Cleavage in Nemertoderma westbladi (Nemertodermatida) and its phylogenetic significance
Cleavage in Nemertoderma westbladi (Nemertodermatida) and its phylogenetic significance
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DOI：
10.1007/s00435-004-0105-8
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发表时间：
2004-11-01
期刊：
影响因子：
1
通讯作者：
Raikova, O
中科院分区：
文献类型：
--
作者：
Jondelius, U;Larsson, K;Raikova, O
最近的核糖体和蛋白质编码核基因的系统发育分析将海洋蠕虫置于纽皮动物门中，作为两侧动物中最古老的谱系之一。为首次报道纽皮虫的早期发育过程，我们对韦斯特布氏纽皮虫的早期胚胎卵裂进行了研究。用干涉显微镜研究活胚胎，用共聚焦激光扫描显微镜切片或研究固定的胚胎。最初，胚胎的分裂是放射状的，但随后，微粒体顺时针移动，产生螺旋图案。四细胞阶段的特点是由大单体和小单体的二重奏，因此类似于从Acoela成员报道的二重奏分裂。然而，随后的阶段不同于acoel二重奏模式，也不同于四重螺旋卵裂。本文还讨论了对目前以纽皮动物门和无腔动物门为早期两侧分支的系统发育假说的最优化的卵裂模式。
Recent phylogenetic analyses of ribosomal and protein coding nuclear genes place the marine worms within the Nemertodermatida as one of the oldest lineages among the bilaterian animals. We studied the early embryonic cleavage in Nemertoderma westbladi to provide the first account of nemertodermatid early development. Live embryos were studied with interference microscopy and fixed embryos were either sectioned or studied with confocal laser scanning microscopy. Initially the divisions in the embryo are radial, but then micromeres are shifted clockwise generating a spiral pattern. The four-cell stage is characterized by duets of macromeres and micromeres and thus resembles the duet cleavage reported from members of the Acoela. However, subsequent stages differ from the acoel duet pattern and also from quartet spiral cleavage. The optimization of the cleavage pattern on current phylogenetic hypotheses with Nemertodermatida and Acoela as early bilaterian branches is discussed.