Rorqual Whales have an amazing nerve structure in their mouths and tongues that can stretch out to double their length and recoil like a bungee cord, say scientists from the University of British Columbia (UBC) in Canada, the Smithsonian Institution, and Stanford University, both in the US.
Rorquals include the blue whale, the largest animal that ever lived, the fin whale, and the northern minke whale.
The elastic nerves explain how the huge animals are able to balloon an immense pocket between their body wall and overlying blubber to take in prey during their feeding dives.
The research team reported its findings in the academic journal Current Biology. (Image: www.cell.com)
“This discovery was totally unexpected and unlike other nerve structures we’ve seen in vertebrates, which are of a more fixed length.”
“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.”
Human nerves cannot stretch without being damaged. In the case of rorquals, the largest group of baleen whales, their nerve cells are packaged within a central core in such a way that each nerve fibre is never really stretched – it simply unfolds.
UBC zoologist, Robert Shadwick, said:
“Our next step is to get a better understanding of how the nerve core is folded to allow its rapid unpacking and re-packing during the feeding process.”
Expansion of the ventral grooved blubber during a fin whale feeding dive. (Image: University of British Columbia)
Do other animals have this feature?
The scientists do not yet know whether similar nerve features are present in other animals. Perhaps chameleons’ tongues and the ballooning throats of frogs have similar bungee cord-like nerves.
Nick Pyenson, who used to be at UBC as a postdoctoral researcher, and is now at the Smithsonian’s National Museum of Natural History, said:
“This discovery underscores how little we know about even the basic anatomy of the largest animals alive in the oceans today.”
“Our findings add to the growing list of evolutionary solutions that whales evolved in response to new challenges faced in marine environments over millions of years.”
Part of a tongue nerve at its initial length prior in smaller image, and after it is manually stretched in larger picture. (Photo: University of British Columbia)
Citation: “Stretchy nerves are an essential component of the extreme feeding mechanism of rorqual whales,” A. Wayne Vogl, Margo A. Lillie, Marina A. Piscitelli, Jeremy A. Goldbogen, Nicholas D. Pyenson, Robert E. Shadwick. Biology Letters. Published 4 May, 2015. DOI: 10.1016/j.cub.2015.03.007.