WHY does humidity work?

[LeopardTortLover]

Okay, most leopard, sulcata, and any other tortoises that require humidity owners now know that high humidity levels are required for smooth shell growth. I know it has 'something' to do with keratin stacking, rather than the shell growing flat outwards.

But what is the key to humidity? Yes, wild hatchlings live in humid burrows, but what is the science behind humid air? Why does it cause the shells to grow smooth? Does it make the shell-cells slightly hollower so that new growth is flatter?

I can't put a reason to it, but i'm really interested in why it happens. Finding out this would help me to explain to my tutors at college why tortoises require humidity (im on an animal care course now and want to share this new-found knowledge.)

So... any science nerds out there?!

 

[Tom]

I have never been able to find an answer to this question, and believe me, I have looked.

I've heard all sorts of theories and suggestions, but I don't know if anyone knows the actual answer. I think it might have to do with interior cellular pressure. Kind of like "turgor pressure" in plant cells. Of course, my theory is just a guess too.

I would love to learn more if anyone has any knowledge of this stuff.

 

[Kapidolo Farms]

Hi,

I have a speculative answer, not one based on a lengthy lab trial series.

Bone and keratin compete for shape of the shell.

Keratin is composed of protein laid down as an extracellular matrix. It is not a living tissue like skin, it is like a mat of hair. But once those components of the matrix is made extracellular (think about two part epoxy) it is flexible for some time before it "cures" or becomes rigid.

The scutes grow out from their edges. Once laid down it can not be re-absorbed for other physiological needs.

The underlying bone is alive, vascularized tissue. The calcium in the bone can be taken from the shell, and used in other bones for growth. The bones in the shell are similar in appearance to a spider web under each scute. The web fills in over time until it is a complete shield. That web must grow in two directions at once, at the tips of each strand, as the scute gets bigger and inbetween the strands to fill in the gaps (those gaps are called fenestra).

The bone is also flexible, (think about braces pulling teeth into place in your jaw bone).

The moisture keeps the keratin from curing faster than the bone can grow. Low calcium in the diet will allow the keratin to win as well, to low, and the animal can no longer divert calcium from shell growth to limb growth, and that is one expression of metabolic bone disease.

In the wild this process is mediated by two things, much slower seasonal or annual growth, and the higher moisture of those places that neonates hang out in. As keepers we tend to try to push that growing without the annual slow down or dormancy (good or bad choice its own debate) and if a balance between the nutrients that provide one aspect of growth are out of balance with another, that too contributes to poor shell formation, and it happens more quickly,as we are not letting the rest period occur.

It is my POV, that with proper gut substrate, long fiber, seeds, grain hulls, and an abundance of nutrients, these animals can selectively absorb the nutrients most in demand by hormone and growth feedback signaling in the tortoises. I would say the anecdotal evidence for that is strong.

I also believe that certain genes associated with this process turn on and off, the genes them selves work on signaling too. If we perpetuate that first year of high growth (not necessarily the same 'year' as the first year of life) then those genes run a longer course, and help keep flexibility higher, so a pattern is not 'set' for further growth in subsequent years. This has been seen in other species with other physiological processes.

This too is anecdotal, but can explain why some torts never stop growing with pyramiding, while other do stop. Especially when associated with a change in husbandry.

The lab work to 'prove' these ideas would be a long expensive haul. This is just a guess, I wonder this too. I have read some of the literature about how keratin is laid down, these ideas fit within those studies, but are not 'confirmed' or 'refuted' by them.

Will

 

[Neal]

I agree with your answer Will, and it is what I have understood about the mechanism of pyramiding as well.

 

[Andrea M]

This is a fascinating thread, thanks for the information

 

[pugsandkids]

Will, wonderful explanation of your theory!

 

[mikeh]

Many thanks for the education Will. Wish there were more threads as such educating us about important inner workings of our animals.

I am noticing how well the tortoises regulate their intake needs of minerals. For about a week they will devour their mineral blocks, following about 2 weeks of ignoring the block. Then the this cycle is repeated.

