Integrative taxonomy of <i>Diaphorocleidus radius</i> n. sp. (Monopisthocotyla: Dactylogyridae), a parasite of nasal cavities of <i>Tetragonopterus argenteus</i> (Characiformes: Characidae) from the Caatinga domain, Brazil

Based on morphological and molecular data, we describe a new species of <i>Diaphorocleidus</i> parasitizing the nasal cavities of <i>Tetragonopterus argenteus</i> from the Lima Campos weir, municipality of Icó, state of Ceará, Brazil. <i>Diaphorocleidus radius</i> n. sp. resembles other congeners in the morphology of the accessory piece, all by having a bifurcated accessory piece (pincer-shaped), composed of two subunits articulated. However, the new species can be easily distinguished from all congeners by the morphology of the sclerotized structures of the haptor (ventral anchor with well-developed superficial root, ornamented deep root, recurved blade, elongated and lightning-shaped tip; and ventral bar robust, plate-shaped, truncated in lateral ends). Phylogenetic analyses of LSU rDNA and COI mtDNA sequences, conducted using Bayesian Inference and Maximum Likelihood, placed <i>Diaphorocleidus radius</i> n. sp. within <i>Diaphorocleidus</i>, grouping it with species parasitizing acestrorhamphid hosts. Genetic distances between <i>Diaphorocleidus radius</i> n. sp. and other congeneric species such as <i>D. armillatus</i> and <i>D. forficata</i> showed clear differentiation. Both molecular markers support the distinctiveness of <i>Diaphorocleidus radius</i> n. sp., consistent with its recognition as a new taxon.