Scientists Shed Light on Rich World of Fish Biofluorescence

Biofluorescence can result in a dazzling display of colors. Now, scientists have identified more than 180 species of fish that glow in a wide range of colors and patterns, unveiling the widespread phenomenon in the tree of life of fishes. The findings could pave the way for the discovery of new fluorescent proteins that could be used in biomedical research.

"We've long known about biofluorescence underwater in organisms like corals, jellyfish and even in land animals like butterflies and parrots, but fish biofluorescence has been reported in only a few research publications," said John Sparks, one of the researchers, in a news release. "This paper is the first to look at the wide distribution of biofluorescence across fishes, and it opens up a number of new research areas."

In order to better study bioflurescence, the researchers began with observation of green eel fluorescence off of the coast of Little Cayman Island. In order to further examine the phenomenon, the researchers embarked on high-tech expeditions to tropical waters off of the Exumas in the Bahamas and the Solomon Islands. During night dives, the researchers stimulated biofluorescence in the fish with high-intensity blue light arrays housed in watertight cases. They then used underwater cameras in order to see the biofluorescent glow.

In the end, the researchers found a veritable zoo of biofluorescent fish, ranging from the cartilaginous to the bony. In the end, they identified more than 180 species of biofluorscent species, including species-specific emissions patterns among close relatives. In addition, the scientists noted that many of these fish had yellow filters in their eyes. This possibly allows them to see the otherwise hidden fluorescent displays taking place in the water. This could mean that biofluorescence may be used for interspecific communication while still remaining camouflaged to predators.

"The cryptically patterned gobies, flatfishes, eels and scorpionfishes--these are the animals that you'd never normally see during a dive," said Sparks in a news release. "To our eyes, they blend right into their environment. But to a fish that has a yellow intraocular filter, they must stick out like a sore thumb."

That's not all the researchers found, though. They also discovered that biofluorescence is extremely variable. It can range from simple eye rings to glowing green mucus secreted on the outside of fishes. The findings could allow scientists to discover more florescent proteins for use in experimental biology.

The findings are published in the journal PLOS One.