Diversity of Pleurostomatid Ciliates: Morphology, Taxonomy and Molecular Phylogeny of Freshwater Isolates Found in a Northern China Wetland, with a Description of Two New Species

Abstract

Ciliates of the order Pleurostomatida play essential functions in microbial food webs from a variety of habitats and have been thought to possess a high level of diversity. Due to undersampling and often absent molecular data, the actual diversity and phylogenetic relationships within this group remain unclarified. To help address this deficiency, a survey of freshwater pleurostomatid ciliates was undertaken in Lake Weishan Wetland, northern China. Here, two new Amphileptus species, Amphileptus sinicus sp. nov. and Amphileptus piscinarius sp. nov., were investigated using modern morphological and molecular techniques. Amphileptus sinicus sp. nov. is characterized by possessing a comparatively large cell size of 330–490 μm, contractile vacuoles on both ventral and dorsal margins, and 8–10 left and 42–61 right kineties. Amphileptus piscinarius sp. nov. is characterized by possessing a cell size of 140–210 μm, a large distinctly developed apical extrusome group, 3–4 contractile vacuoles on the ventral margin, and 6–8 left and 24–28 right kineties. Phylogenetic results based on the 18S rRNA gene data of these two species group them with other congeners, with these data suggesting the genus Amphileptus is paraphyletic.