<P> The swim bladder normally consists of two gas - filled sacs located in the dorsal portion of the fish , although in a few primitive species , there is only a single sac . It has flexible walls that contract or expand according to the ambient pressure . The walls of the bladder contain very few blood vessels and are lined with guanine crystals , which make them impermeable to gases . By adjusting the gas pressurising organ using the gas gland or oval window the fish can obtain neutral buoyancy and ascend and descend to a large range of depths . Due to the dorsal position it gives the fish lateral stability . </P>
<P> The swim bladder normally consists of two gas - filled sacs located in the dorsal portion of the fish , although in a few primitive species , there is only a single sac . It has flexible walls that contract or expand according to the ambient pressure . The walls of the bladder contain very few blood vessels and are lined with guanine crystals , which make them impermeable to gases . By adjusting the gas pressurising organ using the gas gland or oval window the fish can obtain neutral buoyancy and ascend and descend to a large range of depths . Due to the dorsal position it gives the fish lateral stability . </P>
where is the swim bladder located in a fish
where is the swim bladder located in a fish
in the dorsal portion
in the dorsal portion