humidity/oxygen and growth rate

[apophysis]

Do you think humidity/oxygen levels can affect growth rate of tropical species? I was reading this article and find it very interresting.. http://www.arachnoboards.com/ab/content.php?33-Theraphosa-blondi

I`m thinking , let say a theraphosa blondi that is kept high humidity with live plants VS one that is kept on dry substrate with no plants but still access to fresh water ofcourse, both fed as much and kept in same temps, would they grow at same rate?

You who keep theraphosa, pamphos, xenesthis etc in dryer conditionings have you noticed slower metabolism?

Thanks!

 

[spiderengineer]

its an interesting test, but i figure the only true way to see is to get an oxygen tank. use that to pump fresh oxygen and maintain a rich oxygen environment, while having another one with normal house condition oxygen levels.

 

[Zoomer428]

I think heat can along with humidity of course

 

[jayefbe]

I think heat can along with humidity of course

It's been well-known that increased temperatures will increase growth rate. But why would increased humidity increase growth rate?

I read the article, and aside from the fact that it is hypothesized that ancient invertebrates were larger partially due to increased oxygen levels, there's not much that I agree with besides advice on caring for Theraphosa.

First, humidity. The rainforest has almost constantly saturated humidity levels. It's impossible to maintain humidity higher than that, so how can increased humidity lead to increased growth rates? I doubt it plays any role in growth rate as long as it's at sufficient enough levels to keep it alive.

On to oxygen levels. According to the hypothesis, increased oxygen concentrations allowed for greater maximum size of invertebrates, not faster growth rates. My guess is that increasing oxygen levels won't have any effect, especially in comparison to how growth rate is affected by feeding rate and temperature.

 

[spiderengineer]

In the article he wasn't just talking about growth rate that was the main point, but not the only point. In the article he was also talking about the general well being of the T as well. like why less successful egg-sac in captivity and potential longevity as well. He mention that bad molts while mainly due to lack of humidity for younger Ts could be also possibly attributed to not enough oxygen. it makes sense more oxygen means more blood flow for them when they are molting so they can obtain more energy to finish the molting instead of stopping midway threw and just give up and die. Book lungs mean less advance compared to other lungs in animals and so not efficient enough to supply adequate oxygen when abundance of oxygen is not around. so he maybe be on to something and I would love to see a test done about it.

 

[jayefbe]

I understood his point. I still don't find it a compelling one. How different can the oxygen concentration be compared to your room?

 

[spiderengineer]

That's a very good point and it's tricky to answer that, because it is hard to get accurate readies and oxygen level vary with elevation and factors like pressure and wind flow no to mention you can measure in things like part per million because air is all around us. So when measure carbon dioxide in part per million its based how much oxygen there is to carbon dioxide. so you cant really no oxygen levels like you can with other gases in the air. Ocean oxygen levels are easier to get readings surprisingly. since we are talking about the Amazon here were a high concentration of vegetation exist compared to say Arizona. then we can safely assume that oxygen levels are higher. However you are correct when you say how different can the concentration be, but I think we should think who are we applying this to? Obviously we are talking about T's. So to us if we went to both Arizona and the Amazon (at normal sea level elevation) we would not really have a hard time breathing in either location, but can we honestly say that a for a T.? I think it possible we can say that they may have issue (not immediately, but as for longevity and growth? Potentially), because we know that during the prehistoric era there was a much higher oxygen concentration and that allowed for larger animals especially spiders. however as oxygen level decrease those size of spiders could not survive and so the started to get smaller in size. T. Blondi size could be possible because its in a location were like I stated early potentially has high oxygen levels. The whole genus which are found in South America and I believe are the biggest in the tarantula family gives credence to that thinking. Also it takes time to achieve a size of a foot so longevity is definitely needed if they want to get up to a foot, but like the author said is hard to get in captivity unless your lucky or have a wild caught one already.

In fact if you believe in J'ba Fofi or Congolese Giant Spider a mythic monster of the Congos, which is another heavily vegetative area so another possible high concentration of oxygen supports the theory of course this species is not evidence since they are just stories, just thought I would mention it because if it did exist then we are talking about a five foot spider would blow the T. Blondi's record by a land slide

 

[Londoner]

In fact if you believe in J'ba Fofi or Congolese Giant Spider a mythic monster of the Congos, which is another heavily vegetative area so another possible high concentration of oxygen supports the theory of course this species is not evidence since they are just stories, just thought I would mention it because if it did exist then we are talking about a five foot spider would blow the T. Blondi's record by a land slide

Although a five foot T would be an impressive (if somewhat disconcerting) sight, I'm pretty sure it's impossible. The exoskeleton of a tarantula is a limit in itself to "giant" specimens. The exo design would not be able to support the weight of a T several feet in size. I'd say the anatomical design of a tarantula means they've already pretty much reached their limits, size-wise.

