Question

How would changes to the way fish adjust their swim bladder be an advantage? What new niches could they fill?

Answer 1

The swim bladder is an internal gas filled organ that contributes to the ability of bony fish to control their buoyancy and thus to stay at their current water depth without having to waste energy in swimming.The walls of the bladder contain very fe blood vessels and are lined with guanine crystals which make them permeable to gases.Thus by adjusting the gas pressuring organ using the gas gland or oval window,the fish can obtain neutral buoyancy and ascend and descend to large range of depths.One clear advantage is that little to no extra energy is necessary at constant level of water .Only a slight control by use of the prectoral fin is required to balance out the propulsive force of water exiting the gills .Fish with no swim bladder  must use energy constantly by swimming in order to keep from sinking .Another advantage of swim baldder is oxygen storage .They can use this oxygen in the time of their need .Swim bladders in some fishes are known to increase hearing abilities .With the presence of inner air -swim bladder connection ,these fishes have exhibited greater sensitivity to sound .These are the advantages of having a swim bladder .This are the new niches that they could fill.