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.
In the next room, Suzanne Torres explores the dualities of the modern world in 
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