Our Emerald Mithrax crab's sleeping habits...

Just about every night, our Emerald Mithrax crab sleeps in one of two places: On / against / under the sun coral, or on / against / under the stalk of our rose bubble tip anemone. I've attached a picture of him in his favorite spot. We've nicknamed him The Suncup Guardian. Is there a logical explanation for these soft choices of sleep locations?

Additionally, there are times that it appears as though he is asleep and rather than his classic folded-arms position, he'll have one arm stretched up and against something holding it in a "I'm waving to say goodbye!" position... or sometimes not even kept stable, hence his arm will actually move or wave a bit. I know that dogs dream and can enact things that they dream as a result. Do crabs dream?

 

That's pretty cool actually.

Have one of those little guys and he always sleeps tucked up under the temp knob on my heater in the very back...odd.

I would just say that for the majority of marine life, crabs included, the place that is chosen for sleeping is generally chosen due to it's feeling of safety. And since for all the little guy knows, he is on an actual reef, he is probably just getting in what he thinks is the safest spot.

Or maybe the yellow just makes him feel pretty!