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Sorry: I made a mistake or didn't express myself well: actually the DVD I was referring to (Caring for Tortoise Eggs and Hatchlings) showed various well-formed shells, with and without the keratin layer. and one with the plastron removed to show a good spine formation. Deformed carapaces were depicted with living specimens and the commentary encouraged us to imagine the carapace structure, but didn't show it with cross sections.

So I'm still guessing what pyramided scutes lookl ike. Presumablly, if the problem is calcium deficiency, they're not made up of solid bone, ie thickened with extra calcium to make the pyramid shapes, but more like "bubbles" of thinner bone material?

And why do they develop like that (in physiological terms)?

Stuart

OK. This may help.




These show exactly what is going on. In brief:

Where there is a lack of calcium, or D3, or any other problem that results in an inability to absorb and utilise calcium, the bone tries to compensate by becoming thick, fibrous and porous instead of thin and dense. This is why the condition is sometimes also known as "fribrous osteodystrophy". You can clearly see the fibrous, coarse, and weak bone here. It is akin, in many ways, to osteoporosis. Also compare with "rickets". The results are very, very similar. Look again now at the healthy section I showed previously.

In these sections you can also see the areas directly beneath/inside the 'pyramids'.

I would love to see pictures like these of 'power-raised' juveniles that don't show the slightlest external sign of pyramiding.

Thank you very much for the info. Really interesting.

Thanks, Andy.
This makes it much clearer.

Stuart

Marcos mentioned water balance and I think it is interesting.
Trying to find a relation between low relative humidity and pyramiding, one could think that a high humidity environment helps to avoid dehidratation of hatchlings, one cause of acute or chronic renal failure (CRF) . With a renal failure you can have a secondary renal hiperparatiroidism, one cause of MBD.

If this was true (maybe dehidratated animals die first from whatever else before manifesting an MBD) an animal with chronic renal failure would still grow, in which case there could be some pyramiding, or it would be too unhealthy to grow and you would only notice softening of its shell and carapace?
What do the animals that you have found with chronic renal failure look like?

In advance that I don´t think that it is necessary to maintain humid conditions in captivity to avoid dehidratation and that this would not explain why, like some say, an animal kept in a high humidity environment and a high protein diet does not develop pyramiding.

Jordi

“it appears to involve a dehydration of the animals that, for currently unknown reasons, is not compensated by the oral intake of water” (Kruger, 2008).

No comment!!!

Kruger, E. (2008) Moist Root Shelters for Hatchlings. Radiata 17 (2), 14-18

Jordi, that's what I had read about the relation between water balance and calcium metabolism, and then pyramiding.

Regarding your last sentence I have seen 6 months Testudo hermanni that were huge at that age. They were raised at very high metabolic rates (food, calcium, lighting, temperature) and they were completely smooth. I don't know about the state of their liver or kidneys, about their long term survival, about their bone density, I just know I wouldn't try to do that with my own animals but still, I would love to know the reasons and undestand the whole process. That's why I suposse it is a multifactorial issue. I am just talking about the external appeareance, not about the health of the animals or the suitability of those methods. I am sure interesting conclusions could be made.

It is not related to water balance. The remark by Kruger is very informative:

“it appears to involve a dehydration of the animals that, for currently unknown reasons, is not compensated by the oral intake of water” (Kruger, 2008).

What you have to consider here, is that neither the authors of the original paper, nor any one of several others (including Kruger) who have commented upon it, have produced any credible evidence or even a coherent theoretical mechanism for some strange, unknown biological process that affects tortoises (not even turtles) and no other animal. Whatever it is they think is the cause - they cannot explain it! They have produced some weird, and incredible theories, however:

"dehydration reduces the intracellular and intercellular pressure on the soft cartilaginous tissue at the growing gap area”..... “A collapse of this tissue around the gap might be caused by this low pressure. If tortoises are dehydrated for a longer period, the tissue becomes ossified and the collapsed “valleys” between the central parts of the plates are fixed permanently” (Weisner and Iben, 2003).

Think about it. Dehydrated to the point your living cells "collapse".. and become "ossified" ...... OK. An Egyptian Mummy, maybe?

