Coral - Coral

Japanese: サンゴ(珊瑚) - サンゴ

A general term for the species of coelenterates (anthozoans) that form a calcareous skeleton. Existing species are divided into octocorals and hexacorals. Octocoral polyps are characterized by eight tentacles and a septum, are cylindrical, and form colonies buried within a coelom. Under the mouth of the polyp is a coelenteron that does not differentiate into a stomach and a body cavity, and the mouth also functions as a cloaca. Fertilization usually takes place in seawater, and the fertilized egg progresses through a planula larva and then into an epiphytic life, after which it grows by budding. Corals that are prized as ornaments are calcareous skeletons secreted by colonies. Red coral, pink coral, and white coral are well known, and in the vicinity of Japan, they attach to rocks on the seabed several tens to several hundreds of meters deep off the coast of Shikoku, western Kyushu, and the Ogasawara Islands to Taiwan. They are collected with a coral net and used for necklaces and obi clasps. Hexacorals are characterized by having six or a multiple of six tentacles and septa. The scleractinian corals that form coral reefs are included in this category, and generally live on the shallow seafloor of warm seas, and there are many types. Deep-sea species that do not form colonies are also known. Corals have existed widely throughout geological time since the Ordovician period, and many of them are important index fossils.
→ Related topics Coelenterates | Birthstones | Gems

Source : Heibonsha Encyclopedia About MyPedia Information

Japanese:

腔腸(こうちょう)動物花虫類のうち，石灰質の骨格をつくる種類の総称。現生のものは八放サンゴ類，六放サンゴ類に分けられる。八放サンゴのポリプは８個の触手と隔膜とを特徴とし，円筒形，共肉内に埋まって群体を形成する。ポリプの口の下には胃と体腔の分化しない腔腸があり，口は排出腔としても働く。受精は普通海水中で行われ，受精卵は浮遊性のプラヌラ幼生を経て着生生活に入り，この後は芽生によって成長。装飾品として珍重される珊瑚は群体の分泌した石灰質の骨格である。アカサンゴ，モモイロサンゴ，シロサンゴが知られ，日本付近では四国沖，九州西部，小笠原〜台湾の数十〜数百mの海底の岩石等に着生。サンゴ網で採取され，首飾，帯留などに利用される。六放サンゴは６ないしその倍数の触手，隔膜をもつのが特徴。サンゴ礁を形成するイシサンゴはこれに含まれ，一般に暖海の浅海底にすみ，種類が多い。また群体を作らない深海性の種類も知られる。サンゴ類はオルドビス紀以来地質時代に広く存在し，示準化石として重要なものも多い。
→関連項目腔腸動物｜誕生石｜宝石

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