A remarkable feature of the narwhal is its straight and lengthy tusk, which can reach up to three meters. Unlike other mammal tusks, the narwhal’s tusk grows perfectly straight without any curves, emerging as an upper tooth through the whale’s lip on the left side.
Recent research published in Nature Communications uncovered the mystery behind the straight growth of the narwhal tusk. The study revealed that the tusk’s unique pattern of opposing spirals, with one spiral going right and the other left, contributes to its straight form. This finding surprised the international team of researchers led by Henrik Birkedal from Aarhus University, Denmark.
The investigation into the narwhal tusk’s structure began when Birkedal collaborated with colleagues in organic chemistry to explore why certain molecules exhibit handedness. This collaboration led to a deeper examination of the spirals present in narwhal tusks, with biologists from Greenland and physicists from Sweden joining the research team.
Advanced imaging techniques akin to CT scans unveiled that the tusks, predominantly found in male narwhals, consist of dentine and cementum, lacking the enamel layer found in human teeth. The researchers identified two opposing spirals – a left-handed spiral on the outer cementum layer and a right-handed spiral in the inner dentine layer.
Not only did this discovery solve the enigma of the narwhal’s straight tusk, but it also holds promise in shedding light on the structural principles of human bones and other similar biological instances, according to Birkedal.
Renowned narwhal biologist Martin Nweeia from Harvard University, known for his expertise in marine mammal teeth, expressed delight at the in-depth research on the narwhal tusk. While acknowledging the multifunctionality of teeth, Nweeia emphasized that his previous research identified the tusk primarily as a sensory organ rather than for defense or feeding purposes.
Looking to the future, Nweeia emphasized the importance of conducting off-season studies and collaborating with Indigenous communities, particularly in the Canadian Arctic where narwhals reside during summers. Integrating scientific research with traditional knowledge and observations from the Inuit community can provide a comprehensive understanding of these fascinating creatures.
Interdisciplinary collaboration was key to the success of Birkedal’s recent study, highlighting the significance of merging different fields of science to gain insights that would be unattainable through individual efforts. This approach, as emphasized by both Birkedal and Nweeia, underscores the importance of diverse perspectives in advancing scientific understanding.
