A new record of host fish Gymnogobius sp. for glochidia of Pronodularia japanensis , and the availability of host species for the mussel at three paddy field ditches in the Kanto area of Central Japan

Abstract

A new record of host fish Gymnogobius sp. for glochidia of Pronodularia japanensis , and the availability of host species for the mussel at three paddy field ditches in the Kanto area of Central Japan Abstract This study investigates the availability of host species for glochidia of the unionid mussel Pronodularia japanensis at three paddy field ditches of Kyu-Sasagawa River ( Fujioka City, Gunma Prefecture ) , Okanogouyousui ditch ( Fujioka City, Gunma Prefecture ) , and Nagarakuyousui ditch ( Kawajima Town, Saitama Prefecture ) in the Kanto area in Central Japan. The number of glochidia that infected the fishes, the sites infected, and the glochidial encystment rate were determined using formalin-fixed specimens collected from each ditch. Chestnut gobies, Gymnogobius sp., that were infected with glochidia collected from the Okanogouyousui ditch were cultured in a tank ( 6 L, 24–27 ℃ ) for 10 days to study the appearance of the juvenile detached from the fish body. The major host species of glochidia was different in each study area. At Kyu-Sasagawa River and Okanogouyousui ditch, the glochidia were parasitic on only a few species such as Misgurnus anguillicaudatus and Opsariichthys platypus . At Nagarakuyousui ditch, the glochidia were parasitic on several fish species, such as Op. platypus, Oryzias sp., Rhinogobius sp., and Cyprinus carpio . Of three juveniles detached from the gobies, one survived in a test tube ( 30 mL ) for over 62 days at 21 ℃ . Gymnogobius sp. was identified as a suitable new host for the glochidia of P. japanensis .