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Diseases of Aquatic Organisms

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DAO 65:153-157 (2005)  -  doi:10.3354/dao065153

Ultrastructural description of an unidentified apicomplexan oocyst containing bacteria-like hyperparasites in the gill of Crassostrea rizophorae

C. Azevedo1,2,* I. Padovan3, L. Corral1,2, P. Padovan3

1Department of Cell Biology, Institute of Biomedical Sciences, University of Porto, Largo Abel Salazar no. 2, 4099-003 Porto, Portugal
2CIIMAR—Center for Marine and Environmental Research, University of Porto, Rua dos Bragos no. 177, 4050-123 Porto, Portugal 3 Department of Histology and Embriology, Center of Biological Sciences, Federal University of Pernambuco, 50720-230 Recife (PE), Brazil

ABSTRACT: Oocysts of an unidentified coccidian are reported in this study to parasitize the gills of the oyster Crassostrea rizophorae (Mollusca, Bivalvia) collected near the city of Recife (Itamaracá Island, 07°38’00’’S, 34°48’06’’W), Brazil. Oocysts appeared as light and dense forms, both containing rod-shaped, bacteria-like hyperparasites (BL). Both light and dense oocysts were spherical, 4.3 to 4.7 µm in diameter, but denser oocysts had irregular contours. Both forms consisted of a thick dense wall (~165 nm thick) consisting of 3 layers. The outermost, a dense and irregular layer about 25 nm thick, possessed numerous bead-like structures and some slender conical projections (up to 1.5 µm long). The inner layer of the wall was formed by a dense and homogenous layer about 125 nm thick. Between these 2 layers, a thin light layer about 12 nm thick was present. Uninucleated sporocysts occupied the internal space of the oocyst and contained some rod-shaped BL and mitochondria surrounded by numerous ribosome-like particles. The dense forms of the oocysts showed the same structures described in the lighter forms and appeared to be the final maturation form of the oocysts. Free sporozoites were occasionally observed among oocysts.

KEY WORDS: Ultrastructure · Unidentified · Oocyst · Coccidian · Bacteria-like hyperparasite ·Crassostrea rizophorae

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