Big ian lol. yup symbiotic relationship. but tiny anenomes in the claws to keep predators away. in turn the crab feeds them by waving them around and collecting food. they are totally dependant upon the crab.
Jim c, ure in the US right? i have read about them being quite common over your way. if you are in the Uk i can Pm you, i have only ever seen one once complete with anenomes. and snapped it up.