J.I. Ronny Larsson
Lund University
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Archiv für Protistenkunde | 1988
J.I. Ronny Larsson
Summary The paper treats practice and problems with the identification of genera of microsporidia. After a brief review of the techniques, characters useful for the identification of genera are treated in more detail: light-microscopic or electron-microscopic characters; the basic terminology for the morphology and life cycle stages of microsporidia; the shape and size of the spores; the construction of the spore wall, polar filament and polaroplast; the initiation, construction and inclusions of the sporophorous vesicle; the pathological changes induced in the host; and the vertebrate or invertebrate host. A dichotomous key distinguishes between 83 microsporidian genera. The taxo- nomic characteristics of 87 genera, in alphabetical order, are compared in a table. Genera omitted from the key and genera with special problems for identification and taxonomy are commented on separately.
European Journal of Protistology | 1996
J.I. Ronny Larsson; Dieter Ebert; Jiří Vávra; Vladimir N. Voronin
Summary The cytology of a microsporidium identified as Pleistophora intestinalis Chatton, 1907, is described with emphasis on the ultrastructure. The spores are somewhat asymmetrical, ovoid to lightly kidney-shaped, measuring 1.1–1.7 × 2.4–2.7 urn in fresh preparations. The spore wall is three-layered with an approximately 15 nm thick exospore, which is electron-dense with a more dense surface coat. The polar filament is isofilar with 5–8, mostly 6, coils in a single layer, and the polaroplast has two regions with lamellae, the anterior ones more densely packed. All life cycle stages have isolated nuclei and the spores are uninucleate. Merozoites and sporoblasts are produced by plasmotomy, and the sporogony is polysporoblastic. Merogonial stages are enclosed in parasitophorous vacuoles, sporogonial stages in double envelopes: the parasitophorous vacuole and a spor-ophorous vesicle, formed by duplication of the plasma membrane of the sporont. There is some doubt that Pleistophora intestinalis of Daphnia magna and of D. pulex is the same microsporidian species, but that was not proven by the cytological analysis. The identification has been verified by study of material originating from Chatton and of the microsporidium Otto Jirovec, the first reviser, identified as P. intestinalis . The microsporidium is not a Pleistophora species. The new genus Glugoides is established, and placed in the family Glugeidae.
European Journal of Protistology | 1997
J.I. Ronny Larsson; Dieter Ebert; Jiri Vavra
Summary The new microsporidium Ordospora colligata gen. et sp. n. is described with emphasis on the ultrastructural characteristics. The parasite, which is superficially similar to Glugoides intestinalis (Chatton, 1907), invades the gut epithelium of Daphnia magna, where the complete development takes place in a host cell-derived parasitophorous vacuole. Merogonial and sporogonial stages occur together in the vacuole, with presporal stages at the periphery, mature spores aggregated in the centre. All life cycle stages have isolated nuclei. Merogonial plasmodia are initially rounded, later elongated, and they give rise to four merozoites. The bouts of merogony are unknown. The sporont produces two sporoblast mother cells, which often remain coupled. Each cell generates a chain of four sporoblasts. Sporophorous vesicles are not produced. Mature spores are pyriform with a pointed anterior pole and with an obliquely positioned posterior vacuole. Unfixed spores measure 1.33–2.29 × 2.32–3.69 urn. The exospore is uniform, about 11 nm thick. The polar filament is isofilar, 82–85 nm wide, making 5–6 coils in the posterior half of the spore. The polaroplast is uniform, composed of about 28 nm, wide lamellar components, where the lamellae are folded around each other. The discrimination from other microsporidian species and the systematic position are briefly discussed. A new family, Ordosporidae, is established and Endoreticulatus durforti Martinez et al., 1993 is transferred to Ordospora.
