Some lizards have a unique ability to stay underwater for extended periods by blowing out and then rebreathing bubbles of air. This fascinating behavior has recently been confirmed through experiments conducted by Lindsey Swierk and her team at Binghamton University in New York State.
During fieldwork in Costa Rica in 2015, Swierk observed a species of lizard called Anolis aquaticus diving into streams and remaining submerged for surprisingly long durations. Upon filming these lizards underwater, the researchers noticed that they would expel large bubbles from their nostrils, which would then remain attached to their heads before being inhaled again.
In a study published in 2021, Swierk and her colleagues revealed that at least 18 species of Anolis lizards exhibit this bubble rebreathing behavior, allowing them to stay underwater for up to 18 minutes. These lizards possess water-repellent skin that retains a thin layer of air when submerged, giving them a silvery appearance and enabling the bubbles they blow out to remain connected.
To further investigate this phenomenon, Swierk conducted a study where she temporarily altered the lizards’ skin properties by applying an emollient. Lizards treated with the emollient could only produce small bubbles, resulting in reduced underwater endurance compared to untreated lizards.
When placed in a tank of stream water, the untreated lizards stayed submerged 32% longer on average than those with the emollient. Swierk theorizes that by rebreathing the same air and allowing the blown-out bubbles to interact with the fresh layer of air on their skin, these lizards can extract more oxygen and potentially use the air as a makeshift scuba tank.
Additionally, the large bubble may function as a gill, facilitating the exchange of carbon dioxide and oxygen. This mechanism is similar to how certain insects, spiders, and plants survive underwater by utilizing air layers as gills.
While other animals like the star-nosed mole and water shrew also exhibit bubble rebreathing underwater, they may do so for olfactory purposes rather than respiratory adaptation. This remarkable ability of Anolis lizards showcases the diverse strategies that different species have evolved to thrive in their environments.
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