Some European birds can fly 600 miles in a day searching for food. Other animals lie in wait, ready for their prey to stumble upon them. Animals’ lifestyles run the gamut.
Two researchers in the University of Utah’s biology department are curious as to why. How an animal breathes may be an important part of the answer.
Colleen Farmer and David Carrier put alligators on a treadmill to study how they breathed and uncovered a new mechanism?one which may have been present in some dinosaurs.
A muscle pulls a flexible bone in the alligator’s pelvis?the pubis?downward, expanding the volume abdomen and allowing the animal to inhale. Some dinosaurs have similar bone structures.
It’s one of many adaptations that makes it possible for animals to live actively.
Lizards’ bodies twist side to side as they run, preventing them from breathing while they are in motion. To get around this, some lizards use their throats to pump air.
Humans have a muscular floor beneath their lungs, called a diaphragm, which contracts and relaxes to bring air in and out.
And while bones in a bird’s pelvis aren’t flexible, the entire structure moves to support breathing. No one has looked at how the mechanism works for birds in flight yet, Farmer said. A lot of research into breathing mechanisms remains to be done.
Alligators’ hearts and lungs are still something of a mystery.
“They have been studied for hundreds of years and everybody is still scratching their heads,” Farmer said.
Alligators are dinosaurs’ closest living relatives, some believe. Like alligators, some dinosaurs had flexible pelvic bones. It’s possible these bones played a role in expanding the abdomen, facilitating breathing?the same function seen in alligators.
Dinosaurs also had ribs running in front of their stomachs. This setup could have pulled on the belly ribs, expanding them and prompting inhalation.
This function may explain some dinosaurs’ odd pelvic structures. They have long, spindly pelvic bones?not very helpful for locomotion. Breathing, however, does not require sturdy bones.
This theory lends credence to the image of dinosaurs as active creatures.
Oddly, alligators are sit-and wait predators, although they possess a breathing mechanism that should allow them to be more active?possibly a leftover from an earlier incarnation, according to Farmer.
Alligators’ ancestors were smaller and cat-like, but the move into an aquatic environment altered their lifestyles.
In addition to the flexible bone, an alligator’s liver pumps and pushes air?an action that was already known. A muscle pulls the liver backward, increasing volume for inhalation. When the alligator exhales, the liver moves forward, pushing air outward.
Farmer and Carrier began the alligator study by looking at blood flow between the abdomen and the lower limbs during exercise, but stumbled upon the pubic bone’s function in breathing.