The narwhal, Monodon monoceros, has long fascinated sea explorers, scientists and aristocracy. This arctic whale is characterized by a single spiraled tusk extending six to nine feet, emerging from the upper jaw and through the lips of adult males. Some females may exhibit a tusk and, in rare instances, a male with two tusks has been observed. Often associated with the horn of the unicorn, the narwhal tooth has found its way into the books of scientific rarities and mythical tales.
The narwhal's tusk isn't unique at first glance. Elephants, rhinos and walruses all have these long, protruding teeth. But this one is different from any other tooth you've ever seen.
... The soft, sensitive part is on the outside, while the dense, hard part makes up the middle. Ten million tiny holes lie right on the surface on the tusk. Human teeth have these little tubules too, which is why sometimes the cold bothers your teeth, but they're covered with enamel. Imagine having all your nerves exposed in the icy waters of the Arctic. Why would the most sensitive part of a tooth be on the outside?
Function of 'unicorn' whale's 8-foot tooth discovered by Harvard School of Dental Medicine researcher
Nweeia has discovered that the narwhal's tooth has hydrodynamic sensor capabilities. Ten million tiny nerve connections tunnel their way from the central nerve of the narwhal tusk to its outer surface. Though seemingly rigid and hard, the tusk is like a membrane with an extremely sensitive surface, capable of detecting changes in water temperature, pressure, and particle gradients. Because these whales can detect particle gradients in water, they are capable of discerning the salinity of the water, which could help them survive in their Arctic ice environment. It also allows the whales to detect water particles characteristic of the fish that constitute their diet. There is no comparison in nature in tooth form, expression, and functional adaptation.