Host exchange (Wild animal Domestic animal Human) and adaptive radiation in cestodes

绦虫的生活史是由捕食者-猎物关系维持的。在绦虫的进化中，不仅共同进化，而且宿主对环境变化的反应也将是多样性的重要驱动力。本研究从进化轨迹的角度对生态隔离寄主和寄生虫的实验寄生进行了分析。对7种带绦虫(包括10株带绦虫)和2种棘球绦虫(包括6株多房棘球绦虫)在形态、宿主特异性、蛋白质组成、同工酶谱、DNA限制性内切酶分析、DNA指纹图谱和细胞色素C氧化酶亚基I(COI)基因序列分析等方面进行了综合比较。得出的结论是…更重要的是，北海道有两种截然不同的TT病毒株。其中一种在基因和生物学上与在家鼠和大鼠中发现的世界性病毒株很接近。另一种则完全不同，它出现在克利森经济学中。据推测，克氏杆菌最初是由一种已灭绝的猫科动物传入北海道，并通过宿主交换给家猫存活下来的。该毒株的发现对带绦虫的系统发育研究具有重要意义。在一次野外调查中，在老鼠身上发现了Em，这在日本是第一个记录。基于这一发现，老鼠可能在北海道维持Em生命周期中发挥了作用。然而，DNA分析显示，这种分离物与在田鼠身上发现的其他分离物没有区别。因此，流行于北海道的Em是一个遗传上相近的群体。此外，北海道和圣劳伦斯岛(美国)的种群被发现在遗传上接近。据推测，流行于北海道的Em最初是从阿拉斯加传入的，然后迅速扩大了分布。较少

Life cycles of cestodes are maintained by predator-prey relationship. In the evolution of cestodes, not only coevolution but also host exchange in response to environmental changes would be important driving forces of diversification. In this study, experimental parasitisms of ecologically isolated hosts and parasites were analyzed in terms of evolutional trace. Furthermore, field survey was carried out to analyze adaptation mechanisms of cestodes.Seven species of Taenia (including 10 isolates of T.taeniaeformis (Tt) ) and two of Echinococcus (including 6 isolates of E.multilocularis (Em) ) were comprehensively compared in terms of morphology, host specificity, protein composition, isoenzyme pattern, DNA restriction endonuclease analysis, DNA fingerprinting and nucleotide sequence analysis of the cytochrome c oxidase subunit I (COI) gene.In Tt, one isolate showed distinct differences from others in hook morphology, intermediate host specificity and COI gene sequence. It is concluded th … More at there are two distinct Tt strains in Hokkaido. One is genetically and biologically close to the cosmopolitan strain found in the house mice and rats. The other is totally different and found in Clethrionomys. It is hypothesized that Clethrionomys strain was originally introduced into Hokkaido by an extinct feline animal and survived through host exchange to domestic cats. The discovery of this strain is important for taeniid cestode phylogeny study.In a field survey, Em was found in rats ; a first record in Japan. Based on this finding, rats may play a role in maintaining Em life cycle in Hokkaido. However, DNA analysis of this isolate revealed no difference with others found in voles. Therefore, Em prevalent in Hokkaido is a genetically close population. Moreover, the populations in Hokkaido and St. Lawrence Island (USA) were found to be genetically close. It is speculated that Em prevalent in Hokkaido was originally introduced from Alaska and then rapidly expanded its distribution. Less