What is this peekaboo guy?

[treebear87]

Hi there all! Help ID please! I’m thinking these must be worms of some kind??
I discovered this little worm or whatever it is playing peakaboo out of my birdsnest today. There are about 5 of them and they each seem to be coming out of a nodules on the end of a branch…. I don’t think they’ve always been there because I didn’t see the thing coming out till today, but the nubs have probably been forming for a few weeks and I thought they were just new branches forming.
Thank you for any replies
T

 

[treebear87]

Sorry the vid doesn’t seem to work these are a few shots they poke out uncurl do a little twist around and curl back up in

 

[DaJMasta]

Looks like a coral barnacle to me, neat!

 

[ying yang]

+1 on barnacle

 

[vetteguy53081]

Nice. Rare to see live ones. These are related to crabs due to shell and activity classified as sedentary crustaceans which live in shells made of fused plates which are permanently fastened to any hard substrate it can build one.
While cool, it can inhibit coral growth being fused to skeleton of your coral. They need as much food as corals do and will steal food source from coral for survival.
These I believe are called pyrgomatid barnacles