Millipedes that glow in the dark

The following is a guest post from millipede expert Paul Marek.

The eerie glow of a Motyxia millipede (photo by P. Marek)

I study millipedes in the family Xystodesmidae (order Polydesmida).  These millipedes contain hydrogen cyanide as a defensive chemical and use aposematic coloration to warn predators of their toxicity.  Coloration patterns in these species include bright yellows, oranges, reds, and violet.

One nocturnal genus in this family, Motyxia, known only from California, does not display conspicuous coloration.  These millipedes do something even more remarkable—they produce a green bioluminescent glow at a dominant wavelength of 500 nm by way of a biological source of light in their exoskeleton.  Scientists have speculated that the emitted light could be a sexual signal to attract mates, or an aposematic warning glow to announce the presence of a cyanide-based chemical defense.

Motyxia sequoiae by daylight (photo by P. Marek)

So far as is known, millipedes in the order Polydesmida all are blind, suggesting that the predator-warning hypothesis might be more likely.  The source of light in Motyxia is a chemical called pterin, first discovered for its role in butterfly pigmentation but perhaps independently evolved in these unique millipedes to function like a luciferin molecule, similar to the well-known firefly luciferin (the structure of the analogous luciferase molecule for Motyxia is unknown).  Other than the genus Motyxia, there are no other confirmed accounts of bioluminescence among millipedes.

4 thoughts on “Millipedes that glow in the dark”

  1. Hi Aydin,
    Yes! The millipedes can turn their light on & off. The intensity also seems to vary with stimulation. If I find a dark one on the forest floor it will often times glow brighter just by picking it up.

  2. A few years ago when we were camping in central California near Mountain Home above Springville, I returned from a nighttime visit to the toilets to find an astonishing ghost army moving as if in mechanized formation.

    They glowed white (not green), were about 8 inches long and almost 1.5 inches across. Their legs churned along in curling wave patterns and they were at rigidly geometric intervals from each other, each at the apex of a diamond formation near 40 feet long and maybe 25 feet wide, a whole army, as I say, seeming to glide toward (I assumed) a nearby creek. Their unit speed was in consistent unison.

    I was able to see about 8 or 9 but was conscious (imagined? reasoned?) this was a large springtime movement of the population. Kinda scared me at first, but they were oblivious to us or our camp or fire.

    I’d never heard of such a thing, but then I’d never heard of thousands of spiders dropping from the trees until I camped at Yosemite one year.

    Spring is a literally wondrous time of year in the less civilized areas.

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