What makes a narwhal’s tusk so special? Scientists are close to unraveling the mystery

What makes a narwhal's tusk so special? Scientists are close to unraveling the mystery

Narwhals, often referred to as the "unicorns of the sea," boast a distinctive spiral tooth reaching up to ten feet in length. These unusual teeth, the only ones in the animal kingdom with a completely straight growth pattern, are predominantly found in males and some females, with rare instances of having two. The reasoning behind the uniform leftward spiral remains a scientific enigma.

Researchers are now employing advanced imaging techniques to examine the tusks in unprecedented detail, seeking to uncover some of their secrets. Published in the journal Nature Communications, a new study reveals the tusks' fundamental building blocks—tiny, threadlike structures of mineralized collagen that grow in a double helix: one side left-handed, the other right-handed.

This arrangement enables the tusk to grow in a straight line. While similar spiraling structures are common in nature, such as snail shells spiraling both ways, narwhals are unique in having a single left-spiraling tusk. Using powerful x-ray scanners, the researchers analyzed the tusks, discovering that the outer layer, cementum, grows in a left-handed spiral, while the inner layer, dentine, follows a right-handed spiral.

These opposing spirals likely contribute to the tusk's straightness. The exact purpose of the straight tusk, while other tusked animals like elephants have curved ones, remains unclear. One prevailing hypothesis is that the tusk serves as a display to establish social dominance or attract mates, rather than for hunting or directly feeding.

Additionally, the tusk might remain out of the way during "suction feeding" on fish and squid. Future research will delve deeper into the narwhal's skull, focusing on the chamber where the tusk originates, aiming to better understand its growth pattern and potential insights into the animal's life history.