AN ANCIENT CHEMOSENSORY MECHANISM BRINGS NEW LIFE TO CORAL-REEFS

The first scleractinians, progenitors of modern corals, began to appea r 240 million years ago; by the late Jurassic (150 Ma) most families o f modern corals had evolved and begun forming reefs (1, 2). Mechanisms controlling the recruitment of new corals to sustain these structures are, however, poorly understood (3). Corals, like many marine inverte brates, begin life as soft-bodied larvae that are dispersed in the pla nkton (3, 4). As the first step in developing a calcified coral colony , the larva must settle out of the plankton onto a suitable substratum and metamorphose to the single calcified polyp stage cemented to the reef (3, 5). Our analyses of the metamorphic requirements of larvae in divergent coral families surprised us by revealing the existence of a common chemosensory mechanism that is required to bring larvae out of the plankton and onto the reef. This mechanism appears to be quite ol d, predating both the phylogenetic divergence of these coral families and the development of different modes of coral reproduction.