Purpose: The molecular profile of Pararhadinorhynchus magnus Ha, Amin, Ngo, Heckmann, 2018 described from Scatophagus argus (Linn.) off Haiphong in the Gulf of Tonkin, Pacific Ocean, Vietnam is provided for the first time. It was morphologically distinguished from the South Australian species, Pararhadinorhynchus mugilis Johnston and Edmonds, 1947 and Pararhadinorhynchus coorongensis Edmonds, 1973 from mullets. Two other species of Pararhadinorhynchus are also recognized: Pararhadinorhynchus upenei Wang, Wang, Wu, 1993 from China and Pararhadinorhynchus sodwanensis Lisitsyna, Kudlai, Cribb and Smit, 2019 from South Africa. The assignment of Diplosentis manteri Gupta and Fatma, 1980 to Pararhadinorhynchus is not recognized.
Methods: Sequences of the 18S, small internal transcribed spacers (ITS1-5.8S-ITS2) and 28S from nuclear DNA were generated to molecularly characterize P. magnus. The phylogenetic analyses were achieved by comparison of the 18S and ITS1-5.8S-ITS2 region only as the 28S amplified a short region (425-428 bp) that was not sufficient for the present study.
Results: Phylogenetic analyses showed that P. magnus and the other species of Pararhadinorhynchus sequenced were nested within separate clades in the case of 18S gene and suggesting that these species do not share a common ancestor. In contrast, the ITS1-5.8S-ITS2 region shows a close arrangement of species of Pararhadinorhynchus with molecular affinities to the family Diplosentidae, suggesting that final placement of these species in Transvenidae needs further study and revision.
Conclusions: The molecular data from the present study will provide further comparative insights into species of Pararhadinorhynchus and its close affiliation to other acanthocephalan species and genera from different geographical areas.
Keywords: Acanthocephala; Molecular profile; Pararhadinorhynchus magnus; Vietnam.