Reptile & Amphibian Forums

I read your statements on tortoises getting heat from above vs. below.
Could you explain any more on that? What are the heat absorbing
panels (?) they have on their tops but not on the bottom of their
shells? Where do you get that info? I thought it was very
interesting, never seen anything on that. thanks, niki

Hi Niki.

Maybe "panels" are not all that accurate a description of the special areas that absorb the heat. Brian Pursall, in his excellent book "The Guide to Owning a Mediterranean Tortoise" calls them "pores."

The first idea I got about the existence of these pores was when I was a kid and my tortoise "Pierre" died. I thought it would be cool to keep his shell, so I soaked the shell in bleach to get rid of any flesh after his body rotted away. The bleach caused the top layer of the carapice to slough off. It came off in individual scutes. It is really weird, but the carapice is in two layers, one rough outer layer that we can see, the other white and smooth like bone that you can only see when the outer layer comes off. It was then that I noticed the tiny chambers on the underside of the top portion of the shell that sloughed off. They were hollow and filled with air. I didn't put 2 and 2 together at that time.

Years later, I talked to an old tortoise keeper who worked at a reptile shop who told me about them and what they actually did when I commented about the way one of the torts was basking itself under the heatlamp. About five years ago, I bought the above mentioned book and he talks about them there. There are also special blood vessels that are just under the shell that collect the heat from under the pores and distribute it throughout the body of the animal.

Those 2 sources are really the only times I have heard the pores mentioned. I will post some of what Pursall says in his book in another post. He is British, by the way.

The Chelonian shell structure is composed of three major layers that I can see. The top layer is composed of the Scutes which I believe is keratin. This seems to be secreted by the bone. The next layer is a sinuous layer that looks like it contains the blood vessels between the scutes and the bone of the shell which is the next layer. I believe those holes that you are looking at on the inside of the shell are the openings where blood vessels enter the bone of the shell supply blood to the shell. This is probably how the blood is warmed and returned to the rest of the body.
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Ed
Tortoise_Keepers-subscribe@yahoogroups.com
Trying to keep the fun in Chelonian care

There are holes for the blood vessels, but it appears to me (and others) that there are also holes that trap heat from the sun for the vessels to carry around the body.

If there were no holes like those described, how would the underside of the carapace get warm enough to warm the whole body? Only the very top would get warm, like a solid rock.

I have a few questions. This is not an attack. It is just questions. If what you believe is true, then how do other cold blooded creatures retain heat? Do snakes, lizards, Frogs, and others have a shructure to do the same?
What I believe is the answer to the second question is no they do not. I believe the answer to the first question is they use their blood system to move heat through thier body. This would be like with oxgen. Their blood when going through the normal cerculation parten is warmed by the heat source and transported throughout the entire body. That is why I believe that above heat source should not be the only heat source for any reptile. Ambeint heat is more important. Now that isn't to say that basking heat doesn't play a roll in good health. I would say that that has been proven over the years.
Have you ever picked up one of your torts after a long basking period? The top of the shell will differ from the bottom. Now have you ever picked up on from its native land? I'll differ to those of you who have done some herping outside of the us or in the desert. My thaught is that if you go to Africa and find a leopard tort sitting is the hot sun on hot earth, both the top and bottom of the sell is going to be hot.
Now this is just my opion!

Well, those are some good questions. I'll try to answer them the best I can.

Amphibians like frogs and toads really don't use heat from the sun to warm themselves the same way most reptiles, especially tortoises and turtles, do. They are less dependant on basking and just rely on ambient temperature or the temperature of the water. Snakes and lizards probably wouldn't need to have the kind of heating system a tortoise has because they don't have a shell to contend with. A snake or lizard has blood vessels right under the skin on their backs, so they can just heat their blood that way directly. Tortoises and turtles have a thick shell that interferes with the sun's rays, so they need to have a way for the shell to collect the heat and distribute it around the body.

If you pick up a tortoise after it has been basking for any length of time, it's top will be much hotter than it's underside, no matter where it is. That is because it is actually shading the ground where it is sitting, so that sand under it would cool off. The ground isn't just hot for no reason, it is mostly hot from the sun hitting it. I do not believe tortoises use the bottoms of their shells at all for heating. If they did, they would lay on warm rocks or pavement the way snakes and lizards do instead of direct sun basking.

Those are good answers. However, I beleive that reptiles overall depend on ambient temps alot more then we know.
I'll agree with your statement about snakes and lizards basking habits are different then tortioses.

holes that trap heat... hummm, I'll have to give that some thought.
Hey, If you are interested in some good Turtle/tortoise anatomy references let me know, I'll be glad to provide you with some good ones.
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Ed
Tortoise_Keepers-subscribe@yahoogroups.com
Trying to keep the fun in Chelonian care

I would love some. I am always willing to learn.
By the way I was waisting time while my wife shopped at my local Target. I went to my local Pet-not-smart. I was heart broken. They had a Greek in there that was realy wanting a home for X-mas, but my brain said no even when my heart was saying yes. It looked good, but was very light wieght. She was the largest I have ever seen. I asked the kid to get a fecal sent to thier vet, but you know how that goes. I have to tell myself that I can't rescue all of them. Have you heard thier latest marketing gimick. It is cald "Vet sellected". They tried to convince me that they employee a vet who makes all of thier selection of livestock for them. Not just thier store, but the entire company.

"The surface colors of the carapace are colors that absorb infra-red radiation. Also, the surface is covered with minute pores into which the radiation shines but cannot escape. This raises the temperature of the carapace.

The blood circulatory system of tortoises is different from that of mammals. In mammals, the blood flow is directed to the lungs and then to the main muscle groups and organs. In tortoises, a large proportion is directed across the back of the body, under the carapace, to collect the warmth and distribute it around the body."

He then goes on to mention the extreme importance of the number of hours of sunshine a tortoise needs a year. In England, there is not enough hours, having only an average of 1,500, while the Mediterranean has between 2,500 and 3,500 hours a year. He says tortoises in England and other areas where there is not enough sunshine hours must use artificial lighting to supplement the sun. Even the angle of the sun is important, he says.