Some lizards 'scuba dive' by using air bubbles to breathe underwater
Scuba diving isn’t just for adventure seekers anymore. Even the world’s smallest – and apparently the scrappiest – members of the animal kingdom are doing it. A particular type of semi-aquatic lizard has something truly unique to show us about the art of survival with air bubbles in the underwater world.
Mysteries of underwater lizard breathing
The research was led by Lindsey Swierk, an assistant research professor of biological sciences at Binghamton University.
Swierk’s work is centered on the study of water anoles, semi-aquatic lizards native to the tropical rainforests of southern Costa Rica. Her research has unveiled remarkable feats about these fascinating creatures.
“We know that they can stay underwater for a really long time. We also know that they’re pulling oxygen from this bubble of air. We didn’t know whether there was actually any functional role for this bubble in respiration,” Swierk noted.
“Is it something that lizards do that is just a side effect of their skin’s properties or a respiratory reflex, or is this bubble actually allowing them to stay underwater longer than they would, say, without a bubble?”
Lizards dive underwater to survive
What our research team was eager to find out, said Swierk, was the actual role this bubble played in the lizard’s underwater survival.
She questioned – is this bubble a byproduct of the lizard’s skin properties and respiratory reflex, or is it an ingenious tool allowing these creatures to outlast their time underwater?
To disentangle the mystery, Swierk conducted an experiment that involved applying a substance to the lizards’ skin that would prevent bubble formation.
The logic? “Lizard skin is hydrophobic. Typically, that allows air to stick very tightly to the skin and permits this bubble to form. But when you cover the skin with an emollient, air no longer sticks to the skin surface, so the bubbles can’t form,” explained Swierk.
Bubbles are life-savers, quite literally
The recorded findings were compelling. It turned out that the lizards in the control group, which were not subjected to the emollient, could stay underwater an impressive 32% longer than their bubble-deprived counterparts.
“This is really 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,” said Swierk.
Lizards, bubbles, and underwater breathing
The function of these bubbles isn’t just about a lizard’s whim to stay longer in the water. It’s a life or death situation where the ability to stay underwater longer provides the perfect refuge from predators.
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, and they remain very still underwater,” said Swierk.
“They’re pretty well camouflaged underwater as well, and they just stay underwater until that danger passes. We know that they can stay underwater at least about 20 minutes, but probably longer.”
What’s even more intriguing is the question of whether these lizards are using the bubble as a “physical gill.” This term is used for insects that use bubbles to breathe underwater.
Swierk’s graduate student, Alexandra Martin, is working on testing this theory.
Investigating the physical gill hypothesis
Martin’s research involves a meticulous examination of the gas exchange process occurring within these bubbles.
By measuring the concentrations of oxygen and carbon dioxide in and around the bubble as the lizard remains submerged, the team hopes to determine whether there is sufficient gas exchange to classify this bubble as a ‘physical gill.’
Such a discovery would not only deepen our understanding of these lizards’ physiology but could also have broader implications for studying similar adaptations across different species.
Martin is optimistic, stating: “If successful, this finding could redefine how we perceive aquatic adaptations in reptiles.”
Implications for evolutionary biology
The findings concerning water anoles have stirred interest in evolutionary biology, particularly regarding the development of survival mechanisms.
The ability to remain submerged for extended periods may represent a significant evolutionary advantage.
Researchers are now considering whether such adaptations are isolated to specific locales or if they might be more widespread among related species.
Further exploration on the lizard breathing bubbles could provide insights into how these traits evolved and highlight the environmental pressures that prompted such unique adaptations.
Investigating these enigmatic survival strategies enhances our understanding of evolutionary processes, shedding light on the dynamic interactions between organisms and their environments.
The greater impact
When discussing the wider implications of her research, Swierk noted the exciting potential of bioinspired materials.
More broadly, she considers the sheer delight of unearthing new animal behaviors that engage and excite our curiosity.
“I’ve had people talk to me about how much they love scuba diving and freediving, and how they’re interested in how animals might do the same thing,” said Swierk.
“So there’s a great opportunity to get people excited about science by having this relationship between what they love to do and what’s evolved in nature. Even in animals that seem commonplace — you’re always finding new things.”
Her research paper, “Novel rebreathing adaptation extends dive time in a semi-aquatic lizard,” has brought to light a new facet of lizard survival tactics that has been hiding beneath the water’s surface all this time.
The study is published in the journal Biology Letters.
Video Credit: Binghamton University
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