Millipedes of the genus Motyxia are nocturnal detritivores* who protect themselves from predators using cyanide, which they generate internally and discharge through pores. Most creatures that protect themselves in this way also produce a visible signal to predators that they taste foul, usually by being brightly coloured. But being nocturnal, such visible cues wouldn’t be much use to Motyxia. Instead these amazing creatures have come up with a different cue: they glow in the dark.
In an elegant study published in the journal Current Biology, Paul Marek and colleagues made clay models of the millipedes, some of which they painted with a chemiluminescent pigment to make them glow. These were randomly distributed in the millipedes natural habitat and left overnight. The next day they were collected and examined for any signs of attack. Nearly half (48.6%) of the ‘dark’ clay millipedes were attacked, in contrast to 22.4% of the glowing models. They did the same experiment with 164 living millipedes they had collected, half of which they painted to conceal their luminescence. Nearly one-fifth (17.9%) of the ‘dark’ millipedes were attacked compared to only 4.0% of the glowing individuals.
*An organism that feeds on and breaks down dead plant or animal matter, returning essential nutrients to the ecosystem.
Reference (open access, yay!): Marek et al (2011). Bioluminescent aposematism in millipedes. Current Biology, 21 (18):R680. DOI: 10.1016/j.cub.2011.08.012