Tumor formation on the coral Montipora informis

A high incidence of tumors (i.e., abnormal skeletal growth) was observed on Montipora informis Bernard, 1897 (Acroporidae) coral colonies on the shall ow reef flat of Sesoko Island, Okinawa, Japan. Tumors were recognized as sl ightly hemispherical protuberances and were characterized by fewer numbers of polyps per surface area, fewer zooxanthellae per polyp, and finer skelet al structures than normal. In addition, fecundity was significantly reduced in tumored areas. Tumor formation appeared localized, stable and non-epide mic. During the summer of 1998, coincident with the global coral bleaching event, tumored tissue suffered higher mortality than normal tissue. The mec hanism triggering tumor formation remains unknown.