Metchnikovellids is a group of hyperparasites of gregarines inhabiting alimentary tract of polychaetes and some other invertebrates. Despite long history of discovery (first described at the end of 19th century), metchnikovellids remain poorly studied. It is difficult to find and isolate these hyperparasites; publically available molecular data are absent. The most of evolutionary hypotheses, based on morphology, consider metchnikovellids as a deviated group of microsporidia. Recent studies of organisms branching close to animal-to-fungi boundary resulted in recognition of ARM clade (Aphelida + Rozellida + Microsporidia), the members of which were united in the superphylum Opisthosporidia. The position of metchnikovellids may be one of the decisive points to recover the relationships of lineages within ARM clade. We isolated and re-described Metchnikovella incurvata Caullery and Mesnil 1914 from the samples collected at Kandalaksha Gulf of the White Sea, Russia. This metchnikovellid infects gregarines Polyrha