X-rays add new twist to narwhal's spiral tusk
Summary
Scientists have discovered that the narwhal’s spiral tusk has a second internal spiral twisting in the opposite direction to the usual outer spiral. The tusk, which is actually a long canine tooth of male narwhals, has a complex internal structure that may help explain its unique shape and possible functions.Key Facts
- Narwhal tusks are long, spiral canine teeth found mostly in male narwhals.
- The tusk typically twists in a left-handed spiral on the outside, but inside, there is a second spiral twisting the other way.
- The tusk grows to lengths between about 5 feet and nearly 10 feet.
- Female narwhals usually do not develop tusks or have much smaller ones with fewer spirals.
- The tusk may serve as a social status symbol driven by sexual selection.
- Scientists have used advanced X-ray and imaging techniques from facilities in Sweden, Switzerland, and France to study the tusk’s internal 3D structure.
- Narwhals might use their tusks to stun small fish, and the tusk contains many nerve endings possibly used to sense the environment.
- The tusk is made of dentine and cementum, with a tightly organized microscopic structure of mineralized collagen fibers.
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