I just noticed a weird hitchhiker on a new frag

I was feeding my tank today and noticed that there was something on one of the new frags I just picked up. I kept the frag on the sand for a few days and let it open up. After I was happy with it I found a place to put it on the rock. After I moved it the polyps wouldn't open up anymore. It's been a few days and they still haven't opened. I was looking close at it and noticed this barnacle looking thing open and close. I've not seen something like this before. Any idea what it is?



Opened





Closed





I don't think this is the cause of the polyps not opening up unless the movement of it opening and closing is irritating them.