A beautiful green alga of the family Porphyraea (illustration). Before maturity, the body is single-celled and needle-shaped, 4-6 cm tall, with one nucleus at the base. At maturity, an umbrella-shaped reproductive organ forms at the apex of the body, and the nucleus at the base divides to produce multiple nuclei, which then rise by protoplasmic streaming to the umbrella part, where they produce male and female gametes. When fully mature, the umbrella has a diameter of 1-1.5 cm. The stem part deposits calcium carbonate, turning white when it dries. It is found in tropical and subtropical waters where coral reefs are well developed, and it grows particularly well on dead corals. Source: Heibonsha World Encyclopedia, 2nd Edition Information |
カサノリ科の美しい緑藻(イラスト)。成熟前の体は単細胞,針状形で,高さ4~6cmになり,根もとに1個の核をもつ。成熟すると,体の頂端に傘状の生殖器官ができ,根もとの核は分裂して多数の核となり,それらは原形質流動により上昇して傘の部分に移動し,ここに雌雄の配偶子をつくる。傘は十分成熟すると直径1~1.5cmとなる。茎の部分は炭酸カルシウムを沈着させるので,乾くと白色となる。サンゴ礁の発達する熱帯~亜熱帯海域に分布し,とくにサンゴの死骸の上によく生育する。
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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