Glowing organisms have captured our curiosity for centuries, yet scientists are still discovering how they glow—and why
LIKE THE FLICKERING FLAMES OF A CAMPFIRE, luminous life-forms captivate us. Greek philosopher Aristotle first described “fiery” fungi and fish in his treatise De Anima (On the Soul). More than two millennia later, scientists are still discovering new species and what makes them glow—revelations that are changing how we perceive the world.
Fluorescent organisms absorb light and emit it as a different wavelength and color. Bioluminescence is produced through a chemical reaction: a molecule (usually luciferin) is catalyzed by an enzyme so that it reacts with oxygen and releases photons.
Plants and animals that glow do so to lure prey, deter predators, find mates or otherwise communicate. While luminous life is rare on land—including some bacteria, algae, worms, beetles, snails, centipedes and millipedes—more than half of marine organisms, from plankton to sharks, make their own light. Most creatures below about 650 feet must, for as sunlight travels through water, red, orange, green and yellow wavelengths are filtered out until only blue remains. As deep-sea explorer and researcher Edith Widder says, the ocean hosts “the ultimate game of hide and seek.”
Fluorescence and bioluminescence produce energy but no heat. Researchers are tapping into this cold light’s power: They have used fluorescent jellyfish proteins to track neurological impulses and bioluminescent bacteria to test water quality. Yet as marine biologist David Gruber says, luminous life becomes “richer and more mysterious as we study it. If you only see the world from the human spectrum, you are going to lose a lot of the story.”
Indeed, every year tourists travel to view a “bio bay” on St. Croix, one of the world’s few bioluminescent bays that shimmer with plankton. The Virgin Islands Conservation Society (VICS), a National Wildlife Federation affiliate, is fighting to protect this bay from the light pollution and silt that could result from building a proposed educational facility on adjacent U.S. National Park Service land. As VICS’s Michael Baron says, “It would be such a shame to let this little jewel go.”
Chasing the flash of fireflies is a fond summer pastime, but University of Florida entomologist Marc Branham is receiving reports of fields and backyards now void of the beetles’ light. “Firefly numbers seem to be falling,” says Branham, perhaps due to light pollution that prevents fireflies from finding each other. If these scenes fade to black, the loss would be great. For fireflies, and so much more living light on our planet, Branham says, “we are still scratching the surface of understanding their behavior and evolution.”
Anne Bolen is managing editor.
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