female crabs can also store sperm for a period of time so if the crab is new, the eggs may be fertilized.  Fertilized or not though, it doesn't really matter; it will just be food for the coral either way. 
 
sounds like eggs to me too but without a pic we can't really tell you anything for sure.  for all we know it could be a parasitic alien. 
		
	
		
		
		
		
		
	
		
		
	
	
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