WEBVTT - Why Do Scorpions Glow Under Black Light?

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<v Speaker 1>Welcome to brainstuff from how stuff works. Hey, brain stuff,

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<v Speaker 1>Lauren vocal bomb here. Some animals are just over the top.

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<v Speaker 1>Take scorpions. Is it not enough that these stinging arachnids

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<v Speaker 1>can survive some of the harshest climates in the world

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<v Speaker 1>and live twenty five times longer than your average cockroach?

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<v Speaker 1>Or that some species don't need males to reproduce and

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<v Speaker 1>can live up to forty eight hours without oxygen, and

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<v Speaker 1>that all of them will eat almost anything they can subdue,

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<v Speaker 1>even other scorpions. No, it's apparently not enough, because scorpions

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<v Speaker 1>also glow electric cian green under ultra violet light. Why

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<v Speaker 1>they do this is a bit of a mystery, but

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<v Speaker 1>it makes them pretty easy to study. All a scorpion

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<v Speaker 1>researcher and has to do to find scorpions is go

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<v Speaker 1>out into the desert at night with a black light

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<v Speaker 1>and watch those suckers light up like Christmas trees. Chemically speaking,

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<v Speaker 1>nobody's exactly sure what causes scorpions to glow, but we

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<v Speaker 1>know it's power full stuff. When a scorpion is preserved

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<v Speaker 1>in alcohol, the alcohol itself will fluoresce. Scorpion fossils have

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<v Speaker 1>even been induced to glow under black light after hundreds

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<v Speaker 1>of millions of years. What we do know is the

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<v Speaker 1>chemicals that make a scorpion so rave ready are in

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<v Speaker 1>the outer layer or cuticle, of its exo skeleton. Scientists

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<v Speaker 1>call it the highland layer. Scorpions molt their exo skeleton

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<v Speaker 1>every so often in order to grow, and researchers have

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<v Speaker 1>observed that until the slightly mushy outer shell has entirely hardened,

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<v Speaker 1>the highland layer does not fluoresce under UV light. This

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<v Speaker 1>is all pretty weird. Why would an animal evolve to

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<v Speaker 1>glow under ultraviolet light? Researchers have posited a bunch of

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<v Speaker 1>different ideas. Scorpion fluorescence might help them find each other

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<v Speaker 1>in the dark, protect them from sunlight, or even confuse

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<v Speaker 1>their prey. But there's another promising theory that scorpions are

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<v Speaker 1>somehow using their fluorescence to detect UV light, mostly because

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<v Speaker 1>they want to avoid it. There night hunters, after all,

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<v Speaker 1>and a scorpion will always find the darkest place to

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<v Speaker 1>hang out during the day or even in the moonlight.

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<v Speaker 1>A study published in the Journal of Arachnology tested normal

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<v Speaker 1>fluorescing scorpions and a group of scorpions that they had

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<v Speaker 1>reduced the fluorescence of with prolonged exposure to UV light.

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<v Speaker 1>The normal scorpions then reacted more strongly and negatively to

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<v Speaker 1>UV light than the desensitized scorpions. But wait, you might

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<v Speaker 1>be thinking. Scorpions still have eyes, and as it turns out,

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<v Speaker 1>they can visually see light within the ultra violet part

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<v Speaker 1>of the spectrum, but it doesn't seem like the scorpions

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<v Speaker 1>were reacting visually. A separate study published an Animal Behavior

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<v Speaker 1>in basically blindfolded a group of scorpions and found that

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<v Speaker 1>the critters still reacted to the presence of ultraviolet light.

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<v Speaker 1>So it seems that they're using their entire bodies as

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<v Speaker 1>giant UV seeking eyeballs, and that if they sense that

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<v Speaker 1>they're glowing at all, it's time to scurry up somewhere darker.

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<v Speaker 1>Today's episode was written by Jesseline Shields and produced by

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<v Speaker 1>Tyler Clang. For more on this and lots of other

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<v Speaker 1>glowing topics, visit our home planet, how stuff Works dot com.