Morphological variability and molecular characterization of Pomphorhynchus zhoushanensis sp. nov. (Acanthocephala: Pomphorhynchidae), with comments on the systematic status of Pomphorhynchus Monticelli, 1905.

Species of Pomphorhynchus Monticelli, 1905 commonly parasitize the digestive tract of freshwater fishes, and rarely occur in marine fishes and amphibians. In the present study, Pomphorhynchus zhoushanensis sp. nov., collected from the barred knifejaw Oplegnathus fasciatus (Temminck & Schlegel) (Perciformes: Oplegnathidae) in the East China Sea, was described using integrated approaches, including light and scanning electron microscopy, and the sequencing and analysing of ribosomal [small ribosomal DNA (18S) and internal transcribed spacer (ITS)] and mitochondrial [cytochrome c oxidase subunit 1 (cox1)] target regions. The results of the molecular analyses showed that morphological differences in the shape of the neck bulb (symmetrical or asymmetrical) among individuals of P. zhoushanensis sp. nov. are actually intraspecific variations. Moreover, phylogenetic analyses based on the 18S, ITS and cox1 sequences were constructed to evaluate the phylogenetic relationships between the new species and other pomphorhynchid species. The results of the phylogenetic analyses suggested that Pomphorhynchus is not a monophyletic group. Based on the results of the molecular and phylogenetic analyses, the taxonomic importance of the symmetry of the neck bulb for species identification in the genus Pomphorhynchus is questioned.