A general term (illustration) for invertebrates belonging to the Chaetognatha phylum, or one of these species. All arrow worms live a floating life in the ocean. They have fins on the sides of their bodies and are so named because they move quickly and straight like an arrow. About 30 species are known to live in the waters near Japan. Body lengths are usually 1-4 cm, but some, such as the giant arrow worm Sagitta hexaptera , can reach up to 10 cm. Their bodies are colorless and transparent, and are divided into three sections by a diaphragm: the head, trunk, and telson, with three body cavities inside. Source: Heibonsha World Encyclopedia, 2nd Edition Information |
毛顎動物門に属する無脊椎動物の総称(イラスト),またはそのうちの1種を指す。ヤムシ類はすべて海中で浮遊生活する。体側にひれがあり,矢のようにすばやく直進するところからこの名がある。日本近海から30種ほどが知られている。 体長はふつう1~4cmであるが,オオヤムシSagitta hexapteraのように10cmほどになるものもある。体は無色透明で,横隔膜によって頭部,体幹,尾節の3部に区分され,内部は三つの体腔になっている。
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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