SALT LAKE CITY — Lizards may have a more complex breathing pattern than previously thought, according to new research from the University of Utah.
Researchers found monitor lizards breathe the same way as birds, alligators and possibly dinosaurs, with air flowing mostly in a one-way loop. The findings suggest the unidirectional breathing pattern may be more common and have began 20 million years earlier than once believed.
"The discovery is important because it provides new insights into the evolution of the vertebrate respiratory system," said senior author Colleen Farmer. "It suggests that we have had a somewhat anthropocentric view of how other animals work and their evolutionary history. Our new evolutionary insights are leading to new questions about how organisms work, questions that otherwise would have been ignored."
Farmer was prompted to look at the breathing pattern of lizards after she found the same pattern of unidirectional air flow in the lungs of alligators a few years ago.
"Because the conventional wisdom was that this pattern of flow is important to birds in allowing them to support vigorous exercise, such as flapping flight, the discovery in alligators caused me to think about the phenomenon in a new light," she said. "It seems to be important to cold blooded animals that can't fly."
There is a pressing need to understand how these airflow patterns are related to blood flow in the lung, Farmer said. She thinks future research will explore how air moves in the lungs of other amphibians, turtles and lizards and how blood circulates in the lungs.
Researchers were able to identify the airflow pattern in monitor lizards by using CT scans and 3-D images of lizard lungs. Flow meters were implanted surgically in the lungs of five lizards to determine the direction of airflow. Tests were also conducted using the lungs of ten dead monitor lizards to measure air flow and direction.
The study showed air traveled in one direction, with air entering through the trachea or windpipe, into the lung and then looping back in a tail-to-head direction instead of out the way it came in. In contrast, air flows into the lungs of humans and most other animals before going back out the same way.
The study was published online in the journal "Nature" on Dec. 11.