Emerald crabs mating? Possibility..IDK

I don't know if they mate..how they mate, if its a boy or girl lol, but I just put these in my tank. They were stuck together like this when I pulled them out of the bag to acclimate them, then I seperated them when I put them in my tank and now there back on top of each other..Are they mating or just playing?
There are 2 there..BTW

 
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