Taxonomic revision of three species of the genus Genarchopsis (Digenea: Hemiuroidea: Derogenidae) in Japan by molecular phylogenetic analyses

The taxonomic status of three nominal species of Genarchopsis (G. goppo Ozaki, 1925; G. gigi Yamaguti 1939; and G. fellicola Shimazu, 1995) (Digenea: Hemiuroidea: Derogenidae) was investigated by molecular phylogenetic analyses using partial sequences of the genomic ITS-1 region and the mitochondrial COI. The analyzed samples were divided into four groups: Lake Biwa, West Japan, Central Japan and G. fellicola. The Lake Biwa group, a sister taxon to the other three groups, was interpreted as G. gigi, so we concluded that G. gigi is valid; thus, this species is resurrected taxonomically. The specimens from the type host caught near the type locality of G. goppo were included in the West Japan group, so this group was regarded as G. goppo sensu stricto. Because the phylogenetic position of the Central Japan group could not be confirmed, it was identified tentatively as G. goppo, even though this species thus becomes paraphyletic. The taxonomic validity of G. fellicola was reconfirmed. The divergence time of G. gigi is discussed in relation to the geological history of Lake Biwa and the origin of host species.

Highlights► The molecular phylogeny of Genarchopsis goppo, G. gigi and G. fellicola was studied. ► Four groups were detected by the analysis of the sequences of ITS-1 and COI. ► The Lake Biwa group was surmised as G. gigi. ► G. gigi diverged earlier than other three groups including G. fellicola. ► The West and the Central Japan groups were included in G. goppo at present.