A coral reef alive with colour: Researchers reveal 180 species of glowing fish

Biofluorescent fish absorb light from their environment before changing its colour with special proteins and emitting it once more

The first comprehensive survey of biofluorescence in fish has revealed more than 180 different species of marine life that glow in various patterns of neon colours.

“There is a whole light show going on down there," John Sparks, co-author of the new paper published in journal PLOS One told the LA Times. "There have been studies on corals that are biofluorescent, but for fish, virtually nothing was known."

The new research could help expand the use of fluorescent proteins in biomedical research, but has also surprised researchers with the sheer variety on display. Whilst some species simply have glowing eye rings others are cloaked complex, full-body patterns that extend right into the animal’s interior.

"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 Sparks.

"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."

Biofluorescence is different to the more widely known phenomenon of bioluminescence. Animals that bioluminesce make their own light by mixing chemicals within their body, with 80 to 90 per cent of deep sea animals displaying this property. Notable examples including the fearsome-looking anglerfish.

In contrast, animals that are biofluorescent do not create light but absorb it, using proteins to change the light's colour before re-emitting it. Whilst bioluminescent animals glow in the dark, biofluorescent ones rely on ambient light to create the patterns they use for camouflage and attracting mates.

Because of this, most of the examples of biofluorescence are found in animals living in relatively shallow environs - places where light from the surface can still penetrate under water. The researchers found most of the species they documented in the coral reefs of the Bahamas and Solomon Islands.

The researchers also found that some species had adapted to emit patterns that were only visible to members of their own species – an ability that allows individuals to communicate with potential partners whilst remaining hidden to predators. Special cameras with blue lights were used to reveal the full array of colours displayed by the species.

"The cryptically patterned gobies, flatfishes, eels, and scorpionfishes—these are animals that you'd never normally see during a dive," Sparks said. "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."

Read more about the study at Phys.org