Red Gland

Japanese: red gland（英語表記）redgland

...There are two types of fish: those in which the airway formed during the development of the swim bladder remains there throughout life, connecting the swim bladder to the digestive tract (salmon, sardines, carp, eels, etc.), and those in which the airway disappears secondarily and there is no connection between the two (sea bass, red sea bream, Pacific cod, etc.). In swim bladders that lack an airway, a red gland (gas gland) consisting of a collection of capillaries develops in part of the wall, and secretes gases (carbon dioxide, oxygen, nitrogen, etc.) from the blood to regulate the amount of gas in the swim bladder. The swim bladder is not only involved in buoyancy regulation, but in some species it can also be involved in hearing and water pressure sensation, and some fish, such as rockfish and croaker, make sounds by vibrating the swim bladder wall. ...

From [Deep Sea Fish]

…Vertical movement is achieved by adjusting the buoyancy of the swim bladder, so the energy required for vertical movement is thought to be not very large. In fact, the swim bladder of these fish has a well-developed oval and red gland that adjust buoyancy by absorbing and releasing gas between the blood and the swim bladder. The speed of ascent and descent is slow, about a few meters per minute, and the start time and upper limit of ascent are controlled by changes in underwater illuminance and also differ depending on the species. …

*Some of the terminology that mentions "red gland" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…うきぶくろの発生時にできた気道が終生存在してうきぶくろと消化管の間に連絡がある型(サケ，マイワシ，コイ，ウナギなど)と，気道が二次的に消失して両者の連絡がなくなる型(スズキ，マダイ，マダラなど)とがある。気道を欠くうきぶくろでは壁の一部に毛細血管の集合した赤腺red gland(ガス腺)が発達し，血液中のガス(二酸化炭素，酸素，窒素など)を分泌してうきぶくろ内のガス量を調節する。うきぶくろは浮力調節に関与するだけでなく，種類によっては聴覚や水圧感覚に関与することもあり，カサゴやニベのように鰾壁（ひようへき）を振動させて発音する魚もある。…

【深海魚】より

…鉛直移動はうきぶくろの浮力調節により行われているので，鉛直移動に要するエネルギーはそれほど大きくないと思われる。実際にこれらの魚のうきぶくろには，血液とうきぶくろとの間でガスを吸収，放出することにより浮力を調節する機能をもつ，卵状体ovalと赤腺red glandがよく発達している。上昇，下降の速度は，毎分数m程度とゆっくりしており，その開始時刻や上昇の上限は水中照度の変化に支配されており，また種によっても異なっている。…

※「red gland」について言及している用語解説の一部を掲載しています。

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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