I know this wasn't the general thrust of the article, just thought I'd add to the mix haha!

Good luck.

 

[Mrhairyleggs]

whats the possiability of the spiders developing a circulatory system? with increase in size perhaps theres room instead of having a complex track of "wind pipes" maybe there not trantulas more like a five foot araneidae of some sort?? spiders which are persumed the evolution of trantulas could have evolved a solution to that problem.. out of context to original thread apologises, however to think tribal people who claim to encounter these 5 foot beauties time to time cant all be crazy.. perhaps more investigation into the congolese needs tobe done? and recently i would surggest perhaps spiders are evolving at a rate which we're only noticing when we hear of spider attacks in india... bizzare.. gigantic webs in rain forests, and spiders working in a community thought previous there all cannibals? anyway food for thought??

 

[Poec54]

Spiders are mostly water; humidity helps them retain internal fluids, which in turn would promote growth.

 

[jthorntonwillis]

Re: Tarantula ultimate size

But to argue the obvious,look at Coconut crabs...They are Gigantic,live in the Carribean,where the o2 concentration is probably one of the best on the planet...so why aren't there correspondingly huge Ts' ?Methinks as Pp said ,the skeletal structure will not support more weight(mass)

 

[EulersK]

I understood his point. I still don't find it a compelling one. How different can the oxygen concentration be compared to your room?

There are currently medical procedures used to treat cancer, iron deficiency, thyroid issues, etc. that involves putting a person in what amounts to a giant test tube. The tube is then filled with a high concentration of oxygen under slowly increasing pressure. The result? Numbers that are analogous to 150% oxygen in the tank (more pressure allows for more oxygen molecules, allowing for above 100%).

The question is whether putting a tarantula in one of these would increase growth. I'm going to say no. Why? The bug would probably implode first. Remember, exoskeletons don't do well under unnatural pressures. Our squishy bodies allow for contraction and expansion - not so much with tarantulas. Hell, they have to cast aside their skin before they can get bigger.

But let's assume you wouldn't have a tarantula grenade if you could pull off this experiment. I think jatefbe is right in saying that higher oxygen levels have allowed for HUGE bugs in the past, but that is because they evolved the ability to utilize it. Modern bugs probably wouldn't grow faster, and they certainly wouldn't be much bigger, either. The experiment downplays the importance of DNA in growth styles.

 

[natebugman]

I'm going to agree with those that are saying increasing the oxygen level is not going to have any effect on growth rate or maximum size. The arthropods that grew to larger sizes millions of years ago evolved the ability to use that higher level of oxygen allowing them to grow larger. The tarantulas of today have evolved to survive and maximize the efficiency with which they use the amount of oxygen in the air of today. If you give them more oxygen, I don't believe that it will allow them to use more. Now give them more oxygen and their offspring and their offspring and their offspring...for millions of years and then you'd probably see a difference. If you were doing this experiment with aphids, there could be a much faster change in the size/growth rate due to the small generation time, but tarantulas, unlike aphids, are not born pregnant.

As for the idea of giant spiders...it could not happen unless there was a change in the gravitational pull of the earth, or they were aquatic, or some evolutionary change in the exoskeleton making it much, much lighter and stronger. The problem is that as the spider gets larger, the surface area of the exoskeleton increases as a square while the volume/mass increases at a cube. So, a spider that has a cephalothorax 1" by 1" by 0.25", then the surface area is 1 square inch and the volume is 0.25 cubic inches. A giant spider that has a cephalothorax 8" by 8" by 2", the surface area is 64 square inches while the volume is 128 cubic inches. So, as the spider gets larger, the mass of it increases faster than the surface area. To lift the greater mass, the spider must develop more and larger muscles that attach to the surface area of the inner surface of the spider, but the surface area increases at a much slower rate. At some point, the spider's required increased musculature will have no area to attach to, leaving the spider unable to lift its own weight or move.