What color is a lumpfish? The answer is
more complicated than you might expect.
These bumpy, bottom-dwelling fish, found in the
North Atlantic and parts of the Arctic Ocean, come in a variety of colors,
which change as the fish age. However, scientists think they have pinned down
the fish’s true color — fluorescent green.
اضافة اعلان
In a study published this month in the Journal of
Fish Biology, scientists discovered that lumpfish glow under UV light. They
believe these fish use their biofluorescent radiance to identify and possibly
communicate with one another.
In recent years, biofluorescence has been observed
in cat sharks, wombats, flying squirrels, and many other species. And now, add
the lumpfish to nature’s cast of secretly glowing animals.
Lumpfish are solitary creatures that spend most of
their lives on the seafloor. These funny-looking fish latch onto rocks and
seaweed, using a modified pelvic fin on their underside that acts like a
suction cup to help them hang out until something tasty swims by.
They have also become pseudocelebrities on
TikTok,
where a ceaseless stream of videos posted by researchers and fishers have
amassed millions of views.
“It is a pretty clunky, awkward-looking fish,” said
Nathaniel Spada, a research assistant at Woods Hole Oceanographic Institution
in Massachusetts and a part-time lumpfish influencer. He was not involved in
the study, but his Werner Herzog-inspired TikToks about the lumpfish in his lab
have been viewed millions of times.
“I was not expecting it to be as popular as it is,”
he said, “but I should have figured because they really are a cool fish.”
Last year, Dr Thomas Juhasz-Dora, a veterinarian and
doctoral student at the University College Cork in Ireland, became curious when
he looked into the bulging eyes of a lumpfish in his lab — and thought of an
idea. He had seen biofluorescence in other marine species and wanted to know if
his lumpfish possessed the trait. He gathered 11 juvenile lumpfish and photographed
them under different light conditions. Under regular light, they appeared
sea-foam green. But when they were exposed to UV light, their entire bodies
emitted a bright, neon-green glow.
“I was like ‘Wow’,” said Juhasz-Dora, who was amazed
by the intensity of the fish’s biofluorescence. This phenomenon occurs when an
organism absorbs ultraviolet rays, usually invisible to people, and reemits
them as colors that we can see, typically red, orange, or green. This is not to
be confused with bioluminescence, in which animals produce their own light via
a chemical reaction.
As hatchlings, they can be almost any color of the rainbow. As juveniles, the color of their thick, knobbly skin changes to match their surroundings, helping to conceal them from predators.
Many species have special filters in their corneas
that allow them to see biofluorescence without the help of UV light.
Juhasz-Dora suspects lumpfish are equipped with these filters, which would
allow them to somehow signal to their own kind while remaining hidden from
predators.
“It is certainly plausible,” said Elizabeth
Fairchild, a researcher and associate professor at the University of New
Hampshire who studies lumpfish and other commercially farmed aquatic species.
The fish may also use its biofluorescence to attract
prey, but Fairchild’s money is on communication.
“Communication is probably the likely answer,” she
said. “It is just we do not know what they are communicating.”
It is also possible that the biofluorescence serves
no purpose at all. However, Fairchild, who was not involved in the study, said
it was unlikely given the importance of coloration to lumpfish.
“Lumpfish have such crazy color plasticity,”
Fairchild said.
As hatchlings, they can be almost any color of the
rainbow. As juveniles, the color of their thick, knobbly skin changes to match
their surroundings, helping to conceal them from predators. When they reach
adulthood, lumpfish develop pale-gray to light-blue skin. However, this changes
during breeding season, when males turn orange-red and females blue-green.
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. Their
recent discovery “opened the door to new discoveries”, he said.
“It allows us to really see the world from their
perspective, rather than our own.”
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