哈利特角形虫宿主新纪录及两个地理株系的比较

A New Host Record of Ceratomyxa hallettae and the Comparison of Two Different Geographic Strains

【目的】研究哈利特角形虫(Ceratomyxa hallettae)在不同地理分布和宿主种类下的遗传分化。【方法】基于哈利特角形虫的形态学、18SrDNA的分子特征、系统发育、宿主、地理分布等特征对哈利特角形虫中国株系与澳大利亚株系间的遗传分化进行研究。【结果】褐蓝子鱼(Siganusf uscescens)为哈利特角形虫的新宿主;形态学分析显示哈利特角形虫两株系在形态量度上差异较小;分子特征分析显示两株系18S rDNA序列之间存在7个变异位点,且两者相似度为99.60%,遗传距离为0.003 8;系统发育分析表明,哈利特角形虫中国株系聚于海洋角形虫进化支,且与澳大利亚株系形成姐妹群关系。【结论】宿主种类差异与长期的地理隔离可能是造成哈利特角形虫中国株系与澳大利亚株系在分子(18S rDNA)和形态上发生分化的主要原因。综合角形虫的系统发育、地理分布、宿主类群等信息可知,哈利特角形虫的原始宿主可能为单斑裸颊鲷(Lethrinus harak),而褐蓝子鱼应为该寄生虫经历了宿主转移事件而获得的新宿主。

[Purposes]To research the genetic differentiation of Ceratomyxa hallettae from different geographic localities and hosts.[Methods]Based on the morphological characteristics,18 SrDNA sequence features,phylogenetic analysis,host species and geographic distribution of different strains(China and Australia)of C.hallettae to investigate genetic divergence.[Findings]Siganusf uscescens is the new host for C.hallettae.The morphological analysis of C.hallettae from China and Australia showed that there were some slightly morphological differences.The molecular characteristic analysis of both strains showed that there were seven variable sites,and the 18 SrDNA sequence similarity and genetic distance of both were 99.60% and 0.003 8,respectively.Phylogenetic analysis suggested that Chinese strain of C.hallettae was clustered in the clade of marine Ceratomyxa and formed a sister-group relationship with the Australian strain.[Conclusions]The different host species and long-term geographical isolation may be the main reasons for the molecular and morphological differentiation in different strains of C.hallettae.Combining the analyses of phylogeny,geographic distribution and host affinity,the results indicated that the original host of C.hallettae might be Lethrinus harak,and the S.fuscescens should be its new host after the parasite experienced host shift events.