Glow-in-the-Dark Millipede Says 'Stay Away'

Millipedes of the genus Motyxia spend the day burrowed under soil and leaves. They come out to forage at night, when they are sought after by predators. (Photo: Paul Marek)
Millipedes of the genus Motyxia spend the day burrowed under soil and leaves. They come out to forage at night, when they are sought after by predators. (Photo: Paul Marek)

As night falls in certain mountain regions in California, a strange breed of creepy crawlies emerges from the soil: millipedes that glow in the dark. The reason behind the glowing secret has stumped biologists until now.
 
Paul Marek, a research associate in the University of Arizona's department of entomology and Center for Insect Science, and his team now provide the first evidence gained from field experiments of bioluminescence being used as a warning signal. They discovered that the nightly glow of millipedes belonging to the genus Motyxia helps the multi-legged invertebrates avoid attacks by predators.

The findings were published in the Sept. 27 print edition of the journal Current Biology.

Biologists have discovered and described more than 12,000 species of millipedes, but the vast majority remains undiscovered and is thought to number around 100,000.

Just like all other millipedes, Motyxia are vegetarians, feeding mostly on decaying plant material, but in the course of adapting to a lifestyle primarily underground, they lost the ability to see.

"They spend the day burrowed beneath the soil and leaf material, but even though they are blind, they somehow sense when night falls and come to the surface to forage and mate and to go about their millipede business," said Marek, who conducted this work under the NIH Postdoctoral Excellence in Research and Training program in the labs of Wendy Moore, an assistant professor of entomology and curator of the UA Insect Collection and Dan Papaj, a professor of ecology and evolutionary biology at the UA.

"When they are disturbed, they ooze toxic cyanide and other foul-tasting chemicals from small pores running along the sides of their bodies as a defense mechanism," Marek explained. "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."
 
Known as bioluminescence, the ability to glow in the dark is remarkably widespread in the animal kingdom. The most commonly known examples include fireflies, glowworms – which are in fact beetles – and animals inhabiting the pitch-black darkness of the deep oceans.

Read the rest of this September 26 UANow article at the link below.

Date released: 
Oct 14 2011
Contact: 
Paul Marek