Beetles whose flashes punctuate summer skies; killer fish that lure prey with an enticing light; algae that rat out their attackers with a telltale glow. These ominous organisms might seem like creatures from out of this world, but thanks to some clever chemistry, such beings are in fact abundant on our planet. Examples of creatures that generate their own light—a capability known as bioluminescence—are especially common in the ocean, where filmmaker James Cameron purportedly drew inspiration for the glimmering alien life in his new sci-fi flick Avatar.
Although it takes many guises in nature, bioluminescence serves the three basic purposes of "finding food, finding mates and defending against predators," says Edie Widder, co-founder, president and senior scientist at the Florida-based Ocean Research and Conservation Association (ORCA). Even in dim or dark environments where the sun's rays cannot penetrate, such as caves or much of the oceans, many animals still have eyes—oftentimes extra-large ones—in order to glean information from the few stray photons available. Some 80 to 90 percent of deepwater, oceanic life has developed the ability to produce light, taking advantage of the transparent, though predominantly dark, medium in which it lives.