By Stephen Beech via SWNS
Scuba-diving lizards described as "the chicken nuggets of the forest" use a bubble to breathe underwater and escape predators, reveals new research.
Water anoles - a type of semi-aquatic lizard found in the tropical forests of Costa Rica - utilize the unique technique to avoid birds and snakes that prey on them, say American scientists.
Dr. Lindsey Swierk, of Binghamton University in New York, had previously documented the species using a bubble underwater.
When the lizards feel threatened by a predator, she says they dive underwater and produce a bubble over their heads to breathe.
Dr. Swierk said: “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.
"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?”
To investigate whether the bubble serves a functional role in respiration or is merely a by-product, Dr. Swierk applied a substance to the lizards’ skin surface that would prevent bubble formation.
She said: “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.”
Dr. Swierk recorded the number of bubbles that the lizards could produce and how long they could stay underwater and compared them to lizards in a control group that were allowed to breathe normally.
The findings showed that the lizards in the control group could stay underwater 32% longer than those with impaired bubble formation.
Dr. Swierk said: “This is really significant because this is the first experiment that truly shows the 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.”
The study, published in the journal Biology Letters, confirmed that the bubble helps lizards stay underwater for longer periods, providing them with a refuge from predators.
Dr. Swiek said: “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.
"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.”
Dr. Swierk now wants to establish whether lizards are using the bubble as something called a "physical gill".
A physical gill occurs in insects that use bubbles to breathe underwater.
Dr. Swierk explained that insects have smaller oxygen requirements, and the amount of oxygen that diffuses from the water into the air of the bubble is enough to sustain them.
She said water anoles are likely too big to be supported merely by the oxygen that's diffusing into a bubble.
Dr. Swierk added: “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.
“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.”
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