Morphological and phylogenetic characterization of a novel Unicauda species, infecting the kidney of Astyanax altiparanae (Teleostei: Characidae) in Brazil.

During a parasitological survey of Astyanax altiparanae captured in the Mogi Guaçú river, Pirassununga, state of São Paulo, Brazil, a new species of myxozoa was observed infecting the kidney of 30 of 42 specimens. Plasmodia of the new myxozoa, referred to herein as Unicauda whippsi n. sp. were spherical and varied from 450 to 1000 μm in length. The mature spore was elongated and measured 11 ± 1.2 (10-12) μm long by 5.4 ± 0.6 (4.7-7.2) μm wide. Polar capsules of unequal length with the filament coiled 7-9 times and a unique caudal process characteristic of the genus Unicauda, were recorded. Phylogenetic analysis demonstrated that U. whippsi n. sp. clustered with members of the genus Unicauda and Myxobolus, confirming it's placement within the family Myxobolidae. This is the first record of a species of Unicauda infecting characiform fish, as well as the first registered occurrence of species of this genus in South America.