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Recently I had the pleasure and privilege to visit a new exhibit at the American Museum of Natural History in New York City. The exhibit is called “Creatures of Light” and it features organisms that produce their own biofluorescence and bioluminescence. I was given a tour of the exhibit by David Gruber and John Sparks, both National Geographic Society / Waitt Foundation Grant recipients. David Gruber has been contributing with the development of the coral wall as part of an NSF Communicating Science to Public Audiences grant, and John Sparks is the curator of the exhibit. The subject is fascinating but there’s still many questions surrounding this ability to glow. I caught up with David Gruber and John Sparks at the New York exhibit for clarification on some questions regarding their fascinating research.
Q: What is the difference between bioluminescence and biofluorescence?
A: Bioluminescent animals produces their own light, but
biofluorescent animals absorb light and re-emit it as a different color.
Some animals are both bioluminescent and biofluorescent, such as the
palm-sized hydromedusae jellyfish Aequorea victoria. Along the
ring of this crystal jellyfish are glowing orbs, known as photocytes,
which produce blue bioluminescent light that no one sees. This is
because a green biofluorescent compound surrounds the photocyte,
immediately capturing the blue light and re-emiting it as an eerie green
flash. Corals (relatives of jellyfish) are almost exclusively
biofluorescent, and when illuminated with blue or violet light, kick it
back out as neon orange, green and red.
A: Love and war seem to be the most compelling reasons for many of the creatures that developed these glowing properties. Of course, there are other reasons such as a cell expelling light to burn off potentially dangerous excess energy, or an anglerfish luring its meal with an hypnotic glowing bait. But, we’re mostly familiar with luminescence used for predator deterrence and mating attraction. For example, the cookiecutter shark (Isistius brasiliensis), a small but vicious species that bites off cookie-sized plugs of flesh from its prey – tuna, dolphins, whales and other sharks. Its belly is covered tiny lights (photophores), except for a small region, that serves as a kind of optical illusion to make this shark appear much smaller to predators swimming underneath, when they attack what appears to be a tiny fish, they get a surprise – a bite taken out of them. Also, there is a polychaete worm called Odontosyllis phosphorea. Right after a full moon, the females ascend from the bottom and secrete a green luminescent slime along with their gametes. This signal attracts the males who, in turn, spill their gametes into the billowing green luminescent cloud. While ascending from a night dive in the Bahamas I once witnessed this Disco-like mating ritual. While creatures have evolved varied and sophisticated methods to take advantage of luminescence the primary components are two molecules, luciferin and luciferase, bioluminescence’s fuel and sparkplug. Some organisms make their own luciferin, many get it from their diet, and some even form partnerships (symbioses) with bioluminescent bacteria. Interestingly, the functions we observe today in many groups (e.g., fireflies, ponyfishes) are quite different from what these creatures originally used bioluminescence for.
A: Most people usually think of fireflies and jellyfishes when they hear the term bioluminescence, so the perception is that luminescence is a rare occurrence. However, it’s almost everywhere in the ocean as well as more common on land than most people think. Humans have evolved as daytime creatures –our ancestors waking at dawn and sleeping at night for millennia. Conversely, creatures that inhabit the permanently dark depths of the oceans find bioluminescence essential for their survival and communication. When diving at night, when you turn off the lights, its often an underwater lightshow, the ocean’s Las Vegas.
Back at the Creatures of Light Exhibit
I walked into a soothing dark space filled with music, a dreamy melody composed by Tom Phillips specially for the exhibit. I felt as if I was in a dream and was curious to touch, see, learn and explore the many interactive stations, cool displays, and dimly lit spaces glowing with bioluminescence. I had flashbacks of being a kid and running around the backyard among the many fireflies. I began to ponder how does one get interested in this world and what sort of knowledge and equipment are necessary to capture their essence. David Gruber and John Sparks kindly illuminated my curiosity.
