Morphological aspects of Henneguya aequidens n. sp. (Myxozoa: Myxobolidae) in Aequidens plagiozonatus Kullander, 1984 (Teleostei: Cichlidae) in the Amazon region, Brazil.

A new species of Myxosporea, Henneguya aequidens sp. n. (Myxozoa: Myxobolidae), was described based on its ultrastructural features. This is a parasite of the freshwater fish Aequidens plagiozonatus, in the Peixe-boi River, Pará, Brazil. This parasite was found in the gills, in the form of whitish ellipsoid cysts with mature spores inside them. The average spore body was 15 ± 0.9 μm in length (n = 30) and 6 ± 0.8 μm in width (n = 30), and the tail measured 27 ± 0.5 μm in length (n = 15). The spores showed typical features of the genus Henneguya with two valves of equal size and two symmetrical polar capsules of 3 ± 0.3 μm in length and 2 ± 0.3 μm in width. Each polar capsule had a polar filament forming a helix from the apical region to the polar caps, with four to six turns. Based on the ultrastructural differences in morphology of these spores, the location of the parasite, and its host specificity, this parasite was described as a new species.