Specific Diseases

Coral Hyperplasms

Area of accelerated growth on the surface of a brain coral, Diploria strigosa, Puerto Rico. Photo by E. C. Peters
Appearance	Some corals, particularly brain corals, can have a roughly circular area in which the pattern of the ridges or corallites is distinctly different and usually enlarged, protruding somewhat above the surface of the colony and altering the pattern of the ridges or corallites adjacent to it so that it appears to be compressing the growing tissues. Microscopic examination of tissues from such an area revealed an increase in the number and size of cells and proliferation of all types of tissues. This type of growth has been termed a hyperplasm. It appears that such growths originate from a single budded polyp that undergoes localized, rapid growth, while retaining functional fusion of its tissues with those covering the normal colony skeleton (see Loya et al., 1984).
Area of accelerated growth on the surface of a brain coral, Diploria clivosa, Florida Keys. Photo by E. C. Peters
Appearance - continued	In Diploria clivosa, protruding areas of the skeleton and tissue have been found with what appears to be an abnormal distribution of symbiotic algae in the tissues, apparent as a darker brown color alternating with areas of lightened tissues on the ridges and valleys which might have lost the algae. This condition has only been observed in late spring in the Florida Keys. Subsequent examinations of the same corals later in the year showed no sign of the hyperplasms, which may have formed the basis of the knobs which give this species its common name, "knobby brain coral."
Cause	The cause(s) of hyperplasms in hard corals are unknown. Probably mutations of the genome and/or programmatic changes in gene expression of the coral cells are responsible for these skeletal anomalies, but whether a particular agent, such as ultraviolet radiation, is responsible for a particular mutation has not been determined. Additional studies are needed.
Distribution	Hyperplasms or areas of accelerated skeletal deposition have been observed in several species of corals from the Great Barrier Reef, Caribbean Sea, Hawaii, the Flower Garden Banks in the Gulf of Mexico, and the Florida Keys.
Impact	Hyperplasms do not seem to cause significant damage to the coral colony, but more study is needed on these skeletal anomalies.

Specific Diseases