Researchers have discovered that fire salamanders can produce a striking cyan-green fluorescence when exposed to ultraviolet light.

Fire salamanders are famous for their vivid yellow and black warning colors, but part of their appearance remains invisible to human eyes. Researchers have found that when ultraviolet light strikes the animals, their skin and defensive secretions emit a cyan-green fluorescence that may persist for more than 24 hours after the secretions are released.

The fluorescence is strongest in the salamanders’ yellow underside and along the sides of the body. It originates mainly from skin glands and the substances they produce, suggesting that the phenomenon is closely connected to the same tissues involved in the animal’s chemical defenses.