Glossary

gas bladder

Gas-filled sac with 1-3 chambers, situated just below the vertebral column in most ray-finned fishes. Its primary function is to aid in buoyancy by offsetting the weight of heavier structures such as bone, but is also used for respiration or sound production in some species. Often reduced in benthic fishes and sometimes absent altogether. Also known as the air or swim bladder.

Used in 104 species profiles

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Related terms

benthic
Inhabiting or relating to the bottom of a body of water, e.g., a benthic organism.
buoyancy
The tendency or capacity to rise, float or sink in water.
Ostariophysan
Fish of the superorder Ostariophysi, members of which are characterised by possession of a Weberian apparatus, i.e., the anterior four or five vertebrae are modified as a protective casing for the bony ossicles which connect the inner ear and swim bladder. The order contains such orders as Cypriniformes, Characiformes, Gymnotiformes, and Siluriformes.
pseudotympanum
Translucent, triangular area in the humeral region, behind the opercle, without muscle and where the anterior part of the gas bladder is in direct contact with the skin. It is hypothesised to function as a hearing aid in many juvenile characoids and is present in adults of certain species, notably members of the family Cheirodontidae.
respiration
The process by which an organism acquires the oxygen necessary for metabolism and expels excess carbon dioxide formed during energy-yielding reactions.
vertebral column
The backbone; the spine; in fishes, the vertebrae running from skull to caudal fin which protect the spinal cord and haemal artery as well as providing attachment for certain muscles used for swimming.
Weberian apparatus
Anatomical structure connecting the swim bladder to the inner ear found in members of the fish superorder Ostariophysi. Conveys sound and changes in pressure, and comprises four or five modified vertebrae.

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