I have a hundred or so of these things in my tank and I went through 40 or so pages on the hitchhiker thread on the other reef forum with no luck. There is two crossed in the middle of the picture. There is no body and they get thicker as they go out. I have seen one or two on the glass and they don't have a body or shell. They do reel in and the size retracted is about 1/4 of the expanded length.