Some lizards can stay underwater for longer by exhaling and rebreathing air bubbles, something that has been suspected since the behaviour was first observed, but this experiment confirms it.
Lindsay Swierk of Binghamton University in New York was doing fieldwork in Costa Rica in 2015 when she noticed that some lizards (AnoleWhen people approached, the lizard would jump into the stream and stay underwater for long periods of time. Her team filmed the lizard underwater and saw it blow large bubbles out of its nostrils while still attached to its head, then inhale them again.
Swierk wrote a short paper describing the behavior in 2018. In 2021, she and her colleagues published a paper detailing the behavior in at least 18 species. Anolis The lizard can rebreathe bubbles underwater and remain underwater for up to 18 minutes.
All of these species have water-repellent skin that is covered by a thin layer of air underwater, which is why they appear silvery and why the large bubbles they blow stay stuck together.
Swierk took his research a step further by using a paintbrush to apply a type of moisturizing agent called an emollient to the heads of freshly captured lizards, temporarily stopping the skin from repelling water.
The lizards were only able to blow out small bubbles. “For obvious reasons, we didn’t put any emollient on their nostrils, so they were able to rebreathe a little bit,” Swierk says.
The lizards were then placed in clear plastic tanks filled with river water to see how long they could stay underwater before being released. The lizards that had been sprayed with plain water stayed underwater for an average of 32 percent longer than the lizards that had been sprayed with the softening agent.
Swierk thinks that by simply breathing the same air again, the lizard could take in more oxygen. And when the expanding bubbles combine with a thin layer of fresh air on the lizard’s skin, more oxygen gets trapped inside the bubbles. In other words, the thin layer of air on the skin could act as a scuba tank.
In addition, the large bubbles act as gills, allowing carbon dioxide to dissolve into the water and oxygen to diffuse in. Many insects, spiders, and plants are known to be able to live underwater thanks to a layer of air that acts as gills.
Star-nosed moles and water shrews also blow bubbles underwater to rebreathe, which is thought to be a way of smelling while diving.
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