The swim bladder of modern bony fishes?

The swim bladder of modern bony fishes is indeed a fascinating adaptation that evolved from ancestral structures similar to lungs. This organ allows bony fishes to control their buoyancy in water, enabling them to maintain their position within the water column without expending energy swimming. The connection between the swim bladder and the lungs can be traced back to ancient fish that had a functional lung for respiration, which later evolved into the swim bladder in bony fishes.

This transition illustrates a significant evolutionary innovation, as it allowed for a more efficient means of buoyancy control compared to using swim bladders derived from other structures. The evolution of the swim bladder showcases the adaptability of fish in aquatic environments, making it a defining characteristic of modern bony fishes.