Validation of the trichomycete Paramoebidium chattoni (Amoebidiales, Mesomycetozoea), a common and cosmopolitan black fly endosymbiont.

Paramoebidium, along with Amoebidium, constitute the Amoebidiales, which is phylogenetically embedded within the protist clade Ichthyosporea (Mesomycetozoea). However, the order is conventionally included within the trichomycetes, an ecological and polyphyletic group of arthropod-gut endosymbionts. Paramoebidium chattoni (Léger and Duboscq) Duboscq et al. is regarded as nomen nudum because the species was incorrectly published, and its taxonomic situation has never been addressed. Thus, P. chattoni is validated here with a description and neotypification to formalize the species and to guarantee the maintenance and correct use of its name. This common species has a wide geographical range and inhabits the digestive system of aquatic black fly larvae, where it frequently appears together with other gut endosymbionts, including P. curvum.