Synchronous mass spawning of Montastraea annularis (Ellis & Solander) and Montastraea faveolata (Ellis & Solander) (Faviidae : Scleractinia) at Rosario Islands, Caribbean Coast of Colombia

Montastraea annularis (Ellis & Solander, 1786) and Montastraea faveolata (E llis & Solander, 1786), two hermaphrodite broadcasting species, are among t he most important reef-building corals of the Caribbean. These species have recently been separated, but this separation has been questioned. Spawning of the two species was observed on the Caribbean coast of Colombia in 1997 , 6 and 7 d after the full moons from August to October in M. faveolata and September to October in M. annularis. During three different nights in whi ch mass spawning was observed, including the major event in September (appr oximately 90% of all colonies spawned), these species were synchronous and spawning started 2.5 h after sunset (40-50 min of time span). Additionally, the same spawning behavior was observed once on October 1998. Timing recor ds of 17 colonies in 1998, during the birth stage, indicate that M. annular is colonies spawned longer (20:40-21:45) than M. faveolata (20:46-21:20). P revious observations and our findings suggest that there is a great predict ability in the number of days after full moon and of hours after sunset (6- 8 4 2-4 h), which has been concordant in all the localities. The spawning l ength, whereas similar, has been variable (minutes to hours) among sites an d years. A latent potential for hybridization between M. annularis and M. f aveolata, as well as the variation in synchrony and time span, deserves add itional investigation.