Glow-in-the-Dark Millipede Explained

To outwit predators, insects have evolved all sorts of defenses, from spraying noxious fluid to playing dead. A California millipede, as it turns out, just glows.

The multilegged invertebrate of the genus Motyxia is not only the only millipede known to glow in the dark, it’s also the first to use bioluminescence as a defense strategy, according to a new study. The blind critter generally spends its days burrowed under organic matter, coming out at night to forage and mate and otherwise “go about their millipede business,” study leader Paul Marek said in a statement.

“Some millipede species that are active during the day display bright warning colors to announce their defenses to predators, but because Motyxia are out when it’s dark, we hypothesized they use their greenish glow in place of a warning coloration,” said Marek, of the University of Arizona.

To test the hypothesis, Marek and colleagues set up an experiment in the field with non-glowing and glowing “millipedes”—actually bronze casts that played the part of millipedes for the purposes of the research.

The results, published September 27 in Current Biology, revealed that “four times as many non-glowing millipedes showed evidence of attacks compared to their glowing peers. Similarly, in the clay group, non-luminescent models were attacked twice as often than those that emitted the glow,” according to the press statement. (Get the full details about Marek’s experiments here.)

The glowing millipede. Photograph courtesy Paul Marek.

Bioluminescence—or light produced naturally via a chemical reaction in an animal—is widespread in nature. But it’s most common in the sea, where glowing marine life-forms are the main source of light in the dark depths, according to the University of California, Santa Barbara. On land, bioluminescence is most often found in insects—like the well-known firefly—or fungi, like this glowing mushroom found a few years ago in Brazil.

But, thanks to modern science, more creatures are starting to emit their own special glow—from cats to pigs to monkeys. For instance, scientists at the Yerkes National Primate Research Center in Atlanta are using green fluorescent protein in rhesus macaques (see picture) to study Huntington’s disease, which destroys nervous system tissue, Chris Combs reported in 2009 in a National Geographic News photo gallery of glowing animals.

“In 2008 the researchers infected unfertilized monkey eggs with an HIV-like virus, which changed the eggs’ DNA to include the defect that causes Huntington’s. The virus also introduced a protein that would make rhesus monkeys fluoresce under ultraviolet light—making it easier to study the effects of the disease on the monkeys’ brains,” he wrote.

And the glow isn’t always green—in 2007 scientists made a cat fluoresce red (see below), a development that may improve the study of genetic diseases.l OnIicinriginates in an organism.

A fluorescent cat glows red in ultraviolet light, while a non-fluorescent cat appears green.

Photograph by Choi Byung-kil/Yonhap via AP, originally published in a gallery of glowing animals.

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Meet the Author
Christine Dell'Amore, environment writer/editor for National Geographic News, has reported from six continents, including Antarctica. She has also written for Smithsonian magazine and the Washington Post. Christine holds a masters degree in journalism with a specialty in environmental reporting from the University of Colorado at Boulder. Her book, South Pole, was published in 2012.