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[Kapidolo Farms]

This is hardly any theory I would presume to call mine. I spend way to much time fooling with ideas in conversation with many folks here and elsewhere in one on one e-mails. At best I have done a mediocre job of condensing many peoples' thoughts and ideas into a few short paragraphs here. More often than not, the tone of the question enables the writing of answers.

Some really good questions have been hitting TFO lately. I am glad for that. Sometimes the energy here is not anything I can find traction on.

Will

 

[mikeh]

Will, based on that theory how would you explain pyramiding not occurring on the plastron?

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[Levi the Leopard]

Also, "humidity" isn't the specific magical answer. It's hydration. A young tortoise raised humid is well hydrated.
To literally answer your question I'd say, "Humidity works because it keeps them well hydrated and that hydration allows them to grow properly.". Then Will's answer explains further into the science of how that is.

There are those that have raised smooth tortoises by keeping them well hydrated without housing them in a humid environment, like you, right Neal?

I am going to re read through your post will...to try and really grasp it.

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[tortadise]

Also, "humidity" isn't the specific magical answer. It's hydration. A young tortoise raised humid is well hydrated.
To literally answer your question I'd say, "Humidity works because it keeps them well hydrated and that hydration allows them to grow properly.". Then Will's answer explains further into the science of how that is.

There are those that have raised smooth tortoises by keeping them well hydrated without housing them in a humid environment, like you, right Neal?

I am going to re read through your post will...to try and really grasp it.

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Good points Heather. I was merely going to touch on the humidity being a part of many. Hydration is one of them. Good UV is also another. Pending on husbandry and growth rates also can dictate how much hydration, minerals, calcium, exercise etc... that will balance the proper growth. As Will stated ounce the keratin grows or "expands" it stays. If less than par conditions are kept but still within a certain. perimeter the animal can still grow smooth but slower. Its very dangerous messing with what I like to call, controlled natural variable. Like a dry spell or drought or even extra cool spring in the wild. These can alter the growth of wild specimens. As well alter captive specimens. Or in lack of better terms different growth. Sometimes you will see pyramided wild tortoises. Or excelleratedly large growth rings or keratin layers. Kinda like a tree in a sense. Arborist can look at rings of trees and tell what drought, wet, or average seasons of growth trees underwent. You can also do somewhat the same with tortoises. But much more goes into a tortoise than a tree to keep it alive. Blah blah. My take on it.

Heather I have raised many young specimens of Sulcata without being enclosed and kept humid and achieved the same results of smoothness and good growth. Its easier to achieve best results by adding humidity as an aid of hydration in my experience. I prefer to use the easiest method, and that's more humidity with multiple soaks, semi wet food, early morning fogs, and hot temperatures.

 

[Neal]

Yes, I have had sulcatas, leopards, and stars grow smoothly without sustained humidity.

 

[Levi the Leopard]

Re: RE: WHY does humidity work?

Heather I have raised many young specimens of Sulcata without being enclosed and kept humid and achieved the same results of smoothness and good growth.

Its easier to achieve best results by adding humidity as an aid of hydration in my experience.

I prefer to use the easiest method, and that's more humidity with multiple soaks, semi wet food, early morning fogs, and hot temperatures.

Thanks for chiming in!

I also think it is easier to re create a mini Africa (for small sulcata and leopards) with the hot and humid chamber. This keeps them properly hydrated like it would if they had hatched in their native environment. I'd much rather do this than to house them dry and only try compensate their hydration needs with extra soaks.

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[Kapidolo Farms]

Re: RE: WHY does humidity work?

Will, based on that theory how would you explain pyramiding not occurring on the plastron?

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A few things come to mind,

1, I have seen abnormal plastrons. I dont know that I would call them pyramided.

2, the spine plays a role in pyramiding, it is more bone still.

3, it is more flat and a simpler structure.

4, as a base, the weight of the animal relative to its mass will keep it flat, like in a form.

5, secondary sexual charateristic, hormonal signaling, and in males it will change shape.

Swinging in the dark.

Will