Strange crab behavior

[sicklidkid]

Hi i have 2 emerald crabs in my 55 gallon FOWLR. Recently i saw one of them open up its underside and it looked like it was picking stuff out of it and eating it :? . Its kinda gross. I was just wondering if anyone could tell me what it is doing.
THANKS

 

[Brad]

I remember watching my banded coral shrimp reach inside himself and do a little housecleaning. I suppose I would do that also, if I could.