What is burrowing in my Brain?!

[FishyMel]

There is something that has a canal in my brain's skeleton, and I find it very worry some. The brain is healthy but I'm worried this thing could hurt it. I simply didn't notice this when I purchased it.
You can kind of see it in the picture but it is hard. The animal goes into hiding when its hole is disturbed and I can't kill it with tweezers. What should I do? Is this a parasite that is going to kill it and the whole tank? I really like this brain it is one of the nicest specimens I've seen. Help.

The brain full view

 

[GoingPostal]

Have you ever seen it? I would try luring it out at night with some food to see what you are dealing with, maybe a trap.

 

[FishyMel]

Many in the general reef forum thought it might be a gall crab? How common are these in the reef world?

 

[Saldarya]

I dont think they are overall real common. That being said, I do have one living in an Acan. Doesnt really bother the coral. It is my understanding that in time the coral will simply grow around it and in short imprison the crab.

Again, if the coal looks healthy, feeds, etc....I wouldnt worry about it, just nature