the soft coral-derived diterpenes to inhibit ce ll division suggests that they may have potential applications in canc er chemotherapy.