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Picturing Science: Capturing Coral’s Glow

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These staghorn corals contain fluorescent molecules, which absorb light and then emit it at a different wavelength.
© AMNH/D. Gruber

Stony corals are living animals that are only two cell layers thick, but over time, their calcium carbonate skeletons can form massive limestone islands. Some contain fluorescent molecules, proteins in their tissue that absorb light from an external source and emit light back at different wavelengths. Marine biologist David Gruber uses a painstaking method of underwater photography to get striking images of fluorescent corals, including images of moon coral and staghorn coral currently on display in the exhibition Picturing Science: Museum Scientists and Imaging Technologies.

“You shine a specific wavelength of light to stimulate the protein—usually blue or green—and the corals emit back in otherworldly greens and reds,” explains Gruber, a research associate in the Museum’s Division of Invertebrate Zoology, “You have to photograph underwater in the dark at night with specially-filtered strobes because you’re only interested in the light emitted by the corals and other reef-dwelling organisms.”

Gruber photographed these corals in the northern Red Sea in Eilat, Israel, in May 2010, as part of his research into the patterns and functions of fluorescent proteins. Fluorescent proteins have been found to be useful tools in studying AIDS, Altzheimer’s, cancer, and other diseases, as well as in basic biological research.

Tagging subject proteins with fluorescent proteins allows researchers to track cell processes as never before. In 2007, for example, a team at Harvard injected red, green, and blue fluorescent proteins into a mouse brain to differentiate neurons, resulting in an explosion of color they dubbed a “Brainbow.” The significance of this technique was underscored by the 2008 award of the Nobel Prize in Chemistry to three scientists for their work on the green fluorescent protein, known as GFP, which is found in the Aequeoria victoria jellyfish—one of the fascinating organisms featured in the Museum’s upcoming exhibition Creatures of Light: Nature’s Bioluminescencewhich opens on Saturday, March 31.

Gruber, who helped photograph a panorama of a coral wall for Creatures of Light, traveled to the Caribbean in December to confirm a suspicion that there are even more fluorescent organisms in the sea than previously thought. Fish have traditionally been held to be only bioluminescent, that is, generators of their own light from within, but Gruber and a Museum team that included Curator John Sparks last year observed what looked to be an eel emitting fluorescence. The results of this recent trip were more than promising. Says Gruber, “We found lots of fluorescent fish!”

Picturing Science: Museum Scientists and Imaging Technologies is on view in the Akeley Gallery.