Acro question

[CoralKing]

There are two rounded growths on an Acropora loisetteae in my tank. At the center of these rounded extensions, there appear to be some type of filter-feeder produding from a tiny opening. When cyclopeeze is added, these protrusions seem to pulsate. They appear visually different from the polyps.

Does anyone know what they might be? I thought I remember reading somewhere that there are parasitic crabs that may live within acros, and form a rounded protrusion around themselves.

Thanks

[reefersnob]

Barnacle?

[CoralKing]

Here are two macro photos of the growths on the coral:

http://i183.photobucket.com/albums/x283/j770/c2.jpg
http://i183.photobucket.com/albums/x283/j770/c1.jpg

In the second photo, there is a small, thread-like projection from the rounded area. Upon feeding, this thread-like structure pulsates.

Does anyone have any ideas of what it could be?

Thanks