# What determines shell color for tortoises???



## TortieLuver (Jul 15, 2011)

So another forum member brought up a very interesting question/topic and I thought it would be good to start another thread and hear everyone's thoughts on this question:

Hi Christy. Looking at the picture with all your leopards gives me a chance to ask a question I have been wondering about. They are all different in coloring. Have you had them all since hatchlings? Have they kept their original coloring, ie. blacker babies are darker adults, lighter babies are lighter adults? Or has their original coloring made any difference in their final look?

Read more: http://www.tortoiseforum.org/Thread-Somebody-s-Hungry#ixzz1SFS4wV7l

With referring to Leos, I also think you have to look at the subspecies, as there are varying differences in shell pattern and color between a pb and pp. I have noticed that many of my hatchlings I have raised up keep their same color and the ones that are lighter stay lighter and the ones that are darker go darker. However, I stay in contact with people who I have sold my hatchlings to and I am quite surprised sometimes when I see them and they are either much darker than they were when I had them or have even gone lighter (blonde). 

The question is having a blonde/high-blonde genetic or not? Is it nurture or nature sort of speak? Environment or genetic.

I have read prior threads on this subject and some beliefs were that temperature played the major role in determining the shell color/pattern. That when kept in the 70s during the first couple years they will be darker and those kept at an overall 24/7 temp being higher 80s-90s will have lighter shells.

Then I spoke awhile back with another forum member and they said this, "The leopards will grow a lighter color if they're grown rapidly; even if they're grown rapidly in cooler or warmer temperatures. They tend to grow rapidly in warmer temps, but if they were growing rapidly in cooler temps, they would still be light in color (meaning, it's based on the growth rate, not the temperature). I don't think light color is genetic at all. 

I would like to hear other opinions on this topic


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## yagyujubei (Jul 16, 2011)

I guess I don't get the whole darker/lighter thing. Leopards are black and white. Are you saying darker means having more black in the pattern? If you see a zebra with more stripes, do you say it's darker? No. Of course the pattern is genetic, same as stars and radiateds. When I see these threads, usually half the answers are reattern, and half are re:darker color in the "white" areas, which is environmental staining. How growth rate relates to shell color doesn't make a bit of sense to me at all. What people refer to as "rapid growth" is really just normal growth, in fact I believe that slow growth is a pyramiding factor. Just because the current climate in Africa produces slow growth in the wild does not mean that that is the ideal, or even close to it. I would say that you might be feeding too much if the tortoise is getting FAT, not if it's growing faster than those who are fed less.


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## paludarium (Jul 16, 2011)

A field research in northern Tanzania showed that wild leopard tortoises living in the drier habitats tended to have the sparse carapacial coloration, while animals in the wetter, darker habitats seemed to have buff coloration with black spots. 

http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2028.2000.00237.x/abstract

According to the author, shell colors of the tortoises in drier habitats are lighter, and those in wetter habitats are darker. I just don't buy that. There are too many variations between dry and wet climate regions, e.g. humidity, shelters, foods and UVB. Temperatures and growth rates, probably too. 

Erich


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## DesertGrandma (Jul 16, 2011)

Hi Christy. Thanks for re-posting the question. Seems the answer is not a simple one. Anxious to hear more...


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## N2TORTS (Jul 16, 2011)

Many folks , think tortoise shell is just bone, it is actually covered with living tissue composed of keratinized epidermis covering the underlying dermal plate which is itself connects to the chelonians vertebrae and rib cageâ€¦..
In general, reptiles have two sets of cells that produce color, the melanocytes and the chromatophores:
Melanocytes are present throughout the basal layers of the epidermis. During the skin-renewal phase of epidermal growth, the melanocytes send pseudopodia into the melanin-bearing keratocytes to transfer the melanin to the new cells. In crocodilians, iguanids and snakes, these melanin-bearing keratocytes are in the ÃŸ-layer; in other reptiles, they occur in both the a- and ÃŸ-layer.
The chromatophores are layered upon one another in the outer portion of the dermis. A layer of xanthophores (yellow pigment cells) erythrophores (reddish-purple pigment cells) and other fat-soluble pigment cells lay just under the basal membrane of the epidermal layer. Under the xanthophores are several layers of iridiophores which produce iridescent colors in the range from blue to gold, as well as white (guanophores and leucophores).The presence or absence, and density and distribution when present, of the melanocytes and chromatophores within each layer will determine the color of the reptile.

HAPPY TORT~N 
JD~


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## Yvonne G (Jul 16, 2011)

Yeah...what he said.


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## Tom (Jul 16, 2011)

JD, did you really write all that? 

In my group of Gpp, I have three that are growing slower than the rest. My only "blonde" is one of my smallest, slowest growing torts, and they are all wet and warm all the time. They all started together in a 3x5' tub and now they are all in a 4x8' enclosure. They have all been together there whole lives and eaten the same foods and had access to the same graze, etc...

I think Erich might be on to something there, because ever since I started the "wet" routine, all of my sulcatas have shown much darker new growth than what I saw in the past.

In Leopards, from what I have seen, there is no consistent pattern. We see blondes from time to time from a variety of environments, feeding routines and temperature gradients. This leads me to think its genetic. However, ALL of the leopard tortoises that I saw down in the generally cool, wet weather of the Southern Cape of Africa were very dark. I saw about half a dozen wild ones and several hundred captives and ALL of them were dark and all of them were living outside. We had some days where the high reached into the 80's or 90's early in the trip, but as Fall set in, toward June, we had some days that didn't get out of the high 40's or low 50's, followed by nights below freezing.

SOOOOOO, lots of conflicting info here... I don't have the answer, but there is what I've seen.


