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...

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. The ultrastructural study revealed that the plasmodial wall was composed of two membranes, had numerous pinocytic canals and was in direct contact with the basement membrane of the vessel. The development of the parasite was asynchronous, with mature spores, immature spores and young developmental stages randomly distributed throughout the plasmodium. The prevalence of the parasite was 4.4%, with male and female fish being infected

COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPES

FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP

06/59075-6

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