Adding another piece to the Camallanidae puzzle: description of Denticamallanus peruensis n. sp. from Centromochlus heckelii in the Peruvian Amazon, with implications for the monophyly of Denticamallanus Moravec & Thatcher, 1997.

During a helminthological survey conducted in the Peruvian Amazon, nematodes representing an undescribed species of Denticamallanus Moravec and Thatcher, 1997 (Camallanidae: Procamallaninae) were recovered from the intestine of Centromochlus heckelii (De Filippi, 1853) (Siluriformes: Auchenipteridae). The new species, Denticamallanus peruensis n. sp., is described herein based on an integrative taxonomic approach combining detailed morphological analysis using light and scanning electron microscopy with molecular characterization of the partial 18S rDNA gene. Denticamallanus peruensis n. sp. is distinguished from its congeners by the morphology of the male caudal extremity, which forms broad lateral lobes giving a spade-like appearance, the arrangement of caudal papillae (one pair of preanal and four pairs of postanal papillae), and spicule length (50-100 μm). Phylogenetic analyses based on Bayesian inference methods recovered the new species within a well-supported clade of Spirocamallanus spp., whereas other species currently assigned to Denticamallanus formed a separate lineage, indicating possible non-monophyly of the genus. This study represents the first description of a Denticamallanus species from C. heckelii in the Peruvian Amazon and increases the number of recognized species within the genus. In addition, these findings challenge the expanded generic diagnosis recently proposed for Denticamallanus and reinforce growing evidence that buccal capsule morphology alone may not reliably reflect evolutionary relationships within Camallanidae.