Glow-Worms Get a Leg Up

SCIENCE

Teachers, scroll down for a quick list of key resources in our Teachers’ Toolkit—and don’t forget to take this week’s Nat Geo News Quiz!

Discussion Ideas

The cool Nat Geo Kids article says millipedes (and every other bioluminescent organism) owe their glow to “special substances called proteins.” According to the “Chemistry” section of our encyclopedic entry, there are actually two types of special substances responsible for millipede bioluminescence. What are they?
- Luciferin, a generic term for the chemical that actually produces light. The teal glow of Motyxia millipedes is due to the specific arrangement of luciferin molecules.
- Photoprotein. Bioluminescent organisms use either luciferase or a photoprotein, and millipedes have a unique photoprotein. According to our encyclopedic entry, “Photoproteins combine with luciferins and oxygen, but need another agent, often an ion of the element calcium, to produce light.” The photoprotein in millipedes is unusual—it actually needs an ion of the element magnesium to produce light.

According to our encyclopedic entry, bioluminescence is usually a defensive adaptation, an offensive adaptation, or an adaptation for attraction. What type of adaptation have the California millipedes developed?
- It’s a defensive adaptation. Millipedes light up to warn predators they are toxic. (Special glands produce cyanide—the brighter the glow, the more cyanide produced.)

According to Nat Geo Kids, millipedes’ bioluminescence “may have first developed not to fend off enemies, but to help them deal with California’s hot, dry environment.” Read through our encyclopedic entry on adaptations. What is the name of this unusual type of adaptation?
- An exaptation is an adaptation that was developed for one purpose, but used for another.

How did bioluminescence help millipedes adapt to the hot, arid climate of the Sierra Nevada foothills?
- According to Nat Geo News, “millipedes have trouble metabolizing oxygen when it’s really hot, which creates chemical byproducts such as peroxide. The bioluminescent proteins help neutralize these byproducts and prevent harm to the millipede.”

Extra Credit: Researchers found that “bioluminescence—the ability to give off light—may have first developed not to fend off enemies, but to help [millipedes] deal with California’s hot, dry environment,” and “the warmer the environment, the dimmer the millipedes glow.” Of the two species of millipede above, which species do you think lives in a warmer environment? Which species do you think is an newer branch of the millipede family tree? Which species do you think is more toxic?
- Warmer climate: M. bistipita, on the right, lives in warmer climates. The chemicals in bioluminescent proteins help it cope with the heat.
- Younger species: M. sequoiae, on the left, is a newer branch on the millipede family tree. It evolved after M. bistipita, using already-developed bioluminescence to help fend off predators.
- More toxic: M. sequoiae, which has more predators than M. bistipita, also contains more cyanide.