The Swim Bladder of a Goldfish

Goldfish Swim Bladder Anatomy

A goldfish’s swim bladder consists of two small gas-filled sacs located near its dorsal region. The gas-filled sacs of the swim bladder have the ability to expand and contract from the ambient pressure of the surrounding water. The swim bladder sac material contains crystal guanine making it impermeable to gasses. A goldfish can add or subtract air into its swim bladder through its gas gland. By creating lactic acid and carbon dioxide, the hemoglobin of goldfish’s blood looses oxygen and some of that oxygen is diffused into the swim bladder. Through what is called the oval window, these gases can also be diffused back into the blood stream.

Function of a Swim Bladder

The swim bladder in a goldfish work similarly as a ballast tank in a submarine does. By adding or subtracting air in the swim bladder, the buoyancy of the goldfish allows it to sit submerged at certain depth with out an extra effort. The location of the swim bladder in the dorsal region gives the goldfish lateral stability and keeps it from rolling over upside down. Not only does it help with the buoyancy and stability of the goldfish, it assists in its sense of hearing.






photo credit: ellenm1