Keratin and Pyramiding
Reprinted from email with permission from Paula Elis. Morris

The Malphigian cells are responsible for the production of keratin and lie under the scutes, the turtle's "skin" (its pattern on the carapace). It's like human finger and toenails, but while ours generates from a root at the first joint of our digits and grows outward, the keratin on a turtle/tortoise grows concentrically and is very soft until it hardens upon exposure to air. It is hypothesized that covering it with over-the-counter treatment preparations may prevent necessary hardening. This keratin "skin" can also bleed. Keratin is generated in a ring that raises slightly once it's stopped growing, producing the annuli. Bumpiness or pyramiding can occur more readily since the keratin is added over the entire surface of the scute from below, growing as the exoskeleton underneath it grows.

Growth varies, so determining their age by the annuli doesn't work. My 1996 box turtle hatchlings "hibernated" in their terrarium in an unheated room and they came out of hibernation with those white rings that indicated to me that they'd grown while asleep. Perhaps it just wasn't cold enough for them to slow the growth process.

Information I heard about at the Herpfest states that the captive diet of hatchlings is going to be excessive and cause pyramiding, no matter what. It has come to light that a hatchling's yolk sac produces nourishment for upwards of 9 months to a YEAR in the wild. A study on desert tortoises was done (I think this'll be presented soon, and I know CTTC had a speaker, a graduate student, who did research on this and the conclusions are amazing). Since protein occurs in both plant and animal matter, the bumpiness would cover all terrestrial species who are fed by attentive keepers, me included, if the yolk is also providing nourishment.

My herbivore hatchlings are fairly bumpy--perhaps from all those greens and weeds, while my three-toed box turtle hatchlings are perfectly formed because of their primarily-night crawler diet; they nibble at veggies, but prefer the live stuff. The general perception is that hatchlings need to eat often to grow to a size that allows them to ossify (harden) and protect themselves from possible predators. But if the yolk sac reabsorbs where we can't see it and continues to provide nourishment like it seems to do for desert tortoise hatchlings, is it a regional adaptation, or--and this is more likely--is it applicable to all terrestrial/semi-aquatic animals?

I'm trying to understand hatchling development. It's such a fascinating area of study and, now that we're producing our own hatchlings from the wild-caught parents, I think it's going to be the anomalous development of our hatchlings that will educate us towards what's the right thing to do. As natural as possible isn't always... possible. We have so much to learn.

Also here is a great site:

http://www.turtlestuff.com/pyramid.html
 

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