Certain whales have the capability of opening their jaws wide enough to swallow vast amounts of food and water -- an act that otherwise would break the mouths of other mammals. Scientists looked at a fin whale's anatomy and found that it -- and other whales -- have special stretchy nerves. Reuters reports:
When the fin whale gets ready to eat, Earth's second-largest animal opens its mouth so wide that it can gulp an amount of water larger than the volume of its own body as it filters out meals of tiny fish and shrimp-like krill.
When feeding, this whale measuring up to about 88 feet (26.8 meters) long and 70 tons increases its swimming speed, opens its mouth and lunges in the ocean.
The force of water rushing into the mouth during "lunge feeding" turns the tongue upside down and expands the bottom of the oral cavity into a huge pouch between the body wall and the overlying skin and blubber. As it closes its mouth, the whale filters out seawater through plates in the mouth while eating huge quantities of small prey.
In other animals and humans, this would cause significant damage to the nerves in the mouth and tongue, which have a fixed length.
But scientists revealed on Monday how the fin whale and its closest cousins, including the even-bigger blue whale, do this without shredding their nerves. These nerves, they said, can stretch to double their usual length and recoil like a bungee cord without harming the nerve fibers.
The strategy, [A. Wayne] Vogt writes, is “simple yet elegant”. Each nerve contains bundles of fibres, called fascicles, which sit at its core and are highly folded. The fascicles are surrounded by a thick wall made of two proteins: sturdy collage and stretchy elastin. When a whale lunges, the fascicles and collagen fibres unfold, while the elastin fibres stretch. Once the collagen fibres unfold fully, they become taut, stopping the nerve from stretching any further (and potentially breaking). As the whale closes its mouth after a lunge, the elastin fibres pull the nerve back into its original shape.
And that’s it. The nerve fibres themselves don’t actually stretch. It’s more that they unfold. But that still makes them special. Other nerves that reside in the neck and ribcage of a fin whale don’t have this property, and are barely more extensible than those in your face. Those in the whale’s face, by becoming stretchier, allowed it to evolve its extraordinary style of feeding and its record-breaking size. Without stretchy nerves, fin and blue whales would never have become the giants that they are.
