Copepods - Copepods

Japanese: カイアシ類 - カイアシるい（英語表記）copepod

A general term for small crustaceans classified as Copepoda in the subclass of the class Gnathopoda. They are also called Copepoda. Researchers call them Copepoda. Generally, they are 1-4 mm long. Many of them appear as marine plankton, and they live from the surface to the deep sea. They are classified as pelagic and coastal based on their habitat, and surface, mesopelagic, and deep based on their depth, but they move vertically day and night to avoid bright light. There are freshwater and brackish species, and some are significantly deformed due to parasitic life. The basic structure consists of an anterior body with the head and first thoracic segment fused together, and a posterior body with four segments in females and five segments in males. Long forked limbs branch off from the terminal segment of the posterior body. The appendages are not significantly differentiated, but the first antennae are long, which helps with movement and can also serve as a grasping organ during mating. They collect minute plankton by filtering it with the hairs on their second maxillary foot, and carry it to their mouths with the current of the water. The subclass Copepoda is divided into 11 orders, including Calanoida and Cyclopoida. There are more than 8,000 species in the world, of which about 500 are said to be found in Japan, and many of them serve as indicator species for warm and cold waters. (→ Gnathopoda, Arthropods)

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

Japanese:

顎脚綱カイアシ亜綱 Copepodaとしてまとめられる小型甲殻類の総称。橈脚亜綱（ぎょうきゃくあこう，じょうきゃくあこう，とうきゃくあこう）の名もある。研究者の間ではコペポーダと呼ばれている。一般に体長 1～4mm。海産のプランクトンとして出現するものが多く，表層から深海までにわたる。生息海域から外洋性と沿岸性に，深度から表層性，中層性，深層性とに分けられるが，明るい光を避けて昼夜垂直移動を行なう。淡水産種，汽水産種もあり，また寄生生活により変形の著しいものもある。基本的な体制は，頭部と第1胸節の癒合した前体と，雌では 4節，雄では 5節の後体からなる。後体の末節に続いて長い叉肢が分岐している。付属肢の分化は顕著でないが，第1触角が長く，運動を助けるほか，交尾の際の把握器官となることもある。微細なプランクトンを第2顎脚の毛でろ過して集め，水流によって口に運ぶ。カイアシ亜綱はカラヌス目 Calanoida，キクロプス目 Cyclopoidaなど 11目に分類される。世界に 8000種以上，そのうち日本産は約 500種といわれ，多くのものは暖流，寒流など水域の指標種となっている。（→顎脚類，節足動物）

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