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. glaucomaMüller, 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.

One freshwater species of the genus Cyclidium, Cyclidiumsinicum spec. nov. (Protozoa; Ciliophora), with an improved diagnosis of the genus Cyclidium.

The morphology and infraciliature of one freshwater ciliate, Cyclidium sinicum spec. nov., isolated from a farmland pond in Harbin, northeastern China, was investigated using living observation and silver staining methods. Cyclidium sinicum spec. nov. could be distinguished by the following features: body approximately 20-25×10-15 µm in vivo; buccal field about 45-50 % of body length; 11 somatic kineties; somatic kinety n terminating sub-caudally; two macronuclei and one micronucleus; M1 almost as long as M2; M2 triangle-shaped. The genus Cyclidium is re-defined as follows: body outline usually oval or elliptical, ventral side concave, dorsal side convex; single caudal cilium; contractile vacuole posterior terminal; adoral membranelles usually not separated; paroral membrane 'L'-shaped, with anterior end terminating at the level of anterior end of M1; somatic kineties longitudinally arranged and continuous. Phylogenetic trees based on the SSU rDNA sequences showed that C. sinicum spec. nov. clusters with the type species, Cyclidiumglaucoma, with full support. Cyclidium is not monophyletic with members of the clade of Cyclidium+Protocyclidium+Ancistrum+Boveria.