Ultrastructural Description of Microsporidium brevirostris sp. n., Parasite of the Teleostean Brachyhypopomus brevirostris (Hypopomidae) from the Amazon River
Edilson Matos；Carlos Azevedo
fish parasite ； microsporidian ； Microsporidium brevirostris sp. n. ； spore ； ultrastructure
|Volume or Term/Year and Month of Publication||
43卷3期（2004 / 09 / 01）
261 - 267
Brachyhypopomus brevirostris sp. n. (family Hypopomidae), a fish from the estuarine region of the Amazon River, collected near the city of Belém, Brazil, is parasitized by numerous microsporidian spores that form xenomas. These xenomas are found in the skeletal muscle adjacent to the abdominal cavity. The xenoma wall, with an irregular surface, consists of concentric laminated layers of compressed cells, possibly fibroblasts. Developing cells are in direct contact with host cell cytoplasm. Among the mature spores, small groups of juxtaposed immature spores are observed. The spores are ellipsoidal and uninucleate, measuring ~2.95×1.68 μm (n=50). The isofilar filament (~55 nm diameter), consists of a regular coil in a single layer with 9-10 (or rarely 8) turns surrounding the posterior vacuole of the spore. The vacuole occupies about half of the total volume of the spore. The angle of tilt of the turns is ~37°. The spore wall is in direct contact with the cytoplasm of the host cells. A few larger grouped spores, measuring ~6.9×2.5 μm (n=20), were observed mainly at the periphery of the most xenomas. The filament consists of two or three irregular layers of coils with 27-28 turns surrounding the posterior vacuole. The ultrastructural morphology of the spores and host specificity suggest that they may be included in the collective group of new Microsporidium species and named Microsporidium brevirostris. The taxonomic affinities and morphological comparisons with other similar species of some genera were discussed.