Abstract / Introduction / Summary:
An ovigerous female of a freshwater fish parasite Argulus coregoni Thorell, 1864 was collected in the middle reaches of the Naruse River at Sanbongi-Saida, Osaki, Miyagi Prefecture, northern Honshu, Japan. The female was found on the body surface of one Japanese barbel [Hemibarbus barbus (Temminck and Schlegel, 1846)] among 177 individuals composing 69 Japanese barbel, 80 pale chub [Opsariichthys platypus (Temminck and Schlegel, 1846)], 16 Japanese dace [Pseudaspidus hakonensis (Günther, 1877)], seven pike gudgeon [Pseudogobio esocinus (Temminck and Schlegel, 1846)], four ayu [Plecoglossus altivelis altivelis (Temminck and Schlegel, 1846)], and one swamp moroko gudgeon [Gnathopogon elongatus elongatus (Temminck and Schlegel, 1846)]. These fishes were caught using a cast net on 12 October 2022 and transported alive to a laboratory in Tokyo, where they were examined the next day. Since the female of A. coregoni might have detached from a fish and then become attached to a different fish (Japanese barbel) during fish catch and transportation, a wild host in the Naruse River is not determined herein. The present collection of A. coregoni represents its first record from Miyagi Prefecture. In northern Honshu, A. coregoni has so far been reported from two prefectures (Fukushima and Akita), and Miyagi is the third prefecture where the species occurs. A possible wild host of A. coregoni in and near the sampling area is also discussed.