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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 2857

Wilhelm Foissner and Helmut Berger; Identification and Ontogenesis of the nomen nudum Hypotrichs (Protozoa: Ciliophora) Oxytricha nova (= Sterkiella nova sp. n.) and O. trifallax (= S. histriomuscorum). Acta Protozoologica 38:215-248, 1999

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Oxytricha nova and O. trifallax were named and established as viable genetic systems (via frozen resting cysts) by molecular biologists, but never determined or described in a scientific way. Thus, their identity is unknown and both are nomen nudum species according to the International Code of Zoological Nomenclature. In the present paper, this bewildering situation is rectified by investigating offspring of the original populations. It is shown, by a detailed literature review and morphological and ontogenetical analysis, using live observation, silver impregnation and scanning electron microscopy, that both populations belong to a single morphotype, viz, Sterkiella histriomuscorum (Foissner, Blatterer, Berger and Kohmann, 1991), a cosmopolitan species very frequent in limnetic and terrestrial habitats. However, on the molecular level, O. nova and O. trifallax are very distinct, suggesting that they are different species. Thus, S. histriomuscorum is a complex of sibling species. For the sake of nomenclatural continuity and priority, we suggest identifying O. trifallax as S. histriomuscorum and establishing O. nova as a new species, Sterkiella nova sp. n. Both species are diagnosed by a combination of morphological, ontogenetical and gene sequence characters. Field populations of S. histriomuscorum should be designated as gene sequence "Sterkiella histriomuscorum complex" if no molecular data are available to decide whether they belong to S. nova, S. histriomuscorum, or to another not yet described species of the complex.