Morphometric and molecular analyses of two digenean species from the mullet: Haplosplanchnus pachysomus (Eysenhardt, 1892) from Vietnam and Provitellotrema crenimugilis Pan, 1984 from the Russian southern Far East

Adults of Haplosplanchnus pachysomus (Eysenhardt, 1829) were found in the intestine of Liza engeli (Bleeker) from the coastal waters of Cat Ba Island, Ha Long Bay, northern Vietnam. Additionally, Provitellotrema crenimugilis Pan, 1984 was discovered in Liza haematocheila (Temminck & Schlegel) from Vostok Bay, Gulf of Peter the Great, southern Far-East Russia. Data concerning morphology, 18S rDNA and 28S rDNA of these worms were obtained.The molecular data confirmed the validity of these species and showed that specimens identified as H. pachysomus are closely related to specimens of H. pachysomus found in Spain, and that P. crenimugilis is closely related to Haplosplanchnus purii. Molecular differentiation of P. crenimugilis and H. purii was 0.92% by combined ribosomal gene sequences that confirmed species validity. Molecular differentiation between P. crenimugilis and H. purii, on the one hand, and H. pachysomus, on the other hand, was much higher, suggesting that the sequence for H. purii in GenBank is for a misidentified species of the genus Provitellotrema Pan, 1984.