Tuxedo Urchin Infection/Injury?

[empresto]

Ten days ago I got a blue tuxedo urchin at my LFS.  It's been happily munching on coraline algae and roaming my tank under a pile of shells and other small pieces of hard scape since it was acclimated to the tank.

 

This morning, when I walked past the tank, I noticed that it now has a green discoloration at its widest point of one of the blue stripes on its body and I'm not 100% sure, but it looks a bit like the tube feet in this region are less healthy than the rest.  The pictures below are attempting to show this region but my camera is having trouble focusing close up due to refraction issues (it kindly obliged for the picture by staying on this side for me 🙂 ).

 

I'm unsure as to whether this spot was there when I bought it or not since it has kept itself pretty well completely covered in shells since before it was bagged for me and stayed that way until this morning.  It's still moving around this morning with similar behavior to the last ten days, just lighter shell cover.  You can see it's still wearing a number of shells.

 

Any thoughts?  I can't imagine how it might have injured itself overnight, so I'm guessing it is an infection of some kind.  I'm not aware of any treatments for sensitive inverts like this for infections, but open to suggestions.  Mostly just interested if others have had experience with this.

 

[MainelyReefer]

Given keeping an urchin is so new to you, perhaps it is just the expansion of your own awareness of the urchin and what you are seeing is normal.  I vote take no action, maybe put in some nori and see if it needs supplemental feeding at the most.

[empresto]

Thanks @GraniteReefer !  I agree taking no action since I don't have a known cause is the best at present.  I also forgot to mention that I have fed nori twice in the last 10 days.

I should mention this is not my first urchin, just the first one I've had to look like it has an injury or infection.

[Tired]

That does look kinda odd. Are some of the spines missing at the edges of the stripe? 

 

If you happen to notice it on the sandbed or on a small item you can lift, tuxedo urchins are safe to handle. You could always pick it up for a better picture. You shouldn't pull it off something solid, but if it's liftable anyway, may as well take a closer look. Their spines aren't sharp at all, they're like a hairbrush. 

 

I don't know that there's much you can do either way, aside from making sure nothing is picking at it. 

[empresto]

Update:

The urchin died sometime between the 28th and 29th of December.  The spot in question, after the urchin had passed and flesh, spines, and tube feet had gone, showed signs of having been cracked/fractured.  I'm going to chalk this one up to miss handling before I received it from my LFS and some resulting infection.