Evidence for a clade composed of molluscs with serially repeated structures:: Monoplacophorans are related to chitons
Evidence for a clade composed of molluscs with serially repeated structures:: Monoplacophorans are related to chitons
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DOI：
10.1073/pnas.0602578103
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发表时间：
2006-05-16
影响因子：
11.1
通讯作者：
Nishiguchi, Michele K.
中科院分区：
文献类型：
--
作者：
Giribet, Gonzalo;Okusu, Akiko;Nishiguchi, Michele K.
单placophorans是软体动物门中最稀有的成员之一。在著名的第二次加拉西亚深海探险中，人们发现了第一只活着的单placophoran，这是自寒武纪以来人们只从化石中知道的。这些软体动物的解剖结构震惊了动物界，因为它们有连续重复的鳃、肾和八组背腹侧的足部牵张肌。在被认为是独立的软体动物谱系中，如石鳖和深海单placophorans的器官序列被认为是祖先软体动物分割的遗留物，并被普遍接受为支持与环节动物的直接关系。我们获得了一种南极深海单placophoran物种的标本，用于分子研究。第一批关于单placophora的分子数据，与迄今为止收集的最大的软体动物数据集一起分析，清楚地表明单placophora和石鳖形成了一个分支。这种“序列”概念可能会彻底改变软体动物的系统学，并可能对后生动物的进化产生重要影响，因为它允许对软体动物的原始分割进行新的解释。
Monoplacophorans are among the rarest members of the phylum Mollusca. Previously only known from fossils since the Cambrian, the first living monoplacophoran was discovered during the famous second Galathea deep-sea expedition. The anatomy of these molluscs shocked the zoological community for presenting serially repeated gills, nephridia, and eight sets of dorsoventral pedal retractor muscles. Seriality of organs in supposedly independent molluscan lineages, i.e., in chitons and the deep-sea living fossil monoplacophorans, was assumed to be a relict of ancestral molluscan segmentation and was commonly accepted to support a direct relationship with annelids. We were able to obtain one specimen of a monoplacophoran Antarctic deep-sea species for molecular study. The first molecular data on monoplacophorans, analyzed together with the largest data set of molluscs ever assembled, clearly illustrate that monoplacophorans and chitons form a clade. This "Serialia" concept may revolutionize molluscan systematics and may have important implications for metazoan evolution as it allows for new interpretations for primitive segmentation in molluscs.