Remember how, as a kid you used to put up those little glow-in-the-dark stars and planets on your walls? Or perhaps you had a friend who did? We used to leave the lights on as long as possible so that our stars could “charge up” and glow even brighter.

As a kid, I had no idea how these little stars were able to absorb light. Today, though, I know that it’s because of phosphors. A phosphor is a substance that can, after absorbing light, radiates it back. Glow-in-the-dark toys are typically made using one of two phosphors—Zinc Sulfide or Strontium Aluminate. The latter is newer and lasts longer.

As much as I loved glow-in-the-dark toys as a kid—I think I might just love glowing animals more. We’ve known for some time about bioluminescent animals—like fireflies and most deep sea animals—that can create their own light through the combination of luciferin and luciferase, which results in the emission of a photon of light. But more recently, scientists have discovered more than 180 species of biofluorescent fish. Unlike bioluminescent fish, biofluorescent fish possess a protein that absorbs light, transforms it, and then re-emits it as a different color.

“There is a whole light show going on down there,” said John Sparks, who is a curator of ichthyology at the American Museum of Natural History. Sparks is also the author of a recent paper on biofluorescent fish, published in PLOS ONE.

Sparks and his team made several deep-sea dives while researching, using “specially designed blue lights,” since biofluorescence is less detectable to the human eye than bioluminescence. The images they captured were stunning:

biofluorescent fish john sparks

John Sparks and his team discovered over 180 species of biofluorescent fish.
Image: Sparks et al. / PLOS ONE

As intrigued as I am? Be sure to read the full paper by Sparks et al here.