X-ray study reveals new secrets of narwhal’s twisted tusk
▼ Summary
– Narwhal tusks contain a second internal spiral oriented opposite to the outer left-oriented spiral, as reported in a new Nature Communications paper.
– The tusk is a canine tooth in the left upper jaw of male narwhals, growing up to 2 meters long, and is linked to Inuit legend of a woman transformed into a narwhal with her twisted hair becoming the tusk.
– Tusks likely evolved through sexual selection as social status indicators, since females usually lack them and live longer, though the exact function remains debated.
– Narwhals use tusks to stun small Arctic cod while hunting, and possible use as weapons is suggested by tusks found embedded in other narwhals.
– The tusks have millions of nerve endings, potentially enabling narwhals to sense temperature or salinity changes in the water.
CT scans have pulled back the veil on a hidden layer of complexity within the narwhal’s iconic tusk, revealing a structure far more intricate than the single, smooth spiral visible to the naked eye. While the tusk’s exterior coils in a left-handed direction, researchers have discovered a second, internal spiral that twists the opposite way. This finding, detailed in a new paper published in Nature Communications, adds a fresh dimension to our understanding of a tooth that has captivated human imagination for centuries.
Long before science offered explanations, medieval Europeans believed these elongated teeth were the horns of unicorns, attributing to them magical healing properties. Though that myth has been dispelled, the tusks remain sought-after curiosities in Canada and Greenland, and they continue to intrigue researchers investigating their unusual biology. The new study indicates that the tusk’s architecture is not a simple single helix, but rather a composite of two opposing spirals, a discovery that raises fresh questions about how this structure forms and functions.
Inuit tradition offers a more poetic origin story, telling of a woman dragged into the ocean by a harpoon rope who was transformed into a narwhal, her twisted hair becoming the tusk. Biologically, the tusk is an elongated canine tooth that erupts through the upper lip of male narwhals, typically when they are two or three years old, and can grow to lengths of 1.5 to 2 meters. While most males develop a single tusk, some may grow two, and rare individuals may have none at all.
The evolutionary purpose of this remarkable appendage remains a subject of active debate. Most experts agree it likely emerged through sexual selection, serving as a signal of social status. The fact that females usually lack the tusk, and generally outlive males, suggests it is not essential for basic survival. However, its precise role is still unclear. Narwhals have been spotted using their tusks to stun Arctic cod while foraging, and there is circumstantial evidence they might be used in combat, as some individuals have been found with tusk fragments embedded in their bodies. Adding another layer of intrigue, the tusk is packed with millions of nerve endings, hinting that it may function as a highly sensitive sensory organ capable of detecting shifts in water temperature or salinity.
(Source: Ars Technica)
