Morphology and Molecular Phylogeny of Three Freshwater Scuticociliates, with Establishments of One New Genus and Three New Species (ciliophora, Oligohymenophorea)

The morphology and molecular phylogeny of three freshwater scuticociliates, Variuronema elegans gen. nov., spec. nov. (type species), V. similis spec. nov. and Uronema rigidum spec. nov., collected from Qixing River Wetland, northeastern China, were investigated using live observation and silver carbonate staining methods; the phylogenetic placements were inferred from the small subunit rRNA gene. Variuronema gen. nov., assigned to the family Uronematidae, is distinguished from the other genera mainly by its membranelles 1 and 2, each consisting of four longitudinal rows of kinetids, and the paroral membrane extending anteriorly to the front part of membranelle 3. The phylogenetic analyses indicate that: (1) Variuronema spp. form an independent, fully supported clade. However, its position among other uronematids is unresolved. (2) The family Uronematidae is not monophyletic based on the SSU rRNA gene, which is in accordance with previous studies.