LIGHTS ALIVE! Hey, it's dark! But who cares? Lots of living things can turn on their very own night-lights - bioluminescence

Ranger Rick, Jan, 1999

You've seen a glow-in-the-dark toy before, right? It seems to light up like magic. But a living thing that glows in the dark is even more amazing. Believe it or not, such creatures exist in dark places all around the world. Just look at all the fireflies twinkling against the night shadows on these two pages. They're making their own light and using it to send signals to each other in the dark.

WHAT, HOW, AND WHY? The trick of making living lights is called bioluminescence (BYE-oh-loo-muh-NESS-ens. Bio- means "life" and luminescence means "light.") The light is powered by special chemicals. Quite a few living things have light-producing chemicals in their bodies. Different ones work together in different ways to make different lights. Green- or yellow-colored lights are common in bioluminescent things living on land. Under the sea, blue lights are more common. There are also living lights that glow red, purple, or orange. Some lights are weak and some are bright. Some flash and some stay on all the time. What better way to get a message across in the dark than by sending light signals? That's one thing bioluminescence is really good for. The signals can act as a code to say something like, This is me. Who are you? or Hey, come over here!

GLOWERS AND FLASHERS An adult firefly can attract a mate in a very special way. How? By flashing its taillight (above left). Glowing spots on a click beetle look more like a set of headlights (below).

ALL ABOARD? It's easy to see how the railroad worm (1) got its name. All lit up, it looks like a train passing in the night. Sometimes it blinks its "window" lights to scare off a predator. The worm's red "headlight" helps it see. When it shakes its head (2), the worm looks very annoyed.

LAND FLASHERS One place to look for bio-luminescence is in the insect world. Maybe you've seen fireflies light up the sky on a summer night. Fireflies aren't flies at all--they're beetles. There are many different species (kinds) of fireflies, each with its own special flash pattern. For example, some fire off a series of quick flashes, while others flash slowly. Some flash while they fly in a straight line, while others have a zigzaggy flash flight. Each species plays its own "flashlight duet." The male flashes part of the pattern, and then the female answers with her part. That's how they recognize and find each other during their mating season. But a few use their lights to play a deadly trick. A female of one species may flash a pattern that calls over the male of another species. When the male comes in to mate, she gobbles him up! Even young fireflies glow. Have you ever seen a tiny spot of light on the ground on a summer night? That likely was a firefly larva, called a glowworm. Besides glowing insects, there are also bioluminescent worms, millipedes, centipedes, snails--and even mushrooms!

UNDERWATER LIGHT SHOW If you think there are lots of natural night-lights on land, just wait. There are many, many more living things that light up the seas. In certain places, even the water's surface sparkles. And that's not just moonglow. It's millions of tiny plants and animals--called plankton--all flashing at once. (continued on page 9)

"FIRE" WOOD? Animals aren't the only living things that light up. That eerie glow at right is a chunk of rotting wood. It shines because a glow-in-the-dark fungus is growing inside it. Some people call this glow "foxfire." Looks like a beetle turned up for the light show!

WOODLAND LAMPS The cluster of mushrooms below glows with enough light to ready by. Why would mushrooms shine? They might look more inviting to night creatures that eat them. The animals then may spread the mushrooms' seed-like spores.

BRIGHT EYES A flashlight fish (right) doesn't make its own light. Glowing bacteria live in pouches under its eyes. The fish uses the "flashlights" to find food at night. It also has built-in "shades" that it can slide up to cover the patches of light. "Blinking" may help the flashlight fish either attract prey or confuse predators.

ERRRRPPP--WHOOSHHHH! The shrimp below can play "keep away" even in the dark. The fish was all set for a shrimp treat, when suddenly its prey vomited and then beat a hasty retreat. The most amazing part is that the throw-up glows! That may confuse the predator--like when an octopus squirts a cloud of ink at an enemy.

(continued from page 6) Why does some plankton all of a sudden light up? Most of the time, it's to surprise or spook a predator. Many deep-sea creatures do the same thing. Imagine that you were in some dark place. A sudden flash of light would probably startle you too. But not all bioluminescent sea creatures light up to scare off an enemy. Different ones use their lights for different reasons--like finding mates or food.

You may not see bioluminescence very often. But it's a lot more common than you might think. And it adds holiday sparkle to a dark world all year long! =

Rangers: Want to see more cool night-light animals? You can find their photos and learn more about bioluminescence on the Internet. Go to www.hboi.edu/marine/biolum/maintemp.html. Or you might try out The Bioluminescence Coloring Book, complete with facts, fun, and glow-in-the-dark paints! To order a copy, have an adult call 1-800-444-2524. The money from the sale of this book goes to help scientists study ocean bioluminescence. Turn the page now to meet one of those scientists. --Ranger Rick