MEPS 124:181-188 (1995)  -  doi:10.3354/meps124181

Allogeneic and xenogeneic interactions in reef-building corals may induce tissue growth without calcification

Frank U, Brickner I, Rinkevich B, Loya Y, Bak RPM, Achituv Y, Ilan M

Tissue growth without the deposition of calcium carbonate skeletons was recorded in 2 Red Sea hermatypic cnidarians during competitive interactions. Tissue contacts between allogeneic colonies of the hydrocoral Millepora dichotoma resulted in unilateral overgrowth. In 39% of the assays the overgrowing tissue did not secrete a skeleton for up to 10 wk. These tissues were loosely attached to the overgrown branch, and rapidly advanced by up to 25 mm within the first 2 wk. Thereafter, tissue growth slowed down or stopped and calcium carbonate was deposited over the subordinate branch, starting at the original contact area. In xenogeneic interactions between the scleractinian coral Cyphastrea chalcidicum and the cirriped barnacle Savignium dentatum, tissues of the coral always overlaid the plates of the barnacle without depositing calcium carbonate as long as the barnacles were alive (up to 5 yr). Calcium carbonate was deposited by the coral's tissue on the barnacle's plates only following barnacle death. In both cases, the non-calcifying overgrowing tissues lacked polyps but appeared normal in histological sections and contained typical cnidarian cells and endosymbiotic zooxanthellae. This type of tissue growth without calcification is a newly described allogeneic/xenogeneic response elicited by hermatypic cnidarians.


Coral . Cirripedia . Growth . Calcification . Competitive interactions . Histocompatibility


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