Allogeneic cellular reactions between intra-specific types of a solitary ascidian, Halocynthia roretzi.

Coelomic cells from a solitary ascidian, Halocynthia roretzi, exibit a nonphagocytic cellular reaction against coelomocytes from different species and another individuals of the same species. The reaction was denoted contact reaction. While xenogeneic contact reactions were always observed, allogeneic reactions were observed in most but not all combinations of individuals. Three variant types of H. roretzi (Type A, B, C) inhabit the coast of northern Japan. They are reproductively isolated under natural conditions. Non-reactive combinations exist between the different types, in all possible combinations. The paterns and frequencies of reactivities between different variants are almost the same to those observed within a single type. The results of the alloreactivity suggest that the three types of H. roretzi became separate from each other very recently and still remain intra-specific variants.