Last updated: October 13, 2017 at 16:32 pm
The narwhal (Monodon monoceros) can slow its heart to as little as 4 beats per minute during a dive. A study published in 2014 revealed significant changes in heart rate when alternating solutions of high-salt and fresh water are exposed to the Narwhal’s external tusk surface. The narwhal’s tusk is also the world’s most sensitive tooth.
Nweeia, M. T., Eichmiller, F. C., Hauschka, P. V., Donahue, G. A., Orr, J. R., Ferguson, S. H., Watt, C. A., Mead, J. G., Potter, C. W., Dietz, R., Giuseppetti, A. A., Black, S. R., Trachtenberg, A. J. and Kuo, W. P. (2014), Sensory ability in the narwhal tooth organ system. Anat. Rec., 297: 599–617. doi:10.1002/ar.22886
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Jeffrey Gallant is the Editor-in-Chief and Records Keeper of the Diving Almanac. He is also a contributing editor of DIVER Magazine, and the scientific director of the Greenland Shark and Elasmobranch Education and Research Group (GEERG). Jeffrey started diving in 1982.