HCA: Hermit Crab Association

I had discovered, one of the two large PP's (cue ball sized)i had purchased from petco 2 to 3 weeks ago was becominginactive and hadn't moved from the same spot for awhile. I pickedhim up, and he left his large pincher claw behind!!. I discarded the claw and put him in an iso tank. A couple hrs later i picked himup again and to my horror, the remainder of his appendages weredetached!!! There was nothing but a torso and the tiny back feetleft in his shell!! He expired shortly after. Has anyone ever heard of this? I have never had a crab lose a limb. All the other crabs seem fine. Also the subject crab wasalso doing fine until recently. He was active and eating (alot)too. Could he have outgrown his shell? His body appearedvery tight inside the shell. I had a couple of shells bigger thanhis, but he never changed. Would outgrowing the shell causea lack of circulation and limb loss? I'm at a loss, as my tank conditions are ideal. I was under theunderstanding that hermit crabs do not carry contagious diseases.I'm hoping this is the case, as i have 13 more.

It could be stress. Crabs can go into post-purchase stress. Being taken from the wild and then going from supplier to store then to your home can be stressful and stressed crabs become lethergic (inactive) and their limbs can fall off. With new crabs you are suppose to ISO them for a month to destress (don't handle them at all) and then put them with the other crabs. Most crabs after destressing will adapt to captivity but some crabs don't recover from the stress. I had the same problem with a crab and he died a month later.There can be another reason. Did you smell a dead fish smell? If not, he could not have died and could have been molting (sheding his exoskeletion)

Hermit crabs can transmit diseases to other crabs, that is one of the big reasons to ISO newbies away from the main tank. However, it does sound like your crab was under stress, as Chibieevee said. I did have a crab go through that, two years ago, but he came from extremely poor conditions. It was horrifying to watch! I'm so sorry you had to see that too. Injuries and stress are the main causes of limb dropping, even in crabs that previously seemed fine. With PPS, it seems to come on pretty quickly.