鲶病原粘孢子虫米氏碘泡虫不同株系的比较研究

【目的】研究米氏碘泡虫（Myxobolus miyairii Kudo, 1919）不同寄生部位和不同地理分布的株系差异和遗传分化情况。【方法】基于形态特征、组织向性、地理分布、18S rDNA序列相似度、遗传距离、系统发育，对米氏碘泡虫各株系进行比较分析。【结果】米氏碘泡虫各株系孢子形态特征基本一致；米氏碘泡虫重庆株系1（鲶鳃腔膜寄生），重庆株系2（鲶肠寄生）和江西株系（鲶肠寄生）间相似度为98.6%~99.9%，遗传距离为0.000~0.013；系统发育分析显示，米氏碘泡虫重庆株系2先与江西株系聚支，其形成的进化支再与重庆株系1形成姐妹群关系。【结论】序列比较和系统发育分析结果表明，米氏碘泡虫并没有形成地理种群特有的单系，而是依据寄生部位形成肠寄生支系和鳃腔膜寄生支系。宿主种类相同的条件下，较之于地理隔离，寄生部位差异对于米氏碘泡虫种群分化的影响更大。【意义】本文米氏碘泡虫各株系的比较研究及其结果，为人们进一步了解该寄生虫的进化生物学特征积累基础资料。

Comparative study on different strains of catfish pathogen Myxobolus miyairii

Background] Myxobolus miyairii Kudo, 1919 is a pathogenic parasite of Silurus asotus Linnaeus, 1758 which is an economically important fish in China. The parasite was first discovered in Japan, and subsequently found in China and Russia, successively. Purposes and Methods] To investigate the strain divergence of M. miyairii from different parasitic sites and localities, the comparative study was carried out based on morphological characters, histotropism, geographic distribution, 18S rDNA sequence similarity, genetic distance and phylogeny. Results] The morphological characteristics of the spores from different strains of M. miyairii were generally consistent; the similarity and genetic distance among Chongqing strain 1 (gill cavity membrane), Chongqing strain 2 (intestine) and Jiangxi strain (intestine) was 98.6%~99.9%, and 0.000~0.013, respectively; phylogenetic analysis showed that the Chongqing strain 2 and Jiangxi strain clustered together and were sistered to Chongqing strain 1 of M. miyairii. Conclusion] Results from sequence comparison and phylogenetic analysis indicated that M. miyairii did not form monophyletic lineages specific to geographic populations, but rather clustered according to the parasitic sites of host; based on promise of the same host, the parasitic site change may have a greater impact on the population divergence of M. miyairii than that by geographic isolation. Significance] The comparative study of various strains of M. miyairii and its results are of great significance for people further understanding the evolution characteristics of M. miyairii.