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A new study from the University of British Columbia shows that gigantic whales have nerves like bungee cords.
Nerves aren’t known for being stretchy, but researchers have discovered that the nerves in the mouths and tongues of rorqual whales can more than double their length with no trouble at all.
"These large nerves actually stretch and recoil like bungee cords," said A. Wayne Vogl of the University of British Columbia. "This is unlike other nerves in vertebrates, where the nerve is of a more fixed length that has enough slack in it to accommodate changes in position of the structures the nerves are supplying."
To eat, rorqual whales open their mouths and lunge while their tongues invert and their mouths fill like giant water balloons full of floating prey. The whales' nerves are stretchy so they can withstand the tissue deformation. (Photo Credit: Vogl et al./Current Biology 2015)
The study was reported in the Cell Press journal Current Biology on May 4th and shows that those stretchy nerves support the animals: unique and extreme feeding strategy. Rorqual whales represent the largest group among baleen whales, weighing in at an impressive 40 to 80 tons. To eat, the whales open their mouths and lunge while their tongues invert and their mouths fill like giant water balloons full of floating prey. Those prey are concentrated by slowly expelling the water through baleen plates. The volume of water brought in with a single gulp can exceed the volume of the whale itself.
"Rorqual whales attained large body size with the evolution of a bulk filter feeding mechanism based on engulfing huge volumes of prey-laden water," Vogl said. "This required major changes in anatomy of the tongue and ventral blubber to allow large deformation, and now we recognize that this also required major modifications in the structure of nerves in these tissues so they could withstand the tissue deformation."
Segment of a nerve of the rorqual whale tongue at its initial length prior to being stretched (top left). The nerve has been manually stretched until it abruptly stiffens and resists further extension, and is more than twice its initial length (bottom). (Photo Credit: Vogl et al./Current Biology 2015)
Vogl and his team did not expect to make the discovery, and it was only made after one of the members of the lab picked up a dull white cord-like structure and stretched it. At first the team thought they were dealing with a blood vessel, but upon further inspection they realized it was nerve, unlike any they had seen before. The nerves of other species are generally surrounded by a thin collagen wall, and any stretch can pull and damage the nerves.
The researchers don't know yet whether anything similar will turn up in other animals -- the ballooning throats of frogs, for example, or the long and fast tongues of chameleons. They plan to keep studying the whales' nerves in greater detail, in hopes of understanding better how the nerve core is folded in such a way to allow its rapid unpacking and re-packing as the entire structure is stretched and then relaxed again.
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