Peridinium (English spelling)

Japanese: ペリディニウム（英語表記）Peridinium

A genus of unicellular dinoflagellates consisting of two hemispherical or conical shells joined together, the upper shell is made up of 14 armor plates and the lower shell is made up of seven armor plates. The tips of the upper and lower shells are often sharp and horn-like. The body is dorsoventrally shaped, with two flagella emerging from the center of the ventral surface, one of which extends around a horizontal groove in the center of the body and the other extends backward along a vertical groove. These two flagella allow the organism to rotate its body as it swims. In addition to asexual reproduction by binary fission, the organism reproduces sexually by forming male and female gametes.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

2個の半球状ないしは円錐状の殻部が上下に合わさってできた単細胞性の渦鞭毛藻の1属で，14枚の鎧（よろい）板で上殻を，7枚の鎧板で下殻をつくる特徴がある。上殻と下殻の先は角状にとがるものが多い。体には背腹性があり，腹面の中央部から2本の鞭毛が出るが，そのうちの1本は体の中央部の横溝を巻くようにのび，他の1本は縦溝に沿って後方にのびる。これら2本の鞭毛により体を回転させながら泳ぐ。生殖は2分裂の無性生殖のほかに雌雄の配偶子形成による有性生殖を行う。

出典　株式会社平凡社世界大百科事典第２版について　情報

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