Molecular phylogeny of Urosomoida agilis, and new combinations: Hemiurosomoida longa gen. nov., comb. nov., and Heterourosomoida lanceolata gen. nov., comb. nov. (Ciliophora, Hypotricha)

For years, systematics of three species, Urosomoida agilis (Engelmann, 1862) Hemberger in Foissner, 1982, Urosomoida longa (Gelei and Szabados, 1950) Foissner et al., 1991 and Oxytricha lanceolata Shibuya, 1930, has remained unresolved due to lack of adequate molecular data. Though, it is known since several years that the three species are not very closely related. In the present paper, 18S rRNA gene sequences for two key species, U. agilis and U. longa, and their morphology and morphometry have been analyzed. Molecular phylogeny inferred from maximum likelihood, neighbour joining and maximum parsimony methods has adequately removed ambiguity over their systematics. In phylogenetic trees, U. agilis clustered consistently with non-stylonychine oxytrichids. Both Urosomoida longa and Oxytricha lanceolata clustered consistently away from U. agilis and O. granulifera, the type species of the genera Urosomoida and Oxytricha, respectively. As a result of the current molecular phylogenetic investigation and based on previously inferred morphological and morphogenetic data it is proposed to remove Urosomoida longa and Oxytricha lanceolata from Urosomoida and incertae sedis in Oxytricha, respectively, and establish two new generic combinations, Hemiurosomoida longa gen. nov., comb. nov. and Heterourosomoida lanceolata gen. nov., comb. nov. for them.