Multidisciplinary characterization of the new species Copemetopus mystakophoros and its symbionts with a proposal for the new class Copemetopea (Alveolata: Ciliophora)

The history of the genus Copemetopus is tortuous and studded with several misattributions. It was erected by Villeneuve-Brachon in 1940 after the discovery of Copemetopus subsalsus in saline ponds along the French coast of the Mediterranean Sea near Sète and associated with the class Heterotrichea in the family Metopidae, close to Bryometopus. After a long series of systematic revisions, it is now clear that Copemetopus is not a heterotrich and that it falls in the subphylum Intramacronucleata. Nevertheless, a lot more work is needed to fix the complex taxonomic status of the genus, which lacks a precise taxonomic collocation (it is presently referred to as incertae sedis). In the present study focused on a multidisciplinary and detailed description of a new species, of the genus, Copemetopus mystakophoros sp. nov., we also propose the erection of the new class, Copemetopea cl. nov. After careful literature and data revision, we believe that members of Copemetopus require a higher-ranked taxon in the phylum Ciliophora, given their molecular and morphological peculiarities.