Self-discrimination in colonial invertebrates: genetic control of allorecognition in the hydroid Hydractinia.

Sessile, colonial invertebrates display the ability to distinguish between their own tissues and those of unrelated members of the same species. These allorecognition responses play a fundamental role in maintaining the genetic and physiological integrity of the colony. While allorecognition responses have been observed in all major colonial invertebrate taxa, the genetics of the response has been addressed only in the ascidian Botryllus and, more recently, in the hydroid Hydractinia. In Botryllus, allorecognition is controlled by a single co-dominant locus. This review focuses on current developments on the genetics of allorecognition in Hydractinia.