The water anole (Anolis aquaticus) seems to be able to breathe underwater by using a bubble of air trapped on its nose.
Bubble on the nose
This extraordinary behaviour has been observed and filmed for the first time by ecologist Lindsey Swierk of Binghamton University, New York. “They are probably extracting lower concentrations of oxygen every time they’re respiring the air bubble, but it might just be enough to keep them underwater for long enough that they can escape a threat,” she said. Even though the bubble is relatively large, it remains attached to the lizard’s head rather than floating off to the surface.
The bubble only remains in place for a second before the bulge completely disappears. This process repeats every few seconds as inhalation and exhalation of the air bubble allows for some exchange of fresh air among these air pockets.
Several aquatic insects and spiders have special adaptations —some hairy protrusions or other texture, combined with a hydrophobic or waxy coating—that allow them to trap a layer of air, called a “plastron,” to breathe underwater. In some cases, it has been shown that these bubbles actually function as gills—oxygen diffuses into the bubble from the surrounding water while carbon dioxide diffuses out. Whether this is also the case with the lizard, it being much larger, is another question.
In moving water, such as the stream in which this lizard lives, there may be some re-oxygenation of the bubble air by diffusion from the water. In the absence of significant gas exchange between the water and the air bubble in between breaths, the bubble trick could also be a way of suppressing a breathing reflex in the lizards.
There may be alternative explanations, and a diving duration of 16 minutes does not seem too long, taking into account a dive response, the lower temperature and lower metabolic rates of reptiles and a high anaerobic capacity indicated by lactate accumulation.