Molecular phylogenetic analyses indicate multiple independent emergences of parasitism in Myzostomida (protostomia)
Molecular phylogenetic analyses indicate multiple independent emergences of parasitism in Myzostomida (protostomia)
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DOI：
10.1080/10635150500481317
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发表时间：
2006-04-01
影响因子：
6.5
通讯作者：
Eeckhaut, I
中科院分区：
文献类型：
--
作者：
Lanterbecq, D;Rouse, GW;Eeckhaut, I
化石记录表明，粘口目动物是一种神秘的海洋蠕虫类群，传统上被认为是环节动物，近 3.5 亿年来一直与棘皮动物，尤其是海百合表现出共生关系。所有已知的现存须口虫都与棘皮动物相关，并侵染其体皮、性腺、体乳或消化系统。利用来自代表 9 个属的 37 个须口虫物种的核 (18S rDNA) 和线粒体 (16S 和 COI) DNA 序列数据，我们在此报告了第一个须口虫的分子系统发育，并研究了它们各种共生关联的进化。我们的分析表明，长鼻目和咽目这两个目并不构成自然类群。性状重建分析强烈表明（1）所有现存的足口科动物的祖先都是一种外共生动物，它首先侵染海百合，然后是小行星和蛇尾类动物，（2）足口虫中的寄生现象独立出现多次。
The fossil record indicates that Myzostomida, an enigmatic group of marine worms, traditionally considered as annelids, have exhibited a symbiotic relationship with echinoderms, especially crinoids, for nearly 350 million years. All known extant myzostomids are associated with echinoderms and infest their integument, gonads, celom, or digestive system. Using nuclear (18S rDNA) and mitochondrial (16S and COI) DNA sequence data from 37 myzostomid species representing nine genera, we report here the first molecular phylogeny of the Myzostomida and investigate the evolution of their various symbiotic associations. Our analyses indicate that the two orders Proboscidea and Pharyngidea do not constitute natural groupings. Character reconstruction analyses strongly suggest that (1) the ancestor of all extant myzostomids was an ectocommensal that first infested crinoids, and then asteroids and ophiuroids, and (2) parasitism in myzostomids emerged multiple times independently.