Although reptiles can't actually breathe underwater, some, known as ‘bimodal breathers’, have found ways to top up their oxygen levels while submerged. Some turtles increase their dive time by absorbing oxygen through blood-vessel-lined sacs called bursae in their cloaca (the single rear-body opening in reptiles, amphibians and birds); the water anole has been recorded re-breathing from air bubbles trapped on its head during subaquatic forays; and sea snakes can exchange gas through their skin, which may account for 30 per cent of their oxygen uptake.
Maintaining a low oxygen concentration in the blood helps to extract it from sea water, but can also compromise brain function. However, it seems the blue-banded sea snake has a solution. Scientists have discovered a hole known as a foramen in the top of the snake’s skull, linking its brain to a large network of oxygen-gathering blood vessels in its head.
Main image: Banded sea krait (Laticauda colubrina) © Getty Images
