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

寄生蜂的生命周期是由捕食者-猎物关系维持的。在物种的进化过程中，共同进化和宿主交换对环境变化的响应都是物种多样化的重要驱动力。本研究对生态隔离寄主和寄生虫的实验寄生行为进行了进化分析。此外，还进行了野外调查，分析了寄生蜂的适应机制。对7种带绦虫（包括10株带绦虫（Tt））和2种棘球绦虫（包括6株多房棘球绦虫（Em））的形态、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）基因的核苷酸序列分析进行了综合比较。在Tt中，一个分离株在钩形态、中间宿主特异性和COI基因序列上与其他分离株存在明显差异。结果表明，北海道有两种不同的Tt菌株。其中一种在基因和生物学上与家鼠和大鼠身上发现的世界性菌株接近。另一个则完全不同，可以在《圣经》中找到。据推测，Clethrionomys菌株最初由一种已灭绝的猫科动物引入北海道，并通过宿主与家猫交换而存活下来。该菌株的发现对带绦虫的系统发育研究具有重要意义。在实地调查中，在老鼠体内发现了Em；这是日本的第一个记录。基于这一发现，大鼠可能在维持北海道Em生命周期中发挥作用。然而，该分离物的DNA分析显示与田鼠中发现的其他分离物没有差异。因此，在北海道流行的Em是一个基因接近的人群。此外，北海道和美国圣劳伦斯岛的种群遗传接近。据推测，北海道流行的Em最初是从阿拉斯加传入的，然后迅速扩大了分布范围。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