A new subfamily, Pseudohaploporinae subfam. n. (Digenea: Haploporidae), with morphometric and molecular analyses of two new species: Pseudohaploporus vietnamensis n. g., sp. n. and Pseudohaploporus planilizum n. g., sp. n. from Vietnamese mullet.

Adult specimens representing Pseudohaploporus vietnamensis n. g., sp. n., Pseudohaploporus planilizum n. g., sp. n., and Pseudohaploporus sp. were collected from the intestines of Osteomugil engeli (Bleeker, 1858), Moolgarda seheli (Forsskål, 1775), and Planiliza subviridis (Valenciennes, 1836) from Vietnam. The new genus Pseudohaploporus n. g. is similar to the genus Haploporus Looss, 1902 in morphology and host-specificity. Species of Pseudohaploporus and Haploporus both possess an elongated body, a long oesophagus, an intestinal bifurcation behind the ventral sucker, a large hermaphroditic bursa, vitellarium consisting of two compact accumulations, concretions in the excretory vesicle, and numerous small eggs that contain miracidia with a pigment eye, and both infect mullet. In contrast to Haploporus, both species of the genus Pseudohaploporus possess two testes. These species differ from each other morphometrically. Pseudohaploporus planilizum sp. n., in comparison with P. vietnamensis sp. n., possess a larger maximum and mean size for the body length, oral and ventral suckers, pharynx, oesophagus length, hermaphrodite bursa, and egg width. Molecular data (ITS and 28S rDNA sequences) support the validity of the new genus and the two new species and indicate the presence of another representative of this genus, Pseudohaploporus sp. Phylogenetic reconstructions show that Pseudohaploporus formed a well-supported clade within a large clade that represents the Haploporidae Nicoll, 1914. Based on morphological and molecular data for P. vietnamensis sp. n. and P. planilizum sp. n., we erected a new subfamily, Pseudohaploporinae subfam. n., which appears to be a sister taxon to Haploporinae Nicoll, 1914. Molecular data show that Pseudohaploporus differ from other haploporids at a level similar to that between other subfamilies.