Morphology and small subunit rDNA-based phylogeny of a new Henneguya species, infecting the ornamental fish Corydoras leucomelas from the Peruvian Amazon

•A new species of Henneguya (Myxosporea) is described.•Morphological and molecular data of the new species are provided.•This is the first Henneguya species reported in a fish from Peruvian Amazon.

A new species of Myxosporea, Henneguya loreotoensis n. sp. is described parasitizing the gill filaments from 17 of 35 specimens (48.5%) of Corydoras leucomelas (Siluriformes: Callichthyidae) caught in the Nanay River, near village Ninarumi, in the Loreto state, Peru. Mature spores were ellipsoidal in shape from the frontal view, measuring 36.2 ± 0.1 μm (36.1-36.3) in total length, 14.3 ± 0.1 μm (14.2-14.4) in body length, 5.1 ± 0.1 μm (4.9-5.3) in width and 21.9 ± 0.1 μm (21.8-22.0) in the caudal process. The two polar capsules were symmetrical and elongated, measuring 5.1 ± 0.1 μm (4.9-5.3) in length and 2.4 ± 0.2 μm (2.1-2.7) in width, containing a polar filament with five coils arranged obliquely to the longitudinal axis. The sporoplasm was binucleate. Partial sequencing of the ssu-rDNA of H. loretoensis n. sp. resulted in a total of 1676 nucleotides, and this sequence did not match any of the myxozoan available in the GenBank. The phylogenetic analysis shows H. loretoensis n. sp. as a sister species of Henneguya paraensis, another amazonian myxozoan parasite of Cichla temensis (Perciformes: Cichlidae).

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