When I lived in Virginia in the Denbigh area I used to buy fresh oysters by the bushel and shuck them myself. Very frequently, after opening up an oyster, I would find a small crab living inside, which I would promptly eat, raw. They were called called commensal crabs since they were just living with the crab - they weren't parasites. They were about the size of a nickel, very much alive, very plump, and their shell was so paper thin they were almost transparent. I heard they were a real delicacy and that people saved them as they found them and fried them up whole in butter after a shucking session. I never tried that, I would just put them on a cracker with cocktail sauce and eat them whole, with their legs waving in the air right there. Really freaked my kids out! Has anyone heard of these crabs, also?