tailess?

There are quite a few (4 I believe) kinds of manx rats depending on body shape and exactly how much of the tail there is. Some manx have no tail vertebrae and some only have a few. Where did you get him from? Are you sure he's a genetic manx and just hasn't been docked?

I've heard some pretty nasty stories with the breeding of them, but the most common issue seems to be rectal prolapse. Just watch his poos I suppose. If he ever seems like he is having trouble, get him to the vet.

It sounds like your are right, that she is genetic. That's good. At least you don't have to worry about it too much then.

I hope to see pictures of her sometime! Does she have any friends?

In your case, it''s the age and not the procedure itself that would be dangerous. There is a higher chance of something bad happening with anesthesia in older rats, just like with older people. Neutering is just as safe as any other surgery, but it's still a surgery.