Fine structure of a new species, Loma myrophis (Phylum Microsporidia), parasite of the Amazonian fish Myrophis platyrhynchus (Teleostei, Ophichthidae)

A new species of a microsporidian, Loma myrophis n. sp., was found in the sub-epithelial gut tissue of the Amazonian teleost fish, Myrophis platyrhynchus (fam. Ophichthidae), forming small whitish xenomas. Each xenoma consisted externally of a thick wall formed by one layer of fibrous material surrounded by aggregate and concentric fibroblasts. Inside, there was a hypertrophic host cell with a hypertrophic branched nucleus surrounded by a hypertrophic cytoplasm containing intermingled life cycle stages, mainly mature spores. Among these cells several extruded polar filaments were observed. Sporonts were surrounded by numerous blisters with dense contents, which appeared to discharge their contents into the parasitophorous vacuole around the parasite. All spores were ellipsoidal and uninucleate, and measured about 3.45 x 1.71 mum (n = 50). The polar filament was isofilar and consisted of a single coil with 13-14 turns, surrounding the posterior vacuole that occupied about half of the total volume of the spore. The xenoma, formation of the parasitophorous vacuole and the morphology of the spores were basically like those of the genus Loma. In this paper, we describe light and electron microscopical data of the xenoma, life cycle and the spores of a new microsporidian species, Loma myrophis.