-Priyanti, Subject Matter Expert at Edumarz
Solution: The air bladder in Pisces is very important in providing them proper regulation of buoyancy. This organ is found only in bony fishes (Osteichthyes) and emerge as a sac-like outgrown from the dorsal wall of oesophagus. The air bladder is hydrostatic and by secreting and absorbing gases to and from it, these fishes can sink or rise to maintain a particular level in water without making any muscular movements. Sometimes the air bladder also assists in respiration. Cartilaginous fishes (Chondrichthyes) do not have this organ, consequently they have to keep swimming to avoid sinking.