New morphological features and phylogenetic insights of Dioctophyme renale from wild carnivores and a domestic dog in South America

<i>Dioctophyme renale</i> (Nematoda: Dioctophymidae) is a globally distributed monotypic nematode species of significant zoonotic relevance. This parasite infects a broad range of mammalian hosts, including wild and domestic carnivores, as well as humans. In Brazil, infections have been reported in both domestic and wild animals, although morphological and molecular data remain limited. This gap, combined with its zoonotic potential, highlights the need for further research. The present study provides an integrative taxonomic description of <i>D. renale</i> specimens recovered from mammals in the Brazilian Atlantic Forest biome, including 22 wild carnivores that were roadkill victims and one domestic dog. This highly urbanized biome is considered a conservation hotspot. A total of 68 nematodes were recovered from the maned wolf (<i>Chrysocyon brachyurus</i>), brown-nosed coati (<i>Nasua nasua</i>), lesser grison (<i>Galictis cuja</i>), and one domestic dog (<i>Canis lupus familiaris</i>). These wild species, affected by deforestation and roadkill, are increasingly exposed to humans and domestic dogs. Ultrastructural analyses revealed novel morphological features relevant to species diagnosis, including five cephalic papillae in the lateral field and distinctive details on the ventral surface of the copulatory bursa. Phylogenetic analyses based on the 18 S rRNA gene placed <i>D. renale</i> into two well-supported clades differentiated by geographic region, whereas the mitochondrial COI marker grouped Brazilian samples within a South American clade alongside sequences from Argentina and Peru, suggesting genetic structuring driven by geography rather than host species. A more comprehensive understanding of this structuring will require broader sampling across hosts and localities. The novel morphological traits identified herein, together with molecular data, refine the species diagnosis and provide new insights into the phylogeny of <i>D. renale</i>, contributing to the understanding of genetic diversity within the genus.