Anole lizards have adapted their own version scuba diving

A new study led by Binghamton University has revealed how some Anolis lizards, or anoles, can submerge themselves underwater for up to 16 minutes at a time. The anoles have adapted their own natural version of a scuba tank by “rebreathing” air that is trapped between their skin and the surrounding water.

“Rebreathing had never been considered as a potential natural mechanism for underwater respiration in vertebrates,” said study co-author Professor Luke Mahler. “But our work shows that this is possible and that anoles have deployed this strategy repeatedly in species that use aquatic habitats.”

Anoles live along neotropical streams and frequently dive underwater for refuge. While documenting this behavior with a GoPro in Costa Rica, Professor Lindsey Swierk was shocked to see an anole submerge itself for such long periods. 

“It’s easy to imagine the advantage that these small, slow anoles gain by hiding from their predators underwater – they’re really hard to spot!” said Professor Swierk. “But the real question is how they’re managing to stay underwater for so long.”

The researchers conducted experiments to study underwater respiration in several distantly related species of semi-aquatic anoles. They found that the lizards can respire underwater by ‘rebreathing’ exhaled air that is held in a bubble that clings to their snout.

“We found that semi-aquatic anoles exhale air into a bubble that clings to their skin,” said study lead author Chris Boccia. “The lizards then re-inhale the air, a maneuver we’ve termed ‘rebreathing’ after the scuba-diving technology.”

The experts believe that the function of the anoles’ hydrophobic skin may have shifted throughout evolution to facilitate rebreathing in species that regularly dive. The team’s findings strongly suggest that specialized rebreathing is adaptive for semi-aquatic habitat specialists. 

The researchers used an oxygen sensor inside the bubbles to determine whether anoles were consuming oxygen from them. Just like a scuba tank, the oxygen concentration in an anole’s air bubble was found to decrease over the length of the dive.

“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 Professor Swierk. 

“For example, the rate of oxygen consumption from the bubble decreases the longer an anole dives, which could possibly be explained a reduction in an anole’s metabolic rate with increased dive time,” added study co-author Alexandra Martin.

The researchers are planning future projects to better understand the evolution of the physiology related to rebreathing. 

“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,” said Swierk.

The study is published in the journal Current Biology.

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By Chrissy Sexton, Earth.com Staff Writer