Also, in that state, even drinking water does not help? I think we are talking about "Return of the Living Dead" here!

Obviously, there can be a link between renal dysfunction and bone formation, as Jordi states. Renal secondary hyperparathoidism. However... that is not the case in the vast majority of these animals. It is comparatively rare in tortoises. Where it is present, you would also get clear indications and (usually) additional symptoms typical of renal failure and an increase in serum parathyroid hormone (PTH).





Andy

Don't know about these "forced" (what Marcos calls "power-raised") tortoises that are apparently smooth.

I'm still trying to understand the "evidence" of those (such as the Fifes) who claim increased humidity for hatchlings and little ones prevents pyramiding. (cf Jordi's question about the "relation between low relative humidity and pyramiding") Their results seem incontrovertible. But how can external humidity affect internal bone structure? Pyramiding has to be caused by dietary factors,as Andy has just very clearly argued in this thread. Yet Fife and so many others keep arguing that it's to do with humidity.

Tonight I've just been reading Andy's article about microclimates, referred to in another thread.
He comments that in the tortoises allowed access to suitable microclimates:
"Growth is relatively slow, and carapace development is very smooth and free of ‘lumps’ or ‘pyramiding’."

This seems to support the "humid-hide argument". More than seems. Does?
But if it does (and Andy will clarify this for us, I'm sure) could it be not for the reasons the humid-hide people argue? (Well, they don't argue, they just assert that it's not diet, but humidity, as if there's a direct connection). But perhaps there is a connection, but less direct, more subtle,as Andy appears to have already set out here (TT Article: Microclimates in Captivity)

"Tortoises maintained on flat surfaces where burrowing is not possible, on the other hand, lose fluids via evaporation very quickly, their core body temperatures vary much more widely and more rapidly, and they tend to be more active. This last property is not necessarily advantageous to long-term health, as the main increase in activity is seen in feeding. Animals reared in these conditions therefore tend to grow faster and hence are far more susceptible to developing mineral and trace element deficiencies, especially those implicated in MBD, or metabolic bone disease."

Is this why the humid-hide breeders raise non-pyramided tortoises? They've provided a particularly useful micro-climate! (?)

Stuart

The hides/scrapes I am referring to are not "humid" Stuart. Measurements of such environments in the wild consistently place them in the range of 35-60% RH (max). The hides being recommended by proponents of the "humidity" theory should, according to them, be close to "100% RH at all times".

The key reasons I recommend providing suitable burrow/scrape microclimates are:

1) To prevent chronic dehydration via cutaneous evaporation and respiration;
2) To encourage natural behaviour cycles, including longer dormancy than is typical in captivity; this in turn tends to reduce the over-feeding often seen in captivity, and hence, contributes to better overall growth. This aspect has nothing directly to do with the level of RH available.

It is extremely difficult to achieve really good bone formation on high growth-rate regimes. This has been proven again and again in many different kinds of animals. For example, this is a big issue in the thoroughbred horse breeding industry where rather than MBD it tends to be known as Developmental Orthopedic Disorder (DOD):

"Rapid growth seems to be one of the major factors in the development of DOD. The larger the body size and the faster the growth rate the greater the risk of DOD developing. The high-risk period for the development of bone and joint related abnormalities appears to be from 3 to 9 months of age. This correlates with the peak of lactation in the mare, through weaning to yearling age. During this time growth rates can easily be boosted above average by a combination of overfeeding and inadequate exercise"

"High-energy diets lead to faster growth rates and larger body sizes. High-energy diets fed to weanlings have been shown to consistently produce DOD lesions. Feeding excessive amounts of grain to weanlings or allowing access to unlimited amounts of lucerne are two feeding practices that can result in too much energy in the diet. Apart from being high in energy grain is also low in calcium and high in phosphorus which can lead to imbalances in these important nutrients in addition to high growth rates"

Tortoise keepers - take note! The above applies 100% to tortoises as well. Lucerne of course, is a key ingredient of most pellet tortoise diets... The advice on preventing DOD in horses is, word for word, exactly what we have advocated for tortoises.

"It is better to aim for slow, steady growth rates rather than to feed high energy diets"