Morphological and molecular data for a new species of Pomphorhynchus Monticelli, 1905 (Acanthocephala: Pomphorhynchidae) in the Mexican redhorse Moxostoma austrinum Bean (Cypriniformes: Catostomidae) in central Mexico.

Pomphorhynchus purhepechus n. sp. is described from the intestine of the Mexican redhorse Moxostoma austrinum Bean (Catostomidae) in central Mexico. The new species can be distinguished from the other seven described species of Pomphorhynchus Monticelli, 1905 in the Americas by a subspherical proboscis and 14 longitudinal rows with 16-18 hooks each; the third and the fourth row of hooks are alternately longest. Sequences of the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene and the large subunit (LSU) rDNA (including the domains D2-D3) were used to corroborate the morphological distinction between the new species and Pomphorhynchus bulbocolli Linkins in Van Cleave, 1919, a species widely distributed in several freshwater fish species across Canada, USA, and Mexico. The genetic divergence estimated between the new species and the isolates of P. bulbocolli ranged between 13 and 14% for cox1, and between 0.6 and 0.8% for LSU. Maximum likelihood and Bayesian inference analyses of each dataset showed that the isolates of P. bulbocolli parasitising freshwater fishes from three families, the Catostomidae, Cyprinidae and Centrarchidae, represent a separate lineage, and that the acanthocephalans collected from two localities in central Mexico comprise an independent lineage. In addition, our analysis of the genetic variation of P. bulbocolli demonstrates that individuals of this acanthocephalan from different host species are conspecific. Finally, the distribution, host-association, and phylogenetic relationship of the new species, when placed in the context of the region's geological history, suggest that both host and parasite underwent speciation after their ancestors became isolated in Central Mexico.