Hidaberi sea anemone - Hidaberi sea anemone

A marine animal belonging to the phylum Cnidaria, class Anthozoa, subclass Hexacorallia, order Actiniaria, family Actiniidae. It is widely distributed in the subarctic zone surrounding the Arctic. Among the families that have a spear filament at the lower end of the septum, the family Actiniidae is characterized by the fact that the septum cannot be clearly divided into two sets of large and small, that it has a well-developed mesogel-like perioral muscle, and that it has two types of nematocysts on the spear filament, one of which is a nematocyst with an unclear boundary between the sting axis and the flagellum (called a short-base b type flagellate nematocyst). When the tentacles of this species are spread, they are 4 to 30 cm high and 5 to 15 cm wide, and the area around the mouth plate is significantly folded, with numerous short tentacles there. The tentacles vary in color from gray-brown, white, to orange, and the body wall is smooth and can vary in color from ochre, white, to orange. There are many spear holes in the body wall from which white spear threads emerge. Those found in the Atlantic Ocean belong to the original subspecies, while those found in the Pacific Ocean, such as Japan and North America, are distinguished as the subspecies M. senile fimbriatum . In Japan, they are found in abundance on the seabed several tens of meters below the intertidal zone on rocky coasts in the Tohoku region and Hokkaido.

[Hiroomi Uchida]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

刺胞(しほう)動物門花虫(はなむし)綱六放サンゴ亜綱イソギンチャク目ヒダベリイソギンチャク科に属する海産動物。北極を取り巻く亜寒帯に広く分布する。隔膜下端に槍糸(やりいと)をもつ諸科のなかで、ヒダベリイソギンチャク科は隔膜を大小2組に明らかに分けることができず、よく発達した中膠(ちゅうこう)性の周口筋をもち、槍糸に2種類の刺胞をもち、その一方が刺糸軸部から糸鞭(しべん)部への境がはっきりしない刺胞（短基b型有鞭刺胞とよばれる）であることを特徴とする。この種は触手を広げると高さ4～30センチメートル、幅5～15センチメートルで、口盤の周辺は著しく褶曲(しゅうきょく)し、そこに無数の短い触手をもつ。触手の色は灰褐色、白色、橙(だいだい)色などの変異があり、体壁は滑らかで、色彩は黄土色、白色、橙色などと変異に富む。体壁には多くの槍孔(やりあな)があり、そこから白い槍糸を放出する。大西洋産は原名亜種に属し、日本や北アメリカなど太平洋のものは亜種M. senile fimbriatumとして区別される。日本では東北地方、北海道の岩礁海岸の潮間帯より数十メートルの海底に多産する。

［内田紘臣］

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