Akanishi - Akanishi

A gastropod shell of the family Muricidae in the phylum Mollusca. It is found throughout Japan from southern Hokkaido to Kyushu and the Korean peninsula, living on sandy and muddy bottoms from the intertidal zone of inland bays to depths of about 20 meters. It is said to have recently been introduced into the Black Sea. It is a large species, with a shell height of about 20 cm and a shell diameter of about 17 cm. The shell is thick and hard, with a low, fist-shaped spiral spire. The shell base color is pale bluish brown with thin spiral ribs and black spots on top. The body layer is large, and usually has a low, horn-shaped protrusion on the shoulder. The shell opening is wide, and the inner surface of the adult shell is a red smooth layer. The operculum is leathery, thick, large, and dark brown. The nucleus is on the outside. The spawning season is summer, and many egg capsules are laid on pebbles, shells, or sunken wood on the seabed. The egg capsules are called naginata nightshade due to their shape. They are carnivorous and feed on useful bivalve mollusks. The flesh is edible and somewhat tough but tasty. The shells are used as materials for crafts.

[Takashi Okutani]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

軟体動物門腹足綱アクキガイ科の巻き貝。北海道南部から九州までの日本各地と朝鮮半島に分布し、内湾の潮間帯から水深20メートルぐらいまでの砂泥底にすむ。最近、黒海にも移入したといわれる。大形種で、殻高20センチメートル、殻径17センチメートルぐらいになる。殻は厚くて堅く、螺塔(らとう)は低く拳(こぶし)形。殻の地色は淡い青褐色で細い螺肋(らろく)があり、その上に黒い斑条(はんじょう)がある。体層は大きく、肩に通常低い角(つの)状の突起ができる。殻口は広く、成貝では内面が赤色の滑層となっている。蓋(ふた)は革質で厚く大きく暗褐色。核は外側にある。産卵期は夏季で、海底の小石や貝殻または沈木などに多数の卵嚢(らんのう)を産み付ける。卵嚢はその形からナギナタホオズキとよばれる。肉食性で有用二枚貝を食害する。肉は食用となり、いくぶん堅いが美味である。殻は細工物の材料に利用される。

［奥谷喬司］

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