Self or Non—self Recognition in Compound Ascidians

SYNOPSIS. Certain species of compound ascidians have an ability to distinguish self colonies from non—self colonies within the same species. This ability, called colony specificity, is manifested by the fusibility between colonies. The fusibility among colonies of Japanese Botryllus is genetically controlled by a series of multiple alleles at a single locus. The fusibility is determined by a factor(s) in blood, so that the fusibility can be altered by the exchange of blood. It is suggested that rejection, called “nonfusion” reaction, may occur from the interaction between blood cells and blood humoral factor(s).