SEXUAL AND ASEXUAL PRODUCTION OF PLANULAE IN REEF CORALS

Electrophoresis was used to provide genetic evidence of the mode of production of brooded planulae in each of four species of scleractinian coral collected from the central region of the Great Barrier Reef [Australia] during September, October and November 1984. Comparisons were made of the multi-locus genotypes of planulae and their broodparents for two ahermatypic (non zooxanthellate) species, Tubastraea diaphana and T. coccinea and two hermatypic (zooxanthellate) species, Acropora palifera and Seriatopora hystrix. For both ahermatypic species, all planulae were found to be genetically identical to their broodparents, including 91 planulae which were heterozygous for at least one locus. These results are consistent with asexual (ameiotic) reproduction. In contrast, non-parental genotypes were detected in the majority of hermatypic broods, which is consistent with expectations for sexual reproduction with at least some outcrossing. These data confirmed that brooded planulae may be produced both sexually and asexually and countered the suggestion that electrophoretic studies of hermatypic corals may be weakened by the contaminating effect of the enzymes of their symbiotic zooxanthellate.