Here's a testiment as to how hardy crabs are.
I had some liverock that was only "so-so" that I did not have room for in my tank. I put the rock in a 7 gallon bucket filled with saltwater and put the bucket into my garage. Mind you now, this was around mid to late October. It wasn't exactly warm and toasty if you get my drift.
Well, I did no water changes. There was no aeration. Heck, I even put a lid on the bucket. It stayed stagnant this way for THREE WEEKS!
Well, I sold the rock and the person came over to get it late at night. As we picked the pieces out of the bucket, my hands were getting frozen because the water was so cold.
At the bottom of the bucket was a medium sized crab. I could not tell if it was an emerald or what. Let's just say it was extremely fiesty for being in sub 50 degree water with no light, heat, air or food for three weeks straight.
In my experience, crabs are not delicate creatures. Shrimp on the other hand, could not have survived that type of treatment.
But as I had mentioned earlier, if you can take it into the pet store, somebody else will buy it.