(Source: Wikimedia Commons)
Relative uses glowing protein to remove reactive compounds produced by desert heat; evolution repurposed it to ward off predateion
Some Americans tackled the dry heat of the Nevada desert with a cool glass of lemonade. If you're a millipede you're not so lucky, though, and you have to find different ways to beat the heat.
National Geographic has a cool video segment on Motyxia sequoiae, a millipede species that today inhabits the upper elevations of the Sierra Nevada mountain range. Studies have indicated that today these creepy crawly mountain dwellers use their bioluminescence to warn predators that their bodies are packed with a deadly toxin -- cyanide.
The glow is derived from a protein known as Luminodesmus. Today this eye-catching trait used as a tool to reduce predation. But new research suggests that the protein might have originally evolved to serve a far different biological need -- homeostasis.
Fluorescent members of the Motyxia millipede genus use their glow to warn predators that they're packed with cyanide. [Image Source: Fine Art America]
A new study published in the April edition of the prestigious peer-reviewed journal PNAS examines the ancestry of this glowing mountain millipede. Researchers use genetic, molecular, and physiological analysis to show that another millipede species -- Xystocheir bistipita -- is more closely related to M. sequoiae than previously thought. X. bistipita inhabits the lower elevations of the Sierra Nevadas and the Californian desert plains. The breakthrough was the discovery that X. bistipita produced a more weakly bioluminiscent version of the Luminodesmus protein.
While it does produce a small amount of glow, the primary purpose of the protein in the desert relative appears to be to deal with the reactive oxygen species (ROS) whose production is accelerated by the dry desert heat.
A map shows the range of different Motyxia species. [Wikimedia Commons]
Researchers suggest that M. sequoiae evolved from X. bistipita (or a close relative) and that over time the functionality of the Luminodesmus protein was coopted from a ward against heat-related chemical damage into a ward against predation. This makes sense as at higher altitudes ROS production would be less of a threat. In light of the documented biomolecular and genetic similarities researchers sugget the desert species be renamed Motyxia bistipita.
In honor of this intriguing new work, NatGeo posted video of these nifty arthropods doing their thing. M. sequiae measure 3 to 4 cm (1.2-1.6 in.) long and 4.5 to 8 mm (0.177 to 0.315 in.) wide when fully grown. Their body is composed of 20 segments.
Sources: PNAS [abstract], NatGeo on YouTube
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