Normally, the skin of a juvenile lumpfish appears a pale greenish blue. But when scientists at the University College Cork in Ireland photographed this squishy bottom-dwelling fish under ultraviolet (UV) light, they saw something surprising. The animal’s body lit up with an intense green glow.

“I was like, ‘Wow!’” says Dr. Thomas Juhasz-Dora, a veterinarian who led the study. “It reminded me of a Christmas ornament.” His team realized that the lumpfish is biofluorescent—its skin can absorb invisible energy waves from a light source and reemit them as a visible glow. Juhasz-Dora believes this ability helps lumpfish identify and communicate with one another.