Why Do Scorpions Glow Under Ultraviolet Light
If you ever felt the urge to shine an ultraviolet light on a scorpion, you probably noticed that it glowed. But why We have the answer.
glowing-scorpion Move over, glow worms. The scorpions are here to light up the night.
Picture a scorpion and you most likely imagine the notoriously poisonous creature scurrying around with its tail held high in the air. What you probably don’t picture is a group of scorpions glowing a bright bluish green under the starlight. That’s right, scorpions are fluorescent.
But what makes them glow? And why on earth would they need to glow in the first place? Let’s take a look.
what makes scorpions glow under black light?
Do scorpions glow? Yes. That’s an easy question to answer. It’s a bit more difficult to pin down what exactly causes them to glow. In fact, scientists are still working on finding a firm answer to that question.
What scientists do know is that something in the scorpions’ exoskeletons cause them to glow. Scorpions, along with other arthropods and insects, have an outer layer called a “cuticle.” Unlike the cuticles on your fingers, which are made of hard or dead skin, the cuticle on a scorpion is a part of its exoskeleton. This cuticle has a thin section called the “hyaline layer.” The hyaline layer is what reacts to ultraviolet (UV) light, such as black light or moonlight, and causes the scorpion’s body to glow.
The hyaline layer is really strong and truly stands up to the tests of time. In fact, scientists have found that even fossilized scorpions glow under UV light. Additionally, when scientists preserve scorpion specimens in liquid-filled jars, the hyaline layer can make the liquid glow! Crazy, right?
Q. Why do scorpions glow under black light? What might the evolutionary advantage be?
A. Certain molecules in one layer of the cuticle, the tough but somewhat flexible part of a scorpion’s exoskeleton, absorb the longer wavelengths of ultraviolet light and emit it in different wavelengths that are visible at night as a blue-green glow.
While observing scorpions, scientists have noticed that the creatures don’t glow immediately after molting. Rather, the cuticles have to harden completely before they shine blue-green in the starlight. But scientists still don’t know if the glowing material comes from a chemical reaction in the hardening process, or if the scorpions actually secrete the glowing substance.
Why do scorpions need to glow?
So why would a scorpion need to glow in the first place? As a predatory nocturnal creature, wouldn’t it want to stay hidden? Here again, scientists haven’t yet nailed down an answer to this mystery. But they haven’t given up on trying, either.
One of the most interesting hypotheses is that the scorpion uses its exoskeleton as a giant eye. California State University arachnologist Carl Kloock has suggested that the scorpions use their exoskeletons to detect UV light, so that they know when it’s night and time to eat.
Kloock is still testing his theory but has noticed that scorpions who aren’t really hungry won’t come out to hunt on nights when there’s a lot of moonlight. If they do need to eat, however, they’ll come out and hunt regardless of how bright the night is.
Why do scorpions glow under UV light?
Most scorpion species are fluorescent, which means they glow when exposed to ultraviolet ( UV ) light – in this case, a dazzling blue-green color.
All species of scorpions are known to emit blue-green fluorescence, a phenomenon called photoluminescence, which means that they can excite their organic molecules and re-radiate light by absorbing specific wavelengths of light.
We do know how they fluoresce, and that is due to the presence of beta carboline in their exoskeleton. Beta carboline will fluoresce when exposed to UV light, causing the scorpion to glow an eerie greenish blue glow.
So why do scorpions have carboline in their exoskeletons? Carboline chemicals are found in many animal cells, not just scorpions, and are thought to be sunscreens that protect epidermal cells by reflecting or scattering UV radiation.
Because scorpions appeared over 400 million years ago, research suggests that the oxygen levels were lower then, which means that UV light from the sun was pretty intense. It makes pretty good sense that these animals would be exposed to powerful UV radiation and would need to have or to develop some sort of protection, which could explain the presence of the carbolines.
Scorpions have this ability because their outermost cuticle contains fluorescent compounds such as beta-carboline, 7-hydroxy-4-methylcoumarin, and phthalates that absorb light in the ultraviolet range. Their shells containing fluorescent compounds act as light energy collectors, converting the energy received from shorter wavelengths of UV light into longer wavelengths of green light. This cuticle emits fluorescence with greater intensity as the scorpion ages. The researchers believe that this energy conversion and transfer is sensed by the scorpion’s central nervous system and can help them find shelter based on the intensity of the light to which they are exposed. The fluorescent substances in scorpion shells not only function during their lifetimes, but their remnants can be detected after they die and even after they become fossilized and still fluoresce.
SCORPIONS FLUORESCE when exposed to ultraviolet (UV) rays, producing a bright blue -green light that emanates from a layer within their exoskeleton. As for why scorpions glow, that’s been a subject of fierce speculation that continues to bewilder scientists.
Being ambush predators, scorpions don’t like to move around much when targeting prey.
“If they’ve got to move around to see whether they are in shade or under cover, they are probably going to expose themselves to anything that they’re trying to catch,” Ken explained. “You can get UV from the Sun but also the Moon, which is the reflection of the Sun and the Moon. It appears that because the whole of the body of the scorpion fluoresces, the theory is that whole of the scorpions’ body acts like an eye.”
This fluorescent layer of the scorpions’ exoskeleton is subject to change during periods of moulting, when their outer ‘shell’ becomes very soft. Ken said it takes about 90 minutes for this outer layer to harden. After analysing this transition of the scorpions’ exoskeleton, scientists gained unique insights into the scorpions’ fluorescence
“During that hardening, they don’t fluoresce. It’s only when they’re hard,” Ken said. “There’s a chemical in the cuticle that causes it to fluoresce and that chemical isn’t there just after they moult.
“Imagine if a scorpion had just its tail underneath a leaf that was protecting it but the rest of the body was out in the open, then if the whole of the body acts like an eye it would realise that its tail is being protected. Being under a leaf, the tail wouldn’t fluoresce because it doesn’t get the moonlight UV. It can sense how much of its body is protected.”
