Abstract / Introduction / Summary:
Argulus coregoni Thorell, 1864 was collected from the body surface of ayu, Plecoglossus altivelis altivelis (Temminck and Schlegel, 1846), in the middle reaches of the Toyo River at Kiyosaki-Yokohata in Shitara, Aichi Prefecture, central Japan. One of five ayu examined was infected with two (male and female) adults of A. coregoni. This collection represents the second record for A. coregoni from ayu in the Toyo River. In Aichi Prefecture, the species has been collected only from the Toyo River system. The life cycle of A. coregoni using ayu as its host in the middle reaches of the river is also discussed.