Morphology and molecular phylogeny of two new marine euplotids, Pseudodiophrys nigricans n. g., n. sp., and Paradiophrys zhangi n. sp. (Ciliophora: Euplotida).

The morphology, infraciliature, and molecular phylogeny of Pseudodiophrys nigricans n. g., n. sp., and Paradiophrys zhangi n. sp., isolated from a sandy beach near Qingdao, China, were investigated. Pseudodiophrys is characterized by the Diophrys-like ciliature pattern, but having only a single, reduced undulating membrane. Pseudodiophrys nigricans, the type species by monotypy, is described from live and silver-impregnated specimens. Paradiophrys zhangi is similar to the type species Paradiophrys irmgard but can be recognized by its border body and the number (7 vs. 8-10) and arrangement (in rows vs. sparsely distributed) of the frontoventral cirri. Small subunit (SSU) rRNA gene sequence data support the validity of both species. Phylogenetic analyses based on the SSU rRNA gene sequence data currently available for uronychiids and other related taxa indicate that P. nigricans is most closely related to Diophrys scutum and Diophrys apoligothrix, while P. zhangi clusters most closely with Apodiophrys ovalis within a clade that also includes two other Paradiophrys species.