n. sp. (Cnidaria: Myxosporea) parasitizing (Bloch 1794) from Tartarugalzinho river, eastern Amazon.

The Amazon basin has the largest number of fish in the world, and among the most common fishes of the Neotropical region, the threespot () is cited, which in relation to its microparasitic fauna, has described only 1 species of the genus , . The Myxozoa class is considered an obligate parasite, being morphologically characterized by spores formed by valves connected by a suture line. This study describes a new species of sp. in the Amazon region for . This parasite was found in the host's pyloric caeca and caudal kidney, with mature spores with a total spore length of 38.4 ± 2.5 (35.9–40.9) m; the spore body 14.4 ± 1.1 (13.3–15.5) m and 7.3 ± 0.6 (6.7–7.9) m wide. Regarding its 2 polar capsules, they had a length of 5.1 ± 0.4 (4.7–5.5) m and a width of 2.0 ± 0.1 (1.9–2.1) m in the same pear-shaped, and each polar capsule contained 9–11 turns. Morphological and phylogenetic analyses denote that this is a new species of the genus .