An ultrastructural study of Nosema locustae Canning (Microsporidia) from three species of Acrididae (Orthoptera)статья
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Дата последнего поиска статьи во внешних источниках: 25 апреля 2017 г.
Аннотация:Nosema locustae is a pathogen of orthopterans with an unusually wide host range. It is the only microsporidian that has been developed as a microbial control agent. In spite of its practical importance the ultrastructure of N. locustae life stages other than spores, has not been studied. The insects used in this study, all in the family Acrididae, were the Migratory locust, Locusta migratoria migratorioides (Oedipodinae), the South American locust, Schistocerca cancellata (Cyrtacanthacridinae), and the grasshopper Dichroplus schulzi (Melanoplinae). All insects were reared routinely in the laboratory. The spores of N. locustae used for the experimental peroral inoculations were all of North American origin. Fat body cells were the predominant site of parasite development, though infection of tracheal epithelium cells and haemocytes also occurred. Ultrastructure of meronts, sporonts, sporoblasts and spores is described. The fine morphology of N. locustae stages is typical for microsporidians of the genus Nosema. Nuclei were always in diplokaryotic arrangement. Transition from meront to sporont was characterized by striking changes in parasite ultrastructure: appearance of electron dense granules (50-100 nm in diameter, presumable RNP complexes) in the nucleoplasm, and stacks of ER cisternae and prominent vacuoles in cytoplasm. The beginning of sporogony was marked by an increase in size of parasite cells due to extensive vacuolization. Tubule-like structures appeared in the host cell cytoplasm during parasite sporogony. Elongated conglomerates of electron dense material were scattered in the host cell and eventually ornamented the outersurface of the parasite membrane, forming an electron dense layer around sporonts. Spores were diplokaryotic, measured 4.95 +/- 0.07 x 2.65 +/- 0.04 mum (mean +/- SE, n = 24) on fresh smears and 3.49 +/- 0.18 x 1.73 +/- 0.04 mum (n = 10) on ultrathin sections, and had electron-dense cytoplasm in which all internal structures typical of microsporidian spores were recognizable. The polaroplast was lamellar, the endospore was 200-300 nm thick, and the exospore was 40-50 nm. The polar filament was isofilar, arranged in 17-18 coils. Our study did not reveal any difference in the morphology of N. locustae while developing in the three different hosts.