Dactylogyrus oryziasi n. sp. (Monogenea: Dactylogyridae) is described from the gills of the southern medaka Oryzias latipes (Temminck and Schlegel, 1846) (Beloniformes: Adrianichthyidae) collected from an irrigation canal, Tokushima city, Tokushima Prefecture, Shikoku, Japan. This new species resembles Dactylogyrus rysavyi Ergens, 1970 in having a coiled penis passing through a tube of an accessory piece associated with a sigmoid rod, and shapes of haptoral parts, but these species differ from each other by turns of the penis and a connection point between the rod and tube of the accessory piece. This is the first record of Dactylogyrus from beloniform fish.
2017 The Japanese Society of Systematic Zoology