Taxonomy, geographic distribution and molecular phylogeny of two freshwater Frontonia (Ciliophora, Peniculida), including a new cryptic species Frontonia paraleucas sp. nov.

The ciliate genus Frontonia, one of the most species-rich groups of the order Peniculida, is widely distributed across a variety of habitats. However, the definition and identification of isolates are challenging, as there are few reliable characters, and these may overlap among congeners. In the present study, we describe two easily confused species, including a new form F.