Identification of chaetognaths as protostomes is supported by the analysis of their mitochondrial genome
Identification of chaetognaths as protostomes is supported by the analysis of their mitochondrial genome
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DOI：
10.1093/molbev/msh229
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发表时间：
2004-11-01
影响因子：
10.7
通讯作者：
Le Parco, Y
中科院分区：
文献类型：
--
作者：
Papillon, D;Perez, Y;Le Parco, Y
确定神秘的门，如毛颚类的系统发育位置是生物学家长期面临的挑战。毛颚类（或箭虫）是一种小型的、两侧对称的后生动物。在过去的几十年里，它们在后生动物中的关系一直受到强烈的争论，因为胚胎学和形态学特征与两个主要的分支共有：后口动物和原口动物。尽管最近的尝试基于分子数据，毛颚类的亲和力尚未令人信服地定义。为了回答这个基本问题，我们确定了完整的线粒体DNA基因组Spadella cephaloptera。我们报告了三个独特的特征：它是已知的最小的后生动物线粒体基因组，缺乏atp8和atp6以及所有的tRNA基因。此外，系统发育重建表明，毛颚类属于原口类。这意味着一些胚胎学特征观察毛颚类，如肠道与口不产生于囊胚孔（deuterostomy）和中胚层来源于原肠（肠腔），可能是祖先的特征（plesiomorphies）的bilaterians。
Determining the phylogenetic position of enigmatic phyla such as Chaetognatha is a longstanding challenge for biologists. Chaetognaths (or arrow worms) are small, bilaterally symmetrical metazoans. In the past decades, their relationships within the metazoans have been strongly debated because of embryological and morphological features shared with the two main branches of Bilateria: the deuterostomes and protostomes. Despite recent attempts based on molecular data, the Chaetognatha affinities have not yet been convincingly defined. To answer this fundamental question, we determined the complete mitochondrial DNA genome of Spadella cephaloptera. We report three unique features: it is the smallest metazoan mitochondrial genome known and lacks both atp8 and atp6 and all tRNA genes. Furthermore phylogenetic reconstructions show that Chaetognatha belongs to protostomes. This implies that some embryological characters observed in chaetognaths, such as a gut with a mouth not arising from blastopore (deuterostomy) and a mesoderm derived from archenteron (enterocoely), could be ancestral features (plesiomorphies) of bilaterians.