National Geographic Society Newsroom

Love and War: The Essence of Luminosity

When I think of luminosity I think of the brightness of the sun or associate it with technology, light bulbs, light emitting diodes, and of course, the energy sources that make it possible. In many ways, creating light has promoted the “nightlife” or our ability to see, signal, and interact in darkness.  Just a trip...

When I think of luminosity I think of the brightness of the sun or associate it with technology, light bulbs, light emitting diodes, and of course, the energy sources that make it possible. In many ways, creating light has promoted the “nightlife” or our ability to see, signal, and interact in darkness.  Just a trip to Times Square in NYC can provide us with all the latest and greatest ways to project ideas and propaganda.  There’s no doubt that “artificial light” has profound functional, economic, and scientific applications, and even social meaning, but how do other creatures produce light and particularly why has it evolved in the ocean?  What are they signaling and what can we learn from the meaning of their essence?

 To be or not To be Luminous

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.

 Q: How does bioluminescence evolve in organisms?

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.

Q: Where in the Ocean can we find these creatures that glow?

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.

Q: Tell us about the technology that you are creating to capture images of bioluminescence.

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.

 Beyond the beauty of this dream-like scenario, there must also be some novel applications to understanding a bit more of this new research frontier.  According to Gruber and Sparks “Scientists are now using bioluminescent compounds from marine animals to help track and destroy cancer cells. Cancer cells are notorious for hiding out among healthy cells before they start replicating uncontrollably.  Yet, using luminescent compounds, these hidden cancer cells are easily detected and this can help scientists find cancer-fighting drugs that can effectively target them. In brain research, biofluorescent compounds from corals and jellyfishes are enabling the real-time visualization of neurons firing which is being used in medical research as well as in brain-machine interfacing technology”. In fact, the Nobel Prize in Chemistry in 2008 went to a team of scientists responsible for discovering and developing the green fluorescent protein, GFP.  This discovery has allowed the visualization of processes that were previously invisible, such as the development of nerve cells in the brain or how cancer cells spread.  There’s no doubt that the future applications that stem from this research are bound to have profound effects on humans.

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.

 About the Explorers

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.

About National Geographic Society

The National Geographic Society is a global nonprofit organization that uses the power of science, exploration, education and storytelling to illuminate and protect the wonder of our world. Since 1888, National Geographic has pushed the boundaries of exploration, investing in bold people and transformative ideas, providing more than 14,000 grants for work across all seven continents, reaching 3 million students each year through education offerings, and engaging audiences around the globe through signature experiences, stories and content. To learn more, visit or follow us on Instagram, Twitter and Facebook.

Meet the Author

Fabio Esteban Amador
Fabio Esteban Amador is an archaeologist, science communicator and visual artist. He uses visualization tools to get people excited about seeing, understanding and preserving their world and history. He is currently using gigapan technology, underwater imaging systems and aerial photography and video to capture art and culture around the world. Lately he has focused in the development of a new concept, strategy and workshop called the Art of Communicating Science, aimed at using creativity and visual technologies in exploration, discovery and story telling. He started his career as an art student at the School of Visual Arts in NYC and followed his interests in becoming an expedition artist by graduating as an archaeologist from the State University of New York at Buffalo. Lately, he has focused on the archaeology and exploration of caverns in Quintana Roo, Mexico, photo-mosaicking shipwrecks in Latin America and the Caribbean and capturing images and video from aerial platforms to document archaeological sites to create digital elevation models. Amador’s continued effort in communicating science has allowed him to use photography, cinematography and other multi-media tools to reach large audiences through his public lectures at universities, presentations at international scientific and professional symposia, publications in scholarly journals and on National Geographic’s Explorers Journal and NatGeo News Watch online blogs. Currently, he is a senior program officer for the National Geographic Society / Waitt Grants Program, promoting and coordinating scientific and exploratory research around the world. He is also an associate research professor at George Washington University and Executive Director and President of Fundacion OLAS, an organization devoted to capacity building for Latin American scholars dedicated to the study and preservation of the submerged cultural heritage.