urchin spine

Hi guys! I was wondering to get some help, yesterday I saw this in my pincushion urchin, at first I thought it was just sand that somehow got on him, but when I watched him today the white thing was still on him. I took several pictures, but the one on the post is the best one I got. It would...

So I added a pencil urchin to my 29 gallon tank about a month ago and noticed right away that one of his spines looked wrong. It was much shorter than the others, red, and bulbous on the end with a hole in its tip that had a white protrusion in the center. I looked into this and couldn’t find...