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Millipedes center of program
Above is a slide of a Motyxia millipede, one of the few millipedes on Earth that has the ability to glow in the dark. Dr. Paul Marek discussed on Thursday a unique experiment he performed to help determine why these millipedes glow. (Bulletin photo by Ben R. Williams)
Tuesday, January 14, 2014
By BEN R. WILLIAMS - Bulletin Staff Writer
Dr. Paul Marek’s inventive millipede research has shed some light on an unusual species.
Marek, a professor in the entomology (insect) department at Virginia Tech, spoke Thursday at the Virginia Museum of Natural History (VMNH) as part of the museum’s “2nd Thursday Science Talks” series.
Among other topics, Marek discussed a 2011 experiment he conducted in California with the assistance of two undergraduate researchers to determine why a species of bioluminescent (glow-in-the-dark) millipede glows.
The glowing millipedes belong to the genus Motyxia, Marek said, and all eight species within the genus can be found only in three counties in California, in the foothills of the Sierra Nevada mountains.
Unlike fireflies, Marek said, Motyxia millipedes don’t “flash” their lights; their entire bodies glow constantly, although the glow briefly intensifies if they are handled or disturbed.
Motyxia millipedes resemble a number of millipede species that can be found in the Appalachians, Marek said, and like these species, they can produce poisonous cyanide to deter predators, although not enough to kill a person.
With the exception of one East Asian species, Motyxia millipedes are the only bioluminescent millipedes, Marek said.
“Bioluminescence is a very unique feature,” he said. “We want to know why. What’s the reason for this emission of light?”
There were three main theories why the millipedes might glow, Marek said: to attract mates, to attract prey and to warn predators.
Attracting mates was crossed quickly off the list, Marek said, because Motyxia millipedes are blind.
“Because they’re blind, we can effectively cross off mate recognition,” he said. “Fireflies use their bioluminescence to find mates; these millipedes are blind, so they can’t see one another.”
Attracting prey also could be crossed off the list, he said, because like Appalachian millipedes, Motyxia millipedes feed on decaying leaves.
“These millipedes are closely related to the millipedes in Appalachia,” Marek said. “They produce cyanide. Like the millipedes in Appalachia, they have bright coloration. It’s a really good possibility that this bright bioluminescence evolved to warn predators of their toxicity, like the Appalachian millipedes.”
To test the theory, Marek and his team created a unique field experiment.
Marek’s wife, Charity, who is a metalsmith, created a bronze cast of a Motyxia millipede, which was used to create a mold to make clay decoy millipedes. The group made 300 millipedes, half of which were coated with glow-in-the-dark paint.
They also collected 164 live Motyxia millipedes, half of which were painted to conceal their natural luminescence.
Around dusk, the 300 clay millipedes and 164 live millipedes were set out at random intervals in a field inside the range of the Motyxia millipedes.
“For the live millipedes, we had to tether them to the ground… so the millipede wouldn’t walk out of the experiment,” Marek said. “We set the experiment up at dusk, let it run overnight, and collected them back up at the dawn.”
The hypothesis, Marek said, was that more of the non-glowing millipedes (and clay millipedes) would be eaten by predators than glowing ones.
Even so, the results were surprising, Marek said.
“What we found in the morning was really quite amazing,” he said. “There was a lot of carnage. More than double the number of non-luminescent millipedes were preyed upon relative to the luminescent ones.”
“By using the clay millipedes in addition to the live millipedes,” he added, “we found that light, in and of itself, is effective at deterring predators.”
During the presentation, Marek also discussed millipede mimicry, millipede taxonomy (the science of classification) and Illacme plenipes, a California millipede that, with up to 750 legs, has the distinction of being “the world’s leggiest animal.”
Illacme plenipes had not been seen since government scientists discovered it in 1921, Marek said, until he and his brother rediscovered it in 2006.
During the lecture, Marek frequently cited and spoke highly of the work of the late Dr. Richard Hoffman, the late curator emeritus of recent invertebrates at VMNH, who studied millipedes extensively. Hoffman died in 2012.