shell disease?

noticed a small light colored circular patch on my O. s.'s tail tonight. it doesn't look eaten away. is this the beginning of the shell disease they are prone to?
Possibly. It usually starts on the carapace and top of the abdomen, but if there was damage to the telson, it could start there.
My female OS arrived in the mail with clear signs of shell disease - several small, discolored ulcers on her back (carpace? thorax? whatever it is called . . .). The ulcers seemed to grow over time. She has had a 30 gallon tank with a long pvc tunnel all to herself. Last week she molted. She has been shy about coming out of the pipe, but yesterday she took some food and it looked like the ulcers were gone. Is it possible that she has healed?
Sorry, I never got around to taking pictures of shell disease. Next time I have and O.s. with shell disease, I'll try to get come close-ups of it. (Hopefully, that won't be any time soon.) One of the G. chiragra used in "Fastest Claw" had it, if you have access to that program.

There may be different "shell" diseases in different species. Hemisquilla frequently get a black shell rot. O. scyllarus get the rusty brown lesions that appear to start out as a bacterial infection.

If the ulceration does not penetrate the newly forming cuticle, animals do heal. Usually you will see some discoloration and perhaps some "bumpiness", but that will clear up during the second molt.

As I have said before, there is some danger of this disease spreading from on animal to another, but the use of a uv fliter can greatly reduce the this.

it is a rust colored mark, he wont let me get a good enough look to tell for sure, but it looks to just be on the surface and hasn't eaten away at his shell pretty much all i can do is keep his water quality good, and hopefully he'll fight it off?
Well, I got a good look at her and the lesions are GONE! I'm amazed. I thought she was history.