The anemone-crab mutualism is ubiquitous in temperate and tropical marine environments. In this symbiosis, one or more anemones live on a shell inhabited by a hermit crab and reciprocal phoretic, trophic, and defensive benefits are exchanged between the partners. Sea anemone-hermit crab symbionts belong to three families: Hormathiidae (Calliactis and Paracalliactis), Sagartiidae (Carcinactis and Verrillactis), and Actiniidae (Stylobates). Hermit crabs establish most partnerships by detaching anemones and placing them on their shell; sea anemones can also mount shells unaided, triggered by a mollusc-derived substance in the periostracum of the shell. At least partial cooperation by the anemones is necessary for successful establishment of the symbiosis. Here, we expand the evolutionary framework for hormathiid symbionts by generating a phylogeny with at least one member of each actiniarian symbiotic genus with hermit crabs using five molecular markers (16S, 12S, 18S, 28S, CO3). We not only corroborated the results from a previous study by finding two origins of hermit crab symbiosis within Hormathiidae, but also found additional origins for hermit crab symbiosis within Actiniaria. We provide for the first time evidence of a close relationship between symbionts Carcinactis dolosa and V. paguri. The ability to secrete chitin by the ectoderm of the column is inferred to be broadly convergent within Actiniaria whereas the secretion of a chitinous carcinoecium by the pedal disc is a distinct but convergent morphological adaptation of several lineages within Actiniaria. Our finding of multiple origins for both the hermit crab and gastropod symbioses suggests that the shell-mounting behavior might only have been the precursor of the hermit crab association among Calliactis spp.

中文翻译：

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海葵（Cnidaria，Anthozoa，Actiniaria）和寄居蟹之间的共生关系的起源和演变，另外还有关于海葵-腹足动物协会的注释。

在温带和热带海洋环境中，海葵-蟹的共生普遍存在。在这种共生中，一个或多个海葵生活在寄居蟹居住的贝壳上，伙伴之间交换了相互的隐喻，营养和防御优势。海葵寄居蟹共生体属于三个科：:科（Calliactis和Paracalliactis），Sa蛾科（Sagartiidae）（Carcinactis和Verrillactis）和猕猴桃（Actiniidae）（Stylobates）。寄居蟹通过分离海葵并将它们放在壳上来建立大多数的伙伴关系。海葵还可以在软体动物的壳骨膜中由软体动物来源的物质触发而独立安装贝壳。成功建立共生关系，海葵至少需要部分合作。这里，我们使用五个分子标记（16S，12S，18S，28S，CO3），通过与寄居蟹的每个猕猴桃共生属的至少一个成员进行系统发育，从而扩展了类群共生动物的进化框架。我们不仅通过发现Hormathiidae内两个寄居蟹共生的起源来证实先前研究的结果，而且还发现了Actiniaria内寄居蟹共生的其他起源。我们首次提供了共生性杜鹃与V. paguri之间密切关系的证据。可以推断该柱的外胚层分泌甲壳质的能力在猕猴桃内广泛收敛，而踏板盘分泌几丁质鳞癌是对猕猴桃内多个谱系的独特但趋同的形态适应。