Morphology and molecular phylogeny of Holostichides terrae nov. spec. (Ciliophora: Spirotrichea) with discussion on the possible non-monophyly of Holostichides

Abstract

In a study to investigate ciliate diversity, we discovered a new soil ciliate. Holostichides terrae nov. spec. was examined and identified based on observations of living cells and stained specimens. In addition, the nuclear SSU rRNA gene along with morphology was analyzed to infer its phylogenetic position. The new species closely resembles H. dumonti, but can be distinguished by the morphology of the pharynx (with rod-shaped structure vs. lacking) and the number of frontoterminal cirri (invariably two vs. usually more than two). Molecular analyses indicate that the genus Holostichides is not monophyletic, and H. terrae is closely related with the genera Birojimia and Hemicycliostyla, both of which have a pharynx with rod-shaped structures, as also seen in H. terrae.