Coral Reef Project—Papers in Memory of Dr. Thomas F. Goreau. 11.

Interspecific Aggression by Scleractinian Corals. 2. Why the Race is Not Only to the Swift

Species specific aggressive interactions have been found among West Indian and Indo-Pacific scleractinian corals. When the polyps of different corals touch each other, the species which are "stronger" aggressors extrude mesenterial filaments over their "less aggressive" neighbors, dissolving those tissues within reach by extracoelenteric forms of digestion. Interspecific aggression by corals may occur under natural or experimental conditions. For any population, the interactions of different species have a definite and consistent hierarchical structure.

Most highly aggressive species belong to the suborder Faviina, have massive or encrusting growth forms, construct relatively small coralla, and are usually minor components of coral reef communities. They use aggressive interactions as a defense against overgrowth by the more rapidly expanding ramose and foliose corals, and to clear space for their own growth. Some faviids are moderately strong aggressors which construct primary reef framework in many West Indian habitats. Ramose and encrusting corals of the family Acroporidae, which occupy an intermediate position in the aggression hierarchy, also construct reef framework; interspecific aggression is common in mixed acroporid reefs. Weak aggressors include the foliose agariciids, which may form the predominant cover in deep reef zones.