That's new growth. It's perfectly normal for a wild caught tortoise that's not used to getting a lot of food all the time all at once to put on these wide growth lines.
I'd also like to address the growth on the top of the carapace. It looks to me as if you have this tortoise under a light that's too hot and too close to the tortoise. The new growth up topside is quite dry and burned-looking. Might be from where she lived before she came to live with you.
Russian tortoises come from a geographic area that has very little available tortoise food, that's why the tortoise has evolved to be such a small species. They have to wander over great distances to find food. When they come to live in a captive situation, they don't have to wander so far to find food, and they are given an abundance of it. So they put on a lot of growth. Nature tries to keep the silhouette of the animal the shape it's supposed to be, so that's why you see wider lines on certain parts of the body.
Thanks guys. Got such bad advice starting off. Needs a new tank then I think but in the mean time what should I do? Turn the light off most of the day and keep it on just enough for heat?
Thanks guys. Got such bad advice starting off. Needs a new tank then I think but in the mean time what should I do? Turn the light off most of the day and keep it on just enough for heat?
Not really.. looking at buying a tortoise table or making one. Going to get that sorted for her. I had no idea that was wrong or I’d definitely have changed it! Thanks a lot guys. It’s quite hard running a complex marine reef fish tank (plus a second marine fish tank with a Lionfish in) and School and a tortoise!! Ha, I’ll get her sorted!! Soaked her for half an hour today and she was having a drink so she seemed to enjoy it tonight.