Schmidingerothrix extraordinaria nov. gen., nov. spec., a secondarily oligomerized hypotrich (Ciliophora, Hypotricha, Schmidingerotrichidae nov. fam.) from hypersaline soils of Africa

Schmidingerothrix extraordinaria nov. gen., nov. spec. was discovered in hypersaline soils from Namibia and Egypt. Its morphology and ontogenesis were studied with standard methods. Schmidingerothrix extraordinaria is a highly flexible, slender hypotrich with an average size of 90 × 15 μm. Likely, it prefers a salinity around 100‰ and feeds mainly on bacteria. Schmidingerothrix is extraordinary in having a frayed buccal lip, three-rowed adoral membranelles, only one frontal cirrus, a distinct gap between frontal and ventral adoral membranelles, and a miniaturized first frontal membranelle, while a paroral membrane, dorsal bristle rows, and buccal, transverse, and caudal cirri are absent. The ontogenesis is simple: the opisthe oral apparatus and frontoventral ciliature originate de novo, while parental structures are involved in the development of the ciliature of the proter. This special organization is used to define a new family, the Schmidingerotrichidae, which is likely related to the Cladotrichidae. Schmidingerothrix extraordinaria is very likely a secondarily oligomerized hypotrich, and the reduction occurred possibly very long ago because no traces of the ancestral ciliature remained in the ontogenetic processes. Possibly, the simple ciliature is an adaptation to highly saline habitats, where competition is low and bacterial food abundant.