The DARK side?

[jrh3]

.I will just leave this as food for thought....all over the world there are deep caves that never see light....yet we still see them teeming with life.....invert life to be specific....and arachnids specifically are pretty much always present in numbers.

Another thing to add is when they are in their burrows there is know way for them to tell night or day either right? If they only emerge once a week then light must not be a requirement. Most, but not all things that require light are because they need UVA or UVB absorption to process diffrent things.

 

[Justin H]

The activity rate of tarantulas is tied to their circadian rhythms. This is well documented: here's an example, here's another, and another. However, studies like this one and this one observe that a number of typical circadian responses are absent in certain Ts.

Light may not be essential to the survival of tarantulas and may not be a circadian cue for them, but it's probably important for something (considering they evolved in the presence of light). I would hesitate to raise them in complete darkness, but there's not enough evidence to make an argument against it. I imagine it would take generations and generations before you saw any damage caused by these conditions.

Another thing to add is when they are in their burrows there is know way for them to tell night or day either right? If they only emerge once a week then light must not be a requirement. Most, but not all things that require light are because they need UVA or UVB absorption to process diffrent things.

Most cave-dwelling species we have studied exhibit circadian rhythms. This study goes over a variety of evidence that secluded organisms have other means of detecting day/night that we don't understand yet. This is why I said earlier that light may not be a circadian cue for tarantulas.

edit: fixed that last link

 

[cold blood]

ing they evolved in the presence of light). I would hesitate to raise them in complete darkness,

Ive been not only raising large numbers in complete darkness for 5 years, but breeding them as well.

The lone thing one will notice, is simply that they rarely hide....unless of course light hits them.

 

[Justin H]

Ive been not only raising large numbers in complete darkness for 5 years, but breeding them as well.

The lone thing one will notice, is simply that they rarely hide....unless of course light hits them.

I hear ya. It's not something I can tell you not to do. You've obviously had enough experience/success to know when something makes a difference or not.

But I think it's prudent to hesitate to raise any organism with normal access to light in complete darkness. We know that altering environments like this can cause long-term changes to an organism's genome. Cavefish are a classic example of this. But you would never see the effects of this in your bedroom. There's a guy who's been raising fruit flies in darkness for ~60 years and is just now starting to observe small changes in DNA.

I hesitate in prudence, not because I think I'll hurt my Ts. I'm not offended at all if you choose to keep them in the dark.

 

[jrh3]

How would keeping them in a closet that only gets a small amout of light from the bathroom window? This would open up a whole new room for me to keep tarantulas, lol.

 

[Dennis Nedry]

How would keeping them in a closet that only gets a small amout of light from the bathroom window? This would open up a whole new room for me to keep tarantulas, lol.

If it’s dimly lit it’s probably not that different to the darkest parts of the rainforest floor

I'm actually completely with @viper69 on this one. A circadian rhythm has nothing whatsoever to do with hiding from predators.

I said they react to light cues which would help them avoid diurnal predators, I didn’t say anything about their circadian rhythm

We know they can survive without light and they don't necessarily depend on it - after all, they are very hardy - but there may still be effects that are to small to see in our limited captive populations

I don’t doubt that they might be affected by not getting a day/night cycle but seeing as we know they don’t absolutely need it to maintain good health then it’s not exactly a requirement

 

[Greasylake]

@Sarkhan42 You asked before about what we might want to see, why not some sort of study on tarantulas and lighting?

 

[Vanisher]

I just made a guess tha small amount of lighting could be good for them to distinguish day from nightcycle! Yes, many tarantulas spend their life in a burrow BUT comes out at night to feed. Maybe this has nothing to do with decreased light? Maybe they feel that the temperature drops and exit the burrow fir that reason? I havnt got a clue? It would have been intresting to hear what a arachnologist says! But one thing is clear though! Less light is far better than much light!

 

[cold blood]

I hear ya. It's not something I can tell you not to do. You've obviously had enough experience/success to know when something makes a difference or not.

But I think it's prudent to hesitate to raise any organism with normal access to light in complete darkness. We know that altering environments like this can cause long-term changes to an organism's genome. Cavefish are a classic example of this. But you would never see the effects of this in your bedroom. There's a guy who's been raising fruit flies in darkness for ~60 years and is just now starting to observe small changes in DNA.

I hesitate in prudence, not because I think I'll hurt my Ts. I'm not offended at all if you choose to keep them in the dark.

