Lungs can be good for more than just breathing, University of Utah biologists have discovered. In alligators and their relatives, they also are vital to graceful, splash-less swimming, all the better to glide up to prey.
Graduate student T.J. Uriona, who is in line to receive his Ph.D. degree this spring, and his mentor, C.G. Farmer, published a study on the subject in The Journal of Experimental Biology. Published on the Web March 14, it is the magazine's cover article.
Farmer an assistant professor of biology most recently appeared in Utah Scientific on Feb. 18, in an article about her discovering how alligators, caymans and crocodiles use an extra heart valve to aid in swift digestion.
The new report may help in understanding whether and how other animals besides crocodilians use their lungs while beneath the water's surface.
"Alligators have devoted a lot of their muscle-skeletal system to helping them breathe," Uriona said in a telephone interview. "Most mammals, for example, use their rib cage and their diaphragm muscles" to breathe.
Alligators evolved from land animals "about the size of a cat, maybe a little bit bigger, and they ran around on all four legs," he added. "Quite a different creature than you see today."
In making the transition from land to water, the researchers wondered, did some of the typical functions of their lung muscles change?
To find out, they implanted electrodes over alligators' breathing muscles. When the incisions healed, they placed the animals in water and watched to see if the electrodes recorded any unusual activity.
"We were excited when we saw that they were using these muscles that they usually use to breathe, when they were underwater," he added. The alligators had to be using the muscles for some other purpose.
Farmer and Uriona placed a small device called an inclinometer on alligators to check what was happening when the electrodes showed activity. The inclinometer, which he described as a kind of digital level, indicated that specific breathing muscles got a workout when the gator dove, headed up to the surface or rolled.
"From that we were able to correlate its muscle activity in the alligator's diaphragm ... and some other respiratory muscles," he said.
"They were using the air inside their body to dive down or to roll to one side or the other. That was pretty exciting, because it shows they were using their lungs not only to breathe but to move around in the water."
A U. press release notes that this means alligators slide through the water without a ripple by using these specialized muscles to shift their lungs like "internal flotation devices."
Their lungs may be used underwater in a way that's somewhat analogous to a fish's use of its swim bladder. Fish can inflate or deflate the bladder to control buoyancy. But the reptile's lung shifts may be more sophisticated.
Uriona said he and Farmer would like to research how widespread the adaptation is. "We've looked at one frog ... that has some muscles attached to their lungs. And they seem to be using this muscle that's attached to their lungs to help them move around in the water."
Another subject was the snapping turtle, a vicious reptile with a fierce, tearing, lightning-fast snap."That's the scariest thing!" Uriona exclaimed. "Working with alligators, it's fun compared with working with snapping turtles."
E-mail: [email protected]