Illuminating BioluminescenceNaturally produced light-emitting chemicals offer undersea advantages to (clockwise from top left)
a pelagic worm, squid, krill, scaleless black dragonfish, and deepwater jellyfish.Though research on bioluminescence recently garnered a Nobel Prize, the phenomenon is still poorly understood, according to a new paper reviewing recent discoveries about bioluminescence's benefits, its evolution, and the surprising diversity of ways plants and animals generate glowing substances.(Also see "Glowing Animals: Pictures of Beasts Shining for Science.")Eighty percent of all creatures known to produce their own light live in the ocean, according to the report, published today in the journal Science.

"There are no hiding places in the open ocean, so a lot of animals have evolved this trick of hiding in the dark depths during the day and coming up to eat at the surface water under the cover of darkness," said Edith Widder, a marine biologist at the Ocean Research and Conservation Association in Fort Pierce, Florida."This means they spend most of their lives in near darkness," she said. "And bioluminescence is very useful in that kind of environment"—be it for finding food and mates, thwarting predators, or simply lighting the way.—Ker Than

Image courtesy Edith Widder, ORCA