First molecular characterisation of Rhabdias stenocephala (Nematoda: Rhabdiasidae) and a new host record in anurans from the Caatinga domain, Brazil

This study provides the first molecular characterisation of Rhabdias stenocephala (Nematoda: Rhabdiasidae), a parasite of Leptodactylus macrosternum Miranda-Ribeiro, (Anura: Leptodactylidae) from the Caatinga morphoclimatic domain, Brazil. Nematodes were collected from five hosts in a conventional agricultural area within the Caatinga morphoclimatic domain. Specimens were consistent with R. stenocephala, based on the anterior region with a marked constriction, a barrel-shaped buccal capsule with thickened walls and tail morphology. For molecular characterisation, a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) gene was amplified and sequenced. Only a single sequence of the COI gene (707 bp) was successfully retrieved from a single specimen. Phylogenetic analyses, including available Neotropical Rhabdias species, showed congruent topologies between maximum likelihood and Bayesian inference for well-supported clades. The species Rhabdias stenocephala representative analysed here grouped within a fully supported clade comprising sequences of uncertain identity, named R. cf. stenocephala from L. latrans and L. macrosternum, with low intraclade genetic distances (2.3–3%). These results provide first genetic data for R. stenocephala, extend its host range to L. macrosternum and document its first record in the Caatinga morphoclimatic domain.