Masato Nitta

A new species of Dactylogyrus (Monogenea: Dactylogyridae) parasitic on an endangered freshwater fish, Rhodeus atremius atremius, endemic to Japan

A new dactylogyrid monogenean Dactylogyrus bicorniculus sp. nov. is described from the gills of the kazetoge bitterling, Rhodeus atremius atremius (Jordan and Thompson, 1914), an endemic species in Japan, from Saga Prefecture, northern Kyūshū. D. bicorniculus sp. nov. resembles Dactylogyrus bicornis Malevitskaja, 1941 and Dactylogyrus lophogonus Zhang and Ji, 1980 because they have two common features, a large V-shaped ventral bar and well-developed second marginal hooks. However, the new species is distinguished from these congeners by a shorter penis and an accessory piece. A phylogenetic analysis of 28S rDNA shows that D. bicorniculus sp. nov. is a basal species with the T-shaped ventral bar in the genus. The new species has strict host-specificity to R. a. atremius, one of the endangered freshwater fishes in Japan, and may face the danger of co-extinction with its host.

A new species of Furcohaptor Bijukumar & Kearn, 1996 (Monogenea: Diplectanidae) parasitic on Cynoglossus robustus Günther (Pleuronectiformes: Cynoglossidae) in the Seto Inland Sea, Japan, with comments on its systematic position and an amended generic diagnosis of Furcohaptor

Furcohaptor brevis n. sp. is described from the gills of Cynoglossus robustus Günther caught in the Seto Inland Sea off Hiroshima Prefecture, Japan. Although Furcohaptor Bijukumar & Kearn, 1996 has been assigned to the Ancyrocephalinae Bychowsky, 1937 in the Dactylogyridae Bychowsky, 1933, this genus is transferred to the Diplectaninae Monticelli, 1903 in the Diplectanidae Monticelli, 1903 based on both morphological and molecular data. An amended generic diagnosis is provided.