Taxonomy and molecular phylogeny of three freshwater scuticociliates, with descriptions of one new genus and two new species (Protista, Ciliophora, Oligohymenophorea)

Three freshwater scuticociliates, Apouronema harbinensis gen. nov. spec. nov., Cyclidium vorax spec. nov., and C. glaucoma Müller, 1773, collected from rivers in Hulan District, Harbin, northeastern China, were investigated using morphological and phylogenetic criteria. Apouronema gen. nov., assigned to the family Uronematidae, is mainly distinguished from the other genera of the family by its paroral membrane extending anteriorly to the middle of membranelle 1. Apouronema harbinensis spec. nov. is defined by body size in vivo about 45–55 × 20–25 μm, buccal field about 70–80% of cell length; 12 or 13 somatic kineties; membranelle 1 having two rows, with 16–18 basal bodies in each kinety; membranelle 2 and membranelle 3 both having two rows each; scutica X-shaped with five pairs of basal bodies. Cyclidium vorax spec. nov. is characterized by the following features: body size 35–40 × 18–20 μm in vivo; 9 or 10 somatic kineties; membranelle 1 having two longitudinal rows, much shorter than M2; M2 triangle-shaped. The phylogenetic analyses show that: (1) Apouronema clustered in the Uronematidae clade, and grouped with genera Uronemita and Uronema; (2) Cyclidium vorax spec. nov. grouped with C. glaucoma and C. sinicum, which supports the assignment of the new species to the genus Cyclidium; (3) Cyclidium remains non-monophyletic with the addition of the new sequence.