Whales have elastic nerves

Vogl et al./Current Biology 2015

Whales have elastic nerves

When hungry, a blue whale pumps its tail and fluke, accelerating through swarms of krill and other small animals with a lunge and a gaping jaw that can dangle nearly perpendicular to its body. The volume of briny, prey-laden water engulfed can often surpass the original volume of the leviathan—the largest known animal that has ever existed. To accommodate the big gulp, a family of baleen whales called rorquals (Balaenopteridae) that includes blue, fin, and humpback whales have evolved unique features such as highly flexible jaw joints, a deformable tongue that inverts into a sac to hold the seawater, and grooved ventral blubber—stretching from the mouth to the belly button—that can balloon to several times its original size. Now, a new study has identified another necessary adaptation: nerves in the whales’ tongue and mouth that, as seen above, can extend to more than double their original length, a team of researchers reports today in Current Biology. Stretching vertebrate nerves normally leads to pain, paralysis, or even the detachment of nerve roots from the spinal cord. Rorquals’ nerves extend, however, thanks to folded bundles of nerve fibers in each nerve’s core that are surrounded by a thick wall of folded collagen and elastin—the same protein that keeps skin elastic. When the whales’ mouths expand, the nerve bundles, collagen, and elastin unfold until the collagen stiffens, preventing overelongation, and the elastin like a bungee cord snaps the nerves to their previous shape.

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