Audrey Velasco

The transparent teeth of this dragonfish evolved for one lethal purpose

Five hundred meters below the ocean’s surface off the coast of California lives a creepy looking sea monster with a huge jaw and sharp rows of teeth. Even creepier, these teeth are transparent. Now, scientists think they know what makes them this way.

Researchers collected 10 dragonfish (Aristostomias scintillans, pictured) with a fishing net. They analyzed 40 of their teeth using detailed imaging to capture the teeth’s colors, makeup, and structure.

Like human teeth, the dragonfish’s teeth have a dense inner dentin layer surrounded by an outer enamellike layer. Dispersed throughout the enamel, however, the researchers found tiny nanocrystals that prevent light from reflecting off of the teeth’s surface and camouflage them in the deep ocean, the team reports today in the journal Matter. The teeth are also thinner than most predators’, which helps them scatter less light and appear translucent.

Despite dragonfish’s small size—only about 15 centimeters long—they are apex predators and can kill fish up to 50% of their size. Their teeth may be key: Because the fish have jet-black mouths, their teeth are practically invisible, so most prey never see them coming.