Critical revision of the family Plagiopylidae (Ciliophora: Plagiopylea), including the description of two novel species, Plagiopyla ramani and Plagiopyla narasimhamurtii, and redescription of Plagiopyla nasuta Stein, 1860 from India

To date, the family Plagiopylidae comprises four genera: Plagiopyla, Lechriopyla, Pseudoplagiopyla and Paraplagiopyla. Despite its cosmopolitan distribution, only a few species currently comprise the genus Plagiopyla, and their data are often incomplete, whereas the other genera are monotypic. Indeed, these anaerobic ciliates are a somewhat challenging issue for protistologists: they have a cryptic lifestyle, they are not easily cultivable and they possess few and cryptic taxonomic features, which makes it extremely difficult to identify them at species level. In the present paper we provide a revision of the family Plagiopylidae based on morphological and molecular analyses, together with the description of two novel species of Plagiopyla, P. ramani sp. nov. and P. narasimhamurtii sp. nov., and a redescription of P. nasuta, all collected from the freshwater Kolleru Lake (Andhra Pradesh, India). We applied an integrative taxonomic approach to characterize these organisms, while introducing the description of novel morphological features not recorded in previous works. After critically revising the family Plagiopylidae, we propose the exclusion of the genus Paraplagiopyla from this family and that the genus Lechriopyla should be considered a junior synonym of Plagiopyla. We consequently propose L. mystax as Plagiopyla mystax comb. nov.