Phylogenetic positions of two crytophorid ciliates, Dysteria procera and Hartmannula derouxi (Ciliophora: Phyllopharyngea: Dysteriida) inferred from the complete small subunit ribosomal RNA gene sequences

The complete small subunit rRNA (SSrRNA) gene was sequenced for two poorly known marine crytophorid ciliates, Dysteria procera Kahl. 1931 and Hartmannula derouxi Gong et Song, 2004. The phylogenetic positions within the class Phyllopharyngea were deduced using Bayesian, distance matrix and maximum parsimony methods. Dysteria procera and Hartmannula derouxi, together with other available ciliates of the class Phyllopharyngea, form a monophyletic clade with strong bootstrap support in all the tree construction methods (values of 100% Bay, 100% LS, 100% NJ, 100% MP). The SSrRNA genealogy showed that the class Phyllopharyngea contained two monophyletic subclasses Chonotrichia and Suctoria, while the subclass Phyllopharyngia was paraphyletic. Our results revealed that some taxa of the subclass Chonotrichia (e.g. Isochona species) had a close relationship with the subclass Phyllopharyngia, suggesting that heteromeric nuclear apparatus and the dorsal-reduced ciliature are likely phylogenetically informative. Additionally, consisting with traditional morphological descriptions, dysteriids may be a specialized group within the class in our phylogenctic trees.