Leopard Tortoise

[Lisamn]

And how often do you supplement with D3 if not providing UV?

[Lisamn]

Just done a (very brief) bit of research and it seems that tyrosinase activity would tend to decrease at approx 37 °C, therefore melanin production would probably be inhibited, so I guess torts kept at higher temps than this might show effects with regards to colouring.

[EJ]

I have to disagree with you on the calcium content in the keritin layer of the shell. I believe that is how the shell gets it's white color... why a Sulcata lightens up... the source of the those squiggly lines that so many keepers or concerned when the keritin layer takes up calcium. I would think the calcium would add hardness to the keratin layer of the shell... which is why I believe the scutes become brittle and less plyable as they develope.

Sorry I don't know the mechanism... but... there is a change to the structure of the scutes on the shell that I believe is the uptake of calcium.

I think we could have a better conversation if you could dumb it down a little.

It seems like you are trying to impress more than properly communicate. I hope you don't take offense at this. I'll admit that I'm really ignorant when it comes to the vocabulary you are using and I have an AS degree in biology along with priding myself in having an extensive herp library... not to mention access to the internet. I get the feeling you are trying to say some neat stuff... I'm not getting it all without breaking out the books or researching every other sentence.... and I don't have time for that until Tuesday.

Originally Posted by Baoh

To clarify, for leopards under higher heat indoors, with or without UV, they were higher white in my observations. For sulcatas kept indoors without access to sunlight, even with heat, they were darker in my observations.

I do not know if it is actually a bleaching effect in dark sulcatas placed outdoors that lighten, but I do observe them to lighten with prolonged exposure to sunlight regardless. I do agree that it probably is bleaching in those cases, as it goes for human hair, but I have not tested that.

Keratin has no significant calcium in it. Keratin-based tissue is typically unmineralized (including the beta-keratins we would be discussing in relation to chelonians). Calcium would have no reason for incorporation, as it would interfere with the toughness of the polymerized end product of hydrogen bonding that characterizes the strength of beta-keratin sheets. Anything extra added means something less of a stable construct. Pigment is a fair trade because the cost of including it is in exchange for an improvement in crypsis and thermoregulation potential. Calcium would yield what advantage in the resultant structure? Nothing readily apparent to me. It would be a double cost. 1) It would be at the expense of other systems that utilize calcium such as structurally (skeletal) or as an electrolyte (or in muscle contraction). 2) It would be at the expense of structural integrity of scales, scutes, beaks, and claws. Also, what would be the mechanism for the keratin to have calcium incorporated later? It is dead beyond the finest growth layer. There is not a transport mechanism such as microvascular network beyond that very thin growth margin. It relies on self-assembly and H-bond strength to render its tough nature. There would be nothing to move Ca from A to B at a point beyond initial assembly, so there is not a way for there to be a step that comes later unless it (the conduit) has not been revealed yet (and having looked at photomicrographs of scute structure some time ago, I did not see any).

Yes, melanin production can be partially in response to UV exposure, but it can also be expressed in ectotherms due to a lack of light or heat. Darkening makes for a more effective ability to absorb and retain thermal energy. Animals with a more rapid and transient response achieve a quicker effect via chromatophore (especially melanophore) shifts (more accurately, pigment translocation). Many lizards, for instance, show this effect when cold or otherwise distressed.

As a mammal, my hair has significant visible melanin regardless of exposure (and lightens with exposure). My skin's visible content increases in response to UV exposure. My colleague from Kenya's apparent level does not visibly shift like mine.

I measured the enzyme's functionality in terms of a few things. One was simply enzymatic kinetics work via substrate consumption/alteration rate over a time course with known starting levels of substrate and measurable end products (as well as some ITC binding work). I also looked at unfolding or melting events, as well as looked for hysteresis, via differential scanning calorimetric methods and dye-labeled fluorescence. Finally, I looked, via an electrophoretic method, at molecular weight compared to known markers and observed, post-purification and temperature cycling, what kind and percentage of degradation products (dimers, higher-order aggregates, and fragments) resulted. I may pick it up some day again, as it is sort of novel, but I am more of a product driven kind of guy, so my interest is more related to the products I develop, patents I might be awarded, and stuff like that. I do not have a definitive super-strong answer based on what I did. More of a body of evidence supporting a particular hypothetical hunch I had. To make it ready for publication in a highly reputable journal would take more resources than I am currently willing to devote, IMO. Without giving my work away, that should provide some measure of an answer to your question. I hope it did, although it may require some familiarity with these analytical techniques to glean the full value in/of the response.

[TillyTortoise]

What's he saying please?

[EJ]

Hopefully he is not insulted by my request to dumb it down because it does look interesting and a source of interesting debate.

I think I got the gist of it but can't respond in like fashion without looking up exactly what he's saying.

There's alot of jargon that I recognise which is derived from lizard and snake breeding that I see when discussing color morphs... I kinda tune it out when I get to that level... that which I don't understand.

Originally Posted by TillyTortoise

What's he saying please?

[Lisamn]

Originally Posted by TillyTortoise

What's he saying please?

I understand the tyrosinase/heat stuff (I think) and how it could possibly alter shell colouring (after doing a bit of my own reading). Like EJ though, will have to go and do a bit more reading to get a better handle on the keratin/calcium point.

PS - do you, or anyone else reading this thread, know what RF marbling is?

[EJ]

Cherryhead tortoises are capable of develping a leopard like pattern on the shell. It is most evident on the plastron. This pattern is the most distinguishing character feature of the Cherryhead Red Footed tortoises.

Originally Posted by Lisamn

I understand the tyrosinase/heat stuff (I think) and how it could possibly alter shell colouring (after doing a bit of my own reading). Like EJ though, will have to go and do a bit more reading to get a better handle on the keratin/calcium point.

PS - do you, or anyone else reading this thread, know what RF marbling is?

[FLINTUS]

Annoyingly I'm not allowed to post links to other forums but here are pics of two very high marbled cherry.



The keeper is American and I believe has a website called the tortoisecove. He has some stunning torts including hypo redfoots.

[Lisamn]

Originally Posted by EJ

Cherryhead tortoises are capable of develping a leopard like pattern on the shell. It is most evident on the plastron. This pattern is the most distinguishing character feature of the Cherryhead Red Footed tortoises.

Ah, I see. RF = Red Foot. I should have worked that one out really, shouldn't I! Thanks.

And thanks to Flintus for the pics.

[EJ]

What are the conditions under which they are kept. You can increase the red by feeding foods high in beta carotene.

Originally Posted by FLINTUS

Annoyingly I'm not allowed to post links to other forums but here are pics of two very high marbled cherry.



The keeper is American and I believe has a website called the tortoisecove. He has some stunning torts including hypo redfoots.