Fire Salamanders Glow Under UV Light After 250 Years

For over 250 years, scientists have pored over every detail of fire salamanders, making them one of the best-studied amphibians in Europe. Yet it took one researcher with a UV flashlight on a rainy night to reveal their glowing secret.

Evolutionary biologist Bernat Burriel-Carranza was walking through Spain with a blacklight when he spotted a fire salamander crossing the road. The moment he pointed the beam at it, a bright, speckled pattern lit up along its sides.

The discovery marks the first time anyone has documented biofluorescence in fire salamanders. Unlike bioluminescence where animals make their own light, biofluorescent creatures absorb light at one wavelength and re-emit it at another.

Scientists used to think only ocean animals and bugs could pull off this glowing trick. But recent years have brought surprise after surprise, with the trait popping up in reptiles, birds, and now these black-and-yellow amphibians that call Europe's damp forests home.

After that first sighting, Burriel-Carranza and his team spent months searching forests in Spain and Germany with UV lights. They found the glow concentrated in the salamanders' yellow spots, the same markings scientists believe warn predators to stay away.

The plot thickened when researchers swabbed the salamanders' toxic skin secretions. The slime glowed too, suggesting the fluorescence comes from the same glands that produce their poisonous defense spray.

When the team examined tissue samples under microscopes, they found fluorescent compounds circulating through the salamanders' bloodstreams and glands. Only some tree frogs had shown this before, using special molecules called hyloins to light up their see-through skin.

Why This Inspires

Nobody knows yet what chemical creates the salamanders' glow, but researchers think it might be a molecule completely new to science. That a creature studied for two and a half centuries can still surprise us shows how much wonder remains in the natural world.

The salamanders might use their glow to spot each other on dark forest floors during breeding season in fall, when moonlight carries more UV wavelengths. Or they could be doubling down on their "danger, stay back" message to predators by making their warning colors visible even at night.

The discovery reminds us that even the most familiar creatures can hold extraordinary secrets just waiting for someone to shine the right light.