Molecular and morphological characterisation of Pharyngostrongylus kappa Mawson, 1965 (Nematoda: Strongylida) from Australian macropodid marsupials with the description of a new species, P. patriciae n. sp.

BACKGROUND: Pharyngostrongylus kappa Mawson, 1965 is a nematode (Strongyloidea: Cloacininae), endemic to the sacculated forestomachs of Australian macropodid marsupials (kangaroos and wallaroos). A recent study revealed genetic variation within the internal transcribed spacer region of the nuclear ribosomal DNA among P. kappa specimens collected from Macropus giganteus Shaw and Osphranter robustus (Gould). This study aimed to characterise the genetic and morphological diversity within P. kappa from four macropodid host species, including M. giganteus, O. robustus, O. antilopinus (Gould) and O. bernardus (Rothschild). METHODS: Specimens of P. kappa from M. giganteus and Osphranter spp. from various localities across Australia were examined. The first and second internal transcribed spacers (ITS1 and ITS2, respectively) were amplified using polymerase chain reaction and sequenced. Phylogenetic methods were used to determine the interspecific diversification within P. kappa and its evolutionary relationship with other congeners. RESULTS: Morphological examination revealed that P. kappa from M. giganteus, the type-host, can be distinguished from those in Osphranter spp. by the greater length and number of striations on the buccal capsules. DNA sequences showed that P. kappa from M. giganteus was genetically distinct from that in Osphranter spp., thereby supporting the morphological findings. Based on these finding, a new species from Osphranter spp., Pharyngostrongylus patriciae n. sp., is described. CONCLUSION: Pharyngostrongylus patriciae n. sp. from Osphranter spp. is distinguished from P. kappa based on molecular and morphological evidence. The study highlights the importance of combining molecular and morphological techniques for advancing the nematode taxonomy. Although ITS genetic markers have proven to be effective for molecular prospecting as claimed in previous studies, future utilisation of mitochondrial DNA to validate ITS data could further elucidate the extent of speciation among macropodid nematodes. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13071-018-2816-6) contains supplementary material, which is available to authorized users.