Hydra (English spelling)

Japanese: ヒドラ（英語表記）Hydra

A general term for species belonging to the genus Hydra, order Medusa, class Hydrozoa, family Hydra, family Cnidaria. The body is generally 1-1.5cm long and cylindrical, with 6-8 long tentacles around the mouth at the tip. There is a mouth and a stomach cavity next to it, but no anus. There are only polyp-type (→ polyps), and no medusa-type (→ jellyfish) stage. They mainly reproduce by budding, but are dioecious and also reproduce sexually. They live in ponds and swamps all over the country, attaching themselves to fallen leaves and aquatic plants in the water, and catch and eat water fleas with the nematocysts on their tentacles. In addition to the Hydra japonica (sometimes called Yamatohydra to distinguish it from other species), which is widely distributed throughout Japan, there are even smaller related species such as the genus Hydra, H. parva , and the green hydra, H. viridissima , which is found in Europe. (→ Cnidaria, Hydrozoa, Invertebrates)

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

Japanese:

刺胞動物門ヒドロ虫綱花クラゲ目ヒドラ科ヒドラ属に属する種の総称。体は一般に 1～1.5cmの細長い円筒形で，先端にある口の周囲に 6～8本の長い触手をもつ。口およびそれに続いて胃腔があるが，肛門はない。ポリプ型（→ポリプ）のみで，クラゲ型（→クラゲ）の時期はない。おもに出芽により繁殖するが，雌雄異体で，有性生殖も行なう。各地の池や沼などにすみ，水中の落ち葉や水草の上に付着し，触手上にある刺胞でミジンコなどを捕えて食べる。なお，日本各地に広く分布するヒドラ Hydra japonica（他種と区別するためにヤマトヒドラと呼ぶこともある）のほか，近縁種にさらに小型のヒメヒドラ H. parva やヨーロッパ産のグリーンヒドラ H. viridissima などがある。（→刺胞動物，ヒドロ虫類，無脊椎動物）

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