Light dependancy

[Aillith]

Now I've read that scorpions + direct sunlight = bad
And I know some of you have lighting set-ups to give your scorpions day/night cycles.

I was wondering if anyone knew if scorpions needed some amount of light to suvive?

ie. Can they survive if kept in a completely dark room with no exposure to any sunlight at? If so, how does this effect their growth?

AND

does the type of light matter to a scorpion.

ie. Can they survive in set-ups that provide day/night light cycles with the use of -only- artificial lighting, -or- do they need real sunlight.


I ask for several reasons.
1. It's an interesting train of thought.
2. I am running out of room in my living room and so am considering relocating my scorp enclosures to a more out of the way place. I have a spare walk-in storage room in my apartment but it has no windows.

 

[Mark Newton]

I think it probably depends on the species to some degree. Troglodytes clearly dont require light and therefore any cycle. I cant imagine that burrowing scorpions require light either as they shun light and quickly retreat to their subterranean darkness. I cant imagine there has been too much research conducted in this field as it would be a very difficult thing to study and return significant conclusions on. However I think there are some scorpions that are partially diurnal and they may have developed some type of light dependancy, but I'm not aware of any in Australia. My scorpions see some ambient natural light every day, but never direct and I dont think it bothers them too much, but its hard to say for sure.

 

[EAD063]

There are some in the US that have a kind of light dependancy, or tolerance as you might say. A couple centruoides don't mind hanging out during the day.

Day and night shouldn't matter too much. I don't let it affect how I store everything.

 

[Arachno Kid]

I dont know about light but I would say that some scorps definatly require heat and stuff, light really isnt a big issue with my scorps, they just like to chill on their terricota pieces when its warm.

Day and night shouldn't matter too much. I don't let it affect how I store everything.

Same here.

Like mark said it probally depends on the species

 

[skinheaddave]

The answer is yes -- and no. As Mark said, there are definitely troglodytes that do not see light in their lifetimes. That being said, these species are few and far between. If you can get your hands on the chapter in "Scorpion Biology and Research" by Philip Brownell on sensory ecology, there is a beautiful bit about how S.mesaensis (an obligate burrower inhabiting a desert environment) will approach the edge of its burrow towards the end of the day. Since heat takes time to diffuse through sand, this actually exposes it to the hottest part of the daily temperature cycle at that point in its burrow (still cooler than the surface temperature at the peak, but quite warm). It also allows the scorpion a glimpse of the last bit of sunlight. This sort of behaviour -- approaching the entrance of a burrow -- is not unique to this species and is, in fact, quite common. Thus, a good number of burrowing species are going to be getting a slight glimpse of light towards the end of the day.

There are also scorpions, particularily in forest environments, who do not show such a rigorous nocturnal schedule. Combined with those scorpions that opt to live in scrapes, under bark or in litter rather than the far more optically isolated burrows, you can see that the vast majority of scorpions actually do get some exposure to daylight -- even if it is the last reminants of the day.

And now onto the neat stuff. First of all, scorpions have sunglasses. Without getting into too much detail, scorpion eyes can adjust their sensitivity (I believe by several orders of magnitude, may be wrong on this one) throughout the day. The interesting thing is that it does not seem to be directly in response to light, per se, but in response to their circadian clock. So it isn't so much like those photo-sensitive glasses that automatically change when you step outside -- more like if you had glasses that automatically darkened every morning and cleared every evening, regardless of what else had gone on. So clearly scorpions have adapted to a world with sunlight. But do they NEED it?

There only seem to be two things that scorpion eyes do really well. The first is pick up on light to aid them in navigation. They are negatively phototaxic -- so they will avoid bright light. It also seems that they use light to find darker spots to hide when escaping -- so they will run to underneath a darkened bush preferentialy to some open bit of terrain (see Camp & Gaffin, I believe, for details). It has also been theorized that they may use stars to navigate, but evidence for this is still tenuous. Needless to say, none of this has very much to do with sunlight, other than the fact that the avoid it.

The second function is the establishment of a circadian rhythm. The circadian clock is the mechanism that gives organisms their internal sense of time. We have one -- which is why when we get on a plane and travel half way around the world we get pretty confused. The light outside tells us that it is daytime, but our own internal clock tells us it is night. Fortunately, the clock is good at taking input in the form of Zeitgebers (literally "time givers"). Light is a powerful zeitgeber for many animals, ourselves included. That is why, a few days after our plane trip, we have usually adjusted quite nicely to the new time zone. Scorpions work much the same way, taking that last little bit of daylight and using it to reset their circadian clock. Thus, their internal clock runs on a 24 hour cycle.

In the absence of light the circadian clock starts to "free run." It may run on a cycle of more than or less than 24 hours, but the long and short of it is that you start to lose your sense of time. For a human example, you need to go to individuals who have been detained for one reason or another in total darkness -- prisoners in the "hole", people smuggled in cargo containers etc. who report having no sense of how long they were there. Scorpions do the same thing in conditions of total darkness (and constant temperature -- but thermal zeitgebers was the subject of my undergraduate thesis and the manuscript I am currently working on, so you don't want to get into that with me unless you have a week to listen to my ramblings). Even a brief period of light -- say 10 minutes every day -- keeps them nicely on track.

