DAO 53:55-60 (2003)  -  doi:10.3354/dao053055

ABSTRACT: This study reports light and electron microscopical aspects of a myxosporean found in the gills of the freshwater teleost Astyanax keithi Géry, Planquete & Le Bail, 1996 (family Characidae), collected from the estuarine region of the Amazon River, near Belém, Brazil. The prevalence of infection was 23%. In interlamellar spaces of the gills, ellipsoidal whitish cyst-like plasmodia structures were present, which contained spores. The spores had a spermatozoa-like appearance (47.8 ± 0.71 µm in total length) with a fusiform body (15.2 ± 0.77 µm in length, 5.7 ± 0.71 µm in width and 4.2 ± 0.31 µm in thickness), and each of the 2 valves presented a tapering tail (32.6 ± 1.11 µm in length). The valves surrounded a binucleate sporoplasm cell and 2 polar capsules (5.0 ± 0.13 µm in length, 1.5 ± 0.07 µm in width) that contained 8 to 9 coils of the polar filament. In the sporoplasm, several unique sporoplasmosomes were visible. A synoptic table of spore measurements of known Brazilian Henneguya species is presented. The spores differed from those of previously described species. Based on spore morphology, it is concluded that this species belongs to the family Myxobolidae, genus Henneguya, and that it constitutes a new species: H. astyanax n. sp.

KEY WORDS: Ultrastructure · Henneguya · Myxozoa · Parasite · Teleost