What color is a lumpfish ( Cyclopterus lumpus )? The answer is more complicated than one might expect.
These lumpy, bottom-dwelling fish are found in the North Atlantic and parts of the Arctic Ocean. They are found in a variety of colors, which change as they age. But scientists think they’ve figured out the fish’s true color: fluorescent green.
In a study in the Journal of Fish Biology , scientists found that lumpfish glow under ultraviolet light.
They believe that these fish use their biofluorescent glow to identify themselves and possibly communicate with each other.
In recent years, biofluorescence has been observed in cat sharks, wombats, flying squirrels, and many other species. Now the lumpfish enters the group of animals that shine in secret.
Lumpos are solitary creatures that spend most of their lives at the bottom of the sea. These curious-looking fish cling to rocks and algae, using their pelvic fin on the underside that acts as a suction cup to help them hang out until something tasty swims by.
They have also become celebrities on TikTok, where a relentless stream of videos posted by researchers and fishermen has racked up millions of views.
Last year, Dr. Thomas Juhasz-Dora, a veterinarian and PhD student at University College Cork, became curious when he looked at the bulging eyes of a lumpfish in his lab and had an idea.
He had seen biofluorescence in other marine species and wanted to know if his lumpfish possessed the trait.
He collected 11 juvenile lumpfish and photographed them under different light conditions. Under normal light, they appeared green. But when exposed to ultraviolet light, their entire bodies glowed a bright neon green.
Biofluorescence occurs when an organism absorbs ultraviolet rays, normally invisible to humans, and re-emits them in colors that we can see, usually red, orange or green.
Not to be confused with bioluminescence, in which animals produce their own light through a chemical reaction.
Many species have special filters on their corneas that allow them to see biofluorescence without the help of ultraviolet light.
Juhasz-Dora suspects that lumpos are equipped with these filters. This would perhaps allow them to send signals to their own kind while remaining hidden from predators.
The fish could also use its biofluorescence to attract prey, but the bets are on it for communication.
It is also possible that biofluorescence is useless. But some think it’s unlikely given the importance of coloration to the lumpfish.
How and why biofluorescence evolved in lumpfish is one of many questions raised by Juhasz-Dora’s discovery.
He and his colleagues are now investigating whether lumpfish can control their biofluorescence.
With information from the New York Times.