0 an organ like a bag inside a fish that holds air so that it does not sink and stays in the correct position --
At this point, the free oxygen in the arterial capillaries diffuses into the swim bladder via the gas gland.
The fish contracts its sonic muscle fibers against the swim bladder to produce the croaking sound.
In appearance, they greatly resemble the typical cods, from which can only be distinguished by their skeletal features and the structure of the swim bladder.
After hatching, the larvae live among the plankton until they develop a swim bladder and transform into adults.
Deep-water teleosts, which do not have a swim bladder, have few lipids and proteins, deeply ossified bones, and watery tissues that maintain their buoyancy.
The fish produces the sound using the muscles of its modified swim bladder.
It is capable of filling its swim bladder with air and absorbing oxygen from it.
Since the shallows were subject to occasional oxygen deficiency, the ability to breath atmospheric air with the swim bladder became increasingly important.
