A Fiddler Crab, sometimes known as a Calling Crab, may be any of approximately 94 species of semi-terrestrial marine crabs which make up the genus Uca. This crustacean is named for the fiddle-shaped large claw of the male crab. This entire group is composed of small crabs — the largest being slightly over two inches across. Fiddler crabs are found along sea beaches and brackish inter-tidal mud flats, lagoons and swamps.
Like all crabs, Fiddler Crabs shed their shells as they grow. If they have lost legs or claws during their present growth cycle a new one will be present when they molt. If the large fiddle claw is lost, males will develop one on the opposite side after their next molt. Newly molted crabs are very vulnerable because of their soft shells. They are reclusive and hide until the new shell hardens.
Found in mangroves, salt marshes, and on sandy or muddy beaches of West Africa, the Western Atlantic, Eastern Pacific and Indo-Pacific, Fiddler Crabs are easily recognized by their distinctively asymmetric claws.
Source: en.wikipedia.org/wiki/Fiddler_crab - 21.05.2010