Secret of Firefly's Light Show Is Illuminated

Betsy Mason
Dallas Morning News

July 16, 2001

Now you see 'em. Now you don't.

For centuries, firefly
enthusiasts have asked, "How do they do that?" Scientists may finally
have found the answer.

The chemistry that lights the firefly
lantern was known, but until now, nobody could figure out how the bugs
turn their lights on and off so quickly and precisely.

"It was a
nice mystery to solve," said Barry Trimmer, a neurobiologist from Tufts
University in Massachusetts, who led the team that made the discovery.

What the researchers found was an unexpected new role for a versatile molecule known as nitric oxide.

In humans, nitric oxide acts as a messenger involved in a variety of tasks—from aiding brain signaling to controlling blood flow and penile erection.

Nitric oxide may have a hand in firefly romance as well. As the fireflies entertain humans all summer long with a magical light show, they are actually cruising the sultry nights in search of love.

"Male fireflies fly around flashing their advertisement," said evolutionary ecologist Sara Lewis of Tufts, one of the authors of the study, which was reported last month in the journal Science.

Females on the ground respond with their own flash, beckoning the males to fly closer and flash again. This firefly foreplay can go on for an hour or more. The flash patterns are specific to individual species, ensuring that the right bugs get together.

"The ability to control the timing of the flash is key to their successful courtship," says Lewis. "Without that they'd be lost."

Internal Chemistry

Fireflies, which are actually beetles, light their lanterns using a chemical reaction that occurs in specialized cells in their abdomens. Many other species, such as jellyfish, use a similar chemical soup to create their glow.

The firefly is rare, however, in its ability to turn the glow on and off in a fraction of a second.

The specialized cells contain a mixture that lights up when hit with oxygen. In fireflies, oxygen is carried to the cells through tiny tubes. Where the air tubes enter the cells, densely packed bodies known as mitochondria "eat" the oxygen before it can light the lantern.

The researchers discovered that nitric oxide can momentarily stop the mitochondria's meal, thereby allowing the oxygen to enter the glow cell and turn on the light. Because nitric oxide is a very short-lived gas, the fireflies can use it to flash their lights quickly.

"Nitric oxide seems to be turning up in a lot of different places, and this is one of the most unusual places. It's a really novel finding," said Lewis.

Helen Ghiradella, a firefly expert at the University of Albany in New York, agrees. "In terms of understanding what a cell can do, it's amazing. It's big news in a lot of senses," she said.

Broader Implications?

The finding may shed light outside the flashy world of the firefly. "It could have important consequences for looking at nitric oxide signaling in humans," said Trimmer.

"This is a very exciting new way of thinking about how cells talk to each other," said Carl Nathan, an expert on nitric oxide at Cornell University in Ithaca, New York. "It very likely does serve a purpose in humans—we just don't know what the purpose is."

Trimmer attributes the success of the study to a unique collaboration of scientists from diverse disciplines.

Other authors were Thomas Michel, a cardiologist from Brigham and Women's Hospital in Boston, and June Aprille, a cell biologist from Tufts.

Copyright 2001 The Dallas Morning News.