Secret of Firefly’s Light Show Is Illuminated
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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,
Firefly on Leaves
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.
A firefly's light comes from a
chemical reaction that takes place
in special cells in their abdomen,
called photocytes. The photocytes
contain two chemicals that are
essential to making light, luciferin
and luciferase (named after
Lucifer, the fallen angel of light).
Photograph by Frank Lane Picture
Agency/CORBIS
What the researchers found was an unexpected new role for a versatile
molecule known as nitric oxide.
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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
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"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
Oceans
reaction that occurs in specialized cells in their abdomens. Many other species,
Volvo Ocean Race
such as jellyfish, use a similar chemical soup to create their glow.
Mount Everest
Expedition
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.
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