Study has shown that lung-feeding baleen Whales possess an “oral plug”, which allows them to swallow underwater food without getting sick.
As the marine mammals thrust though the ocean taking in vast volumes of krill bearing water, this fleshy bulb seals off the airways to stop water entering the lungs.
It shifts when swallowed to block off upper airways (nasal cavities). While the entry to the larynx and lower airways are closed by the laryngeal sac, the opening to the larynx opens.
This leaves a path between from mouth to stomach through which krill — filtered out of the water by their bristle-like ‘baleen’ plates — can then be ingested.
The hollow organ known as the larynx forms an air passage close to the lungs. It contains the vocal chords and allows whales the ability to sing.
No anatomical feature like an oral plug has even been seen before in any other animal, reported the research team from the University of British Columbia.
Study has shown that baleen whales or fins which eat lunges are equipped with an oral plug in their mouths. It allows them to consume food underwater while not drowning.
The study was conducted by marine biologist Kelsey Gil and her colleagues at the of University of British Columbia.
Dr Gil said, “We found a structure that we could see in fin whales. This is probably the same structure as in all lunge-feeding mammals, or rorquals.”
She added, “We have called it the “oral plug”, and it blocked the channel between the mouth and the pharynx.”
It means that a whale’s lungs are protected when it lunges.
It’s similar to when our nostrils are blocked by a human’s back uvula.
Because it is not easy to study the anatomy of whales, dissections often involve trying to remove specimens from dead carcasses that were left on the shore.
However, in the current study Dr Gil and her collaborators were able study unwelcome parts of whales that had been collected from a Icelandic commercial whaling station.
The study included manipulating anatomical structures to observe how they moved.
To determine the movement of these whales when contracted, the team looked into the structure and function of their muscle fibers.
“It is impossible to study it in a live whale so we use tissue from deceased whales and apply functional morphology for assessment of relationship between structure and function,” the biologist said.
The biologist stated that it would be amazing to interact with whales live in their natural environment, however, this would require technological advancements.
‘It would be interesting to throw a tiny camera down a whale’s mouth while it was feeding to see what’s happening,’ Dr Gil noted.
“But it would be safe to eat, and that the product is biodegradable.
According to paper author and zoologist Robert Shadwick, the combination of the whales’ oral plug and closing larynx is central to how lunge-feeding evolved — which, in turn, allowed the mammals to grow to such colossal sizes.
He said that bulk filter feeding on krillswarms was highly efficient, and it is the only way of providing the enormous amount of energy required to sustain such large bodies.
The zoologist stated, “This wouldn’t be possible without special anatomical characteristics we’ve described,”
Dr Gil stated that’very few animals that can feed on prey by swallowing water’ and that the oral filter is likely to be an animal-specific protective device that allows lunge feeding.
The fleshy bulb is used to seal off airways in order to prevent water from entering their lungs. This can be seen above, showing the way they breath at the surface of the sea. They swallow and their oral plug moves to block the upper airways (nasal cavity). The entrance to the larynx (bottom) is also closed. This leaves a path between from mouth to stomach through which krill — filtered out by their ‘baleen’ plates — can then be ingested
The University of British Columbia research team reported that an anatomical feature such as the oral plug (pictured), has never been observed in an animal before.
With their initial study complete, the researchers are now looking to further explore the mechanisms at play in the whale pharynx and the small oesophagus that serves to transport hundreds of pounds of krill to the stomach in less than 60 seconds.
Dr Gil said that it is important to understand how and what whales eat in order to help protect them and their ecosystems from the human impact.
And — on a more whimsical note — biologists are still to determine whether whales do things like cough, hiccup, or even burp.
‘Humpback whales blow bubbles out of their mouth, but we aren’t exactly sure where the air is from — it might make more sense, and be safer, for whales to burp out of their blowholes,’ Dr Gil mused.
Full results of this study have been published in Current Biology.
EXPLAINATION ON WHALE SONGS
For many years, it was thought that whales only sang for mating.
Some experts believe that songs help mammals explore the environment.
Researchers recorded the humpback whales’ ability to change their call when they moved to different pastures to follow the song of other animals.
This song can be used to help whales locate one another in new waters and form groups.
Researchers recorded the humpback whales’ changing calls as they moved to different pastures to be in tune with other songs (file photo).
Because whales can be shy and vocalize differently, it is difficult for scientists to learn how they sing.
The vocal boxes of humpback whales vibrate low at frequencies when air is forced over them.
These vocal chords may be connected to the lungs by special air sacs.
This allows the whales air to flow between their lungs and sacs.