Final answer:
The swim bladder is the structure that allows bony fishes to manage their buoyancy by exchanging gases with their blood.
Step-by-step explanation:
The structure that allows bony fishes to control their buoyancy using gases from their blood is known as the swim bladder. This gas-filled organ functions like a balloon that can fill or deflate to help the fish maintain its desired depth in the water column.
The swim bladder is connected to the bloodstream, enabling it to exchange gases directly, which affects the bladder's volume and thus, the buoyancy of the fish.
The swim bladder is considered homologous to the lungs of terrestrial vertebrates and lungfish, underscoring the evolutionary connection between aquatic and land animals.