Meet the scuba-diving lizards! These incredible creatures, known as anoles, have a hidden trick up their sleeves – they can breathe underwater using air bubbles. This discovery has captivated scientists, revealing a fascinating adaptation never before seen in lizards.
The story began in 2018 when researchers captured the first footage of a stream anole (Anolis oxylophus) breathing underwater with a bubble of oxygen surrounding its snout. Since then, they’ve found at least 18 more species of anoles with this incredible ability, including the water anole (Anolis aquaticus).
But scientists were curious: did these bubbles actually help the lizards stay submerged for longer periods, or were they simply a side effect of their water-repellent skin? To answer this question, researchers tested nearly 30 water anoles. They found that those using air bubbles stayed underwater 32% longer than those without bubbles!
This extra time underwater is likely a crucial adaptation for evading predators. Imagine these little lizards darting into the water to escape danger, their bubbles allowing them to remain submerged for longer, increasing their chances of survival.
“There are a lot of threats in their environment, and it makes sense that they would evolve a unique way of dealing with them using the resource – water – that they have available,” said Lindsey Swierk, assistant research professor in biological sciences at Binghamton University.
These semi-aquatic water anoles are often found near riverbanks in the forests of Costa Rica and Panama. They are relatively small, growing up to 8 inches long. When threatened, they have been observed jumping into the water to escape.
“We know that they can stay underwater at least about 20 minutes, but probably longer,” Swierk added.
So how does this underwater breathing work? When an anole dives, it exhales, creating a bubble around its head. This bubble is held in place by the lizard’s water-repelling skin. As the anole breathes in and out, the bubble expands and contracts, effectively redistributing air on and within the lizard’s body, providing enough oxygen for long dives.
To test this, scientists collected 28 water anoles from the Rio Java in Costa Rica. They applied a substance to 13 of the anoles’ heads to prevent their skin from repelling water, effectively blocking the formation of the bubble.
The results were clear: anoles with the substance applied could only stay underwater for an average of 254 seconds, whereas those without the substance remained submerged for an average of 325 seconds, a difference of 71 seconds. This proves that the air bubbles are essential for extended dives.
Swierk believes that the difference in dive times could be even more significant in the wild, where anoles face real predators. “The pressure to stay concealed from a real predator, which we didn’t use in our study, could nudge the control group’s dive times much longer,” she explained.
While anoles are unique in their use of air bubbles for underwater breathing, they are not the only animals to employ this strategy. Diving beetles, for example, carry trapped air behind them, acting as a “physical gill” to exchange oxygen with the water.
This discovery opens up a whole new world of questions about the evolution and adaptability of anoles. The research team is now eager to investigate whether water anoles use their breathing bubbles in the same way as diving beetles, further unraveling the mysteries of these incredible creatures.
