This project is a renewal of prior supported work and it will work on the structural characterization of the complex (polymeric) natural inducer of larval settlement of the common Caribbean coral, Agaricia humilis on the surfaces of the crustose coralline red alga, Hydrolithon boergesenii . The extent to which larval recognition of this purified natural inducer (when attached to artificial substrata and deployed in the ocean) contributes to the substratum-specific settlement and metamorphosis of A.humilis larvae in the natural coral reef environment will be determined. Antibodies to the purified inducer will be used, in high-resolution immunocytochemical studies, to determine whether the inducer is produced by the crustose coralline red algal itself, or by its associated microbial epibionts. The significance of this project lies in the fact that it will provide the first complete structural elucidation of a complex, polymeric natural inducer of larval settlement and metamorphosis; the first experimental test of the hypothesis that larval recognition of a defined natural inducing molecule is responsible, in part, for substratum-specific settlement and larval metamorphosis in the natural environment; and the first definitive resolution of the source of such a natural inducer. This study thus will provide the necessary information for later ecological investigations of the hypothesis that changes in larval substratum (chemical) recognition may provide an important axis for the rapid evolution of niche diversification mechanisms and, ultimately, speciation in coral reef and other benthic marine organisms.
