A narwhal tale with a twist
Up to two metres long and twisted into a perfect spiral: The narwhal’s tusk is one of the most unusual structures in the animal kingdom. An international research team, including scientists from the Paul Scherrer Institute PSI, has now for the first time deciphered how this helix is organised inside the tooth – with a surprising twist. At the nanometre scale, the building blocks of the spiral rotate not just one way, but in two opposite directions.
King Frederik III knew the true origin of unicorn horns, and in the 17th century he sent an expedition to Greenland to probe the reality behind the precious horn. That’s because the mythical creature lives there, in Arctic waters, and has fins rather than hooves. The expedition was successful and bestowed on the Danish ruler a throne made entirely of “unicorn horns” – and with that, prestige and power in Europe. Even though the legendary horn is not a horn at all, but “merely” a tooth.
A tooth, however, that is quite unique in the animal kingdom. While other long teeth – such as the tusks of elephants and walruses, or the incisors of beavers – simply follow a curved shape, the male narwhal’s tooth grows forwards in a screw-shaped form. Usually it is the left upper canine that twists in an elegant counterclockwise spiral, piercing the upper lip and reaching lengths of up to two metres – sometimes up to half the animal’s body length.
It was precisely this unusual growth that aroused the curiosity of an international and interdisciplinary research team. Using state-of-the-art X-ray methods, the researchers wanted to find out whether the direction of rotation of the visible spiral was already determined by the arrangement of its nanometre-sized building blocks.
Read more on the PSI website
Image: Narwhals – often called the “unicorns of the sea” – have fascinated people for centuries with their long tusks. Now an international research team has used X-ray light to reveal the internal structure of this unique tooth for the first time, from nanometre to centimetre scale.
Credit: © Carsten Eqevanq, Greenland Institute of Natural Resources, North West Greenland (2021)