Myxobolus cuneusn. sp. (Myxosporea) infecting the connective tissue ofPiaractus mesopotamicus(Pisces: Characidae) in Brazil: histopathology and ultrastructure

Abstract

Summary :The characteristics of Myxobolus cuneus n. sp. and its relationship to the host Piaractus mesopotamicus are described based on light and electron microscopy and histological observations. Polysporic plasmodia measuring 20 µm to 2.1 mm in size were found in 63.3 % of the P. mesopotamicus examined. The parasite was found in the gall bladder, urinary bladder, gills, spleen, fins, head surface, liver and heart. Generative cells and disporoblastic pansporoblasts occurred along the periphery of the plasmodia, and mature spores were found in the internal region. The mature spores had a pear shaped body in frontal view, with a total length of 10.0 ± 0.6 µm and a width of 5.1 ± 0.3 µm (mean ± SD). The spore wall was smooth with sutural folds. The polar capsules were elongated, were pear shaped, and equal in size (length 5.7 ± 03 µm; width 1.7 ± 0.2 µm), with the anterior ends close to each other. The polar filaments were tightly coiled in 8-9 turns perpendicular to the axis of the capsule. The plasmodia were always found in connective tissue (wall of the arterioles of the gill filaments, serous capsule of the gall bladder, middle layer and subepithelial connective tissue of the urinary bladder, connective tissue between the rays of the fins, subcutaneous tissue of the head surface and fibrous capsule spleen). The parasite caused important damage in the gills, where development occurred in the wall of gill filament arterioles; a mild macrophage infiltrate was also observed. In advanced developmental stages, the plasmodia caused deformation of the arteriole structure, with a reduction and, in some cases, obstruction of the lumen. The parasite was found throughout the period studied and its prevalence was unaffected by host size, season or water properties. 'hôte, ni par l'environnement (saison, propriétés de l'eau). Résumé : MYXOBOLUS CUNEUS

Myxosporidiosis in intensively-reared Piaractus mesopotamicus: Histopathological diagnosis by means of Ziehl-Neelsen staining

“…(8.94±0.82μm) in the present observations with M. inaequus (19.8 μm) (Kent & Hoffman 1984), M. maculatus (21.0μm) (Casal et al 2002), M. serrasalmi (7.0-9.5μm) (Walliker 1969) and M. cuneus (10.0±0.6μm) (Adriano et al 2006), morphological similarities were seen, but not biometric ones. In relation to M. inaequus and M. maculatus, there were differences in the morphology of the ϐilaments of the polar capsules.…”

“…In comparison with M. cuneus, there were morphological and biometric similarities, suggesting that the parasites found here was possibly M. cuneus. Although not present in the gills as observed by Adriano et al (2006) but, rather, in the kidneys, it can be supposed that this species may reach any organ through the bloodstream. All the parasites mentioned are included among the myxosporidians that parasitize freshwater ϐish in South America.…”

Parasitic infections of Piaractus mesopotamicus and hybrid (P. mesopotamicus xPiaractus brachypomus) cultured in Brazil

“…Some species of myxosporidans have been described in P. mesopotamicus, such as Henneguya lutzi, Henneguya piaractus, Henneguya pellucida, Myxobolus colossomatis and Myxobolus cuneus (ADRIANO et al, 2006;EIRAS et al, 2008), but this is the first report of the occurrence of Henneguya sp. and Myxobolus sp.…”

Phylogeny, ultrastructure, histopathology and prevalence of Myxobolus oliveirai sp. nov., a parasite of Brycon hilarii (Characidae) in the Pantanal wetland, Brazil

“…The ultrastructural analysis revealed that sporogenesis in M. oliveirai sp. nov. followed the general pattern of other Myxobolus species (Current et al 1979, Casal et al 1996, 2002, Adriano et al 2006) and the plasmodium wall consisted of a single membrane, which was continuous with pinocytic canals extending to the ectoplasm, as seen in some Myxobolus species (Current et al 1979), but differed from others delimited by a double membrane (Casal et al 2002(Casal et al , 2006.…”

“…Myxosporean parasites are among the most important fish pathogens (Schmahl et al 1989) and more than 2,300 species have been reported to infect fish (marine and/or freshwater fish) in either their natural environment or on farms (Adriano et al 2006, 2009a, b, Feist & Longshaw 2006, Eiras et al 2008, Azevedo et al 2009). The Myxobolus Butschli, 1882, is the genus with the greatest number of species (approximately 790 valid spe- cies) (Eiras et al 2005, Lom & Dyková 2006) and many of these species are reported as pathogenic to fish (Kent et al 2001, Feist & Longshaw 2006.…”