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Light and electron microscopical data on the spores of Thelohanellus rhabdalestus n. sp. (Myxozoa: Myxosporea), a parasite of a freshwater fish from the Kwanza River, Angola


The myxosporean Thelohanellus rhabdalestus n. sp. (Myxozoa: Bivalvulida), a parasite of the freshwater fish Rhabdalestes maunensis (Fower) collected from the Kwanza River, Angola, is described based on light and electron microscopical studies. The parasite occurs in irregular, milky-whitish, cyst-like plasmodia (up to 0.8 mm in diameter) in close contact with the liver and heart. The spores are pyriform, with slight tapering anterior and round posterior ends, and measure 16.8 ± 0.5 μm (n = 50) long, 10.2 ± 0.6 μm (n = 50) wide and 5.6 ± 0.8 μm (n = 25) thick. The spore wall is partly surrounded by a discontinuous, closely adhered, external coat of electron-dense material of variable thickness (up to c.35 nm). A single flask-shaped polar capsule [7.2 ± 0.3 μm (n = 50) long and 4.0 ± 0.4 μm (n = 50) in diameter] lies close to the apex of the spores and contains a polar filament with six or seven (rarely eight) coils oblique to its longitudinal axis. Based on morphological and ultrastructural differences, compared with other members of Thelohanellus Kudo, 1933, and judging from the host-specificity of previously described species, we consider this species new to science. This is the first reported myxosporean from the Angolan fauna.

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This study was supported by the António de Almeida Foundation, Porto, Portugal, and the National Institute of Fisheries Research (INIP), Luanda, Angola. We would like to thank for technical assistance Ângela Alves and J. Carvalheiro. The various aspects of this work complied with the current laws of the countries in which they were carried out.

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Correspondence to Carlos Azevedo.

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Azevedo, C., Samuel, N., Saveia, A.P. et al. Light and electron microscopical data on the spores of Thelohanellus rhabdalestus n. sp. (Myxozoa: Myxosporea), a parasite of a freshwater fish from the Kwanza River, Angola. Syst Parasitol 78, 19–25 (2011).

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  • Transmission Electron Microscopy Observation
  • Semithin Section
  • Polar Capsule
  • Spore Wall
  • Polar Filament