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## N2TORTS (Jul 16, 2011)

Tom said:


> JD, did you really write all that?



No " Sally " Did .........





emysemys said:


> Yeah...what he said.



ha ha .... Emy'....hey they asked !


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## Yvonne G (Jul 16, 2011)

Well, then...that is one intelligent 'too!


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## TortieLuver (Jul 16, 2011)

Thanks guys to everyone sharing. I thought Joy (desertgrandma) was on to a great question that I'm sure many people have wondered about from time to time and it's nice to hear everyone's answers, even if they are opposite or across the board, as it is all informative

JD~was that in English Great information!![/font]


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## N2TORTS (Jul 16, 2011)

TortieLuver said:


> Thanks guys to everyone sharing. I thought Joy (desertgrandma) was on to a great question that I'm sure many people have wondered about from time to time and it's nice to hear everyone's answers, even if they are opposite or across the board, as it is all informative
> 
> JD~was that in English Great information!![/font]





Cockatooish.....and about 50 research papers later ....." Sally " reads and writes alot! 
and Tom ,your right it holds true in the genes and passed down the family chain. But at one time there was an initial building foundation to acquire the variance of colors within any species.
Look at it as a " micro " evolution, within the different locals where they may be found and most likely due to stay camouflaged with the surrounding area where they reside.


JD~


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## Saloli (Jul 21, 2011)

N2TORTS said:


> Many folks , think tortoise shell is just bone, it is actually covered with living tissue composed of keratinized epidermis covering the underlying dermal plate which is itself connects to the chelonians vertebrae and rib cageâ€¦..
> In general, reptiles have two sets of cells that produce color, the melanocytes and the chromatophores:
> Melanocytes are present throughout the basal layers of the epidermis. During the skin-renewal phase of epidermal growth, the melanocytes send pseudopodia into the melanin-bearing keratocytes to transfer the melanin to the new cells. In crocodilians, iguanids and snakes, these melanin-bearing keratocytes are in the ÃŸ-layer; in other reptiles, they occur in both the a- and ÃŸ-layer.
> The chromatophores are layered upon one another in the outer portion of the dermis. A layer of xanthophores (yellow pigment cells) erythrophores (reddish-purple pigment cells) and other fat-soluble pigment cells lay just under the basal membrane of the epidermal layer. Under the xanthophores are several layers of iridiophores which produce iridescent colors in the range from blue to gold, as well as white (guanophores and leucophores).The presence or absence, and density and distribution when present, of the melanocytes and chromatophores within each layer will determine the color of the reptile.
> ...



Thats good, to add a little to that some yellows, most oranges and some reds are carotenoid based pigments which a photo sensitive. That means they tend to break down over time due to exposure to light. Think of the goldfish that turns white when fed a poor quality food then turns back to orange when it's diet is improved.


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## DesertGrandma (Jul 22, 2011)

This is all very interesting and much more complex than I ever expected. So, to break it all down, when you acquire a hatchling you really have no idea what it will look like as an adult. It may or may not look like it's parents when it is grown up. It would be interesting to see more photos of leos as adults alongside pics of them as babies, climate they have lived, what their diets have been, etc. etc. Even hatchlings within the same clutches seem to grow at different rates. It's the old nature vs. nurture question.


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## almondthomas (Jul 26, 2011)

Tortoises shell color are very different we have seen.Tortoise shell covered with living composed of the underlying dermal plates which is itself connects to chelonians vertebral cage.


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## HLogic (Jul 26, 2011)

Following up on what Sally said (as if our brains weren't bleeding enough already)...

Tortoises may vary somewhat from their genetic base coloration but have much less ability than certain other organisms to alter their coloration due to acute environmental influences after embryonic development is complete. The cells responsible for the generation of chromatophores, chromatoblasts, are derived from the neural crest in the embryo. These cells migrate from the neural crest to their respective locations and dermal layers early in development. If the migration of these cells is interrupted, disrupted or otherwise altered the overall coloration and patterning of the individual will be affected (e.g. piebald morphs).

There are chelonians that change skin coloration and patterning brought on by environmental factors. Males of the genus _Indotestudo_ and _Batagur_, for example, are well known for the changes in skin coloration during breeding season. These changes in coloration and pattern are hormone-mediated and are produced by the translocation of pigments within the chromatophores. The head coloration of Red-Footed tortoises is also known to change, typically from red to yellow, during the development from juvenile to adult. The cells responsible for carapacial and plastral pattern and coloration apparently do not contain the mechanisms for dynamic color change, a.k.a. physiological color change. This patterning and coloration is essentially permanent although may be affected by exposure to sunlight, chemicals, disease, etc.

With respect to general dark vs. light of regional populations in those species that have variable coloration, it is not atypical for lighter colored specimens to be found in areas where the intensity or duration of sunlight is greater and darker specimens in more shaded areas. Regions of drier conditions tend to have less canopy and as a result are hotter whereas wetter areas have greater canopy coverage thus more shaded and cooler. In this case, the coloration can be related to thermal regulation - lighter colors reflect heat, darker absorb. It is genetic within the population but of course there are always individuals that will counter the norm. Considering the interbreeding which has occurred across many of the populations in captivity, it is no surprise 'unusual' variations might be found.


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## DesertGrandma (Jul 26, 2011)

Searching around on the web, it is interesting to see some leopards that people say are snow leopards. To me they appear much the same as some of the pardalis pardalis babies that are getting a lot of new white growth on this forum. But the one that JD recently posted is definitely very white all over, with a just a touch of black markings. Is it possible to know a snow leopard when it is a hatchling, or is that something that takes time/growth to know for certain? Thanks everyone for posting so much interesting information!!


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