What are my electric blue crabs doing?

[michad]

So I have these two Electric Blue Crabs (in addition to about 18 Blue Leg Hermits) and three times now I've caught them in this pose:
http://www.michad.org/images/DSC_2137.jpg

Once I pulled them apart and separated them...should I do that again? They've been in this position for over 12 hours now. Are they fighting? Mating? Comparing notes?

[LeslieH]

Male crabs will frequently lock onto or carry around a female prior to mating. that ensures another male won't out compete him.