my longspine urchin lost its spines for about a week or so and then he started growing more back and he looks wonderful now, I think it may just be the stress of a new environment, as far as the spines on the floor of the tank, they wont hurt you, I picked mine out to, just grab them from the side.. I didnt touch the tip though, but I'd imagine it wont hurt you if its not on the urchin but I could be wrong. Im just saying I didnt get hurt picking up the spines that were lost.