So in the end, we see that light definitely has an effect. But does a free-running scorpion actually suffer any negative conscequences? Unlike people, scorpions probably don't have the neural mechanisms to get upset over their loss of internal rhythm. They don't really have an emotional context to pain, hardship etc. So a scorpion technically probably can't go "insane." Whether a free-running circadian clock has any particularily significant effect over physiology or behaviour etc. which might influence a scorpion in a captive environment (vs. one in the wild under much more strenuous conditions) I couldn't even speculate on. Needless to say, research even glancing in this direction is going to be exceedingly sparse.

Hopefully there is somthing in there that might help.

Cheers,
Dave

 

[JungleGuts]

I have my scorps near a window(but not in direct sunlight) so they get some daylight. At night i use a red bulb, they have done well like this.

 

[Aillith]

Dave, thankyou so very much for your very informative post. Very very interesting. It has given me alot to think on and consider.

The first thought that comes to my mind - and forgive me for sounding so noob - would be that a free running circadian clock may perhaps shorten a scorpions life span? Perhaps by a little, perhaps by alot?

My reasoning: If living things are designed to live naturally for a set amount of time (eg. a specific number of days or something, say like 5 days), if the internal clock of that creature speeds up (eg. It's only been 3 days but the internal clock of the creature registers 4 days) then the life of the creature would be shortened. It may have only been 3 days, but the body thinks it's been 4, so it only lives 1 more day, instead of 2.

But now reading that back to myself, it sounds half-nonsenicle. :?

 

[Mark Newton]

Ahhh...Dave, now I know who to ask about such things...

I was thinking about our desert burrowers as I know they come to the mouth entrance before dark and at times can be seen to shoot back down the burrow even during the day.

So, I wonder just how much change in behaviour there would be with a scorpion that has had its circadian rhythm screwed around with and would it be detrimental. I agree that changes in temperature throughout the day and throughout the year would have a big impact. Light changes might also influence breeding activity, sealing of the burrow etc, very hard to know and it would be difficult to conclude in captivity. What would be more important, temperature, humidity or duration/timing of light changes? I feel quite sure that parturition is triggered in many of our Urodacus by a combination of temp and humidity. Light may well influence the feeding/activity cycles in temperate species more than tropical species where activity is greater all year round.

Good explanation Dave...:clap: and clearly an area that interests you...I will keep that in mind..:worship:

 

[skinheaddave]

My reasoning: If living things are designed to live naturally for a set amount of time (eg. a specific number of days or something, say like 5 days), if the internal clock of that creature speeds up (eg. It's only been 3 days but the internal clock of the creature registers 4 days) then the life of the creature would be shortened. It may have only been 3 days, but the body thinks it's been 4, so it only lives 1 more day, instead of 2.

The question, then, is whether circadian cycle has a direct effect on physiological activity and cellular biology or whether it can only have an indirect one. Certainly a messed up circadian rhythm would tend to shorten the life of a scorpion in the wild. If it tries to hunt at the wrong time or exposes itself to predators when it otherwise would have been safe then this will affect the scorpion at the population level. The metabolic processes might fail due to starvation -- but it would not match the scenario you propose.

It is not hard, however, to imagine a rather abstract scenario where a compromised circadian clock would shorten the life span at a cellular level. Imagine, if you will, that there is an effect on the cellular ion pumps by a hormone released into the circulatory system on a daily basis. A shortened circadian rhythm would cause the pumps to become active more often, increasing their use per unit of time and potentially leaving inadequate time to replenish energy stores during the "down times." Conversely, a slowed circadian rhythm would force the pumps to stay active longer each time, perhaps causing them to run out of energy. Either way, it could potentially cause premature cellular death.

Keep in mind that none of this has been researched to my knoweldge -- and also that my interest in cellular biology during university was tennuous at best. Still, I think that your proposal is far from impossible -- albeit not quite the way you envisioned it (hint: try to keep the word "designed" out of arguments of that sort, as it tends to upset the academics who have been scarred by the beligerance and fantacism of certain elemens of the creationalist movement ).

Cheers,
Dave

 

[skinheaddave]

Light changes might also influence breeding activity, sealing of the burrow etc, very hard to know and it would be difficult to conclude in captivity.

Which brings up two points. The first is the difference between daily cycles and annual or seasonal cycles. So if a bit of "sunlight" is, indeed, shown to be critical to scorpions then will a cycle of unwavering intensity and duration sufice or, as with some "higher" animals like reptiles, will a yearly cycle be necessary to fulfil their needs?

The second point is the difference between captivity and the wild. If circadian cycle affects "appetite" (for lack of a better word) and your captive scorpion finds itself eating at noon instead of midnight, does it really matter? Obviously to a wild scorpion with a blazing sun, predators aplenty and potentially co-adapted prey species, I imagine it matters a great deal.

Urodacus by a combination of temp and humidity.

