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

绦虫的生活史是由捕食-被捕食关系维持的。在绦虫的进化过程中，协同进化和宿主交换是绦虫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性寄生进行了分析。此外，还进行了野外调查，分析了绦虫的适应机制。（包括10株带状绦虫（Tt））和2株棘球绦虫（Echinococcus）从形态学、寄主特异性、蛋白质组成、同工酶谱、DNA限制性内切酶分析、DNA指纹图谱和COI基因序列分析结果表明，Tt中有一个分离物在钩状形态、中间宿主特异性和COI基因序列上与其它分离物存在明显差异。得出结论， 关于我们 在北海道有两种不同的Tt株。其中一种在遗传和生物学上与家鼠和大鼠中发现的世界性菌株接近。另一种是完全不同的，发现在Clethrionomys。据推测，Clethrionomys菌株最初是由一种灭绝的猫科动物引入北海道的，并通过宿主交换到家猫而存活下来。该菌株的发现对绦虫生殖研究具有重要意义。在野外调查中，在日本首次在大鼠体内发现Em。基于这一发现，大鼠可能在维持北海道的Em生命周期中发挥作用。然而，DNA分析表明，这种分离物与其他在田鼠中发现的分离物没有差异。因此，在北海道流行的Em是一个遗传上接近的种群。此外，在北海道和圣劳伦斯岛（美国）的人口被发现是遗传接近。据推测，流行于北海道的Em最初是从阿拉斯加引进，然后迅速扩大其分布。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