What adaptation allows the arowana to be a facultative air breather in oxygen-deprived environments?
Supplementing oxygen intake by drawing air into its swim bladder lined with capillaries resembling lung tissue
Arowanas possess a critical physiological adaptation enabling them to survive in challenging aquatic conditions, particularly those low in dissolved oxygen. They are classified as facultative air breathers, meaning they have the option to breathe atmospheric air when necessary. This process is facilitated by their swim bladder, which has evolved to be richly supplied with capillaries, giving it a structure highly similar to primitive lung tissue. When the fish takes a gulp of air from the surface, this oxygen-rich air enters the swim bladder, allowing oxygen to diffuse directly into the bloodstream, thus supplementing the oxygen obtained through regular gill respiration. This capability is vital for their predatory behavior near the water's surface.
