Taxonomic and Phylogenetic Studies of Two Brackish Pleuronema Species (Protista, Ciliophora, Scuticociliatia) from Subtropical Coastal Waters of China, with Report of a New Species

Abstract

The genus Pleuronema Dujardin, 1841, with nearly 40 morphospecies, is one of the largest genera in the well-known subclass Scuticociliatia. In the present study, two Pleuronema species were collected from subtropical coastal waters of the East China Sea. The morphology and molecular phylogeny were investigated using modern standard methods. Pleuronema ningboensis n. sp. is mainly characterized by an elliptical body in outline with the right ventrolateral side straight, 16–22 somatic kineties, 3–5 preoral kineties, and the posterior end of the membranelle 2a hook-like. An improved diagnosis of Pleuronema orientale Pan et al., 2015 was provided: body size in vivo usually 90–135 × 45–85 μm, right ventrolateral side convex, 36–51 somatic kineties, 1–5 preoral kineties, one to three spherical macronuclei, membranelle 2a arranged in a zig-zag pattern in middle portion, posterior region hook-like, both membranelle 1 and membranelle 3 composed of three rows of basal bodies. The small subunit ribosomal DNA (SSU rDNA) of two species is sequenced, and their molecular phylogeny is analyzed. The new species Pleuronema ningboensis n. sp. clusters with P. grolierei KF840519, P. setigerum JX310015, P. paucisaetosum KF206430, and P. cf. setigerum KF848875, basically in accord with the morphological characteristics.