Intraspecific recognition system in scleractinian corals: morphological and cytochemical description of the autolysis mechanism.

Intraspecific aggressive interactions have been observed in the scleractinian coral Stylophora pistillata. Extensive field observations suggest that intraspecific interactions result in the formation of necrosis in one of the two competing colonies. The formation of necroses is primarily restricted to those layers that are interspersed with polyps. In a second phase the non-living, central corallum is destroyed by foreign microorganisms. In some cases the necroses are resealed again, either by a living septal layer or by a calcareous plug. Evidence is presented indicating that the enzyme carbonic anhydrase has a role in these activities. First, it is involved in the apical growth of the colony. Using a semiquantitative assay procedure, the highest enzyme level was determined in polyps at the tips of the branches; lower levels were measured in polyps of the foot/trunk region. Secondly, the enzyme was found to be induced in those areas that are in close contact with non-isogeneic tissue. From these data we conclude that carbonic anhydrase is involved in the process of autolytic digestion in response to intraspecific contact of two non-clonemates.