Morphology and ontogenesis of Stylonychia (Metastylonychia) nodulinucleata nov. subgen. (Ciliophora, Hypotricha) from Australia

Using standard methods, we describe the morphology and ontogenesis of a possibly very rare ciliate, Stylonychia (Metastylonychia) nodulinucleata nov. subgen (basionym: Stylonychia nodulinucleata Shi and Li, 1993), isolated from soil of the Murray River floodplain in Australia. Further, we provide an English translation of the Chinese original description. Whether the Australian population is conspecific with the Chinese Stylonychia nodulinucleata requires a careful redescription of the latter. The new subgenus is characterized by a moniliform macronuclear strand and an ontogenetic feature, viz., that all cirri remain intact during anlagen formation. The moniliform macronuclear strand and the curved dorsal kineties resemble the stylonychid genus Coniculostomum. The species is easily recognized by the large size of the body and oral apparatus, the moniliform macronucleus, and the enormous caudal cirri reaching half of body length. Very likely, Stylonychia (Metastylonychia) nodulinucleata has a restricted distribution.