A: Swim bladder, also called air bladder, buoyancy organ possessed by most bony fish. The swim bladder is located in the body cavity and is derived from an outpocketing of the digestive tube. It contains gas (usually oxygen) and functions as a hydrostatic, or ballast, organ, enabling the fish to maintain its depth without floating upward or sinking. It also serves as a resonating chamber to produce or receive sound. In some species the swim bladder contains oil instead of gas. In certain primitive fish it functions as a lung or respiratory aid instead of a hydrostatic organ. The swim bladder is missing in some bottom-dwelling and deep-sea bony fish (teleosts) and in all cartilaginous fish (sharks, skates, and rays).
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Teleost fish in cross section.
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Related Topics: Baroreception
The Editors of Encyclopaedia Britannica
This article was most recently revised and updated by Adam Augustyn, Managing Editor, Reference Content.
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Bladder, membranous sac in animals that serves as the receptacle of a fluid or gas. See gallbladder; swim bladder; urinary bladder.
Related Topics: Bladder cancer Urinary bladder Swim bladder Ureter
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Teleost fish in cross section.
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urinary bladder
Urinary bladder, in most vertebrates, except birds, organ for the temporary storage of...…
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