Researchers have found a type of lizard – referred to as the chicken nugget of the forest – that can hide underwater thanks to a special bubble they produce around their nostrils.
Details of the scuba-diving lizards are published in Biology Letters.
For animals that have adapted to live on land, air-based breathing limits the amount of time they can survive underwater.
Many invertebrates, including species of beetles and spiders, are known to use bubbles of air to extend the amount of time they can spend underwater. These bubbles allow air-breathing animals to inhale previously exhaled air and take in additional oxygen. This behaviour is called rebreathing, inspired by the scuba technology of the same name.
Until recently, there were no known examples of vertebrates using bubbles to rebreathe underwater. In 2021, Lindsey Swierk, an assistant research professor at Binghamton University in New York in the USA, and her colleagues documented rebreathing in several species of Anolis lizards.
One such species, the water anole (Anolis aquaticus), is a semi-aquatic lizard that lives near streams in the forests of southern Costa Rica.
“Anoles are kind of like the chicken nuggets of the forest. Birds eat them, snakes eat them. So, by jumping in the water, they can escape a lot of their predators,” says Swierk. “We know that they can stay underwater at least about 20 minutes, but probably longer.”
The question remains whether the bubble over the water anole’s nostril functionally extended the amount of time these lizards could hide underwater.
To test this, Swierk and coauthors applied a bubble-impairing substance to the skin of one group of lizards.
“Lizard skin is hydrophobic. Typically, that allows air to stick very tightly to the skin and permits this bubble to form,” said Swierk. “But when you cover the skin with an emollient, air no longer sticks to the skin surface, so the bubbles can’t form.”
Swierk’s team then measured how long the control group stayed underwater compared to the bubble-impaired group. They found that the control group stayed underwater 32% longer on average.
“This is significant because this is the first experiment that truly shows adaptive significance of bubbles. Rebreathing bubbles allow lizards to stay underwater longer. Before, we suspected it – we saw a pattern – but we didn’t actually test if it served a functional role.”
