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栃木県大田原市の用水路においてマツカサガイの稚貝を採集
伊藤 寿茂(1), 鬼塚 年弘(2), 丸山 隆(3)
　(1)新江ノ島水族館
　(2)東京大学海洋研究所
　(3)東京海洋大学

Abstract: Three juveniles of freshwater unionid mussel Pronodularia japanensis (smaller than 10mm in shell length) were collected in a paddy field ditch in Tochigi Prefecture, central Japan. The juvenile shell morphology greatly differs from that of adults. Shell of 2.8 mm and 3.1 mm in shell lenght are entirely milky white, and their surface is strongly rugose with pineal sculpture. All three individuals were collected from the bottom ob ditch. The densities of the species were 3.8 inds/m².