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

寄生蜂，寄生蜂，鳞目动物，众所周知是雌雄同体的。自交受精是昆虫生殖生物学的基本策略。然而，通过我们最近对两种感染人类的独立物种带绦虫的线粒体（单倍体）和核（二倍体）DNA的研究，saginata带绦虫和亚洲带绦虫在泰国和中国有杂交或杂交衍生的成年绦虫，这两种绦虫在这些物种的对称分布。这些数据有力地揭示了最终宿主——人类的杂交受精，并引发了“什么是亚洲弓形虫？”它们真的是独立的物种吗？”它仍在辩论中。类似的证据表明，在马达加斯加取样的这种寄生虫的幼虫阶段，种内两种、亚洲和非洲/美洲基因型的猪带绦虫之间存在交叉受精。在马达加斯加，我们可以确认这两种基因型是对称分布的，并且已经确认了一些杂交个体。我们的工作是第一个比较线粒体和核基因在壳类动物或扁形动物。这些都有力地说明了杂交受精在胚胎生殖生物学中的作用。对棘球绦虫的分子研究也表明，棘球绦虫属包括9个独立种，不是一个单一种，而是5种。在这些种中，多房棘球绦虫是高致病性的，已知有3个基因型（北美、亚洲和欧洲），但我们已经确认了另外一个基因型，蒙古基因型。我们的研究小组开发的免疫和分子诊断工具已经成功地证实了关于寄生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.