The boa constrictor has a reason for its name. To kill its prey, a boa will coil around it, squeezing hard enough to stop the prey's blood from flowing, and then, stretching its jaws open to devour it whole. They are known to eat rodents. Some of their larger relatives, anacondas, can eat capybara and deer, and there have been instances of pythons eating people.
They can do this for up to 45 minutes.
Dr. Brainerd and her colleagues discovered that boa constrictors are able to breathe under cramped conditions because of their rib cage which expands to draw air into their lungs. Their work was published in a journal. Their findings show how snakes have come to thrive in so many parts of the world.
John Capano, an evolutionary biologist at Brown University and an author of the study, said that large prey ingestion really opened up all these new avenues for snakes to evolve.
Taking in and releasing air is more complex than it appears.
Allison Hsiang, a computational paleobiologist at Stockholm University who was not involved in the study, saidBreathing is one of those things that seems simple.
Humans and birds use air sacs. The rib cage is the most important part of a snake's body and it requires a lot of food to maintain.
According to Dr. Brainerd, snakes are all ribs. The animals breathe by slowly expanding a section of their rib cage.
The ribs are compressed while they are squeezing. Ingesting prey expands ribs. It was not clear how boas could breathe.
Something had to happen with the evolution of their lung ventilation system in order for them to become small-headed animals that eat big meals.
Scientists theorize that snakes are most likely changing the area of their rib cage that is expanding when they eat prey. One option would be to use the entire rib cage to draw air into their lungs.
The research group visualized a boa constrictor's rib cage during constriction using 3-D X-ray technology. The team used metal markers no bigger than half a millimeter in the ribs and vertebrae to image the snakes. They filmed these regions with X-ray video and used a blood pressure cuff to mimic what nature would do when these snakes constrict their prey.
When resting, boa constrictors use their ribs to breathe. The ribs further down the snake's body began to expand when the blood pressure cuff was wrapped around them.
The team believes that the ability to modify rib engagement emerged before snakes' ability to eat large prey. They say that without this breathing adaptation, snakes may not have become such a diverse class of reptiles.
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