Ink gland

Japanese: 墨汁腺 - ぼくじゅうせん（英語表記）ink gland

An organ unique to cephalopod mollusks, it is a gland that secretes ink (commonly known as squid ink) located in the ink sac, located just dorsal to the anus above the rectum. The ink sac is dropper-shaped, and the ink duct (ink duct) has two sphincters near the opening to control the discharge of ink. Ink glands or ink sacs are thought to be unique to the Coleoidea, a bibranch class, and appear in fossils. They are not found in nautiluses or other cephalopods. They also appear early in development, and the hatched larvae (which are different from general "larvae" in the case of cephalopods) already have the ability to spit ink.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

軟体動物頭足類特有の器官で，直腸上の肛門のすぐ背側にある墨汁囊ink sac中にあって墨汁ink(いわゆるイカの墨)を分泌する腺。墨汁囊はスポイト状で，輸管(墨汁管)には開口近くに括約筋が二つあって墨汁の排出を制御できる。墨汁腺ないしは墨汁囊は二鰓（にさい）類Coleoideaに特有のものと考えられ化石にもあらわれる。オウムガイ類や他の頭足類にはみられない。また，発生初期からあらわれ，孵化（ふか）幼生(頭足類の場合一般の“幼生”とは異なるが)はすでに墨汁を吐く性質をもっている。

出典　株式会社平凡社世界大百科事典第２版について　情報

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