A NEW SPECIES OF HALIPEGUS (TREMATODA: DEROGENIDAE: HALIPEGINAE) IN LITHOBATES SPECTABILIS (ANURA: RANIDAE) FROM RESERVA DE LA BIOSFERA BARRANCA DE METZTITLAN, HIDALGO, MEXICO.

While surveying the parasites of the leopard frog Lithobates spectabilis in the Barranca de Metztitlán Biosphere Reserve, Hidalgo, Mexico, we found several specimens of an undescribed species of Halipegus (Trematoda: Derogenidae: Halipeginae) in the buccal cavity of this species of frog. The objective of this study was to describe the new species using an integrative approach, incorporating morphological data, multivariate analyses (principal and discriminant components), and phylogenetic analyses based on partial sequences of the conserved ribosomal regions (28S rDNA) of DNA and the mitochondrial subunit of the cytochrome c oxidase I gene (COI mtDNA). The methods of maximum likelihood, Bayesian inference, and maximum parsimony were used to determine the relationships of the new species to other hemiurids. Halipegus metztitlanensis n. sp. differs from its congeners mainly by the combination of the following characters: the distance from the ventral sucker to the right anterior testis, the distance from the ventral sucker to the left posterior testis, the length and width of the ovary, the width of the left testis, the distance between the oral sucker and the ventral sucker, and the length of the egg filament. The new species was recovered as a distinct group separate from other hemiuroideans based on the 28S rDNA and COI mtDNA phylogenetic analyses. This is the first report of a hemiurid trematode infecting the endemic leopard frog in Hidalgo, México and the second species described from the country.