title: On the cytology of Jirovecia caudata (Léger and Hesse, 1916) (microspora, bacillidiidae).
abstract: The cytology of a microsporidium identified as Jirovecia (Mrazekia) caudate (Léger & Hesse, 1916), the type species of the genus Jirovecia Weiser, 1977, is described with emphasis on the ultrastructure of the mature spore. The hosts were Limnodrilus hoffmeisteri and an unidentified species of Tubificidae (Oligochaeta), collected from a brook in southern Sweden, not Tubifex tubifex, the type host. The dimensions of the spore and the caudal spore projection varied more than the size range reported in the description of the species. The exospore is characteristic, with a surface layer resembling a unit membrane and a wide, dense, basal layer. The surface layer remains attached also to mature spores. The caudal projection is formed only from exospore material, and it is ornamented with longitudinal ridges. The polaroplast has an anterior region with closely packed lamellae and a posterior section with wider lamellae or tubules. The polar filament has a wide, straight, anterior part, a zone with successively reduced diameter, and a posterior, narrow section, arranged as an incomplete coil. The filament is easily extruded, and the length and size difference between the wide and narrow parts is apparent also using light microscopy. Membrane-lined compartments and aggregates of granular material are present close to the posterior pole. The species status of the microsporidium and the cytological characteristics of Bacillidium-Jirovecia species are discussed.
authors.affiliation: Department of Zoology, University of Lund, Sweden.
authors.forename: J I
authors.initials: JI
authors.lastname: Larsson