Not just your scorpions. I think it is generally accepted that these have an effect of many species. I've often wondered if an abundance of small prey items might have a direct effect of some sort on the timing of partuition. Also, if certain compounds present in a seasonal prey item of certain scorpions might induce parturition at the appropriate time to ensure the young get all the small things to eat? Unfortunately, scorpion nutrition is even more poorely studied than circadian cycles etc.

Cheers,
Dave

 

[Mark Newton]

It is not hard, however, to imagine a rather abstract scenario where a compromised circadian clock would shorten the life span at a cellular level.

I think we already have the answer to that....biologically at least. Proven fact that people who work night shift have a significantly higher incidence of many different ailments and die 5-10 years younger on average than those that work diurnally. However, humans have a pineal gland and produce melatonin, which is a chemical who's levels are controlled by photoperiodism. Do scorpions have a pineal gland? I dont think so, but they may have something similar. It has been shown that Urodacus have some form of light sensitive capability within their metasoma. This might be to do with backing out of the burrow when removing dirt. But, physiologically..probably, but at what level and how?

 

[Mark Newton]

I've often wondered if an abundance of small prey items might have a direct effect of some sort on the timing of partuition. Also, if certain compounds present in a seasonal prey item of certain scorpions might induce parturition at the appropriate time to ensure the young get all the small things to eat?

Thats an interesting thought. Now we're getting into some serious ecological interaction stuff. This may be the case with opportunistic scorpions such as the Buthids. Although realistically, that would probably be an annual thing as insect booms at least in this part of the world normally occur in spring and scorpions dont 'usually' have young in spring as it means summer is around the corner and summer is not a good time for a young scorpion to be facing. Mating normally occurs in spring. But in tropical climates things might be different...read...would be different and in such environments who knows what environmental factors may trigger all sorts of life changes. Interesting thoughts.

 

[skinheaddave]

Do scorpions have a pineal gland?

Neurohaemal organ of the scorpion Heterometrus swammerdami
Muhammad Habibulla
In Heterometrus swammerdami there are no known endocrine glands. In the brain and the subesophageal ganglion there are
groups of specialized neurons. These nerve cells synthesize a variety of biologically active compounds. Some of these products can clearly be visualized with special staining methods in paraffin sections under the microscope. Since the nervous tissue is enveloped with four layers thick perineurium, a ‘blood brain barrier’ exists. For this reason the synthesized neurosecretory material cannot be discharged directly in to the haemocoel and must be delivered to the cephalic blood vessels. The neurosecretory product is transported through the axons and the neurofiber tract pathways, forming neurohaemal organs terminating in the blood vessels surrounding the cephalothoracic nerve mass. A variety of specialized neurons which secrete biologically active compounds will be presented and their transport through the nervous system discussed.

So no, scorpions do not have a pineal gland, nor a homologous structure. Not really surprising. But they do seem to have analogous capabilities. Given that this presentation was given all of a year ago, it may be a while before the circadian regulation of any of these substances is known, though.

But in tropical climates things might be different...read...would be different and in such environments who knows what environmental factors may trigger all sorts of life changes.

In the genera of Pandinus and Heterometrus, parturition is keyed to an explosion of smaller, less tough prey items. Remating occurs shortly thereafter and the cycle is repeated annualy. This means that in captivity, reported gestation fluctuates from the wild norm. Then you have something like P.utahensis which has been shown to get knocked up, then delay development for a good portion of the year, allowing for rapid development just prior to parturition ... all during a time of year when both mom and the young have something to eat. These cycles need to be regulated, of course. Interesting area of study, in my opinion.

Cheers,
Dave

 

[John Bokma]

I had a female C. gracilis that loved to sit in the sun (filtered through the window, and low):
http://johnbokma.com/mexit/2006/01/16/female-scorpion-basking.html

I have several C. species that seem to do the same. They sit high up a stick when I have my desk lamp on and it looks like they are taking a sun bath.

 

[~Abyss~]

I don't use any lights with my scorps as form of heat I have heat pads and ceramic heat lamps. They work great for me cus any light won't let me sleep. But they do get natural light that sifts through my window. It's not direct contact light.

 

[EAD063]

I had a female C. gracilis that loved to sit in the sun (filtered through the window, and low):
http://johnbokma.com/mexit/2006/01/16/female-scorpion-basking.html

I have several C. species that seem to do the same. They sit high up a stick when I have my desk lamp on and it looks like they are taking a sun bath.

Mexico is filled with a bunch of day dwellers though right? Like I've heard naturally C gracilis have no problem hanging out in the open, same with exilicaudia from the US.

 

[John Bokma]

I have several C. species that are walking around at the end of the day, or when I have the curtains closed, especially C. flavopictus flavopictus.

C. gracilis is a bit less out in the open. Diplocentrus species I keep prefer to stay well hidden. When I turn off all the lights and check their enclosures about 20 minutes later I might be able to spot some. Same with some Vaejovid species.

I have seen C. gracilis in the open around 5 PM, but at one time it probably was because my partner bumped with her shoe against a piece of lava rock, and at another time I saw a lot of ants walking around and then a C. gracilis running like crazy between them. Probably started to stirr early and bumped into their nest.