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Once the subject of mythical accounts of magical power, the helix-shaped tusk of the narwhal, or "unicorn" whale has proved to be an extraordinary sensory organ, according to a team of researchers from Harvard University, the Smithsonian Institution, and the Paffenbarger Research Center of the American Dental Association Foundation (ADAF) at the National Institute of Standards and Technology (NIST). The team's results were presented Dec. 13 at a technical conference in San Diego.
Measuring up to 2.7 meters or about 9 feet long, the tusk is traversed by up to 10 million nerve pathways. These pathways connect the outside of the tusk to a central core of nerves leading to the animal's brain. Based on experiments with samples of the tusk as well as with a captured narwhal whale, the research team found that the tusk's sensory system may be capable of detecting changes in temperature, pressure, salinity and other factors that may help a narwhal survive its Arctic environment.
Working at NIST, Naomi Eidelman, Anthony Giuseppetti and Frederick Eichmiller of the ADAF examined samples of narwhal tusk with both infrared microspectroscopy and scanning electron microscopy. Their work revealed the tusk's unusual structure.
While most mammalian teeth are softer on the inside and harder on the outside, narwhal tusk appears to be made "inside out," says Eichmiller. The researchers believe the softer outer layers of the tusk may act like a shock absorber to help prevent breaks.
M.T. Nweeia, N. Eidelman, F.C. Eichmiller, A.A. Giuseppetti, Y.G. Jung, Y. Zhang, "Hydrodynamic sensor capabilities and structural resilience of the male narwhal tusk," 16th Biennial Conference on the Biology of Marine Mammals, Dec. 13, 2005, San Diego, CA.
For additional photos see: http://www.nist.gov/public_affairs/techbeat/tb2005_1222.htm#unicorn