(ORDO NEWS) — Whales are big drinkers. In just ten seconds, these giant mammals can drink over five hundred baths of ocean water, filtering out about 10 kilograms of krill in one gulp.
All they have to do is open their mouths and rush forward at about 10 kilometers per hour (6 miles per hour).
The pressure of all this water rushing down the whale’s throat would no doubt be enormous. How does this group of creatures, which includes the right whale, humpback whale, monumental blue whale and many others, ensure that their lungs are not suddenly filled with water?
The autopsy of several fin whales (Balaenoptera physalus) revealed a fat and muscle bag that prevents this species of whale from suffocating. When a whale opens its mouth to eat, this sac rises up and blocks the lower airways.
A similar structure has not been found in any other animal, but the authors suggest that it is likely present in other feeding whales (so-called rorquals), such as humpback whales and blue whales.
“There are very few animals with lungs that feed by swallowing prey and water, so the mouth plug is most likely a protective structure specific to rorquals that is needed in order to feed on lunges,” explains zoologist Kelsey Gil of the University of British Columbia. (Canada).
Although Gil and her colleagues have not seen the mouth plug in action, judging by its structure, they believe it functions like a railroad switch. When the whale breathes, the plug pops out and opens the lower airways. But when the whale feeds, the cork completely blocks this path.
In humans, a flap of tissue known as the epiglottis blocks the way to the lungs when we eat, so that we don’t inadvertently inhale food.
But whales have very different ways of feeding and breathing. When they breathe through the air holes, a fatty plug attached to the soft palate prevents water from entering the mouth from entering the lungs.
However, when eating, this fatty plug must rotate up and back, blocking the way to the whale’s upper respiratory opening and opening the esophagus for swallowing.
At the same time, the force of the oncoming water pushes the whale’s tongue back to the epiglottis, closing the lower respiratory tract as well.
“It’s like a human’s uvula moves back, blocking the nasal passages, and the windpipe closes when food is swallowed,” says Gil.
But unlike the throat structures in humans, whales have to work under a lot of pressure.
“Blood filtering of krill swarms is highly efficient and the only way to provide the huge amount of energy needed to maintain such a large body size,” explains zoologist Robert Shadwick, also from the University of British Columbia.
“This would not have been possible without the specific anatomical features that we have described.”
After all, it takes a lot of energy to keep a 27-meter finned whale swimming.
We still have a lot to learn about these giant creatures and their life under the waves. For example, how do whales blow bubbles? Do they burp or hiccup?
The authors of the current study would like to see how the whale eats and breathes in real time; to do this, they need to create a chamber capable of swallowing.
Meanwhile, the dissection was not carried out on whales caught for scientific purposes, but on samples obtained in 2015 and 2018 in Iceland, where, fortunately, no whales have been killed in the past few years.
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