Description of a New Freshwater Ciliate Epistylis wuhanensis n. sp. (Ciliophora, Peritrichia) from China, with a Focus on Phylogenetic Relationships within Family Epistylididae.

Two populations of Epistylis wuhanensis n. sp., a new freshwater peritrich ciliate, were isolated from different freshwater ponds located in Hubei, China. Their morphological characteristics were investigated using live observation, protargol impregnation, and scanning electron microscopy (SEM). Specimens from the two populations showed identical arrangement of the infraciliature and identical small subunit ribosomal RNA (SSU rRNA) gene and ITS1-5.8S-ITS2 sequences. The zooids present bell-shaped and 90-175 × 27-54 μm in vivo. Macronucleus is variable in shape and located in the middle of cell. Pellicle is usually smooth with 139-154 and 97-105 striations above and below the trochal band, respectively. SSU rRNA gene and ITS1-5.8S-ITS2 sequences of E. wuhanensis n. sp. did not match any available sequences in GenBank. Phylogenetically, E. wuhanensis n. sp. clusters with the other Epistylis within the family Epistylididae, but is distinct from the major clades of Epistylis. Above all, the morphological characteristics and molecular analyses support that the present Epistylis is a new species. Expanded phylogenetic analyses of sessilids based on both SSU rRNA gene sequences and ITS1-5.8S-ITS2 sequences reveal that the genus Epistylis consists of Epistylis morphospecies and taxonomic revision of the genus is needed.