They must also keep swimming to keep from sinking, since most have largely or completely lost the swim bladder, the gas-filled sac that helps most other fish remain buoyant.

它们还必须不停地游动以避免下沉，因为大多数鱼基本上或完全失去了鱼鳔，这个充满气体的囊帮助大多数其他鱼保持浮力。

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Fish generally respire through gills. most bony fish es have a swim bladder a gas-filled organ used to adjust swimming depth.

一般是经由鳃呼吸。大部分硬骨鱼有鳔，这是源于消化管的憩室，司控制浮力或为辅助呼吸器官。

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