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Diseases of Aquatic Organisms

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DAO 51:107-112 (2002)  -  doi:10.3354/dao051107

Ultrastructural data on the spore of Myxobolus maculatus n. sp. (phylum Myxozoa), parasite from the Amazonian fish Metynnis maculatus (Teleostei)

G. Casal1,2, E. Matos3, C. Azevedo2,4,*

1Department of Biological Sciences, High Institute of Health Sciences, 4580 Paredes, Portugal
2CIIMAR‹Centre for Marine and Environmental Research, University of Oporto, 4150-180 Porto, Portugal
3Laboratory of Animal Biology, Faculty of Agricultural Sciences, Belém, Brazil
4Department of Cell Biology, Institute of Biomedical Sciences, University of Oporto, 4099-003 Porto, Portugal
*Corresponding author. Present address: Department of Cell Biology, Institute of Biomedical Sciences, University of Oporto, Lg. Professor Abel Salazar no. 2, 4099-003 Porto, Portugal. E-mail:

ABSTRACT: Light and electron microscopy studies of a myxosporean, parasitic in the intertubular interstitial tissue of the kidney of the freshwater teleost fish Metynnis maculatus Kner, 1860 (Characidae) from the lower Amazon River (Brazil), are described. We observed polysporic histozoic plasmodia delimited by a double membrane and with several pinocytic channels and containing several life cycle stages, including mature spores. The spore body was of pyriform shape and was 21.0 µm long, 8.9 µm wide and 7.5 µm thick. Elongated-pyriform polar capsules were of equal size (12.7 x 3.2 µm) and contained a polar filament with 14 or 15 coils. The spore features fit those of the genus Myxobolus. Densification of the capsular primordium matrix, which increased in density from the inner core outwards, differentiating at the periphery into small microfilaments measuring 45 nm each, and tubuli arranged in aggregates and dispersed within the capsular matrix of the mature spores, are described. Based on the morphological differences and specificity of the host, we propose the creation of a new species named Myxobolus maculatus n. sp.

KEY WORDS: Ultrastructure · Parasite · Myxosporidian · Myxobolus maculatus · Amazonian fish

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