Parasitology | 2011
Karen Luisa Haag; J.I. Ronny Larsson; Dominik Refardt; Dieter Ebert
We describe the new microsporidium Hamiltosporidium tvaerminnensis gen. et sp. nov. with an emphasis on its ultrastructural characteristics and phylogenetic position as inferred from the sequence data of SSU rDNA, alpha- and beta-tubulin. This parasite was previously identified as Octosporea bayeri Jírovec, 1936 and has become a model system to study the ecology, epidemiology, evolution and genomics of microsporidia - host interactions. Here, we present evidence that shows its differences from O. bayeri. Hamiltosporidium tvaerminnensis exclusively infects the adipose tissue, the ovaries and the hypodermis of Daphnia magna and is found only in host populations located in coastal rock pool populations in Finland and Sweden. Merogonial stages of H. tvaerminnensis have isolated nuclei; merozoites are formed by binary fission or by the cleaving of a plasmodium with a small number of nuclei. A sporogonial plasmodium with isolated nuclei yields 8 sporoblasts. Elongated spores are generated by the most finger-like plasmodia. The mature spores are polymorphic in shape and size. Most spores are pyriform (4·9-5·6×2·2-2·3 μm) and have their polar filament arranged in 12-13 coils. A second, elongated spore type (6·8-12·0×1·6-2·1 μm) is rod-shaped with blunt ends and measures 6·8-12·0×1·6-2·1 μm. The envelope of the sporophorous vesicle is thin and fragile, formed at the beginning of the sporogony. Cytological and molecular comparisons with Flabelliforma magnivora, a parasite infecting the same tissues in the same host species, reveal that these two species are very closely related, yet distinct. Moreover, both cytological and molecular data indicate that these species are quite distant from F. montana, the type species of the genus Flabelliforma. We therefore propose that F. magnivora also be placed in Hamiltosporidium gen. nov.
Journal of Invertebrate Pathology | 1990
J.I. Ronny Larsson
Abstract The new microsporidium Napamichum aequifilum, a parasite of the aquatic mite Limnochares aquatica in Sweden, is described based on an ultrastructural investigation. The fusiform sporophorous vesicles, the pyriform spores, the unique plurilayered exospore, and the characteristic crystalline inclusions of the episporontal space are characteristics shared by Chapmanium dispersus ( R. Larsson, 1984 , Protistologica, 20, 547–563). The polar filament and the polaroplast differ in some ways. Some traits of ultrastructural cytology are discussed, with comments on two possible cases of reductions of an anisofilar polar filament. The taxonomic position of the species is discussed, and the new genus Napamichum is established for this species and for C. dispersus.
Archiv für Protistenkunde | 1994
J.I. Ronny Larsson
Summary The microsporidium Trichoctosporea pygopellita gen. et sp. nov., a parasite of Aedes vexans larvae in Sweden, is described based on light microscopic and ultrastructural characteristics. Merogonial stages and sporonts are diplokaryotic. Four merozoites with lobed protrusions are formed by rosette-like division. Sporonts develop into plasmodia with eight isolated nuclei. Sporoblasts are formed by rosette-like budding in a spherical, persistent sporophorous vesicle, generated by the sporont. No inclusions of the episporontal space are visible using light microscopy. Two kinds of projections are formed by the lobed sporogonial plasmodium: chains of globular components, which disappear when the sporoblasts are released, and arrays of persistent fibrillar material, which connect the sporblasts with the envelope of the sporophorous vesicle. Mature spores are oval, with pointed anterior pole, and with about five fibrous posterior projections, which are visible with difficulty using light microscopy, but distinct in electron microscopy. Unfixed spores measure 4.2–4.6 × 6.3–7.0 µm. The spore wall has distinct endo- and exospore layers. The exospore is three-layered, with a lucent surface layer, a median double-layer and an internal granular layer of variable thickness. The polaroplast has two parts: closely arranged lamellae anteriorly, sac-like chambers posteriorly. The polar filament is anisofilar with 3–4, 238–316 nm wide anterior coils and 4–5, 192–209 nm wide posterior coils in a single row close to the spore wall in the posterior half of the spore. The angle of tilt is about 80°. The species is compared to previously described microsporidia of the host, and the taxonomic considerations are discussed.
