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

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.