air bladder

air bladder

noun
1.
a vesicle or sac containing air.
2.
Also called gas bladder, swim bladder. Ichthyology. a gas-filled sac located against the roof of the body cavity of most bony fishes, originally functioning only as a lung, now serving in many higher fishes to regulate hydrostatic pressure.

Origin:
1725–35

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Based on the Random House Dictionary, © Random House, Inc. 2014.
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Collins
World English Dictionary
air bladder
 
n
1.  ichthyol Also called: swim bladder an air-filled sac, lying above the alimentary canal in bony fishes, that regulates buoyancy at different depths by a variation in the pressure of the air
2.  any air-filled sac, such as one of the bladders of seaweeds

Collins English Dictionary - Complete & Unabridged 10th Edition
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American Heritage
Science Dictionary
air bladder  
  1. An air-filled sac in many fish that helps maintain buoyancy or, in some species, helps in respiration, sound production, or hearing. Also called swim bladder.

  2. See float.


The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

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 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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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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