Light, Electron Microscopy And Histopathology Of Myxobolus Salminus N. Sp., A Parasite Of Salminus Brasiliensis From The Brazilian Pantanal

In this report, we describe the morphology and histopathology of Myxobolus salminus n. sp., a parasite of the gill filaments of wild Salminus brasiliensis (dourado) from the Brazilian Pantanal. The small polysporic plasmodia were ∼100 μm in diameter and the development was asynchronous. The mature spores were oval to pear shaped and had a smooth wall. The spore measurements were (mean ± S.D., with range in parentheses): length 10.1 ± 0.4 μm (9.6-10.5), width 6.1 ± 0.4 μm (5.8-6.6) and thickness 5.0 ± 0.6 μm (4.7-5.3). The polar capsules were elongated and of equal size: length 4.6 ± 0.2 μm (4.3-4.8) and width 1.7 ± 0.1 μm (1.5-1.9). The histological analysis revealed numerous plasmodia in the blood vessels of the gill filaments. The site of parasite development was the wall of the large-caliber blood vessel of the gill filament, with progressive growth towards the lumen, resulting in the obstruction of blood flow, congestion and perivascular edema. 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