INDUCED DEVELOPMENT OF SWEEPER TENTACLES ON THE REEF CORAL AGARICIA AGARICITES: A RESPONSE TO DIRECT COMPETITION

The scleractinian coral Agaricia agaricites often has elongate sweeper tentacles on colony margins close to other sessile animals. Sweeper tentacles can damage tissues of opponents and are probably used in direct competition for substrate space. Furthermore, contact with tissues or mesenterial filaments of other corals, or with tissues of the gorgonian Erythropodium caribaeorum or the zooanthid Palythoa caribbea can stimulate the development of sweeper tentacles by A. agaricites. Depending on both the particular competitor species involved and the distance separating it from A. agaricites, events leading to the development of sweeper tentacles may or may not include tissue loss by A. agaricites. On average the development of sweeper tentacles takes thirty days, and is localized exclusively on tissues close to the region in contact with competitors. Sweeper tentacles do not develop in response to artificial stimuli simulating tactile contact or damage such as occur in natural interactions with other corals. Thus, recognition of competitor tissues appears to be a necessary stimulus for sweeper formation.