Monitor lizards breathe like dinosaurs, say scientists

The one-way breathing of monitor lizards may evolved earlier than previously thought, about 270 million years ago, researchers say.

Cheryl A. Ertelt
A monitor lizard hugs a branch. New research indicates that the one-way breathing pattern of dinosaurs and birds is also shared by monitor lizards.

Monitor lizards breathe by taking in air that flows through their lungs in a one-way loop — a pattern of breathing that may have originated 270 million years ago in the ancestral group that gave rise to dinosaurs, and eventually alligators and birds, a new study finds.

Researchers at the University of Utah, in Salt Lake City, and Harvard University, in Cambridge, Mass., studied unidirectional breathing in monitor lizards, which can be found throughout Africa, China, India and other parts of Southeast Asia. Their findings suggest one-way airflow breathing may have evolved earlier than scientists had thought.

The researchers examined lungs from living and deceased monitor lizards, and found that when these large, often-colorful, carnivorous reptiles breathe, the airflow through their lungs is mostly one-way, unlike in humans and other mammals, which have a "tidal," or two-way, breathing pattern. Human lungs consist of a network of tubes that branch out into progressively smaller airways. Tidal breathing means air enters the lungs through these airways and then flows back out again the same way.

One-way airflow in birds was first suggested in the 1930s, said Colleen Farmer, an associate professor of biology at the University of Utah and senior author of the new study. [Images: Exotic Lizards Pop Out of the Ground in Florida]

"It was first noted in birds that were living in train stations in Europe," Farmer told LiveScience. "They were burning coal to power trains and noticed that only one part of the bird's lung was getting black with soot."

This method of breathing was thought to have evolved in birds to help them extract higher amounts of oxygen from their environment. Since air travels in only one direction through birds' lungs, more oxygen is transferred through their respiratory systems with each breath, which enables them to fly at high altitudes, where oxygen levels are low, without getting winded or passing out.

Similarly, it was speculated that one-way airflow may have helped the ancestors of dinosaurs roam the Earth beginning roughly 251 million years ago, after the Permian-Triassic mass extinction that wiped out up to 70 percent of terrestrial vertebrate species. Following the devastating extinction event, which formed the boundary between the Permian and Triassic periods, the level of atmospheric oxygen was thought to be significantly lower than today's levels.

In 2010, Farmer published a study detailing similar unidirectional airflow in alligators, which suggests the breathing pattern likely evolved about 250 million years ago, when the ancestors of alligators and crocodiles split from the ancient archosaurs, the group that led to the evolution of dinosaurs, flying pterosaurs and eventually birds.

But now, the discovery of one-way airflow in monitor lizards indicates the breathing method may have evolved even earlier — about 270 million years ago — among cold-blooded diapsids, which were the common, cold-blooded ancestors of present-day lizards and snakes, Farmer said.

"We need to look at other animals in different ecological niches, but I would not be surprised to find that this is very common in other cold-blooded vertebrates," she said.

The detailed findings of the study were published online today (Dec. 11) in the journal Nature.

Follow Denise Chow on Twitter @denisechow. Follow LiveScience @livescienceFacebook & Google+. Original article on LiveScience.

You've read  of  free articles. Subscribe to continue.

Dear Reader,

About a year ago, I happened upon this statement about the Monitor in the Harvard Business Review – under the charming heading of “do things that don’t interest you”:

“Many things that end up” being meaningful, writes social scientist Joseph Grenny, “have come from conference workshops, articles, or online videos that began as a chore and ended with an insight. My work in Kenya, for example, was heavily influenced by a Christian Science Monitor article I had forced myself to read 10 years earlier. Sometimes, we call things ‘boring’ simply because they lie outside the box we are currently in.”

If you were to come up with a punchline to a joke about the Monitor, that would probably be it. We’re seen as being global, fair, insightful, and perhaps a bit too earnest. We’re the bran muffin of journalism.

But you know what? We change lives. And I’m going to argue that we change lives precisely because we force open that too-small box that most human beings think they live in.

The Monitor is a peculiar little publication that’s hard for the world to figure out. We’re run by a church, but we’re not only for church members and we’re not about converting people. We’re known as being fair even as the world becomes as polarized as at any time since the newspaper’s founding in 1908.

We have a mission beyond circulation, we want to bridge divides. We’re about kicking down the door of thought everywhere and saying, “You are bigger and more capable than you realize. And we can prove it.”

If you’re looking for bran muffin journalism, you can subscribe to the Monitor for $15. You’ll get the Monitor Weekly magazine, the Monitor Daily email, and unlimited access to CSMonitor.com.

QR Code to Monitor lizards breathe like dinosaurs, say scientists
Read this article in
https://www.csmonitor.com/Science/2013/1212/Monitor-lizards-breathe-like-dinosaurs-say-scientists
QR Code to Subscription page
Start your subscription today
https://www.csmonitor.com/subscribe