Heres the thing...i will use the Milwaukee county zoo...one of the largest, highest rated zoos in the country...as an example.

They have a small mammal bldg...everything in there is nocturnal....the only light in the building are dim red...literally zero light, for decades on end...zero problems with a single animal within....and these are mammals.

For ts, theres no way i could be convinced a t needs light at all...ever... the only thing light provides is something to avoid.

 

[viper69]

And how well do a ts eyes work....from our perspective, id say barely. Their eyes suck...lol

I knew you’d say that hahah. But we don’t live in caves, nor nocturnal

 

[cold blood]

I knew you’d say that hahah. But we don’t live in caves, nor nocturnal

what i wrote had to do with ts, not us.

 

[Justin H]

For ts, theres no way i could be convinced a t needs light at all...ever... the only thing light provides is something to avoid.

Sorry to keep pestering you...

But why not science? Search any scholarly database with the terms "raised in darkness." I can't find a single study in which constant darkness didn't cause a change in the organism over generations (these studies include arthropods). You need electron microscopes and genealogical records to study this sort of change--it's not something you'll see in your bedroom or at the zoo. I'm not making this stuff up.

Drawing conclusions based on anecdotal evidence is just silly here... we are certain that these conditions cause changes in genealogy in all sorts of other organisms, and we know these changes aren't visible to the naked eye. That said, I don't believe that one T breeder can make a lasting impact on the gene pool, so I'm not going to be offended if you choose to keep them this way.

By claiming that you know tarantulas don't need light, you're perpetuating a myth. The fact is, we don't know yet. I'm arguing that the answer is "probably," based on scientific evidence.

 

[cold blood]

But why not science? Search any scholarly database with the terms "raised in darkness." I can't find a single study in which constant darkness didn't cause a change in the organism over generations (these studies include arthropods).

i hear ya, I dont mean to sound rigidly stubborn...its just that its not like i have 2 ts in my always dark room....theres at least 500, and species from all over....none have been exposed to light aside from what i need to see, and all grow well, and breed prolificly....i mean, its not a study, but all those ts, all those productive sacs, a great cumulative growth rate over 5 years...if it was going to cause a problem, its more than reasonable to think i would have seen at least some minute shred of evidence over the years. I havent.

I just fail to see how a creature that avoids light, would need it...what, to tell them when to hide? Without light, they simply choose to hide a lot less IME.

Look, I get what you are saying, most animals do benefit, but to say that because most do, all must, is a stretch.

Look no further than the deepest parts of the ocean and the myriad of animals living in a part of the world that will never see light greater than bioluminescence. So fact is that not all animals require light or light cycles, even if most do....and ts are not like most animals....

If light were important they would have almost certainly developed better sight, instead they rely on vibrations felt throughout the hairs....why...so they can function at their highest levels in total darkness.

We cannot categorically say ts need light, simply because so many (unrelated) other creatures are...the evidence for is just as anecdotal....ie, without proof.

Many keep ts in darkness without issue, that's actually more supportive of no need than a need.

 

[Justin H]

Look, I get what you are saying, most animals do benefit, but to say that because most do, all must, is a stretch.

Hmm... that's not what I'm trying to say. I'll try to be more clear and concise:

Tarantulas evolved in the presence of light. It's the reason they have eyes. When we take other organisms with eyes and begin to raise them in complete darkness, the DNA of their offspring is eventually rewritten. DNA is responsible for all sorts of things, so study results have been all over the place. But one things for sure: DNA changes in response to environment. It's for this reason I would never raise anything in total darkness.

But like I said, it takes hundreds of generations for this to happen. With female tarantulas taking so long to mature, we won't know in our lifetime how they are affected by total darkness, nor is it likely you will have a lasting impact on the gene pool. It's more of a principal thing for me.

 

[cold blood]

Hmm... that's not what I'm trying to say. I'll try to be more clear and concise:

Tarantulas evolved in the presence of light. It's the reason they have eyes. When we take other organisms with eyes and begin to raise them in complete darkness, the DNA of their offspring is eventually rewritten. DNA is responsible for all sorts of things, so study results have been all over the place. But one things for sure: DNA changes in response to environment. It's for this reason I would never raise anything in total darkness.

But like I said, it takes hundreds of generations for this to happen. With female tarantulas taking so long to mature, we won't know in our lifetime how they are affected by total darkness, nor is it likely you will have a lasting impact on the gene pool. It's more of a principal thing for me.

