寄生养殖大菱鲆的海洋盾纤类纤毛虫(弗州拟尾丝虫相似种)的形态学和18S rDNA序列分析

Morphological studies and 18S rDNA sequence analysis of the marine scuticociliate Parauronema cf. virginianum (Protozoa, Ciliophora) isolated from Scophthalmus maximus

从养殖大菱鲆(Scophthalmus maximus)患病鱼体中分离出一种寄生纤毛虫,通过活体观察、碳酸银法染色对其形态学特征进行分析,初步鉴定为弗州拟尾丝虫相似种(Parauronema cf.virginianumThompson,1967)。同时对其18S rDNA序列进行了测定和分子系统发育学分析,结果显示该纤毛虫序列与弗州拟尾丝虫(Parauronema virginianum)存在8个碱基的差异,序列相似性为99%,表明二者的高度相似性。在对本纤毛虫的18S rDNA序列和GenBank中报道的14种相关盾纤类纤毛虫相应序列相似性和进化距离分析的基础上,作者构建了包括迄今所有相关、已知种类的系统进化树。本研究为海水鱼类相关病害的病原鉴定提供了一份新的数据和资讯。

A parasitic ciliate isolated from the cultured flatfish Scophthalmus maximus was analyzed in the present paper. Morphological investigations were performed using living observation and silver carbonate staining method. The data of the body shape, size, structure of buccal apparatus, macro- and micronucleus, as well as the somatic ciliature showed that the parasitic ciliate was similar to Parauronema virginianum. The molecular phylogenetic characters were analyzed to further determine the classification of the parasitic ciliate. The 18S rDNA of the ciliate was sequenced （GenBank accession number is FJ595488）, and it only had 8 different bases compared with those of P. virginianum. They shared 99% similarity insequence. The 18S rDNA of the ciliate was also compared with those of 14 related ciliates. Phylogenetic dendrogram was constructed based on the genetic distance analysis, which revealed that this organism and P. virginianum clustered into one branch, with their genetic distance of 0.005. Based on the obtained results, the isolated ciliate was identified as a Parauronema-similar taxon, that is, P. cf. virginianum.