Morphological and Molecular Characterisation of a New Species of Parastrongyloides (Rhabditida: Strongyloididae) from the Short-Beaked Echidna Tachyglossus aculeatus from Western Australia

Introduction A new species of the nematode genus Parastrongyloides Morgan, 1928 was found in the caecum of six short-beaked echidnas Tachyglossus aculeatus (Shaw, 1792) collected from southwestern Australia between August 1964 and March 2020. Methods Specimens were prepared for microscopic examination as temporary wet mounts, measurements were made using an Olympus DP71 camera with cellSens standard software, figures were drawn using a drawing tube and light micrographs taken. DNA was extracted using a Qiagen blood and tissue kit, amplified targeting the COX1 gene region. Sequences obtained were analysed and edited using Geneious v.8.1 and aligned to existing sequences published in Genbank using MUSCLE. Results Parastrongyloides spratti n. sp. can be distinguished from all other species of Parastrongyloides in having the male caudal papillae arranged as a single median dome-shaped pre-cloacal papilla, three tiny pairs of ventral papillae immediately pre-cloacal, a tiny ventral pair of papillae post-cloacal and the female with four to five pairs of dorsoventral papillae immediately anterior to the vulva. A revised key to the species of Parastrongyloides found in Australia is given. Sequence analysis of the COX1 gene corroborated the species status of P. spratti. Discussion Morphological and molecular analyses support the status of P. spratti as a new species. Parastrongyloides may have an ancient origin in the Australian portion of Gondwanaland.