A thin membranous, sometimes alveolated sac in the dorsal portion of the abdominal cavity. Contains a varying mixture of gases, not identical to the composition of air. May be one, two or three chambered. May be connected to the gut by a tube, the ductus pneumaticus (then called physostomous) or unconnected (then called physoclistous). [ http://www.briancoad.com/Dictionary/S.htm ]

Synonyms: gas bladder swimbladder

This is just here as a test because I lose it

Term information


efo_slim, organ_slim

external definition

Cavitated compound organ that is double-chambered, located in the coelom and used to maintain buoyancy and may function as an acoustic resonator.[TAO]

function notes

May function as one or more of: hydrostatic organ, sound producing organ, sound receptor, respiratory organ

has alternative id


has related synonym

air bladder

fish maw

homology notes

Lungs had already developed as paired ventral pockets from the intestine in the ancestor of Osteognathostomata. (...) In actinopterygian fishes, apart from Cladistia, the ventral intestinal pocket migrates dorsally and becomes the swim-bladder, a mainly hydrostatical organ (reference 1); Comparative transcriptome analyses indicate molecular homology of zebrafish swimbladder and Mammalian lung (reference 2).[well established][VHOG]



taxon notes

Found in Actinopterygii. Often lacking in bottom fishes