DAO 71:169-173 (2006)  -  doi:10.3354/dao071169

Virus-like particles associated with mass mortalities of the pen shell Atrina pectinata in Japan

Yukio Maeno1,*, Tatsuya Yurimoto1, Hiroshi Nasu2, Shiro Ito3, Noboru Aishima4, Tomomasa Matsuyama5, Takashi Kamaishi5, Norihisa Oseko5, Yasunori Watanabe6

1Seikai National Fisheries Research Institute, Fisheries Research Agency, Taira, Nagasaki 851-2213, Japan
2Kumamoto Prefectural Fisheries Research Center, Oyanonaka, Kami-Amakusa, Kumamoto 869-3603, Japan
3Saga Prefectural Fisheries Division, Jonai, Saga 840-8570, Japan
4Fukuoka Fisheries and Marine Technology Research Center, Freshwater Laboratory, Yamada, Asakura, Fukuoka 838-1306, Japan
5National Research Institute of Aquaculture, Fisheries Research Agency, Minami-Ise, Mie 516-0193, Japan
6National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, Maruishi, Hatsukaichi, Hiroshima 739-0452, Japan

ABSTRACT: Mass mortalities of the pen shell Atrina pectinata occurred in the fishing grounds of Ariake Bay, in southwestern Japan, during late spring and summer in 2003 and 2004. Histological examination revealed extensive necrosis in the epithelial cells of the kidney and gill, and impairment of the endothelial cells of the mantle arteria. Although cestode larvae belonging to the genus Tylocephalum were found in the mantle, adductor muscle, kidney, and digestive gland, their prevalence and the intensity of infection were low. Examinations of moribund pen shells for Haplosporidium spp. infection using PCR analysis and for Perkinsus spp. infection using Ray’s fluid thioglycollate medium were negative. Unenveloped virus-like particles were detected by transmission electron microscopy in the cytoplasm of affected kidney and gill cells of moribund pen shells. They were icosahedral spherical and 50 to 55 nm in diameter. These virus-like particles found in moribund pen shells are different from those described in other marine mollusks, and may be the causative agent of the mass mortalities of pen shells.

KEY WORDS: Bivalve · Pen shell · Atrina pectinata · Virus-like particles · Histology · Transmission electron microscopy

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