First morphological and phylogenetic data on Ligophorus kaohsianghsieni (Platyhelminthes: Monogenea) from the Black Sea and the Sea of Japan and molecular evidence of deep divergence of sympatric Ligophorus species parasitizing Planiliza haematocheilus .

Ligophorus kaohsianghsieni (Gusev, ) Gusev, was collected from the so-iuy mullet Planiliza haematocheilus (Temminck & Schlegel, 1845) from the Black Sea and the Sea of Japan. DNA sequences data for L. kaohsianghsieni , as well as its morphological characters from the Sea of Japan were obtained for the first time. Significant morphometric and genetic diversity between specimens of L. kaohsianghsieni from the Black-Azov Sea region and the Sea of Japan were not found. For the first time, the molecular phylogeny of L. kaohsianghsieni based on three fragments of the nuclear DNA ribosomal cluster (18S, internal transcribed spacer 1 and 28S) was reconstructed. Molecular analysis of Ligophorus species from the Atlantic and Pacific Oceans revealed a significant phylogenetic distance between L. kaohsianghsieni and two others species ( Ligophorus pilengas and Ligophorus llewellyni ) from the same host ( P. haematocheilus ) and region. This result indicates the lack of correspondence between the phylogenetic and geographical closeness of the hosts and the relation of their parasites from the genus Ligophorus .