AIMS@JCU, James Cook University, Douglas Campus, Townsville, Queensland 4810, Australia.
Proc Biol Sci. 2012 Feb 22;279(1729):699-708. doi: 10.1098/rspb.2011.1035. Epub 2011 Jul 13.
In sessile modular marine invertebrates, chimeras can originate from fusions of closely settling larvae or of colonies that come into contact through growth or movement. While it has been shown that juveniles of brooding corals fuse under experimental conditions, chimera formation in broadcast spawning corals, the most abundant group of reef corals, has not been examined. This study explores the capacity of the broadcast spawning coral Acropora millepora to form chimeras under experimental conditions and to persist as chimeras in the field. Under experimental conditions, 1.5-fold more larvae settled in aggregations than solitarily, and analyses of nine microsatellite loci revealed that 50 per cent of juveniles tested harboured different genotypes within the same colony. Significantly, some chimeric colonies persisted for 23 months post-settlement, when the study ended. Genotypes within persisting chimeric colonies all showed a high level of relatedness, whereas rejecting colonies displayed variable levels of relatedness. The nearly threefold greater sizes of chimeras compared with solitary juveniles, from settlement through to at least three months, suggest that chimerism is likely to be an important strategy for maximizing survival of vulnerable early life-history stages of corals, although longer-term studies are required to more fully explore the potential benefits of chimerism.
在固着模块化海洋无脊椎动物中，嵌合体可以由紧密聚集的幼虫融合而成，也可以由通过生长或移动接触的群体融合而成。虽然已经证明在实验条件下，孵育珊瑚的幼虫会融合，但尚未研究在广泛繁殖的珊瑚（即最丰富的珊瑚群体）中形成嵌合体的情况。本研究探索了广泛繁殖的珊瑚 Acropora millepora 在实验条件下形成嵌合体的能力，以及在野外作为嵌合体持续存在的能力。在实验条件下，聚集的幼虫比单独的幼虫多聚集了 1.5 倍，对九个微卫星基因座的分析表明，测试的 50%的幼体在同一个群体中具有不同的基因型。重要的是，一些嵌合群体在研究结束时即 23 个月后仍然存在。在持续存在的嵌合群体中的基因型都表现出高度的亲缘关系，而排斥的群体则表现出不同程度的亲缘关系。与单独的幼体相比，嵌合体的大小至少增加了两倍，从定居到至少三个月，这表明嵌合可能是珊瑚脆弱的早期生活史阶段最大限度提高生存能力的重要策略，尽管需要进行更长时间的研究才能更充分地探索嵌合的潜在益处。
