Tardigrada; water bear; bear-animalcule

Japanese: 緩歩動物 - かんぽどうぶつ（英語表記）Tardigrada; water bear; bear-animalcule

A general term for animals belonging to the Tardigrade phylum. They are the smallest multicellular organisms, measuring less than 1mm in length. Their bodies are transparent, cylindrical, and covered with a thin cuticle. In addition to the head, they have four body segments, each with a pair of tardigrades. They generally have two claws at the tip of their feet, suggesting a relationship with onychophora. They lack a respiratory or circulatory system, and sometimes also excretory organs. They have two needles in their mouths, which they use to pierce plant tissue and suck out tissue fluids. They are often found in mosses and leaf litter, but can also be found in freshwater and seawater. They are highly resistant to environmental changes, and can survive for several years in a state of suspended animation even when dry. They can withstand extremely low temperatures. They are relatively rare in the tropics, and the higher the latitudes, the more common species there are worldwide, and the higher the population density. There are about 370 species in the world, of which about 100 are found in Japan. They are placed between pouched animals and arthropods, but are thought to be a group of animals that has devolved during the evolutionary process.

Source: Encyclopaedia Britannica Concise Encyclopedia About Encyclopaedia Britannica Concise Encyclopedia Information

Japanese:

緩歩動物門に属する動物の総称で，和名はクマムシ類。多細胞生物としては最小の部類で，体長 1mm以下。体は透明，円筒形で，薄いクチクラにおおわれる。頭部のほかに4胴節があり，それぞれに1対ずつ疣足 (いぼあし) をもつ。足の先端に一般に2本の爪をもち，有爪動物との関連を思わせる。呼吸器系，循環器系を欠き，ときに排泄器も欠く。口には2本の歯針があり，これで植物体に穴をあけて組織液を吸う。コケ類や落葉土壌中に多いが，淡水や海水中にもみられる。環境変化に対する耐性が大きく，乾燥しても仮死状態で数年間は生存可能という。超低温にも耐えることができる。熱帯には比較的少く，高緯度地域ほど世界的な共通種も多く，個体密度も高くなる。世界に約 370種，そのうち日本産は約 100種。袋形動物と節足動物の中間におかれるが，進化の過程で退化した動物群と考えられる。

出典　ブリタニカ国際大百科事典小項目事典ブリタニカ国際大百科事典小項目事典について　情報

<<: Ganhodoki - Ganhodoki

>>: Campos (English spelling)