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

Based on morphological and molecular data, we describe a new species of Diaphorocleidus parasitizing the nasal cavities of Tetragonopterus argenteus from the Lima Campos weir, municipality of Icó, state of Ceará, Brazil. Diaphorocleidus radius 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 Diaphorocleidus radius n. sp. within Diaphorocleidus, grouping it with species parasitizing acestrorhamphid hosts. Genetic distances between Diaphorocleidus radius n. sp. and other congeneric species such as D. armillatus and D. forficata showed clear differentiation. Both molecular markers support the distinctiveness of Diaphorocleidus radius n. sp., consistent with its recognition as a new taxon.