Scientists believe to have definitely found the answer to the mystery around the “unicorns” of the Arctic. What is the narwhal’s—“unicorn” of the ocean—tusk good for? This question has Wbeen mainly unsettled up to now. But now, American scientists have investigated what is the function of the tusk that projects up to two and a half metres out of its head.
An emerging Narwhal is an exceptionally beautiful and rare sight.
Photo: Deepwave
published Deepwave Report 05
The narwhal, a marine mammal with a body length of up to 4.5 m, lives in the Arctic Northern Atlantic. Its “horn” in reality is a “tusk” that projects from the left side of the upper jaw. Its helical structure, its asymmetrical origin and its apparently irregular distribution among the sexes—most of the males have it, but also some females do—are considered as one of the mysteries of evolution and as unique among mammalian teeth. Up to now, several theories circulated on the function of these teeth, however none of them gained acceptance. Some researchers conjectured that the projection could be a secondary sex characteristic like the lion’s mane or the peacock’s wheel, according to others the males use it for showman-ship and dominance.
Curious dentists
Martin Nweeia, expert for Biomaterial Sciences and restorative dentistry at Harvard School for Dentistry Medicine (HSDM) has investigated the whales and their teeth during four expeditions into the Arctic. He is head of a narwhal-tooth study that since the year 2000 brings together researchers with some of the Inuit elders. That way, the century-old experiences of the Arctic population shall be combined with modern scientific methods and approaches. With success. He and his colleagues now came to a totally new conclusion: They discovered that the tooth of the whale obviously functions as a hydrodynamical sensor. Ten millions of tiny nerve connections are connecting the central nerve of the tooth with its surface, thus making the projection a sensible sensor. Though seeming hard and massive, the tusk works like a membrane with a sensitive surface that can record changes in water temperature and pressure as well as the concentrations of chemical substances.
The horn—sensortooth in the Arctic?
“Why would a tusk break the rules of normal development by expressing millions of sensory pathways that connect its nervous system to the frigid arctic environment?” Nweeia asks. “Such a finding is startling and indeed surprised all of us“ Sensors can help to survive in an extreme environment. The ability to detect chemical gradients with the help of a tooth, on the one hand, helps the narwhals to measure the salinity of the water, thereby providing a better orientation in the Arctic ocean.
On the other hand it could enable the animals to better locate their feed on the basis of the characteristic “chemical trace”. Moreover, Nweeia and his colleagues discovered that the tooth also transmi tactile stimuli and has an important function during the typical “tusking” of the males. Atooth as a multi-task sensory organ—in this complex form and combination there was nothing like that, as to the researcher. “Now that we know the sensory capabilities of the tusk, we can design new experiments to describe some of the unique and unexplained behaviors of this elusive and extraordinary whale”.