gas bladder

anatomy

Also known as: air-breathing organ

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July 22, 2026

Quick Summary

The term "gas bladder" is more commonly known as a swim bladder. This is an internal organ found in most bony fish that helps them control their buoyancy. It contains gas, usually oxygen, allowing fish to maintain their depth without sinking or floating uncontrollably.

In some primitive fish, the swim bladder can also function as a lung or an accessory breathing organ. While most bony fish have a swim bladder, it is absent in cartilaginous fish like sharks and rays, as well as some bottom-dwelling and deep-sea bony fish. The swim bladder can also be used by some fish to produce or receive sound.12

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gar
… called a gas bladder or air-breathing organ, which is vascularized to allow for gas exchange with the body. Their jaws and face form a sharp-toothed beak, and their bodies are encased in an armour of diamond-shaped, thick, enameled (ganoid) scales.
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… called a gas bladder or air-breathing organ, which is vascularized to allow for gas exchange with the body. Their jaws and face form a sharp-toothed beak, and their bodies are encased in an armour of diamond-shaped, thick, enameled (ganoid) scales.
Read More