‘Scuba-diving’ lizards breathe underwater by attaching air bubbles to their snouts

You’re having a bubble! Biologists at Binghamton in the US and the University of Toronto in Canada have found that several species of anoles, a type of lizard often kept as pets, have evolved to breathe exhaled air underwater using a pocket of air clinging to their snouts.

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The team made the discovery after being shocked to observe the lizards spending long periods of time, sometimes up to 16 minutes, underwater despite being only semi-aquatic.

“We found that semi-aquatic anoles exhale air into a bubble that clings to their skin,” said lead author Chris Boccia, who completed the work while studying at the University of Toronto but is now based at Queen’s University. “The lizards then re-inhale the air, a manoeuvre we’ve termed ‘rebreathing’ after the scuba-diving technology.”

The researchers found that all of the anoles they sampled had skin that was hydrophobic, meaning it repels water. They believe that this could’ve allowed them to evolve the ‘scuba-diving’ ability thanks to their frequent diving to hide from predators.

Using an oxygen sensor positioned inside the rebreathed bubble, they found that the oxygen concentration decreased during the dive, suggesting the lizards were using it up.

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The researchers are now planning future projects to further understand the evolution of the physiology and behaviour related to the anoles’ rebreathing ability.

“The finding that different species of semi-aquatic anoles have evolutionarily converged to extract oxygen from their rebreathed air bubbles leads to other exciting questions,” said Lindsey Swierk, assistant research professor of biological sciences at Binghamton University. “For example, the rate of oxygen consumption from the bubble decreases the longer an anole dives, which could possibly be explained by a reduction in an anole’s metabolic rate with increased dive time.

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“Anoles are a remarkable group of lizards, and the number of ways that this taxon has diversified to take advantage of their environments is mind-boggling.”