Molecular phylogeny and ultrastructure of Selenidium serpulae (Apicomplexa, Archigregarinia) from the calcareous tubeworm Serpula vermicularis (Annelida, Polychaeta, Sabellida)
Molecular phylogeny and ultrastructure of Selenidium serpulae (Apicomplexa, Archigregarinia) from the calcareous tubeworm Serpula vermicularis (Annelida, Polychaeta, Sabellida)
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DOI：
10.1111/j.1463-6409.2007.00272.x
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发表时间：
2007-03-01
影响因子：
2.5
通讯作者：
Leander, Brian S.
中科院分区：
文献类型：
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作者：
Leander, Brian S.
古蠕虫是动态的单细胞寄生虫，栖息在海洋无脊椎动物的肠道系统中，特别是悬浮摄食和沉积摄食的多毛类动物。硒属中的某些古生物保留了一些拟形特征，并且对这些物种的了解的提高预计将为了解顶复门进化的最早阶段提供相当多的线索。尽管古蠕虫与一些已知的最臭名昭著的寄生虫（例如隐孢子虫和疟原虫）有关，但目前对该类群的了解还很少。为了提高我们对 archiggregarine 多样性和进化的理解，我描述了 Selenidium serpulae (Lankester) Caullery 和 Mesnil 的一般超微结构和分子系统发育位置。这些寄生虫是从东太平洋收集的钙质管蠕虫（多毛类）的肠道中分离出来的。滋养体（细胞外摄食阶段）呈纺锤形，能够缓慢且连续地弯曲和卷曲，特别是当从宿主上皮脱落时。滋养体表面由 19-23 个纵向折叠、突出的横向折叠和一个坚固的三层薄膜组成，该薄膜被单排微管包围，每个微管都被电子透明鞘包围。观察到了假定的线粒体，但它们不明显并且明显高度减少，这是无氧代谢的指示。来自 S. serpulae 的小亚基 (SSU) rDNA 序列与源自加利福尼亚湾贫氧热液喷口系统环境 PCR 调查的两个（短）序列密切相关，即 C1-E017 (AY046619) 和 C2-E016 (AY046806)。这一结果表明，形态和生命周期与 S. serpulae 非常相似的 archiggregarines 在这个缺氧的生态系统中蓬勃发展。此外，对较大的 SSU rDNA 数据集（不包括较短的环境序列）的系统发育分析表明，与 S. serpulae 最近的姐妹谱系是 S. vivax，这是一种在 sipunculids 肠道中发现的奇怪的带状聚角藻。这种关系得到了比较超微结构数据的支持，并有助于说明阿古格雷寄生虫的多样化和生物地理分布可能比通常假设的更广泛。
Archigregarines are dynamic single-celled parasites that inhabit the intestinal systems of marine invertebrates, especially suspension feeding and deposit feeding polychaetes. Certain archigregarines in the genus Selenidium have retained several plesiomorphic characters, and improved knowledge of these species is expected to shed considerable light onto the earliest stages in apicomplexan evolution. Although archigregarines are related to some of the most notorious parasites known (e.g., Cryptosporidium and Plasmodium), current knowledge of the group is meagre. In an attempt to improve our understanding of archigregarine diversity and evolution, I have characterised the general ultrastructure and molecular phylogenetic position of Selenidium serpulae (Lankester) Caullery and Mesnil. The parasites were isolated from the intestines of the calcareous tubeworm Serpula vermicularis (Polychaeta) collected in the eastern Pacific Ocean. The trophozoites (extracellular feeding stages) were spindle-shaped and capable of slow and continuous bending, and coiling, especially when dislodged from the host epithelium. The trophozoite surface was composed of 19-23 longitudinal folds, prominent transverse folds and a robust, trilayered pellicle subtended by a single row of microtubules, each surrounded by an electron transparent sheath. Putative mitochondria were observed, but they were inconspicuous and apparently highly reduced, a condition that is indicative of anaerobic metabolism. The small subunit (SSU) rDNA sequence from S. serpulae was very closely related to two (short) sequences derived from an environmental PCR survey of an oxygen-depleted hydrothermal vent system in the Gulf of California, namely C1-E017 (AY046619) and C2-E016 (AY046806). This result suggested that archigregarines with a morphology and lifecycle much like that in S. serpulae are thriving in this oxygen poor ecosystem. In addition, phylogenetic analyses of a larger SSU rDNA dataset (excluding the shorter environmental sequences) indicated that the nearest sister lineage to S. serpulae was S. vivax, a bizarre tape-like gregarine found in the intestines of sipunculids. This relationship was bolstered by comparative ultrastructural data and helped to illustrate that the diversification and biogeographical distribution of archigregarine parasites is probably more extensive than usually assumed.