As they squeeze and swallow their meal, this method prevents snakes from suffocating.

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prevents snakes from suffocating
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Snakes that constrict and then swallow large prey have evolved a method of preventing suffocation while doing so.

When the scaley coils closest to the snake’s head are too busy squeezing its meal to death, the reptile can simply shift its breathing pattern to employ ribs and muscles further down its body.


That’s according to a new study that employed an inflated blood pressure cuff to immobilise different areas of the body of boa constrictors while also taking X-ray images to track their ribs’ mobility. The snakes could readily switch to utilise different sets of ribs to draw in air like a bellows, according to the researchers.

A little helmet and a blood pressure cuff were discovered.

Boa constrictors have around 200 pairs of ribs running the length of their body, and they generally breathe by rotating their inflexible rib bones and pumping air in and out with their muscles.

A snake’s lungs, like the rest of its body, are lengthy and extend nearly the whole length of the snake. Gas exchange appears to take place in the section of the lungs closest to the head, which is rich in blood vessels. But the area of the lungs closest to the snake’s tail is more like an empty sack.

When a snake bites and captures its food, the front half of its body is usually totally occupied with constricting the meal. The rib cage then has to stretch wide open as the snake begins to eat what is often a huge animal in comparison to its own size.

“There’s a potential they won’t be able to shift their ribs since they’re already at capacity,” Capano explains.

When Capano and Scott Boback were working in Scott Boback’s lab at Dickinson College, they noticed that when they fed snakes, “it appeared like they were breathing with another area of the body” than when they were “just kind of hanging out on the table at rest,” Capano recalls.

However, it was unclear whether this indicated a genuine change in the snakes’ respiratory patterns. Perhaps the snakes were constantly attempting to move the same ribs in order to breathe, but the physical demands of squeezing and swallowing prey prevented some ribs from doing so?

Capano and a team of researchers reveal how they used blood pressure cuffs on various sections of snakes’ bodies to effectively stop the ribs from moving in the Journal of Experimental Biology. “We put a little helmet on the snake that allows us to measure air flow in and out of it so we could see if it was breathing,” Capano explains. The researchers employed X-rays to observe bone movement inside the snake, as well as nerve signals.

Snakes switched to breathing with a set of ribs back towards the tail when the cuff was placed on the front half of the animal. “When you remove the cuff, they stop moving in the back and return to the front.” Says capano.

Because the ribs at the far end of the snake only became involved when the front section of the snake couldn’t move, Capano believes the bag-like section of lung at the back of the snake essentially acts as a bellows to draw air through the section of lung at the front of the snake where gas exchange takes place.

Thousands of snake species flourish in a variety of settings, including the ground, trees, the water, and even the air (in the case of flying snakes). Snakes evolved ways of hunting rather large creatures, giving them more prey alternatives to exploit, and the long, limbless body has proven extremely adaptable.

“Snakes evolved constriction to achieve this,” explains Elizabeth Brainerd, a biomechanics researcher at Brown University. “Our theory is that there had to be some respiratory advances that went along with that.” “As constriction progressed, it hampered the capacity of those animals to breathe via the ribs in that area.

As a result, there would have been pressure to develop modular breathing, moving breathing to a separate section of the ribcage.”

Brainerd has long been fascinated by the differences in how animals push air into and out of their lungs. “We hardly ever think about breathing, but it’s actually a biomechanical problem,” she explains.

While humans have a diaphragm and a breast bone that snakes lack, Brainerd can’t help but observe that individuals have a pair of more snake-like “floating ribs” that don’t attach to anything in the front.


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