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Myxobolus myleus n. sp. infecting the bile of the Amazonian freshwater fish Myleus rubripinnis (Teleostei: Serrasalmidae): morphology and pathology

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Myxobolus myleus n. sp. is described from the gall-bladder of the freshwater fish Myleus rubripinnis collected near the city of Oriximiná in the Amazon System, Brazil. The spores obtained from the bile contained two equal symmetrical and smooth valves, each forming the spore wall. The spores were large, with a cone-like form, a semi spherical basal contour and measured (in μm) 19.3 ± 0.5 (n = 25) × 8.3 ± 0.5 (n = 25) × 4.0 ± 0.3 (n = 15). The apical end of the spores contained two elongate, equal and pointed conical polar capsules measuring 13.2 ± 0.4 μm (n = 25) in length and 3.0 ± 0.3 μm (n = 15) in width, each having a slightly tapering polar filament with 19 to 21 turns. The polar capsules were extended below at about 4/5 of the total length of the spores. The sporoplasm was binucleate and contained some sporoplasmosomes. All infected fish presented hypertrophy of the gall-bladder due to presence of the brownish parasite floating in the bile. In this paper we describe this new species of myxosporean based on light and ultrastructural observations, together with its associated pathology.

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We thank Joana and João Carvalheiro (ICBAS/UP) for their excellent photographic assistance and Manoel Newton Souza, a technician from the Campus of the UFF in Oriximiná (Brazil), who provided the access to different sites on the Amazon River and for help with the collection of fish samples. This work complies with the current laws of the countries in which it was performed and was supported by the Fundação Eng. António de Almeida (Porto, Portugal), CNPq and CAPES (Brazil) and a Visiting Professorship at King Saud University (Riyadh, Saudi Arabia). We would also like to thank the referees for their comments and suggestions.

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Correspondence to Carlos Azevedo.

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Azevedo, C., São Clemente, S.C., Casal, G. et al. Myxobolus myleus n. sp. infecting the bile of the Amazonian freshwater fish Myleus rubripinnis (Teleostei: Serrasalmidae): morphology and pathology. Syst Parasitol 82, 241–247 (2012). https://doi.org/10.1007/s11230-012-9360-0

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  • Freshwater Fish
  • Polar Capsule
  • Spore Wall
  • Polar Filament
  • Onaka