Molecular phylogenetics of diphyllobothriid cestodes with special reference to the species identification of Sparganum proliferum.

增芽Sparganum proliferum （Ijima, 1905）是增芽性人Sparganum病的一种幼虫虫和病原，其特点是在人体内通过不断的分枝和出芽而发生无杂交，并侵入各种器官和组织。自从Ijima （j . coll . science . impu . university）的首次发现以来。东京，20:1-21,1905)，全球共报告临床病例14例，均为死亡病例。尽管增殖性人类斯巴达病具有很高的医学重要性，但这种幼虫的成虫阶段和生命周期，包括自然界中的最终和中间宿主，尚未为人所知。先前关于S.proliferum的研究主要集中在与一种可能的亲缘种Spirometra erinaceieuropaei （Rudolphi, 1819）进行比较，后者的幼虫期plerocercoid也会引起人类spargosis。然而，重要的定义是其幼虫的无鳞片发育，它引起的致命疾病越来越多。因此，对以往的研究成果进行了总结，认为该菌可能是异常发育的螺旋菌。然而，最近，Kokaze等人(Parasitol.Internat。生物工程学报，46:271-279,1997)分析了线粒体DNA （mtDNA）编码的NADH脱氢酶亚基I （NDIII）基因，发现S.proliferum与Spiro亲缘关系密切。但两者都含有可分化的NDIII基因序列。在本研究中，我们主要基于分子系统发育研究的方法对增菌的种类进行鉴定。首先，我们分析了S.proliferum， Spiro的线粒体细胞色素c亚基I （COI）基因序列。Yamane et al.， 1986 [Diphyllobothrium nihonnkaiense]构建了包括栉虫纲纲（teniides） [Cyclophyllidea: Teniidae]在内的系统发育树，发现s.p ulererum被明确鉴定为伪栉虫纲，与Spiro.erinaceieuropaei序列相似度也很高。其次，加入了从海洋哺乳动物宿主中获得的6种双扇门蓟马。每种系统发育分析都没有发现与S.proliferum序列相同或亲缘关系更近的种，但揭示了S.proliferum与Spiro之间的分化。在较早的时期出现了海洋物种群。此外，还对其遗传距离进行了比较。Erinaceieuropaei与海洋物种之间具有可比性或距离较远。这些结果表明，该菌来源于淡水，可能是狐尾螺的独特种。少

Sparganum proliferum (Ijima, 1905) is a larval cestode and an etiological agent of proliferative human sparganosis, which is characterized by its agamogenesis by continuous branching and budding in the human body, and invasions on every kind of organs and tissues. Since the first finding by Ijima (J.Coll.Sci.Imp.Univ.Tokyo, 20 : 1-21, 1905), a total of 14 clinical cases has been reported in the world and all of them were fatal. The adult stage of this larval cestode and the life cycle including the final and intermediate hosts in nature has not yet been known in spite of the high medical importance of proliferative human sparganosis.Previous works on S.proliferum has been concentrated in comparison with a putative related species, Spirometra erinaceieuropaei (Rudolphi, 1819)[Platyheiminth : Cestoda : Pseudophyllidea : Diphyllobothriidae], of which larval stage plerocercoid also causes human sparganosis. However significant definitions of S.proliferum are the larval agamous development … More and mortal disease caused by it. Thus, earlier works were summarized that S.proliferum might be abnormally developed Spiro.erinaceieuropaei. While, recently, Kokaze et al.(Parasitol.Internat., 46 : 271-279, 1997) analyzed NADH dehydrognase subunit I (NDIII) gene encoded in the mitochondrial DNA (mtDNA) and revealed that S.proliferum was closely related with Spiro.erinaceieuropaei but both contained differentiable NDIII gene sequence.In this study, we focused on species identification of S.proliferum based on molecular phylogenetic studies. First, we analyzed mitochondrial cytochrome c subunit I (COI) gene sequence of S.proliferum, Spiro.erinaceieuropaei and Diphyllobothrium nihonnkaiense Yamane et al., 1986 [Diphyllobothriidae] to construct phylogenetic tree including teniid cestodes [Cyclophyllidea : Teniidae], and revealed that S.proliferum clearly identified as an pseudophyllidean cestode, also showing high sequence similarity with Spiro.erinaceieuropaei. Second, six species of diphyllobothriids obtained from marine mammalian hosts were added in the analyses. Every phylogenetic analysis failed to find out the species which contained identical sequences or more closely related with S.proliferum, but revealed that the divergence between the cluster included S.proliferum and Spiro.erinaceieuropaei, and the marine species cluster had taken place in earlier period. In addition, the genetic distance between S.proliferum and Spiro. erinaceieuropaei was comparative with or more distant than those between marine species. These results indicate that S.proliferum derived from fresh water origin and may be distinctive species from Spiro.erinaceieuropaei. Less