Dragonfish secrets of dental invisibility
Its name might mean “shiny loosejaw”, but its prey don’t see the danger until it’s too late. The unusually crystalline nanostructure of deep-sea dragonfish teeth is unique, rendering them virtually invisible, according to US researchers who have been analysing these teeth for the first time.
The species Aristostomias scintillans is found in depths down to 1200m in the eastern Pacific. The fish, which averages 15cm in length, has a very dark body and is relatively sedentary, waiting for passing prey with jaws apart ready to strike.
However, its powerful, sabre-like teeth present “no contrast to the surrounding blackness of the fish nor the background darkness of the deep sea” – a lethal formula that places the species among the most successful of predators.
10 June 2019
“Their teeth are always exposed, so it’s important that they are transparent so they don’t reflect or scatter any bioluminescent light from the environment,” said Audrey Velasco-Hogan of University of California San Diego’s Jacobs School of Engineering.
She and Dimitri Deheyn, a marine biologist at the Scripps Institution of Oceanography, imaged and analysed the dragonfish teeth using electron microscopy, focused ion beam and nanoindentation tests.
The outer enamel-like layer of the teeth was found to consist of hydroxyapatite nanocrystals, structured to prevent light from scattering or reflecting off the surface. Meanwhile the inner dentin layer was shown to lack the microscopic “dentin tubules” that give human and other animals’ teeth their colour.
“Experimentally, we know that the way to make a material transparent is by reducing its grain size to make it nanostructured,” said Velasco-Hogan. “So to see that is also how Nature is accomplishing transparency is an interesting parallel.”
The researchers believe that their findings could provide “bioinspiration” for researchers looking to develop transparent ceramics.