How dissimilar are the swimming strategies in osteichthyes and in chondrichthyes? Why do sharks need to agitate their body to swim while bony fishes do not?
Bony fishes have a specialized organ known a gas bladder, or swim bladder, whose interior can be filled with gas liberated from gas glands. The swim bladder works as a hydrostatic organ as it varies the relative density of the body regulating buoyancy and the depth of the animal in water.