A: One of the challenging aspects of capturing bioluminescence is that you cannot use any artificial lighting, and you need to rely solely on the light being produced by the animal. One forgets how incredibly sensitive the dark-adapted eye is and few cameras can achieve that level of sensitivity. But, low-light imaging technology has been revolutionized in the past few years and there are several wildly sensitive science-grade cameras. But, they are big and bulky, and not in color. Working with Prof. Vincent Pieribone, a neuroscientist at The John B. Pierce Lab at Yale University, we are working to transform these lab-based cameras into colorized underwater imaging systems. During our Waitt Expedition in June, we will finally put some of these cutting edge imaging technologies into use.
Q: What’s so cool about studying these creatures?
A: It sure beats a typical desk job. We are constantly looking for clues to explain what the glowing or fluorescent properties of each creature are used for or how these phenomena have evolved. Then there is the challenging process of finding, filming and collecting these creatures. This requires exploration that has taken us to unfamiliar places. We are in the ocean diving for at least two months of the year –and much of the diving is done at night, without the aid of lights. This can be unnerving, to say the least when we occasionally catch a glimpse of a large shark in our lights.
Creatures of Light is a unique exhibit for its focus on the different examples of bioluminescence; from fireflies to glowworms, jellyfish, anglerfish to fluorescent corals. It is also sophisticated in how it has combined ipads, music, low light, an information that can be fascinating for a five year old or a seasoned scholar. Personally, I found the entire experience very soothing, I guess because the lights were low, it seemed to be a very relaxing atmosphere and the faint glow that was visible, was organic, natural and alive. I wonder if perhaps the evolution and ability of these creatures to have developed such complex yet simple life ways are due to the tranquility of their dark world. Is light associated with stress, darkness with tranquility? I can think of examples where the opposite could be argued to be true. Perhaps we as humans should think about exploring the night and develop an ability of seeing in darkness. We may discover the inner glow of life.
Dr. David Gruber is a marine biologist who uses extended-range SCUBA and Remote Operated Vehicle technologies to explore the deeper portion of the world’s coral reefs. His research focuses on photosynthesis and biofluorescence and his research team has discovered over 30 novel fluorescent proteins, including the brightest one found to date. He is currently funded by the National Science Foundation to design and engineer a submersible specifically to study bioluminescence and biofluorescence of deep coral reefs. David is committed to communicating science to the general public. His writings have appeared in The New Yorker and The Best American Science Writing and he is the co-author of “Aglow in the Dark: The Revolutionary Science of Biofluorescence” (Harvard University Press, 2006), which he is currently co-producing into a 3-D IMAX film in conjunction with the National Film Board of Canada. David received his PhD in Biological Oceanography in 2007 from Rutgers Institute of Marine and Coastal Sciences. He is a Research Associate in Invertebrate Zoology at AMNH and Assistant Professor of Biology and Environmental Science at Baruch College, City University of New York
Dr. John Sparks is Curator-in-Charge in the Department of Ichthyology at the American Museum of Natural History. He travels the world in search of bioluminescent and biofluorescent organisms, primarily marine fishes. His research is focused on reconstructing the evolution of the bacteria-driven bioluminescent signaling system in ponyfishes—small, laterally compressed fishes that occur in the Indian Ocean and Western Pacific that have light organs surrounding their throats. He is also investigating the evolution of hearing in fishes, the origin and biogeography of Madagascar’s freshwater fishes, and the evolution of bioluminescence across marine fishes. Dr. Sparks’ recent fieldwork includes biotic surveys and inventories of both freshwater and nearshore marine fishes in Madagascar, the Indo-Pacific region, South America, the Caribbean, and the Western Atlantic. He is also a professor in the Richard Gilder Graduate School at the Museum and an adjunct professor in the Department of EEEB at Columbia University. Dr. Sparks received a M. Sc. in biology from the University of Michigan in 1997 and a Ph.D. in ecology and evolutionary biology from the University of Michigan in 2001. He joined the Museum in 2002.
