A New Species of Diaphorocleidus (Monopisthocotyla: Dactylogyridae), a Gill Parasite from Three Neotropical Characiform Fishes from Brazil

PurposeThe members of the genus Diaphorocleidus (Monopisthocotyla: Dactylogyridae) infest the gills, nostrils, and body surface of characiform freshwater fishes from the Neotropical region. We characterize a new species of Diaphorocleidus from the gills of three acestrorhamphid species from the Pardo River (a sub-basin of the Paranapanema River basin) in the state of São Paulo, Brazil.MethodsThis study includes phylogenetic analyses of molecular data (partial 28 S rDNA), as well as morphological and morphometric assessments of parasites collected from the gills of 140 fishes (i.e., 50 A. lacustris, 80 P. bockmanni, and 10 P. fasciatus).ResultsThese analyses indicate that Diaphorocleidus pindamirimn. sp. is closely related to D. neotropicalis but differs primarily in the morphology of the copulatory complex and molecular data. The small subunit of the accessory piece is shaped like a chela (or fishing hook tip), which is not observed in D. neotropicalis, where the small subunit is claw-shaped.ConclusionIntegrating morphological and molecular evidence, we describe a new species of Diaphorocleidus and propose a general morphometric scheme for the genus. These findings underscore that combining morphology with molecular data is essential for robust species delimitation and will advance taxonomic and parasitological research in the Neotropical region.