The Origins of Bioluminesence Sheds Light on These Elusive Millipedes (VIDEO)

Bioluminescence is something that has fascinated scientists for years. Animals glow brightly in the gloom, shining out to either warn away predators or attract mates. Now, scientists have discovered a bit more about the origins of bioluminescence.

"Living things glow in many different colors and for many different reasons, but now we know that the early evolutionary role of bioluminescence may be completely different than its modern day function," said Paul Marek, one of the researchers, in a news release. "This discovery clarifies the evolutionary origins of many complex traits, not just bioluminescence."

In this latest study, the scientists examined bioluminescence in millipedes. More specifically, they looked at the insect, Xystocheir bistipita. This millipede was first found in 1967 and hadn't been seen again until recently.

After sequencing this millipede's DNA, the researchers found that it was related to its luminous cousins that are the only bioluminescent millipedes in the western hemisphere. Unlike fireflies that glow because of an enzymatic reaction between luciferase and luciferin, the millipede glows due to the reaction of a photoprotein that requires magnesium.

The researchers mapped the brightness of light in M. bistipita and its close relatives that live at higher elevation and glow more brightly. He actually demonstrated a gradation of brightness from faint to bright. Then, he reconstructed the evolutionary tree. In the end, the researchers found that there's a functional link between luminescent intensity of displays and toxicity.

"Evolution of a complex feature such as bioluminescence is difficult to understand at first glance but totally makes sense when considered in an evolutionary context," said Marek. "We showed that bioluminescence, a trait typically used as a warning pattern evolved gradually and for a different purpose."

The findings reveal a bit more about the origins of bioluminescence and show the reasons why these millipedes may have developed the trait in the first place.

The findings are published in the journal Proceedings of the National Academy of Sciences.

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