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Narwhal has the strangest tooth in the sea

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5:00pm, May 4, 2014
narwhal illustration

TWISTING TOOTH  Most narwhals grow only one, the left tooth, and it always spirals to the left. Even in the rare cases where a right tusk emerges too, it also spirals to the left instead of having the mirror symmetry usual for mammal body parts. Narwhal tusks can grow to half the animal's body length.

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Sometimes called the unicorn of the sea, the male narwhal’s tusk is actually a tooth, and it grows directly through the whale’s upper lip instead of pushing the lip aside. It’s an exuberantly large version of a canine tooth that grows in a spiral; the only tooth known to do so. Otherwise narwhals are practically toothless, with only vestigial stubs that stop growing during development and rarely emerge into the mouth.

This extreme anatomy has captivated dentist Martin Nweeia, who practices in Connecticut and teaches at Harvard University. For more than a decade, he has pioneered ways to study these difficult-to-reach Arctic whales, and he and his colleagues now describe in the April Anatomical Record that narwhals can detect changes in water salinity using only their tusks. The animals “don’t have a good sense of humor,” though, about being temporarily restrained for the testing, Nweeia says.


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