Many of the world’s scorpions glow a brilliant aqua colour at night under UV torchlight and scientists are trying to find out why.
Here’s a fun holiday activity. Next time you are out in a parched, sandy environment, take along an ultraviolet light. Then, after nightfall, go out into the desert and flash your light around.
You might be surprised to find yourself surrounded by brightly shining blue-green objects scuttling across the sands. That’s because those objects are scorpions.
Yes, that’s right. Scorpions glow in dark conditions under two specific types of light – ultraviolet light and natural moonlight. So even if you don’t have a UV torch but the moon is out, you’ll still be able to see these blue-green arachnids (related to spiders). And be better able to keep out of their way.
It seems the scorpions that glow the brightest are the same scorpions that produce the deadliest effects with their venom.
However, that might not be the reason that they glow. Scientists aren’t exactly sure how this fluorescence benefits scorpions, but some have speculated that it acts as a UV screen to protect them from sunlight, or that it helps them find mates in the dark.
Some have suggested that it is accidental and that the two chemical that creates the glow – which emanates from beneath the scorpion’s exoskeleton – may be the unintended by-products of other chemical reactions going on within their bodies.
Others proposed that scorpions could glow to lure their prey, although several scientists have since shown that insects avoid fluorescent scorpions.
Douglas Gaffin, a scientist from Oklahoma University in the US, has developed an intriguing theory: that scorpion’s glow to convert the dim UV light from the moon and the stars into the colour that their brains are best-tuned to seeing – blue-green.
This could explain why scorpion eyes are so intensely sensitive, to the point where they can detect the faint glow of starlight against the background of the night sky. They amplify those dim signals by turning their entire bodies into light collectors.
And why would they do this? Because, like most other animals, they also have predators. They are vulnerable to owls, large rats, bats, and tarantula spiders. As such, they prefer to live undercover, and instinctively they flee from light to find shelter.
Douglas Gaffin believes that scorpions could easily find such hiding spots by sensing light with their entire bodies. Any object that casts shade on the surface of its exoskeleton potentially reduces the brightness of its glow and reveals a potential hiding place.
Douglas thinks that the scorpion’s body collects UV light from the environment and converts it into blue-green wavelengths, the same wavelengths that scorpions see best.
He even theorises that these signals might travel to the brain via nerve clusters that are spread throughout the body. What this might mean is that a scorpion’s glow could increase the surface area of its eyes by a thousand times.
In other words, the entire body of the scorpion – from the stinging tail to the powerful pincers – effectively functions as one big florescent eye.