Luminous Life

More than four-fifths of Earth’s organisms known to make light live in the ocean. Their glowing existence has perks and pitfalls.

Photinus carolinus and Phausis reticulata. Photo: David Liittschwager

Fireflies flash and streak through a Tennessee summer night, putting on a spectacular light show to seduce prospective mates.

Neonothopanus gardneri. Photos: David Liittschwager

More than 90 species of fungi glow in the dark, including these Brazilian “coconut flower” mushrooms. The light may lure insects that spread mushroom spores.

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Watasenia scintillans. Photos: David Liittschwager

The luminescence of firefly squid makes them visible in an aquarium, but in the ocean it forms an invisibility cloak, so they blend in with the light from above.

Elateridae. Photo: David Liittschwager

In a long exposure, bioluminescence creates streaks of light from the backs of three Brazilian click beetles. They use light to attract mates and, perhaps, to scare off potential predators.

Photo: David Liittschwager

The bioluminescent bay on the Puerto Rican island of Vieques teems with microscopic life-forms called dinoflagellates, which light up whenever water nearby is disturbed. In the distance, light from a local stadium disturbs the horizon.

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Atolla Vanhoeffeni. Photos: Steven Haddock, Monterey Bay Aquarium Research Institute (lights off); David Liittschwager (lights on)

The crown jellyfish lives in the perpetual darkness of the deep sea. If another animal touches it, the bell lights up (lights off). Undisturbed, its bell is transparent (lights on).

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Photos (Clockwise from top left): Pyrosoma sp. (Steven Haddock with David Liittschwager); Scina sp. (Steven Haddock with David Liittschwager); Beroe Forskalii (Steven Haddock with David Liittschwager); Phengodes Laticollis (David Liittschwager). Lights on (all): David Liittschwager

Top left: A pyrosome is actually a colony of many animals. It lights up spectacularly when touched. Top right: Except for its red gut, the body of this shrimplike amphipod is transparent. The antenna tips give off a very blue light. Bottom right: Comb jellies, or ctenophores, have rows of cilia along their sides. When this species is touched, it makes cascading waves of light. Bottom left: At night, the lights from this railroad worm—actually a beetle larva—make it look like a tiny train.

Motyxia sequoiae. Photos: David Liittschwager

A millipede glows in the dark to let mice and other predators know what they’re messing with. Any animal ignoring the warning gets a mouthful of cyanide.

Photo: Ary Bassous

Towers of light, towers of doom. At night, larval click beetles living in termite mounds light up. Creatures drawn to the glow will find themselves devoured.