Fusion to form a chimera has been documented in many marine invertebrate taxa, including poriferans, cnidarians, bryozoans, and colonial ascidians. Allogenic interactions in chimeric ascidian colonies vary widely across taxonomic groups but are poorly characterized in the invasive colonial ascidian Didemnum vexillum. The moderate level of discrimination expressed in the fusion–rejection response of D. vexillum suggests that there is some integration of cells beyond the fusion line in a chimeric colony. We tracked the shifts in representation of microsatellite alleles between fused colonies of D. vexillum to elucidate the extent of genotypic integration in fused colonies and the patterns of changes to the genotypic composition of colonies immediately following chimera formation. By genotyping colonies before and after fusion, we found that allogeneic fusion in D. vexillum may lead to genotypic changes beyond the visible fusion line. Alleles from one colony were found in multiple tissue samples in the chimera 7–10 days after fusion had occurred. In some instances, alleles that were in a single colony prior to fusion were lost following fusion. We observed multiple patterns of allelic change, including both the unidirectional transfer and reciprocal exchange of alleles between fused colonies. Our findings suggest that tissue or cells are exchanged following allogeneic fusion between colonies of D. vexillum and that the genotypic composition of chimeric colonies may be fluid.

中文翻译：

---

侵入性结肠被膜Dedemnum vexillum融合后的基因型变异

融合形成嵌合体已经在许多海洋无脊椎动物类群中得到了记录，包括poriferans，cnidarians，bryozoans和colonish ascidians。嵌合类海鞘菌落中的同种异体相互作用在不同分类组之间差异很大，但在侵袭性殖民地海藻Didemnum vexillillum中表征较差。在维氏假单胞菌的融合-排斥反应中表达的中等程度的区分表明，在嵌合菌落中，融合线以外的细胞有些整合。我们追踪了D. vexillum融合菌落之间微卫星等位基因的表达变化阐明融合菌落中基因型整合的程度，以及嵌合体形成后菌落的基因型组成变化的模式。通过对融合前后的菌落进行基因分型，我们发现维氏假单胞菌中的同种异体融合可能导致超出可见融合线的基因型变化。融合发生后7-10天，在嵌合体的多个组织样本中发现了一个菌落的等位基因。在一些情况下，融合前在单个菌落中的等位基因在融合后丢失。我们观察到等位基因变化的多种模式，包括融合菌落之间等位基因的单向转移和相互交换。我们的发现表明，组织或细胞在同种异体的菌落之间发生异质融合后发生交换。D. vexillum和嵌合菌落的基因型组成可能是流体。