Study: Gators shift lungs

• By SONIA SMITH
• Published: Mar 17, 2008 - Page: 1A - UPDATED: 03.17.08

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That alligator gliding soundlessly through the swamp maneuvers so nimbly in the water by using special muscles to shift the position of its lungs, new research shows.

To move furtively through the water, an alligator can reposition its lungs — and change its center of buoyancy — using its diaphragm with specialized pelvic, abdominal and rib muscles, according to a study conducted by researchers at the University of Utah, published Friday in the Journal of Experimental Biology.

These muscles work in concert to allow an alligator to move the lungs toward the tail when diving, toward the head when surfacing and to the side when rolling, said T.J. Uriona, a co-author of the paper.

Making these internal adjustments helps the alligator dive and roll more quickly and with stealth, Uriona said.
C.G. Farmer, the paper’s co-author, obtained the five juvenile alligators used in the study from Louisiana’s Rockefeller Wildlife Refuge near Grand Chenier.

Alligators are sit-and-wait predators, Uriona said.

“Being able to gradually change their position in the water could help them sneak up on something they want to catch,” he said.
Uriona, a doctoral biology student at the Salt Lake City university, said he was attracted to studying crocodilians because they have an unusual amount of muscles devoted to ventilation.

“It begs the question, why devote so much musculature to breathing if most animals get by fine without having so much?” Uriona said.
He said he and Farmer also wondered how alligators were able to move so agilely in the water without fins or flippers.
Uriona said they hypothesized that alligators used the muscles to move the air-filled lungs inside their bodies in order to hold their positions in the water.

The scientists implanted electrodes in five sets of muscles in the 15-to-20-inch alligators to measure how much the muscles were used when diving and swimming in 100-gallon fish tanks.

They found heightened activity in four of the five muscle groups — the diaphragmaticus (diaphragm), ischiopubis (pelvic), rectus abdominis (abdominal) and internal intercostals (rib) — when the animals were diving or maneuvering in the water. This activity ceased when the animals surfaced.

The alligators had to be killed after the study to check that the electrodes had been implanted in the right places, Uriona said.
He said he enjoyed working with the juvenile alligators.

“Alligators are just so fascinating. It’s just sort of a treat to study them out here in Utah,” he said. “When they’re little, they’re just really fun to be around. They don’t mess up their cages very much, they’re good eaters and they don’t tend to bite you if you’re careful.”
If the researchers had been able to study adult alligators in the wild, they may have seen even more activity in the muscles, which are more developed in adult animals, Uriona said.

During the Triassic Period, which began 250 million years ago, alligators’ cat-sized crocodilian ancestors lived only on land, Uriona said. They became semiaquatic animals during the Cretaceous Period, about 145 million years ago.

It was previously thought that the diaphragmatic muscle evolved to help this crocodilian ancestor breathe while running, Uriona said. This research suggests the muscle instead evolved when the reptiles took to the water.