NONTRANSITIVE PATTERNS OF HISTORECOGNITION PHENOMENA IN THE RED-SEA HYDROCORAL MILLEPORA-DICHOTOMA

Allogeneic assays were conducted in situ on the Red Sea hydrocoral Mil lepora dichotoma. Forty-five pairwise combinations among ten colonies and ten control isografts were set up in four replicates each (180 and 40 pairs, respectively) and followed for up to 8 mo in the Gulf of Ei lat, Red Sea in 1992-1993. In 42 allogeneic combinations we recorded a reproducible and unilateral tissue and skeleton overgrowth which deve loped within the first 10 wk up to 20 mm. Following the development of these primary overgrowths, four types of secondary responses were obs erved among most incompatible combinations: reversals in overgrowth di rectionality, tissue necroses, stand-offs and abnormal growth patterns . Secondary responses within a given set of replicates of most allogen eic combinations were characterized by high variability in type and in tensity of response. Based on the outcomes of primary overgrowths, a c omplex nontransitive hierarchy was constructed for the ten colonies. A ll isografts and three allogeneic combinations fused within 3 wk. Fusi on pattern between the three allogeneic combinations was nontransitive : one M. dichotoma colony repeatedly fused with two other colonies (fo ur assays each). However, these two colonies not only did not fuse wit h each other, but one of them repeatedly overgrew its confrere. In the third compatible combination, the most superior and the most inferior colonies in the network of hierarchies among the ten colonies, fused in all tested assays. These results are compared with allogeneic outco mes in other cnidarians, where nontransitive fusion between allogeneic colonies have never been recorded.