Two New Species of Urocleidoides (Monopisthocotyla: Dactylogyridae) Parasitizing the Gills of Cyphocharax modestus (Characiformes: Curimatidae) Supported by Morphological and Molecular Data

The present study describes two new species of monopisthocotylans parasitizing the gills of Cyphocharax modestus (Characiformes: Curimatidae) from two localities of the Upper Paraná River basin, state of São Paulo, Brazil. Urocleidoides saghirus n. sp. and Urocleidoides taquariensis n. sp. differ from other congeners mainly in the morphology of the accessory piece: comprising two subunits (one scythe-shaped subunit, and one adjacent piece with a narrow base broadening towards the upper end, which is axe-shaped) in Urocleidoides saghirus n. sp., and a straight rod with a bifurcated proximal portion, a distal portion ending in a point, and two curved handles arising from the medial portion and uniting close to the distal portion in Urocleidoides taquariensis n. sp. The phylogenetic analyses revealed Urocleidoides to be non-monophyletic, indicating the need for a taxonomic review. This study provides the first molecular sequences for Urocleidoides spp. parasitizing Curimatidae, including the newly described species. These findings revealed distinct clades and suggested possible host specificity, underscoring the importance of additional research to better understand the phylogenetic relationships within the genus.