We went to mangrove forest this afternoon and the crabs on the mud attracted our attention, since one of its claw is significantly larger than the other. Unfortunately, they were very small and I could not get close that it was hard to get better picture.
mud fiddler crab
mud fiddler crab
Googling “crab one claw”, I learned that they are called Fiddler Crabs.
it is only the male Fiddler crab that has one claw significantly larger than the other. The male uses it to court females. If for some reason the larger claw is lost, he remaining smaller claw will grow larger and the lost claw re-grows as the smaller one! Fiddler crabs can’t swim! ~ http://inchinapinch.com/hab_pgs/marine/mangrove/animals.htm