The Consequences of Complex Larval Behavior in a Coral

The leaf coral Agaricia humilis occurs mainly on the undersides of surfaces in shallow water, a distribution different from the vast majority of corals at our study site in Bonaire, Netherlands Antilles. A series of hypotheses were tested for specific mechanisms that could cause the observed distributions of Agaricia humilis. We found that a suite of larval swimming and settling behaviors, in large part, drives the adult distribution of the species. These behaviors include: (1) swimming behavior that causes larvae to position themselves in shallow water, (2) orientation behavior during settlement that causes larvae to preferentially settle on the undersides of surfaces, and (3) settlement behavior where chemosensory recognition of morphogenic molecules associated with the cell walls of specific crustose red algae is required for induction of settlement and metamorphosis. The consequences of atypical larval behavior are severe and include decreased survivorship, growth, and ability to reproduce sexually.