UV absorption

[Anyfoot]

I don't think we know the answer to this but
I'm interested in your opinions on this subject please so we can at least make an educated guess.

What body parts of the tortoise can actually absorb UV rays?

There's basically, skin, scales and carapace.

I'm thinking skin is a definite yes.

At first I thought no for scales, but then I'm thinking what about snakes that are totally covered in scales so yes, then I'm thinking maybe snakes rely totally on prey for Vitamin D so now I don't know.
Is there a reptile that is covered head to toe with scales and is a herbivore?

I just don't know for carapace. Could it be the new growth that'a going through the supple stage absorbs UV and the old hard keratin does not.

Thoughts please.

Thanks.

 

[Tim Carlisle]

I could be wrong here, but it is my understanding that they absorb little, if any, UVB through their shells. The shell itself is made up of keratin similar to human fingernails. This can block absorption. Ever see water turtles in the wild sunning themselves with their head and legs stretched out? It gives their skin maximum exposure to the sun's rays. Anyway, that's kinda what I read a long time ago.

 

[ColaCarbonaria]

Good question, and I have no idea but you have to think there is something to the outstretched limbs. The 50 pound sulcata certainly does it, as do the redfoots, but any creek or pond you pass around here the cooters and sliders covering th rocks and logs sunning all have their limbs stretched out. Honestly I have always attributed the act to the animal thermoregulating itself and never really thought of th uv aspect!! Sun Worship.

 

[Anyfoot]

I've always been under the impression that they don't absorb UV through the carapace.
It got me thinking the other day when we went to the zoo and the Galapagos torts were sat under uvb lights that were set about 48" above the carapace. As they sprawl out their limbs and head must be another good 12" below the carapace height. That's the limbs 5ft away from a UVB system that projects UVB 4ft at its max.
Also there are many on FB that assume they do absorb UV through the carapace.

How many times have you seen a large species sat under a UVB lamp warming a couple of scutes up. Is this providing a source of vitamin D or just heat?