Light and ultrastructural analysis of Myxobolus insignis (Myxozoa), infecting the Amazonian Fish Semaprochilodus insignis (Prochilodontidae)

A myxosporean infecting the gill filaments of the freshwater teleost Semaprochilodus insignis collected in the Trombetas River (Central Amazonian Region, Brazil) is described using light and electron microscopy. The spores were ovoid in frontal view with round extremities and measured 15.4 ± 0.6 μm in total length, 12.4 ± 0.5 μm wide and 8.1 ± 0.7 μm thick; the spore valves (up to 0.4 μm) were surrounded by an uniform dense layer with variable thickness up to ~1.0 μm) due to the presence of a complex network of anastomosed microfibrils closely adherent to the valves. Two symmetric polar capsules measured 5.9 ± 0.4 μm long and 3.4 ± 0.5 μm wide, each having a polar filament with 7-8 coils slightly obliquely to the longitudinal axis of the polar capsule. The polar capsule wall measured ~0.4 μm thick and was constituted by a hyaline substance (~0.25 μm thick) surrounded by a layer of electron dense granular material (~0.15 μm thick). In this paper we present, by the first time, ultrastructural aspects of the spores of Myxobolus insignis found in a teleost collected from the Amazonian region, which was previously described based on light microscopy (Eiras et al. 2005b).