Ortholinea paraensis n. sp. (Myxosporea: Ortholineidae) infecting the urinary bladder of Ageneiosus ucayalensis Castelnau, 1855 (Siluriformes: Auchenipteridae) in the Amazon region of Brazil.

The present study describes a new parasite species of the myxozoan genus Ortholinea, based on the interpretation of morphological and molecular parameters. This species was found infecting the urinary bladder of the driftwood catfish Ageneiosus ucayalensis, captured in the region of Santo Antônio and Guajará bays, in the Amazonian state of Pará, Brazil. Plasmodia and myxospores were observed in pairs in the urinary bladder, either floating freely or adhered to the mucosa. The myxospores are spherical in the frontal view and valvular, with two equal, sub-spherical polar capsules, oriented divergently, containing 6-7 coils of the polar tubule. Scanning electron microscopy revealed ridges on the surface of the spore, which confer it with the appearance of a ball of wool, covering the entire surface of the valve, a slightly undulating suture line, and the presence of discharge pores for the polar tubule on opposite sides of the suture, that permit the extrusion of the polar tubule. The new species presents morphological characteristics typical of the genus Ortholinea. In the phylogenetic analysis, Ortholinea paraensis n. sp. occupied a basal position within a clade of species from the Amazon region. The sum of the morphological and molecular evidence clearly supports the description of a new species, denominated Ortholinea paraensis n. sp., which is the first Ortholinea species reported from Brazil.