New insights into the narwhal

A new study has revealed that the narwhal’s famous tusk is more complex than previously thought. Using advanced 3D X-ray imaging and tomography, researchers found that the tusk contains two intertwined helical structures rather than a single spiral.

The outer layer, made of cementum, twists in one direction, while the inner dentin structure twists in the opposite direction. These opposing twists meet at the boundary between the two materials and appear to create a natural mechanical counterbalance. This design makes the tusk more resistant to bending and twisting than either a straight rod or a single helix.

The discovery helps explain how microscopic, mineralized collagen fibers are organized to produce the tusk’s large-scale shape. The researchers also hope that studying the tusk’s annual growth layers will eventually provide information about a narwhal’s age, health, and the Arctic environmental conditions it experienced.

The actual purpose of the tusk remains uncertain. It may primarily serve as a sexual signal, although possible roles in sensing, foraging, or competition are still being investigated.

Original article: “X-rays add new twist to narwhals’ spiral tusk” — Ars Technica