Why do scorpions glow under UV light?

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Offline chris

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Why do scorpions glow under UV light?
« on: 20/03/2010 11:32:57 »
One way to spot scorpions at night is with a UV light source - adults glow a greeny blue. Why?

Chris
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Offline RD

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Why do scorpions glow under UV light?
« Reply #1 on: 20/03/2010 14:42:28 »
Fluorescence is possibly a form of sunscreen: converting harmful UV into harmless visible light,
(other forms of sunscreen convert the UV into heat, but that would be undesirable in a very hot environment). 


[less likely explanation] If the visible glow is long lasting it may provide illumination when the scorpion goes into its burrow ...

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[scorpions] are ... fossorial
http://en.wikipedia.org/wiki/Scorpion#Life_and_habits
« Last Edit: 20/03/2010 14:56:34 by RD »

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Offline RD

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Why do scorpions glow under UV light?
« Reply #2 on: 23/03/2010 00:33:24 »
This chap thinks scorpion fluorescence could just be accidental ...

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Wildlife - scorpions
Expert: Jim Harris - 8/24/2004

Question
Is it true that some scorpions glow in the dark?

Answer
... scorpions do "glow" when exposed to a black light. WHY does this happen?  Well, the jury  is still out where that's concerned. Most likely it's an accidental side effect of the chemicals making up the exoskeleton.  One popular theory is that it's a form of built-in sunscreen to protect the scorpion from ultraviolet rays.  Personally, I have my doubts about this; scorpions tend to be nocturnal and I can't see any reason they would need sunblock.  So, as far as I know, the situation is still a mystery. 
http://en.allexperts.com/q/Wildlife-2507/scorpions.htm


The fluorescence could just be a neutral side-effect ...

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Some protein or small molecules in cells are naturally fluorescent, this is called intrinsic or autofluorescence
http://en.wikipedia.org/wiki/Fluorescence_in_the_life_sciences
« Last Edit: 23/03/2010 01:02:04 by RD »

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Offline Geezer

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Why do scorpions glow under UV light?
« Reply #3 on: 23/03/2010 05:45:13 »
Is it 'cos it makes them look cool when they go down the disco? Or maybe it's just because they have really bad dandruff?
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline chris

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Why do scorpions glow under UV light?
« Reply #4 on: 23/03/2010 08:28:10 »
I did some poking around and found that the fluorescence is caused by the accumulation in the mature exoskeleton of a chemical called beta-carboline, which glows under UV.

I am not sure what role this substance performs normally, scorpions not being known as avid clubbers or disco-goers.

chris
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Offline LeeE

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Why do scorpions glow under UV light?
« Reply #5 on: 23/03/2010 16:45:03 »
Actually, there might be some mileage in the sunblock theory precisely because they tend to be nocturnal.

If the scorpion is generally nocturnal its metabolism will be 'tuned' for operating most efficiently at relatively low temperatures (when compared with daytime temperatures) and in the absence of solar radiation.  However, it may then run the risk of overheating if, for any reason, it has to be active during the daytime e.g. if it's disturbed.  In this case, the fluorescence may help to prevent overheating by more effectively re-radiating solar energy.  At the same time, there won't be much risk of UV illumination during the night so there'll be little risk of the fluorescence giving it away while it's hunting.

There's also the possibility that although the fluorescence is swamped, at least to our eyes, by the ambient light level during the daytime, it may be visible to certain predators (I believe that both birds and rodents can see UV light) and act as a deterrent by scaring them off or by warning them that they're poisonous in the same way that many other brightly coloured creatures clearly advertise their poisonous nature to avoid being eaten.  On the other hand though, if a UV aware predator is not scared by the fluorescence and the poison then it's just going to act like a huge sign saying "Food Here!!"
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline RD

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Why do scorpions glow under UV light?
« Reply #6 on: 23/03/2010 17:07:19 »
...I believe that both birds and rodents can see UV light) and act as a deterrent by scaring them off or by warning them that they're poisonous in the same way that many other brightly coloured creatures clearly advertise their poisonous nature to avoid being eaten. 

UV vision isn't a factor unless the scorpion is fluorescing (lower energy) UV, (apparently it's only emitting visible light).
« Last Edit: 23/03/2010 17:15:24 by RD »

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Offline LeeE

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Why do scorpions glow under UV light?
« Reply #7 on: 23/03/2010 17:30:50 »
Fairy nuff.
...And its claws are as big as cups, and for some reason it's got a tremendous fear of stamps! And Mrs Doyle was telling me it's got magnets on its tail, so if you're made out of metal it can attach itself to you! And instead of a mouth it's got four arses!

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Offline Geezer

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Why do scorpions glow under UV light?
« Reply #8 on: 25/03/2010 00:01:59 »
Is this phenomenon unique to scorpions?
There ain'ta no sanity clause, and there ain'ta no centrifugal force Šther.

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Offline RD

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Why do scorpions glow under UV light?
« Reply #9 on: 25/03/2010 01:37:38 »
Is this phenomenon unique to scorpions?

Allegedly this is a video of jellyfish fluorescing under UV ... http://www.youtube.com/watch?v=aAns97EndDQ&feature=related

but they could actually be bioluminescent which is not the same thing: (no UV required).
« Last Edit: 25/03/2010 01:40:38 by RD »