Isopods - Isopods

Japanese: 等脚類 - とうきゃくるい（英語表記）isopod

A general term for crustaceans belonging to the Isopoda order of the Malacostraca. This group includes sea lice and woodlouse, and is generally flattened dorsally and ventrally. They basically consist of a head, seven thoracic segments, and six abdominal segments, but the abdominal segments are fused and there are significant deformations due to parasitic life. They have fixed compound eyes. In addition to terrestrial and freshwater species, many species are known from the intertidal zone to the deep sea zone, and their lifestyles are diverse. Most free-living species are 1 to several centimeters in length, but the largest, the giant isopod Bathynomus giganteus , can reach a body length of 45 cm. There is almost no difference in size between males and females. The hosts of parasitic species are fish and crustaceans, and in these cases the males are always smaller than the females. Protoandrogenous hermaphrodites are also known. Females form a brood pouch at the base of their thoracic legs, in which they raise their eggs. They are divided into 11 suborders, and about 8,500 species are known worldwide. (→ Arthropods, Malacostraca)

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

Japanese:

軟甲綱等脚目 Isopodaに属する甲殻類の総称。フナムシ，ワラジムシなどに代表される一群で，一般に背腹に扁平。基本的には頭部，7胸節，6腹節からなるが，腹節の癒合や，寄生生活による著しい変形がみられる。眼は固定した複眼。陸生種，淡水産種のほか，潮間帯から超深海帯まで多くの種が知られており，生活様式も多岐にわたっている。自由生活種は 1cmから数cmのものが多いが，最大のダイオウグソクムシ Bathynomus giganteus は体長 45cmに達する。雌雄の大きさの差はほとんどない。寄生性種の宿主は魚類と甲殻類で，この場合雄は雌より常に小さい。また雄性先熟の雌雄同体の種も知られている。雌は胸脚の基部に哺育嚢を形成し，この中で卵を育てる。11亜目に分けられ，世界で約 8500種が知られる。（→節足動物，軟甲類）

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