- Researchers recently discovered that several species of semi-aquatic anole lizards can breathe underwater — or rebreathe — for up to 18 minutes.
- They observed that anoles have hydrophobic skin that allows a thin layer of air to form around their bodies when they dive underwater, which they believe aids their rebreathing process.
- When the anoles exhale underwater, a bubble of air forms over their snout and then goes back into their nostrils when they inhale.
- The researchers believe that anoles evolved to rebreathe underwater to avoid predators, although more research is needed to confirm this.
Luke Mahler didn’t exactly set out to study lizards that could breathe underwater. But when he and fellow scientist Rich Glor were out on a research expedition in Haiti in 2009, they noticed some peculiar behavior in some critically endangered Eugene’s anoles (Anolis eugenegrahami) released into a shallow stream. It appeared, much to their disbelief, that they were breathing underwater.
“We were very surprised to find rebreathing in anoles,” Mahler, an evolutionary biologist at the University of Toronto, told Mongabay in an email. “An underwater respiratory behavior like this had never previously been recorded in vertebrates.”
This initial observation kick-started a research project that spanned 12 years, involved 15 international scientists, and required research in several countries, including Costa Rica, Mexico, Colombia and Ecuador. The project culminated in a recent paper published in Current Biology that revealed that several semi-aquatic anole species have the uncanny ability to breathe underwater — or rebreathe — for up to 18 minutes.
“We were … surprised to find it in so many semi-aquatic anole species, many of which are not particularly close relatives,” lead author Christopher Boccia, who recently completed his Master’s degree at the University of Toronto, told Mongabay in an email. “Within the genus Anolis, semi-aquatic habitat specialization has evolved several times independently, and what’s neat is that each time this has happened, specialized underwater ‘rebreathing’ has also evolved.”
So how does it work? The researchers observed that anole lizards have “hydrophobic skin” that is water-resistant and allows for a thin layer of air to form around their bodies when they dive underwater. When the anoles exhale while submerged, a “bubble” of air forms around their snouts, and when they inhale, the bubble simply goes back into their snout.
“Some anoles will do this dozens of times in a single dive, recycling the air in the bubble and using the oxygen within it,” Boccia said.
The study suggests that anole species may have evolved to breathe underwater to escape predators and stay away until the danger has passed. However, this still needs to be confirmed with more field research, the researchers said.
The team is also looking to conduct further research to understand if and how rebreathing helps anoles get rid of excess carbon dioxide and if the process allows them to take in small amounts of oxygen from the water.
“This work arose unexpectedly out of some fortuitous but very basic observations of animals in nature while conducting other ecological research,” Mahler said. “We hope it illustrates the value of discovery-based science. Indeed, many of the most interesting or useful scientific discoveries never could have been predicted in advance.”
Boccia, C. K., Swierk, L., Ayala-Varela, F. P., Boccia, J., Borges, I. L., Estupiñán, C. A., … Mahler, D. L. (2021). Repeated evolution of underwater rebreathing in diving Anolis lizards. Current Biology. doi:10.1016/j.cub.2021.04.040
Banner image caption: Anolis aquaticus from Costa Rica Image by Lindsey Swierk