Crabs Still Alive While in Plastic?

In Costco, they have these whole crabs that are packaged, they looked uncooked. How can they breathe while being wrapped in plastic? Don't they suffocate?

I can't think of any kind of species that could be wrapped in plastic and survive...not even whole crabs!
Not only are they dead, but more than likely they have been processed as well. Leaving the cleaning, steaming and eating for your enjoyment!
Gotta love these questions!