Phylogenetic relationships between Vorticella convallaria and other species inferred from small subunit rRNA gene sequences

Vorticellid ciliates generally dwell in freshwater. In nature, the species have up until now been identified by comparison with previous descriptions. It is difficult to identify between species of the genus Vorticella, because the morphological markers of vorticellid ciliates described in reports are limited and variable. Unfortunately, culturing them has only succeeded with certain species such as Vorticella convallaria, but many others have been impossible to culture. To find out whether the sequence of a small subunit rRNA gene was an appropriate marker to identify vorticellid ciliates, the gene was aligned and compared. Finding a new convenient method will contribute to research on vorticellid ciliates. In strains of V. convallaria, classified morphologically, some varieties of the SSrRNA gene sequences were recognized, but there were large variations within the same species. According to the phylogenetic tree, these strains are closely related. However, the difference was not as big as between Vorticella and Carchesium. In addition, Carchesium constructed a distinct clade from the genus Vorticella and Epistylis. These results show the possibility that the SSrRNA gene is one of the important markers to identify species of Vorticella. This study is first to approach and clarify the complicated taxa in the genus Vorticella.