ASPECTS OF HISTOCOMPATIBILITY AND REGENERATION IN THE SOLITARY REEF CORAL FUNGIA-SCUTARIA

Discoid coralla of the solitary free-living reef coral Fungia scutaria were cut with a rock saw and rejoined in various paired combinations and orientations of autogeneic sections (self to self), isogeneic sect ions (clone-mate to clone-mate), and allogeneic sections (two differen t genotypes). Results of these experiments provide the first evidence of histocompatibility in a solitary coral. Autogeneic or isogeneic sec tions of coralla with one section containing a mouth were joined along cut edges. In all cases, fusion of tissues occurred within weeks, fol lowed by skeletal fusion within months. However, autogeneic or isogene ic sections rejoined along the uncut edges did not fuse. Isogeneic pai rings between two sections with mouths produced neither tissue/skeleta l fusion nor cytotoxicity at the interface. Individual cut sections we re allowed to regenerate. Sections containing the parent mouth did not develop new mouths. However, cut sections lacking a mouth always rege nerated multiple mouths along the cut edge, but not along the uncut ed ge. Sections without mouths cut along a second line parallel to the fi rst cut always regenerated mouths along the cut edge located closest t o what had been the mouth area of the original corallum. The new mouth s eventually developed into individual polyps.