Department of Microbiology, Oregon State University, Corvallis, OR 97331, USA.
J Fish Dis. 2012 Oct;35(10):725-32. doi: 10.1111/j.1365-2761.2012.01407.x. Epub 2012 Jul 19.
Ceratomyxa shasta is a myxozoan parasite of salmonid fish. In natural communities, distinct genotypes of the parasite are associated with different salmonid hosts. To test the hypothesis that genotypes of C. shasta cause differential mortality, the polychaete host was experimentally infected with different parasite genotypes. Genotype I was obtained from Chinook salmon, Oncorhynchus tshawytscha, and genotype II from either coho salmon, O. kisutch, or rainbow trout, O. mykiss, We then challenged four salmonid strains: Chinook and coho salmon that occur in sympatry with the parasite and allopatric Chinook salmon and rainbow trout. Parasite genotype I caused mortality only in Chinook strains, although mortality in the allopatric strain also occurred from exposure to genotype II. A second experiment demonstrated that genotype II could be separated into two biotypes based on differential mortality in rainbow trout and coho salmon. These differential patterns of mortality as a result of infection by certain genotypes of C. shasta support field observations and suggest a co-evolutionary relationship between these parasites and their hosts.
贝氏瓦螨是一种寄生在鲑鱼科鱼类身上的粘孢子虫。在自然环境中，寄生虫的不同基因型与不同的鲑鱼宿主有关。为了验证寄生虫基因型导致死亡率差异的假设，研究人员用不同的寄生虫基因型感染多毛类宿主。基因型 I 来自奇努克鲑鱼（Oncorhynchus tshawytscha），基因型 II 则来自银鲑（Oncorhynchus kisutch）或虹鳟（Oncorhynchus mykiss）。然后，研究人员用四种鲑鱼品系进行了实验，包括与寄生虫共存的奇努克鲑和银鲑，以及地理上隔离的奇努克鲑和虹鳟。结果发现，只有奇努克鲑品系感染基因型 I 后会死亡，尽管地理隔离的奇努克鲑品系在接触基因型 II 后也会死亡。第二个实验表明，基因型 II 可以根据对虹鳟和银鲑的致死率差异分为两种生物型。这些由特定基因型的贝氏瓦螨感染引起的死亡率差异模式支持了野外观察结果，并表明这些寄生虫与其宿主之间存在共同进化关系。
