4:40 pm Apr. 9, 2012
Our fascination with creatures who can produce their own light goes back a long way.
Aristotle called it “cold light,” Shakespeare “pale fire,” sailors recounted “burning seas,” and ancient armies mistook firefly flickers for enemy encampments. The glow hinted at the supernatural, intimating the presence of gods, ghosts, demons, or fairies that haunted the woods or lurked amid the waves.
Now, of course, we understand the science behind the glimmer (more on that below), but the goal of Creatures of Light: Nature’s Bioluminescence, a new exhibition on view now at the American Museum of Natural History and curated by the serendipitously named Ichthyologist John Sparks, is to return to us a sense of wonder at this strange phenomenon.
“We focused on making the show as immersive as possible,” said Sparks. A challenging goal, considering that bioluminescence typically occurs during the darkest times and in the darkest places on earth. Setting up the exhibit, he explained, “we kept having to make it darker and darker” so that conditions in the museum closely mimic the true conditions for bioluminescence in the wild.
“The reason for putting the show together now is that there is so much new research we could focus on,” Sparks explained, adding that the exhibit includes up-to-date observations from his work and that of his collaborators.
Bioluminescence is the result of the reaction between the luciferin molecule and the enzyme luciferease, both compounds that are present in thousands of organisms spread across the tree of life, particularly in the branches containing microorganisms, insects, fungi, and fish. Biologists believe that the phenomenon evolved separately at least fifty times in all those species. The antioxidant properties of luciferin point to one possible evolutionary reason for this trait: as organisms adapted to shallower water, they needed additional protection from damaging ultraviolet rays. But it turns out to have a number of functions, including attracting mates, attracting prey, and evading predators. Yet while we may understand how the light happens, and while recent technological advances have brought scientists a greater understanding of the deep-sea manifestations of bioluminescence, we still know relatively little about a great number of glowing organisms, especially those that live in the deepest seas.
Because of the difficulty of including live creatures in the exhibition, there are only three living specimens in the entire show; as an alternative, the organizers use informative panels, interactive screens, replicas, and simulations to evoke the real thing. From the cartoonishly towering fluorescent jack o’ lantern mushroom that greets visitors at the doors of the exhibit to the larger-than-life-size models of iridescent jellyfish, monstrous angler fish, and other flashily equipped beasts of the deep, the show riffs on nature, exaggerating it for the museum setting, while maintaining a strict verisimilitude when it comes to the nature of the light itself: scientists worked closely with engineers in creating the models and installations, using a spectrophotometer to make sure color and intensity were as accurate as possible.
The show begins on land, first with mushrooms and then on to fireflies, the insects found in the woods and meadows of North America that are possibly the most familiar bearers of bioluminescence. In the dark hall they are represented as convex blinking nubs mounted atop black poles, perfect for impulsive hand-cupping. Hovering above is a terrifyingly large model of the creature, its segmented undercarriage ending in a golden, throbbing rump. Gently lit panels and iPad screens offer diagrams and pithy factoids: the insect is actually part of the Lampyridae family—a member of the beetle order—and some species glow even when they are pupating! Although scientists don’t know why fireflies originally acquired bioluminescence, they know that different species emit light at different wavelengths, and some male fireflies glow brighter than their female counterparts. Others have evolved a flashing pattern, likened in the exhibit to Morse code, to communicate with the opposite sex.
One of the strengths of the exhibition is the way it incorporates oddities and one-offs, like the glow worm, the larval form of a fly-like insect called Arachnocampa luminosa. Unique to New Zealand’s Waitomo caves, these creatures expel a viscous waste fluid that then drips from the rock ceiling. Their rears light the fluid, creating knobby filaments of blue light, which attract and trap prey. Visitors can pop their heads into a cave-like cubby and find themselves surrounded by glowing strings that approximate the glow worm’s gorgeous excrement.
