Abstract / Introduction / Summary:
Both fat minnow Rhynchocypris lagowskii steindachneri (Sauvage, 1883) (Leuciscidae) and dark chub Nipponocypris temminckii (Temminck and Schlegel, 1846) (Xenocyprididae) were recently reported as hosts of Argulus coregoni Thorell, 1864 from the Kushiko River, a tributary of the Hasu River, in Fukui Prefecture, central Japan. However, more recently, because the identification of the former fish species was found doubtful, we reexamined three individuals of leuciscid reported as “fat minnow” and identified them as a morphologically similar congener ic s pecies , ups t ream fat minnow Rhynchocypris oxycephala jouyi (Jordan and Snyder, 1901) (Leuciscidae). Furthermore, to confirm the occurrence of upstream fat minnow in the Kushiko River, we collected fishes in this river in October 2024 and identified specimens of leuciscid as the fish species. As a result of these works, we have concluded that the leuciscid recently reported from the Kushiko River was upstream fat minnow and the record of “fat minnow” was incorrect. Alternatively, upstream fat minnow becomes a correct host name and represents a new host record for A. coregoni because this parasite has never been found from the fish species occurring in the Far East. A specimen of A. coregoni was collected from a dark chub during the sampling in October 2024 and is reported as its third record from this xenocypridid fish.
