Speciation of Taeniid cestodes (Echinococcus spp. and Taenia spp.) in the world and co-evolution of the host-parasite relationship

寄生的绦虫、鞭虫、扁虫都是雌雄同体的。自体受精是绦虫生殖生物学的基本策略。然而，通过我们最近对感染人类的两个独立物种--牛带绦虫和亚洲带绦虫--的线粒体(单倍体)和核(二倍体)DNA的研究，发现泰国和中国存在杂交或杂交衍生的成虫，这些种是共生分布的。这些数据有力地揭示了最终宿主--人类的交叉受精，并推出了“什么是亚洲锥虫？”它真的是独立的物种吗？这一点仍在争论之中。在马达加斯加采集的猪带绦虫幼虫幼虫阶段，也证实了两种亚洲和非洲/美洲型猪带绦虫种内交叉受精的证据。在马达加斯加，我们可以证实这两种基因型是共生分布的，也已经确认了一些杂交个体。我们的工作是第一次比较绦虫或扁形蠕虫的线粒体和核基因。这些数据有力地提示了鞭虫生殖生物学中的杂交受精。棘球绦虫的分子生物学研究还揭示了细粒棘球绦虫不是单个种，而是5个种，共有9个独立种被包括在棘球绦虫属中。在这些物种中，多房棘球绦虫是高度致病的，已知3种(北美、亚洲和欧洲)基因型别，但我们已确认另外1种为蒙古族型别。我们研究小组开发的免疫和分子诊断工具的建立，成功地确认了关于鞭毛虫物种形成和鉴定的新信息。

Parasitic cestodes, Cestoda, Plathelminthes, have well been known to be hermatophroditic. Self-fertilization is the basic strategy for reproduction biology in cestodes. However, through our most recent studies on mitochondrial (haploid) and nuclear (diploid) DNA of two independent species infecting humans, Taenia saginata and Taenia asiatica have revealed that there are hybrids or hybrid derived adult tapeworms in Thailand and China where these species are sympatrically distributed. These data strongly reveal cross fertilization in the definitive host, humans, and launch “What is T. asiatica? Is it really independent species?" It is still under debates. Similar evidence showing cross fertilization between the intraspecies two, Asian and Afro/American genotypes of Taenia solium has been confirmed from larval stage of this parasite sampled in Madagascar. In Madagascar, we could have confirmed that the two genotypes are sympatrically distributed and also some hybrid individuals have been confirmed. Our work is the first one comparing both mitochondrial and nuclear genes in cestodes or platyhelminthes. These all data strongly suggest the cross fertilization in cestode reproduction biology. Molecular studies on Echinococcus spp. have also revealed that E. granulosus sensu lato is not a single species but 5 species, and a total of 9 independent species are included in the genus Echinococcus. Among these species, E. multilocularis is highly pathogenic and 3 (North American, Asian and European) genotypes have been known, but we have confirmed additional one, Mongolian genotype. The new information on the cestode speciation and identification has successfully been confirmed by the establishment of immuno- and molecular-diagnostic tools developed by our research team.