Journal of Invertebrate Pathology | 1987
J.I. Ronny Larsson
Abstract An organism identified as Haplosporidium gammari Ryckeghem, 1930 was studied using light and electron microscopical methods. The presence of haplosporosomes and absence of polar filament and polar capsules verified the classification in the phylum Ascetospora. The cytology of the developmental stages is briefly described. The unicellular spores devoid of an orifice exclude the organism from both families of Stellatosporea, and a new genus and a new family are erected.
European Journal of Protistology | 1994
Jiří Vávra; J.I. Ronny Larsson
Summary Fine structure studies of the microsporidian Plistophora schaefernai Jirovec, 1937 (syn. Pleistophora schaefernai and Microsporidium schaefernai ) revealed that each spore is surrounded by an individual sporophorous vesicle, composed of a thin outer membrane-like sheath and an inner layer of tubular structures. This type of sporophorous vesicle is structurally identical to that of the genus Berwaldia Larsson, 1981. Berwaldia schaefernai (Jirovec, 1937) comb. n. is proposed and its relationship to Berwaldia singularis is established. Although both species are structurally very similar, they differ in spore width, arrangement of polar filament coils and probably in host specificity. Obviously they are sibling species.
European Journal of Protistology | 1992
J.I. Ronny Larsson
Summary The ultrastructural cytology of a microsporidium identified as Bacillidium strictum ( Leger and Hesse, 1916 ) is described. The host was one of 28 investigated specimens of the oligochaete Limnodrilus hoffmeisteri, collected from a small stream in southern Sweden, not the type host Lumbriculus variegatus. The microsporidium occurred together with an eugregarine of the genus Rhynchocystis and an actinomyxidian of the genus Echinactinomyxidium. The 2.0–2.2 × 11.6–13.3 μ great spores (fixed and stained) were slightly smaller than the size indicated in the description. They occurred in spherical, hypertrophic haemocytes. The exospore, which is approximately as thick as the endospore, has a wide, electron-dense basal layer, an external layer resembling a double-membrane, and fibrous, periodically arranged surface projections. The double-layer remains attached to the basal layer. 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, which turns in anterior direction, forms one or two coils around the diplokaryon and the wide filament, and ends in the proximity of the polaroplast. Approximately 100 nm wide tubules, exhibiting exospore construction, are initiated at the onset of sporogony, and persist also in the proximity of mature spores. The species status of the microsporidium and the ultrastructural characteristics of the Bacillidium-like microsporidia are discussed.
European Journal of Protistology | 1990
J.I. Ronny Larsson
The microsporidium Rectispora reticulata gen. et sp. nov., a parasite of male gonads of the oligochaete Pomatothrix hammoniensis in Sweden, is described based on light microscopic and ultrastructural characteristics. Merogonial and sporogonial stages are diplokaryotic. Sporogony is disporoblastic. The spores are cylindrical, often slightly curved and wider in the mid-region, 1.8-2.1 × 8.1-14.2 um long in fixed and stained condition. The spore wall has a ca. 43 mm thick, uniform exospore. The polaroplast has an anterior part with compressed lamellae and a posterior section with 53-128 nm wide tubules. The polar filament has a 181-283 nm wide, straight, short, anterior section in the centre of the spore, an oblique section with tapering diameter, and a long, posterior, 119-178 nm wide section, arranged in (10-)12(-13) isofilar coils, close to the spore wall in the posterior half of the spore. The most anterior and most posterior coils are irregularly arranged, the median coils form a close, regular group. The angle of tilt of the most anterior, regularly arranged coil is ca. 55°. The transversely sectioned filament has distinct concentrical layers of variable thickness and electron density. The diplokaryon occupies the centre of the spore. Sporophorous vesicle absent, but a folded, ca. 16 nm thick envelope, resembling a sporophorous vesicle, is formed by delamination of exospore material. Teratological sporogony was observed. The microsporidium is compared to microsporidia of the genera Bacillidium, Jirovecia and Hrabyeia. The placing of the new genus in the family Bacillidiidae, the distinction of the families Bacillidiidae and Nosematidae, and the various origins of spore-containing envelopes are discussed.