The utility of light is not always so clear-cut. Like plants, the ocean-dwelling monocellular eukaryotes known as dinoflagellates contain chlorophyll, allowing them to photosynthesize the sun’s rays into energy, which they then emit as light when agitated by the movement of the sea. Giving off the largest share of Earth’s bioluminescence, these tiny blinking organisms are present in all of the world’s oceans, and provide necessary nutrients to the rest of the food chain. On their own, their bioluminescence is perhaps a survival technique that startles predators or attracts the attention of their predators’ predators (fairly strategic for a single cell), but these plankton are also found in fixed locations like coral walls. In one dark corner of the exhibition, visitors can see actual dinoflagellates. When I visited, their frantic flashing was slowed to a tired throb, which came as disappointment after reading that travelers to the Bahamas in the 1900’s were said to be able to read at night by the radiance of the sparkling waves.
William Beebe, the first man to visit the deep sea, resorted to simile when he wrote about the glinting display of dinoflagellates swirling before the window of his submersible, describing a view of “naked space itself . . . the shining planets, comets, suns, and stars.”
One of the exhibition’s simulations allows visitors to experience Beebe’s universe for themselves. Motion sensors cause points of light to gather and intensify as each visitor passes through the area, mimicking the way the organisms react to movement in the water. As I passed through, I watched as children sat down and pretended to swim in the pointillist pools, then held out their hands to see the bright dots playing over their open palms. For a long while I watched, mesmerized while the speckles surged and swooped over the surfaces of the room.
“When you see dinoflagellates on film, you see it as a glow,” explained Sparks, “but when you’re down there, there are individual light specks. We wanted to evoke that.”
An even more complex technological presentation in the show is the giant LCD mural that depicts, in high definition and under a variety of lighting conditions (toggled by interactive screens), the rich diversity of bioluminescence found on a single coral wall at Bloody Bay, Jamaica. Photographed by Sparks and a colleague, the images give some idea of how many different manifestations of bioluminescence light the ocean.
Many corals and undersea organisms such as jellyfish also produce fluorescence, the result of a color-shifting molecule distinct from the bioluminescence produced by luciferin, and have developed an array of complex symbiotic neurological relationships with light-producing bacteria. Thick-skinned Angler fish use both a bacterial lure and a fluorescent, net-like beard to entangle prey; the Stoplight Loosejaw emits red light, undetectable by shrimp, to illuminate and catch its meals in the dark of the deep, though the crustaceans may expel a blue screen to enable an escape; sea cucumbers wipe a layer of their shimmering skin on attackers, an altruistic feature that warns off future victims. Flashlight fish, the most adorable (though basically invisible, because of the pitch black of their aquarium) live specimens included in the show, have a transfixing ability to blink the patches of iridescence of bioluminescent bacteria below their eyes on and off as if they were batting their eyelashes.
Sadly, the exhibition’s section on the deepest sea is its least engaging. The larger-than-life models offer unprecedented close-ups of the fantastic beasts of the deep, but even a short film of the ocean floor with illustrative animations doesn’t come close to harnessing the awesome strangeness of the world at the bottom of the sea.
“We still don’t know that much about a lot of these species,” admitted Sparks. Thus the dependence on the museum-standard presentation of the deep ocean, which feels static and stuffy compared to the engrossing interactivity of the earlier sections. It is hard not to feel regret for this last shortcoming, especially since recent years have seen exciting advances in deep water exploration, including director James Cameron’s recent record-breaking plunge to the bottom of the ocean floor. Like Cameron’s dive, which turned up little new scientific information, this final section is both intriguing (because of what it hints at) and yet somehow still disappointing (because of what it misses).
The true purpose of the show, after all, is to connect us with our fellow organisms by making us marvel at the infinite variety of life on earth. It is a noble and necessary task, especially because only a small percentage of humans will ever get to experience the glorious rainbow of deep-sea bioluminescence first hand; the rest of us must console ourselves with the lesser glow of simile and simulation.
Creatures of Light: Nature’s Bioluminescence is on view at the American Museum of Natural History through January 6, 2013