I was target feeding my Black Long-spined Urchin recently, and, as the saying goes, 'Don't bite the hand that feeds you', except apparently my urchin doesn't know this ...
Instead of feeding him Nori with a feeding prong, I thought I'd try a hand feeding
As he was on the front glass, I figured it would be easy to poke a piece of nori into his general area. I held the nori against the glass with 1 finger and slowly pushed it towards him. He started to get the idea and was crawling up the glass towards the nori (and my hand)
I kept my hand against the glass the whole time, and his spines were checking me out, but nothing major ...
He keeps coming up the glass, finds the nori, and then he suddenly flares out and pokes me on a knuckle
I don't know if it was a reaction form him or not, but it hurt at first
I kept my hand in the tank until he grabbed the nori, so my sting was in the water for over a minute
By the time I got my finger to the sink for hot water it was a black dot, like I'd been poked with a pencil
After a couple of minutes of hot water, the pain went away and after a couple of hours the pain was gone
The next day my knuckle was back to normal