A study recently published in Current Biology has found unique tongue anatomy that explains how giant whales are able to swallow large quantities of fish in a single gulp. The secret? ‘’Bungee-cord’’ nerves hidden in their jaws.
Canadian researchers studied several Rorqual whale carcasses in Iceland and concluded that when the animals feed, they are capable of swallowing a volume of water considerably larger than their entire mass, along with their prey. They explained that this impressive feat is possible due to previously unknown elastic fibers that surround the nerves, dubbed ‘’stretchy nerves’’ by scientists.
This is the first discovery of its kind for vertebrates and in any other species stretching mouth nerves (or any other nerves) would damage them severely. They are inflexible and fairly short. Infect, scientists say that the ‘’stretchy nerves’’ don’t really stretch, so much as unfold. They are kept wrapped in the tight coil in the central core most of the time and only change when the animals open their mouths to feed.
Wayne Vogl, a professor in the Celluar and Physiological Sciences department at the University of British Columbia said that ‘’The rorquals’ bulk feeding mechanism required major changes in anatomy of the tongue and mouth blubber to allow large deformation, and now we recognize that it also required major modifications in the nerves in these tissues so they could also withstand the deformation’’.
The discovery was made inadvertently when Vogl’s co-author, Robert Shadwick, picked up a muscle – a long, white cord ‘’in the floor of the mouth’’, grabbed each end and started to stretch it. The cord was able to stretch twice its length and always sprang back to its original size.
When the researchers cut it open, expecting it to be a blood vessel, the cord did not have a hollow inside, but a small, yellowish core running through the middle. Vogl instantly realized it was a nerve, though it was a type of nerve he had never seen before.
He noted that whales have used the same building blocks as other animals, but that they used them in different ways to produce their unique stretching nerves.
The author explained why exactly the discovery is so fascinating – it’s not just the nerves that change and adapt. Tissues in the floor of the mouth change to adapt to great expansion and recoil, and all the ‘’plumbing and wiring’’ of the whales have to adapt to facilitate the change.
Scientists who didn’t participate in the study are also excited and surprised by the findings. Dr Guy Berwick, a Scottish neurologist at the University of Aberdeen, said he spend his entire career studying nerves and muscles and the one thing he tries to avoid at all costs is stretching nerves (both in clinical and personal situations).
Due to their highly fragile nature, nerves don’t typically withstand stretch, but Dr Guy informs that this atypical ability is crucial to the survival of the whales. The nerves don’t just allow whales to capture large quantities of fish, but it also informs the muscles in the floor of the mouth when to contract to squeeze out the water.
The researchers are still trying to find out whether similar stretching nerves can be found in other species such as the ballooning throats of frogs and chameleons.
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