Melody,
I feel for ya lady!! My tank that is infested is over a year old and they are like cockroaches!! They multiply fairly fast. They are not a major problem, but I had some polyps that really looked sick after they had been open & pretty for a month or so and I read in one of my books that one of the signs of polyps not doing so well is the constant presence of bristle worms and sure enough when I when into the tank and lifted just 2 rocks where most of the polyps were, under the rocks were lots of bristle worms! I do pick them out to keep the amount in somewhat control. Now that I have removed a few huge guys and a hundred or so smaller ones, my mushrooms & polyps are open and seems to be a lot happier!! (plus with a 100 less in the tank, less chance of me getting stung by those bristles!)
I really am not 100% sure about the segmented thing, but I do know that I have pulled some out of rocks that I didn't get the whole thing and the larger piece in the rock has lived!! Weeks later when I did manage to get the bugger out, you could still see the damaged end and also see where it was healing...........
Good Luck with the Bristles!!