From blue to green, red or orange: Fish put on new light

(CNN) -- There is a light show in the ocean that you
can't see, but many fish can. There's quite a display of neon greens,
reds, and oranges going on underneath the surface.

Still, the discovery of
what is hidden from human eyes -- biofluorescence in 180 species of fish
-- brings up many questions for researchers.

Do fish use it to communicate with others? Do they use it to mate? What is its function?

Biofluorescence occurs when an organism absorbs blue light, transforms it and emits it as another color.

A team of researchers
from the American Museum of Natural History and other scientific
organizations published a study Wednesday in the online journal PLOS
ONE, reporting the findings of the first in-depth look at
biofluorescence in fish.

"We've long known about
biofluorescence underwater in organisms like corals, jellyfish, and even
in land animals like butterflies and parrots," said the study's
co-author, John Sparks, who is a curator in the Museum's Department of
Ichthyology.

He said the team stumbled
on an eel that glowed green while he and a partner were studying a reef
in the Cayman Islands. The discovery in a photograph of the eel
lighting up underneath the blue lights they used led them to make four
more trips in different parts of the world to get a closer look at the
glow show.

The expeditions to the
Bahamas in the Caribbean and Solomon Islands in the Pacific revealed a
variety of fish living around coral reefs -- including sharks, rays,
eels and lizerdfishes -- that exhibited bioflourescence. s

"Many shallow reef
inhabitants and fish have the capabilities to detect fluorescent light
and may be using biofluorescence in similar fashions to how animals use
bioluminescence, such as to find mates and to camouflage," Sparks
suggested, while adding the reasons will need further study.

So how do the fish
recognize it? Many of them have yellow filters in their eyes, "possibly
allowing them to see the otherwise hidden fluorescent displays taking
place in the water," a news release from the museum of natural history
said.

"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."

Some scientists cautioned that the bioflouresence might look neat in photos using special lights but also have no function.

Nico Michiels, a
zoologist at the University of Tübingen in Germany, and Steven Haddock
of the Monterey Bay Aquarium Research Institute in California, indicated to Science Now
that the need for special technology to view what the website called
weak fluorescence "casts doubt on the usefulness of the coloration in
the fish's dimly lit natural environments."

Sparks said it will be interesting to see what the team finds next.

"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," he said.

He added that there may be fluorescent proteins involved, ones that could be used in biomedical research.