BINGHAMTON, N.Y. - A Costa-Rican lizard
species may have evolved scuba-diving qualities allowing it to stay underwater
for 16 minutes, according to faculty at Binghamton University, State University
of New York.
Lindsey Swierk, assistant research professor
of biological sciences, documented that the water anole (Anolis aquaticus) is
able to breathe under water for long periods of time to escape from predators.
It appears that the species may have formed an underwater respiration system
consisting of a recycled air bubble that clings to the anole's head.
"Diving under water and remaining there
for a long time is an anti-predator strategy for water anoles," said
Swierk. "These lizards aren't particularly speedy, and taking to the water
is a very effective option. (Take it from a biologist who sometimes struggles
to capture her study organism because they're so good at diving.) It's easy to
'disappear' to a predator's eye once you hide under water for a few minutes. I
think that any underwater breathing adaptations in water anoles would have
arisen to extend the amount of time they can stay in their underwater refuge.”
The unique behavior was documented for the
first time by Swierk in a video that shows the anole breathing out and
re-inhaling an air pocket under water. Swierk first noticed this species when
she was walking along the mountain streams in Costa Rica and observed the lizards
dive under water and stay submerged for a long period of time. Further analysis
of the lizards' stomachs uncovered that they eat some insects that are mainly
found under water, hinting that the species may dive under water for reasons
other than just avoiding predators.
"Finding evidence suggesting that water
anoles 'breathe' under water was serendipitous, and not part of my original
research plan," said Swierk. "I was impressed and pretty confused
about the length of the dive, which gave me an itch to take a closer look with
an underwater camera in the next couple of years. That's when I saw that the
anoles appeared to be rebreathing a bubble of air that covered their heads.”
Swierk said she believes the lizard might be
extracting oxygen from these bubbles.
"I think it's possible that some
additional air pockets are being trapped around the anole's head and throat,
and that the inhalation and exhalation of the air bubble allow for some trading
of fresh air among these air pockets, allowing the anole to swap air in its
current air bubble with 'new' air," said Swierk. "It's additionally
possible that the air bubble plays a role in allowing an anole to get rid of
carbon dioxide. I suspect that there might be morphological adaptations, namely
the shape of the top of the anole's head, which allows a large bubble of air to
cling to it easily.”
Swierk's lab plans to conduct several types
of follow-up research on the "bubble-breathing" observation, hoping
to tackle questions related to the antipredator function of the air bubble
breathing in the field, how anole head shape influences bubble formation and
the physiology underlying this potential adaptation.
"If future investigation reveals that
this rebreathing behavior is adaptive, then I would imagine that it is a trait
that evolved over time to allow water anoles, and perhaps similar anole
species, to thrive in their aquatic habitats," said Swierk.
This research is supported by a grant from
the National Science Foundation.
For video go to
https://www.mirror.co.uk/science/lizard-evolves-scuba-diving-skills-14188709
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