A family concept for the genus Stomachicola Yamaguti, 1934 (Digenea: Hemiuroidea) and new hemiuroid species from marine fishes of Vietnam.

New morphological and molecular data generated for hemiuroid trematodes from fishes of coastal waters of Cat Ba Island, Northern Vietnam. The trematode Stomachicola muraenesocis was detected in the intestines of eels Pisodonophis boro. Vietnamese specimens of S. muraenesocis were identical to trematodes from Iran by morphology and molecular data and have some differences with specimens from South Korea by 28S rRNA gene sequence data. Results of p-distance estimation and phylogenetic analysis of Hemiuroidea specimens of Stomachicola differ from other representatives of the superfamily at the level of different families. Based on these data, a new family for Stomachicola was created. A new species of the genus Lecithaster, L. pseudosayori n. sp., from belonid fish species was validated. These trematodes are close to L. sayori and L. confusus by morphological and molecular data, respectively. Two specimens of Lecithocladium sp. detected in belonid fishes were similar to L. excisum by both morphological and molecular data. Phylogenetic tree topologies show agreements about Lecithasteridae species differentiation and definitive host specificity.