Sexual reproduction and external brooding by the Caribbean gorgonian Briareum asbestinum

The reproductive biology of the gonochoric Briareum asbestinum (Pallas), a common Caribbean gorgonian, was studied in the San Blas Islands (Panama), La Paguera (Puerto Rico) and the Bahamas. Of 721 colonies examined at the height of the reproductive season, during the summers of 1985 to 1988, all were either male or female. No hermaphroditic colonies or polyps were observed. The sexratio of Panama populations was significantly biased in favor of males (2.1:1, n=454) over all four years of the study. A significant male bias was also found in populations sampled in Puerto Rico (2.3:1, n=143) and in the Bahamas (2.5:1, n=124). The consistency of this geographically widespread skewed sex-ratio is unique among octocorals and scleractinians. Ooyctes appear annually in September and reach maximum diameter (600 to 900 μm) in June and July of the following year. The 3 to 5 mo developmental cycle of spermaries is shorter than that of females and begins in March. Spawning in males is synchronous and occurs following the full moons of June and July. Fertilization is internal. Embryos are released from polyps very early in development, often whilst still in the process of cleaving. Embryos remain attached to the outside of the colony for 3 to 5 d, many becoming entrapped in mucous sheets secreted by the colonies. Larvae are negatively buoyant and settle rapidly once displaced from the colony. Males become reproductive at smaller branch sizes than females. Reproductive effort (gonads polyp^-1 and total gonad volume polyp^-1) for both males and females increased with increasing branch size and in polyps away from the tip and base of the branch.