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Invertebrate of the Week #20 – Motyxia millipedes (Motyxia sequoia)

Meet the conspicuous glowing millipedes of Sequoia National Park; the brightest of all the Motyxia species. They glow, they make hydrogen cyanide, they star as the main antagonist in the fourth level of an iPad game…what’s not to love?!

Motyxia millipedes are small creatures, reaching only about 4-5 cm in length and just 4-8 mm wide. These exclusively nocturnal millipedes spend their days nestled beneath the soil in live oak and giant sequoia forests. When the sun sets, a currently unknown environmental cue causes them the emerge from their burrows and cruise about in search of the decaying vegetation they feed on.

Nothing unusual there. But what is unusual is the fact that while other nocturnal creatures may be doing their best to remain hidden, Motyxia confidently stand-out. The millipedes emit a bright, steady glow; seemingly without a care in the world as to what may be watching them.

The millipedes are blind, so this illumination is ostensibly not a visual cue intended for conspecific communication. Rather, it is believed to serve as a warning sign (i.e. aposematism) to potential predators, similar to how animals like monarch butterflies use bright colors to communicate to predators like birds that they are toxic.

Why would predators want to avoid Motyxia? It turns out that these millipedes pack a poisonous punch. If you get close to one, you might notice an almond-like odor emitting from their body. That’s a clue to the type of toxin employed by these conspicuous little Polydesmidans. Guess what it is? Hydrogen cyanide.

Motyxia sequoiae bioluminescence. Image: National Geographic.

Though the amount of hydrogen cyanide produced by these millipedes isn’t enough to kill a human or (most likely) other potential mammalian predators, it’s almost certainly sufficient to create enough of a bad experience that an inquisitive animal like a mouse would avoid sampling the next one it encountered.

So next time you find yourself among the Sequoias, keep an eye out for these conspicuous little millipedes and the smell of almonds.

References and Further Reading

Davenport, D., Wootton, D. M., & Cushing, J. E. (1952). The biology of the Sierra luminous millipede, Luminodesmus sequoiae. The Biological Bulletin. 102 (2): 100–110.

Marek, Paul E.; Moore, Wendy (2015). “Discovery of a glowing millipede in California and the gradual evolution of bioluminescence in Diplopoda“. Proceedings of the National Academy of Sciences. 112 (20): 6419–6424.

Marek, P., Papaj, D., Yeager, J., Molina, S., & Moore, W. (2011). Bioluminescent aposematism in millipedes. Current Biology, 21(18), R680-R681.

The lab of Dr. Paul Merek, Department of Entomology at Virginia Tech.

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