Wiktionary
gas bladder
n. (context ichthyology English) An internal organ that fish use to control their buoyancy, allowing them to maintain or change depth by changing their density.
Usage examples of "gas bladder".
Ooryl's body has a muscular gas bladder that allows Ooryl to, among other things, draw in gases and expel them at a controlled rate through pieces of Gand exoskeleton that vibrate and approximate speech.