Redefining the genus Spraguea based on ultrastructural and phylogenetic data from Spraguea gastrophysus n. sp. (phylum Microsporidia), a parasite found in Lophius gastrophysus (Teleostei) from Brazil.

The ultrastructure of the fish-infecting microsporidium Spraguea gastrophysus found in the dorsal ganglia and kidney of the anglerfish, Lophius gastrophysus (family Lophiidae) collected on the Brazilian Atlantic coast is described. Each whitish xenoma (up to 3.1 × 1.8 mm) contains several groups of parasites. The host cells are hypertrophied and contain various parasite life stages including mature spores and several developmental stages with unpaired nuclei. Monomorphic spores are ellipsoidal, lightly curved and measure about 3.35 × 1.71 µm. The spore contains a gradually tapering isofilar polar filament with five to six coils arranged in a single row. The nucleus occupies a central zone of the sporoplasm where also several polyribosomes are presented. The posterior vacuole contains a voluminous spherical and granular posterosome measuring up to ~0.65 µm in diameter. The partial small subunit, intergenic spacer and partial large subunit rRNA gene were sequenced and the phylogenetic analysis places the microsporidian described here in the clade that includes all sequences of the Spraguea genus. The ultrastructural morphology of the xenoma and the spores of this microsporidian parasite, as well as the molecular and phylogenetic analysis, suggest the description of a new species. A redefining of the genus Spraguea is also done.

Light and ultrastructural description of Meglitschia mylei n. sp. (myxozoa) from Myleus rubripinnis (Teleostei: Serrasalmidae) in the Amazon River system.

Meglitschia mylei n. sp. found in the gall bladder of the teleostean fish Myleus rubripinnis (Serrasalmidae) from the middle Amazonian region of Brazil is described using light and transmission electron microscopy. The spores observed in the bile averaged 24.6±0.8 µm long, 8.7±0.4 µm wide and 5.1±0.3 µm thick and were strongly furcate and arcuate ∩-shaped composed of two symmetric equal-sized valves, up to ∼70 nm thick. Each valve possessed one opposed tapering appendage, 20.1±0.7 µm long, oriented parallel towards the basal tip of the appendages and joined along a right suture line forming a thick strand. The strand goes around the central part of the spore, which in turn surrounds two equal and symmetric spherical polar capsules (PC), 2.1±0.3 µm in diameter, located at the same level. Each capsule contains a polar filament with five (rarely six) coils. The binucleate sporoplasm was irregular in shape, contained several sporoplasmosomes, ∼175 nm in diameter and filled all the space of the two caudal appendages. Based on the arc shape of the spore with two tapering caudal appendages oriented to the basis of spores, on the number and position of the PC and of the polar filament coils and arrangements, and on the host specificity, we propose the name M. mylei n. sp. for this new myxozoan. Accordingly, this is the second described species of this genus.