Meeting Abstract
This project examines the fusion outcomes in the invasive colonial tunicate Didemnum vexillum to determine how genotypes may be shared between fusion partners in a chimeric colony. D. vexillum has extensively colonized hard substrate habitats and poses an ecological threat to native fouling communities in numerous locations including New Zealand, Europe, and both coasts of North America. Like many other colonial tunicate species, histocompatible D. vexillum colonies may undergo fusion following physical contact of the tunic. The outcome of allogenic fusion and the level of integration that occurs between zooids and tissues of different genotypes in D. vexillum is currently unknown. While the zooids of stolidobranch tunicate species such as Botryllus schlosseri are connected through a shared blood vascular system which enables free movement of cells throughout fused colonies, zooids in aplousobranch tunicates such as D. vexillum are connected only through the extrazooidal tunic. However, moderate levels of discrimination in the fusion interactions of D. vexillum colonies may indicate that there is some integration of cells beyond the fusion line in a chimeric colony. We tracked the movement of microsatellite alleles between fused D. vexillum colonies to determine the extent of genetic integration resulting from fusion. Alleles from one colony were found to be present in both colonies two weeks after fusion had occurred, and some fused colonies were found to have lost alleles that were present prior to fusion in one colony. In some instances, allelic movement was unidirectional while in other alleles were found to be exchanged reciprocally between colonies. These results indicate that cells are exchanged following allogenic fusion between D. vexillum colonies and that genotypes may be fluid in chimeric colonies.
