From: Roger Greenway, ENN
Published January 11, 2014 08:40 AM

Glowing fish!

As a scuba diver, I have seen all kinds of colorful fish. I have done a few night dives and seen some amazing things, like giant crabs! But I have never seen glowing fish. Perhaps the light I carried on night dives overpowered their glow. Perhaps it takes special techniques for humans to see the glow?

With the help of blue light and special long-pass filters, scientists have uncovered more of the undersea world's secrets. A study published today describes more than 180 species of marine fishes that glow in different colors and patterns, via a process known as biofluorescence. The work was funded by the National Science Foundation.

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Scientists already knew that some marine organisms fluoresce, including corals and jellyfish, but this is the first reported evidence of widespread biofluorescence among fishes.

"There's a whole light show going on down there, and people never see it," said one of the study's principal authors, John Sparks, a curator in the American Museum of Natural History's (AMNH) Department of Ichthyology.

The findings, published in PLOS ONE, will surely lead to new investigations of the function of biofluorescence as well as research related to the evolution and diversification of marine fishes. They could also lead to the discovery of new fluorescent proteins useful in cancer, brain and other biomedical research.

Biofluorescence is a natural process in which organisms absorb light at one intensity, or wavelength, and emit it at a different, usually lower, level--seen as a different color. In the ocean, the researchers found, fishes absorb the higher energy blue light around them and emit it in glowing greens, reds and oranges.

How did the scientists make the discovery? While taking and processing images of biofluorescent coral for an NSF-funded traveling museum exhibit: Creatures of Light: Nature's Bioluminescence, Sparks and AMNH research associate David Gruber (CUNY) were amazed to see, in the background of one image, an eel glowing bright green.

To further explore the phenomenon, they enlisted the help of other researchers and embarked on a series of dive expeditions. Deep underwater near the Bahamas and later the Solomon Islands, the divers shone blue lights on the ocean floor to stimulate intense biofluorescence in fishes. To see through the obliterating veil of blue light, they wore green visors over their masks and equipped their underwater camera lenses with special long-pass filters. (The researchers note that many fishes have long-pass filters in their eyes, which would allow them to see fluorescent displays.)

With the resulting images, analyses of some 12,000 specimens the team collected over four expeditions, as well as studies after hours at public aquariums, the research team discovered that biofluorescence is common throughout the tree of life for fishes. The researchers identified biofluorescence in 16 orders, 50 families, 105 genera and more than 180 species of fishes. These include the two main fish groups: cartilaginous (sharks and rays) and bony fishes (eels, lizardfishes, gobies, flatfishes).

Photo shows a green biofluorescent chain catshark (Scyliorhinus retifer). Scientists already knew that some marine organisms fluoresce, including corals and jellyfish, but the NSF-funded study, The Covert World of Biofluorescence is the first reported evidence of widespread biofluorescence among fishes.

Credit: J. Sparks, D. Gruber, and V. Pieribone  (Permission Granted)

Read more at Research.gov.

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