Redescription and phylogeny of the little-known type species Rhinakis faurei Deroux, 1994 (Alveolata, Ciliophora, Nassophorea)

Ciliates of the class Nassophorea Small & Lynn, 1981, inhabit a wide range of aquatic environments and serve as a trophic link in microbial food webs. However, their diversity remains underestimated. In the present study, the morphology and molecular phylogeny of Rhinakis faurei Deroux, 1994, an insufficiently known nassulid ciliate, were investigated using an integrative taxonomic approach. The studied population was collected from a freshwater pond in Qingdao, China. Details of the live morphology and ciliature of R. faurei are documented for the first time, and an improved species diagnosis is provided. Phylogenetic analyses of the small subunit ribosomal RNA gene sequence revealed that R. faurei clusters within the family Nassulidae de Fromentel, 1874. However, evolutionary interrelationships within the Nassulidae remain obscure owing to under-sampling, the lack of sequence data for most nominal species, and low nodal support or unstable gene tree topologies.