Anole, aquatic, breathing underwater

Anole Lizards That Act Like Scuba Divers With Natural Oxygen Tanks

Semi-aquatic anole lizards use natural oxygen tanks, a bubble of air on their snout to dive underwater. Researchers from Canada and New York studied the phenomena. According to their research, anoles could stay underwater for up to 16 minutes or more. Furthermore, some non-aquatic anoles had a similar but much more limited ability.

By diving, an anole could evade predators in the tropical forests it inhabits. First, the reptiles leap into a stream or pond and dive. Then, they cling to rocks and debris until the danger has passed.

Long ago, the natural oxygen tanks were observed in 2009. Initially, researchers observed an endangered semi-aquatic anole from Haiti. However, an earthquake in 2010 delayed further study.

After many years, evolutionary biologist Chris Boccia from Queen’s University looked for similar behavior. However, he traveled in Costa Rica, Colombia, and Mexico.

Tiny Sensors to Measure Oxygen in Bubbles

Finally, Boccia and Canadian colleagues observed the anoles diving. Then, using tiny oxygen sensors, they could find out if the lizards were breathing underwater.

“This is not as easy as it sounds; bubbles were frequently re-inhaled quickly, and diving anoles do not take kindly to being accidentally poked in the nose with a probe,” Boccia writes. “But we persevered and found that bubble oxygen levels decreased through time, consistent with the respiration hypothesis!”

Meanwhile, Lindsey Swierk, an assistant research professor of biological sciences at Binghamton University, also observed Costa Rican diving anoles. As a “world authority on Costa Rica’s diving anoles,” Boccia invited her to join the other researcher’s project, he writes.

“Over the past few years, I’ve been accumulating evidence that the water anole (Anolis aquaticus) might be a tiny scuba diver in the streams of its home in southern Costa Rica. Anolis aquaticus takes to the water as refuge from predators, swimming and often diving underwater for long periods of time – the record at my study site is currently 16 minutes!” Swierk wrote in 2018.

Below, see a video Swierk shared about the anole lizards breathing underwater.

Rebreathing Air Like Reptilian Scuba Divers

Notably, by placing the sensor inside the air bubble, they found the lizards were inhaling oxygen. Amazingly, they were rebreathing exhaled air which clings to their hydrophobic skin. 

The lead author, Boccia, explained why the researchers used the term “rebreathing.” 

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

Luke Mahler, an assistant professor at the University of Toronto, noted it’s a unique find for vertebrates.

“Rebreathing had never been considered as a potential natural mechanism for underwater respiration in vertebrates,” said Luke Mahler, an assistant professor in ecology and evolutionary biology at the University of Toronto.

Furthermore, Boccia explained that multiple anole species performed rebreathing in the Anole Annals. As well as semi-aquatic anoles, the team found that non-aquatic anoles were capable of basic rebreathing. However, their capacity was much more limited.

“The hydrophobicity of anoles’ scales is likely what enables the air bubble to adhere to the diving anoles’ heads (and thereby also enables re-inhalation). All anoles, therefore, appear to be capable of forming a thin layer (or ‘plastron’) of air along their scales during submersion, but only semi-aquatics appear to make regular use of this ability,” Boccia states.

Perhaps, the anole lizards developed the ability to use natural oxygen tanks as an “evolutionary accident,” he suggests.

More below from Mahler Lab:

Featured image: Screenshots via YouTube