Abstract
Anaerobic protists in general, and ciliates in particular, are important components of anoxic or hypoxic environments, however, their diversity remains underestimated.
Sonderia
is a poorly studied genus that is distributed worldwide and is commonly found in anaerobic environments. In the present study, the taxonomy and phylogeny of three new species, namely
Sonderia aposinuata
sp. nov.,
Sonderia paramacrochilus
sp. nov. and
Sonderia steini
sp. nov., collected from China, were investigated based on microscopic observations and SSU rRNA gene sequencing methods.
Sonderia aposinuata
sp. nov. is diagnosed mainly by having a relatively large body size, a crescent-shaped oral opening, numerous slender extrusomes, one suture on the ventral side and two on the dorsal side, and a buccal cavity that occupies the anterior third of the cell.
Sonderia paramacrochilus
sp. nov. closely resembles
S. macrochilus
but differs mainly by its oral opening being located closer to the anterior cell margin and its spindle-shaped extrusomes.
Sonderia steini
sp. nov. is a freshwater species that can be recognized by its shallow buccal cavity, sparsely distributed rod-shaped extrusomes, and having 68–79 monokinetidal somatic kineties that form sutures on both sides of the body. Phylogenetic analyses based on small subunit ribosomal RNA (SSU rRNA) gene sequence data support the monophyly of the family Sonderiidae, however,
Sonderia
is paraphyletic. The genus
Sonderia
is briefly revised and a key to the identification of species belonging to this genus is supplied.