Yeah, but ts have terrible eyes, to the point that they rely on signals from hairs to identify and capture prey....this gives them a huge predatory advantage in total darkness.

They may have eyes...so do those super deep water fish I mentioned...but they have adapted alternative means to their sight...means which are far superior to their eyes. This indicates to me that they more likely evolved in the absence of light.

 

[Darth Molt]

Hmm... that's not what I'm trying to say. I'll try to be more clear and concise:

Tarantulas evolved in the presence of light. It's the reason they have eyes. When we take other organisms with eyes and begin to raise them in complete darkness, the DNA of their offspring is eventually rewritten. DNA is responsible for all sorts of things, so study results have been all over the place. But one things for sure: DNA changes in response to environment. It's for this reason I would never raise anything in total darkness.

But like I said, it takes hundreds of generations for this to happen. With female tarantulas taking so long to mature, we won't know in our lifetime how they are affected by total darkness, nor is it likely you will have a lasting impact on the gene pool. It's more of a principal thing for me.

But most Ts can’t see more than 2 inches in front of their face that’s why they’ve evolved all the hairs on their legs and body. There’s not much sun light beneath the forest floors plus they are in their burrows during the day so I’m not sure if a cycl is necessary

 

[Justin H]

Yeah, but ts have terrible eyes, to the point that they rely on signals from hairs to identify and capture prey....this gives them a huge predatory advantage in total darkness.

They may have eyes...so do those super deep water fish I mentioned...but they have adapted alternative means to their sight...means which are far superior to their eyes.

I agree that their sight is terrible. They seem to have little purpose other than to detect light... lol. That's my point. They evolved to survive in an environment with light. You stop calling on that DNA and it's going to change.

 

[cold blood]

y evolved to survive in an environment with light. You

By avoiding it? So they need light exposure so they know when to not come out?

 

[Justin H]

By avoiding it? So they need light exposure so they know when to not come out?

Edited my post... not sure what you're asking.

They need to continue to be exposed to light to avoid changes in their DNA.

 

[AphonopelmaTX]

It would be too much trouble to quote all the points made in this discussion so I will just write some stuff and everyone can take from it what they will.

My observations of wild Aphonopelma hentzi in North Texas over many years support many of the points made here.

Do tarantulas need light to survive?
I say no. Wild A. hentzi hide in their burrows during the day and come out at dusk. There is some overlap where one can find A. hentzi out in the afternoon or in the morning, but generally they stay out of the light. I'm not convinced an animal that actively avoids sunlight needs it to be healthy.

A. hentzi in North Texas typically build their burrows underneath large natural structures or in dense vegetation. When they can be found during the daylight hours, they stay within the shade. This tells me there is a threshold of how much light is present before they retreat back into the depths of their burrows. The eyes are playing the primary role in detecting how much light is in the sky. Tarantulas don't always stay a foot or more underground to where they can't see the light. They are sometimes resting at the entrance or somewhere near.

Do tarantulas have a circadian rhythm?
I'm not too sure what the text book definition of a circadian rhythm is so I will just tell you what I have seen. Wild A. hentzi appear to technically be diurnal but use the daylight hours to rest. As stated above, A. hentzi can be found active during the day in the shade and on cloudy days but the majority stay well within the inside of their burrows. The exception being mature males. Males during the breeding season can be found wandering during the late afternoon in broad daylight, but like females and immatures, the majority will be more active at night. Their activity levels seem to be correlated by the amount of light in the sky. To me, it seems it isn't the light itself that a tarantula benefits from, but rather it is an important cue to get back underground or to seek some other shelter to get out of the hot dry air. Such a rhythm could be beneficial to the health of a tarantula by forcing it to remain inactive. Kind of like the spider equivalent of sleep, but technically not sleep since I think they are still alert inside the burrow during the day, they just have to stay still until dusk.

Then there is the matter of burrow plugging. *Sigh* During the summer months when A. hentzi are most active, they will occasionally plug the entrance of the burrow with soil from within. When a burrow is plugged, how would they know when it's dark out unless they have a circadian rhythm? They must have some kind of idea of when it should be daylight and when it should be night without seeing any light at all. If not a circadian rhythm, then perhaps some other environmental cue that tells them that the conditions that caused them to plug the burrow in the first place is gone.