title: Description of Metchnikovella spiralis sp. n. (Microsporidia: Metchnikovellidae), with notes on the ultrastructure of metchnikovellids.
abstract: The present paper reports results of a transmission electron microscopy study of a new metchikovellid microsporidium. It was isolated from gregarines Polyrhabdina sp. inhabiting guts of polychaetes Pygospio elegans sampled at the White Sea silt littoral zone. Free sporogony (FS) occurred in the life cycle of the microsporidium alongside sac-bound sporogony (BS). Free spores resided in a parasitophorous vacuole and were of typical metchnikovellidean structure, uninucleate and oblong. They measured on sections 2·0-3·2×1·3-1·9 μm. The life cycle included pre-sporogonial stages represented by dikaryotic cells and 4-nucleate cells with coupled nuclei. A multinucleate sporogonial plasmodium of FS split in numerous (>10) sporoblasts. In BS segregation of sporoblasts occurred within thick-walled cysts by internal budding. Spore sacs of this microsporidium, measuring on average 11·6×4·7 μm, were limited by a thick electron-dense wall, externally ornamented with spirally wound cords of dense material. These oval spore sacs contained eight barrel-shaped spores, comparable in size and ultrastructure to FS spores. Ultrastructure of both types of spores and intracellular development of the new microsporidium and Metchnikovella spp. were similar, suggesting they belong to the same genus. In this paper we describe a new species Metchnikovella spiralis and discuss morphology of metchnikovellids in the context of putative evolutionary history of Microsporidia.
authors.affiliation: Institute of Cytology,Russian Academy of Sciences,St. Petersburg,Russia.
authors.forename: Y Y
authors.initials: YY
authors.lastname: Sokolova
authors.affiliation: Department of Invertebrate Zoology,St. Petersburg State University,St. Petersburg,Russia.
authors.forename: G G
authors.initials: GG
authors.lastname: Paskerova
authors.affiliation: Institute of Ecology of the Volga River Basin RAS,Togliatti,Russia.
authors.forename: Y M
authors.initials: YM
authors.lastname: Rotari
authors.affiliation: Institute of Cytology,Russian Academy of Sciences,St. Petersburg,Russia.
authors.forename: E S
authors.initials: ES
authors.lastname: Nassonova
authors.affiliation: Department of Invertebrate Zoology,St. Petersburg State University,St. Petersburg,Russia.
authors.forename: A V
authors.initials: AV
authors.lastname: Smirnov
mesh_terms: D000818:Animals; D008018:Life Cycle Stages; D046529:Microscopy, Electron, Transmission; D016814:Microsporidia / Q000145:classification* / Q000254:growth & development / Q000302:isolation & purification / Q000648:ultrastructure; D013172:Spores, Fungal