Morphology, morphogenesis, and molecular phylogeny of Pleurotricha oligocirrata nov. spec. (Ciliophora: Spirotrichea: Stylonychinae)

Pleurotricha oligocirrata nov. spec. was discovered in samples collected from a freshwater wetland in Korea and is described here based on its morphology, morphogenesis, and the nucleotide sequence of its nuclear small subunit ribosomal rRNA (SSU rRNA) gene. In its genus, P. oligocirrata is the only species that possesses one right marginal cirral row. The morphology of P. oligocirrata is as follows: body size 98-148 × 47-72 μm in protargol preparations, colourless and rigid body; contractile vacuole anterior of mid-body near left margin; cortical granules lacking; two macronuclear nodules with two micronuclei; undulating membranes in Oxytricha pattern; 50-62 adoral membranelles, 23-27 frontal-ventral-transverse cirri, one left and one right marginal cirral row; six or seven dorsal kineties, including dorsomarginal rows, with three caudal cirri. The genetic distances between P. oligocirrata and its congeners P. curdsi and P. lanceolata were 0.257%-0.386% (4-6 nt difference) and 0.064% (1 nt difference), respectively.