(Press-News.org) In the mountains of Virginia, millipedes have bright yellow and black colors to warn enemies that they are toxic and not worth eating. Their cousins in California convey this warning in a very different way -- by glowing in the dark.
But bioluminescence at least in one millipede may have evolved as a way to survive in a hot, dry environment, not as a means to ward off predators, according to scientists publishing this week (Monday, May 4) in the Proceedings of the National Academy of Sciences.
The discovery, based on a millipede that hadn't been seen in 50 years, shows that even the seemingly most complex and intricate of traits are actually small evolutionary steps leading to an intricate feature we see today.
"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, an assistant professor of entomology in the College of Agriculture and Life Sciences. "This discovery clarifies the evolutionary origins of many complex traits, not just bioluminescence."
Marek began studying bioluminescence in millipedes seven years ago and the feature always seemed difficult to understand and trace in terms of its early origins.
"Because we're looking at a trait that has been shaped by millions of years of evolution, these traits often bear little resemblance to their ancestral form," Marek said.
But Marek rediscovered a significant piece of the luminosity puzzle while revisiting a Californian millipede that had been literally shelved for half a century.
The bug, Xystocheir bistipita, had been collected in 1967 and was not seen again until Marek rediscovered it during fieldwork in the foothills of San Luis Obispo, California.
Diminutive in size compared to other millipedes, the species lives at a lower elevation with few predators and was not thought to belong to the genus of millipedes that glow called Motyxia -- the only genus of bioluminescent millipedes in the Western Hemisphere.
After sequencing the bug's DNA, he found that it was in fact related to its luminous cousins, and changed its name to Motyxia bistipita.
Unlike fireflies that glow because of an enzymatic reaction between a luciferase and a luciferin, M. bistipita owes its soft green-blue glow to the reaction of a photoprotein that requires magnesium.
This process may have initially evolved for its antioxidant properties to cope with the oxidative stress of living in a low-lying, dry environment.
Bioluminescence was then repackaged as a nocturnal warning signal in millipedes that live at a higher elevation and contend with many more predators.
"After we sequenced them we were able to place the millipede on an evolutionary tree with other bioluminescent species in Motyxia," Marek said. "We demonstrated the faint bioluminescence of the low-lying millipedes represented an older trait and the brighter luminescence of their mountain cousins represented a newer trait."
Marek mapped the brightness of light in M. bistipita, and its close relatives that live at higher elevation and glow more brightly, and demonstrated a gradation of brightness from faint to bright.
To reconstruct the evolutionary tree, Marek and his team included every species in the genus Motyxia and all its closest nonglowing relatives and tested the relationship between them and M. bistipita.
Marek and his team measured light emission photographically in a darkroom by placing individual millipedes in a light tube. The researchers also measured toxicity of the bugs by measuring the volume of cyanide glands that line the sides of the millipedes.
Bugs with larger cyanide glands were also brighter, indicating 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," Marek said. "We showed that bioluminescence, a trait typically used as a warning pattern evolved gradually and for a different purpose."
INFORMATION:
Marek's research is funded by the National Science Foundation and the National Geographic Society.
DOWNERS GROVE, Ill. - May 4, 2015 - The May issue of GIE: Gastrointestinal Endoscopy, the monthly peer-reviewed scientific journal of the American Society for Gastrointestinal Endoscopy (ASGE), features a meta-analysis pointing to botulinum toxin A as a possible obesity treatment; a study reporting that, in some cases, it may be safe to store endoscopes longer than five days after reprocessing; and an article reviewing a promising group of procedures for patients with advanced illness from gastric obstruction.
"Effect of intragastric injection of botulinum toxin A for ...
Scooting around in the shallow, coastal waters of Puget Sound is one of the world's best suction cups.
It's called the Northern clingfish, and its small, finger-sized body uses suction forces to hold up to 150 times its own body weight. These fish actually hold on better to rough surfaces than to smooth ones, putting to shame industrial suction devices that give way with the slightest uneven surface.
Researchers at the University of Washington's Friday Harbor Laboratories on San Juan Island are studying this quirky little fish to understand how it can summon such massive ...
A recent study reported in The Journal of Nuclear Medicine compared use of the novel Ga-68-PSMA-ligand PET/CT with other imaging methods and found that it had substantially higher detection rates of prostate-specific membrane antigen (PSMA) in patients with biochemical recurrence after radical prostatectomy. Discovering a recurrence early can strongly influence further clinical management, so it is especially noteworthy that this hybrid PSMA-ligand identified a large number of positive findings in the clinically important range of low PSA-values ( END ...
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Download study, FAQ and photos: https://cornell.box.com/coral-disease
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"These large nerves actually stretch and recoil like bungee cords," says A. Wayne Vogl of the University of British Columbia. "This is unlike other nerves in vertebrates, where the nerve is of a more fixed length that has enough slack in it to accommodate changes ...
University of British Columbia (UBC) researchers have discovered a unique nerve structure in the mouth and tongue of rorqual whales that can double in length and then recoil like a bungee cord.
The stretchy nerves explain how the massive whales are able to balloon an immense pocket between their body wall and overlying blubber to capture prey during feeding dives.
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"The ...
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The tool is an algorithm called CONSERTING, short for Copy Number Segmentation by Regression Tree in Next Generation Sequencing.
St. Jude researchers created CONSERTING to improve identification of copy number alterations (CNAs) in the ...
