As spectators squealed with delight at fireworks a few nights ago, some no doubt compared the spectacular pyrotechnics to "nature's fireworks" -- the subtler displays of backyard fireflies.
Fireflies, or lightning bugs, are neither flies nor bugs. They are beetles capable of bioluminescence.
The light that fireflies produce, unlike incandescent light bulbs, is cold and produced biochemically with little energy lost as heat. Their bioluminescent organs are located on the abdomen. In the cells of the light organs, which are richly supplied with oxygen, is a chemical called luciferin. When luciferin combines with oxygen in the presence of the enzyme luciferase, the chemical reaction releases energy in the form of light. Reflector cells in the light organs magnify the intensity of the light.
Most local species seem to flash randomly, but each species flashes a distinct Morse code-like pattern. Males flash, females respond, and then they find each other to mate.
Though bioluminescent fireflies are well known, thousands of other species are capable of producing "living light." Many are restricted to the world's oceans. Some are even tourist attractions.
A few years ago my daughter and her husband vacationed in Puerto Rico and took an evening boat ride to see the illuminated waters. Sure enough in the wake of their paddles, the water glowed mysteriously.
In this case it was tiny micro-organisms, dinoflagellates, that created the light. Though the biochemical details vary, the process of light production parallels that of fireflies.
The ocean around the Antarctic is home to shrimp-like crustaceans called krill. They emit bursts of blue bioluminescence, perhaps as a means of communication. The krill eat plankton, and everything from jellyfish and to baleen whales eat krill, so bioluminescent organisms are an important part of the global food chain.
Some bioluminescent organisms outsource their light-producing duties to luminescent bacteria. The Hawaiian bobtail squid provides these bacteria with a place to live in exchange for a lantern. And many tropical fish also use luminous bacteria to create lanterns that can be used for protection, camouflage or communication.
Though the vast majority of bioluminescent organisms live in oceans, the ones we know best, the fireflies, can be seen in our own backyards.
Biologist, author, and broadcaster Scott Shalaway can be heard 8-10 a.m. Saturdays on 1370 WVLY-AM (Wheeling) and online at www.wvly.net. He can be reached at www.drshalaway.com, firstname.lastname@example.org and 2222 Fish Ridge Road, Cameron, W.Va., 26033.