Myriapods - Tasokurui

Among the five classes of arthropods that have adapted to life on land and have a pair of antennae on their heads, this is the general term for the four classes excluding Insecta (Polypoda, Diplopoda, Chilopoda, and Synechopoda). These animals have a distinct head and torso, long torsos, and many limbed segments, and are very similar in appearance to one another. They also share many common characteristics, such as ocelli, tracheal breathing, an open circulatory system, and Malpighian tubules. Their exoskeletons are chitinous or calcareous. They are generally dioecious, and lay eggs that are fertilized by mating or a spermatophore. Most undergo segmental metamorphosis, but some Chilopoda only undergo micrometamorphosis. However, these are also characteristics shared with insects, and the name Myriapoda has become less meaningful in taxonomic terms. There is also a theory that oligopods and diplopods are grouped together as dipterans, and chilopoda, symphysodon, and insectivores as trignathates. Of the four classes of myriapods, only chilopoda have venom claws on their mouthparts and are strictly carnivorous, while the others are scavengers.

[Keizaburou Shinohara]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

陸上生活に適応した節足動物のうちで、頭に1対の触角をもつ5綱の動物群のうち、昆虫綱を除いたほかの4綱（少脚綱(しょうきゃくこう)、倍脚綱、唇脚綱(しんきゃくこう)、結合綱）をまとめて便宜的によぶ総称。これらの動物は頭部と胴部が区別でき、胴は長く、多くの有肢体節からなり、外見上互いによく似ており、さらに単眼、気管呼吸、開放循環系、マルピーギ管など共通の特徴も多い。外骨格はキチン質か石灰質。一般に雌雄異体で、交尾または精包によって受精された卵を産む。変態は多くは増節変態をするが、唇脚類には微変態だけ行うものもある。しかし、これらは昆虫類と共通する特徴でもあり、分類学的に多足類という名称は意義が薄れている。むしろ少脚類と倍脚類をまとめて双顎類(そうがくるい)とし、唇脚類、結合類、昆虫類をまとめて三顎類(さんがくるい)とする説もある。多足類の4綱のうち唇脚類だけが口器に毒づめをもち、完全な肉食動物であり、ほかは腐食性である。

［篠原圭三郎］

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