What's in a Tooth?

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Science  23 Dec 2005:
Vol. 310, Issue 5756, pp. 1900c
DOI: 10.1126/science.310.5756.1900c
CREDIT: GLENN WILLIAMS; INSET: MARTIN NWEEIA

The male narwhal has long fascinated whale researchers, who have puzzled over the function of the 2.5-meter-long spiral tusk that juts out from its upper jaw, like the horn of the mythical unicorn. Now dentist Martin Nweeia, who teaches at Harvard School of Dental Medicine in Boston, has revealed that the tooth is not an icebreaker or a weapon as some have thought, but a sensor.

At the 16th Biennial Conference on the Biology of Marine Mammals in San Diego, California, last week, Nweeia reported from lab studies and narwhal observations in the Canadian Arctic that the tooth has an extremely sensitive surface with millions of tiny nerve endings. It can detect changes in water temperature and pressure, and chemicals that enable the whales to gauge salinity—an indication of ice formation—and find fish to eat.

Nweeia now plans to put water-filled plastic gaskets around 45-cm lengths of teeth on Arctic narwhals and monitor—via brain and muscle electrodes as well as hydrophones—the whales' responses to different salinity levels.

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