Amended diagnosis of the genus Provitellotrema (Digenea: Haplosplanchnidae) with description of a new species from vietnamese mullets.

Morphological and molecular data for a new representative of the genus Provitellotrema (Haplosplanchnidae) from the mullets of the coastal waters of Vietnam were provided in the present study. Morphologically, the trematodes described here are similar to representatives of Haplosplanchnus and Pseudohaplosplanchnus and demonstrate the most closeness to Haplosplanchnus purii by most of the metric parameters. Results of molecular phylogenetic analysis show that the trematodes we found were closely related to Provitellotrema crenimugilis, and H. purii was in the same clade. Genetic distance values between trematodes from new material and P. crenimugilis were 0.69 ± 0.22 % and 10.78 ± 1.01 % by 28S rDNA and mitochondrial COI gene sequence data, respectively. Morphologically, the adult worms of P. crenimugilis and trematodes from our study can be discriminated by several characters, including the distribution of the vitelline follicles, pharynx, and egg size. Based on the results, we conclude that trematodes from our study belong to the new species of the genus Provitellotrema, P. halongensis n. sp. The difference in vitellaria arrangement between new species and P. crenimugilis can be considered a species-specific characteristic within the genus Provitellotrema. An amended diagnosis for the genus Provitellotrema was provided.