tuxedo urchin

I was looking in my tank today and noticed one of my macroalgae seemed to be floating about halfway up the tank. That's annoying since I tied them to rubble with fishing line to keep them in place. I took a closer look. Yep, that's a red tuxedo urchin who decided to "wear" my macroalgae and...

Anyone know what this guy is? He looks a bit weird right now as he went into defense mode and stuck most of his pins straight up. He has a black body, with the 5 black lines separating his body into sections (just like any old tuxedo urchin.) but his pins are half striped white and maroon/red...