Some fish have a hidden superpower—they can glow in vibrant colors under certain kinds of light.
This natural glow, called biofluorescence, happens when an animal absorbs one kind of light and gives off another, often brighter color.
A new study led by scientists at the American Museum of Natural History reveals that this glowing ability is not just widespread in the ocean, but also very ancient and surprisingly diverse.
According to two new studies published in Nature Communications and PLOS One, biofluorescence in fish has evolved more than 100 separate times over the past 112 million years.
Most of these glowing fish are found in coral reefs, which are some of the most colorful and diverse ecosystems on Earth. The first glowing fish may have been eels that lived over 100 million years ago.
Emily Carr, a Ph.D. student at the Museum and the lead author of both studies, explained that while scientists already knew many ocean animals—including sea turtles, corals, and fish—glow under special light, we’re only beginning to understand how and why this glow evolved.
“To figure out what these animals use fluorescence for—like hiding from predators, attracting mates, or hunting—we first have to understand when and how it developed over time,” Carr said.
For the Nature Communications paper, Carr and her team looked at all known cases of biofluorescence in a group of bony fish called teleosts, the largest group of vertebrates on the planet.
They identified 459 glowing species, including 48 that were not previously known to fluoresce.
Their analysis showed that this trait evolved many times independently, especially among fish that live in coral reefs. In fact, reef fish were found to develop biofluorescence at a rate ten times higher than fish from other habitats.
The researchers also noticed a spike in glowing species after the mass extinction event that wiped out the dinosaurs 66 million years ago.
This period also marked the rise of modern coral reefs, which may have played a role in encouraging more fish species to evolve this glowing ability. Carr believes the explosion of life and color in reef habitats likely pushed fish to develop more complex ways of communicating or blending in.
In the second study, published in PLOS One, the team used special lights and filters to examine fish specimens collected over the last 15 years from places like the Solomon Islands, Greenland, and Thailand.
While these fish were already known to glow, the researchers were surprised by just how many colors they emitted—greens, yellows, oranges, reds, and even several colors from a single species. Some fish families showed at least six different glowing patterns, suggesting highly sophisticated signaling systems.
John Sparks, a curator at the Museum and co-author of the studies, said, “The range of colors and patterns we’ve found is incredible. These fish might be using their glow in ways we don’t yet fully understand, possibly to communicate or recognize each other in the dark waters of the reef.”
Beyond the beauty of glowing fish, this discovery could have practical uses. The unique glowing molecules found in these species might help develop new tools in medicine, such as more precise imaging for disease diagnosis or treatment.
These glowing fish are not just a wonder to see—they’re helping scientists unlock secrets from the deep past and may even inspire the next generation of medical advances.
