Fiddler crab

| image = fiddler crab.jpg | image_caption = Red-jointed fiddler crab (''Minuca minax'') | auto = yes | parent = Ocypodidae | includes = * Gelasiminae Miers, 1886 * Ucinae Dana, 1851 }}

The fiddler crab or calling crab can be one of the hundred species of semiterrestrial marine crabs in the family Ocypodidae. These crabs are well known for their extreme sexual dimorphism, where the male crabs have a major claw significantly larger than their minor claw, whilst females claws are both the same size. The name fiddler crab comes from the appearance of their small and large claw together, looking similar to a fiddle.

A smaller number of ghost crab and mangrove crab species are also found in the family Ocypodidae. This entire group is composed of small crabs, the largest being ''Afruca tangeri'' which is slightly over two inches (5 cm) across. Fiddler crabs are found along sea beaches and brackish intertidal mud flats, lagoons, swamps, and various other types of brackish or salt-water wetlands. Whilst fiddler crabs are currently split into two subfamilies of Gelasiminae and Ucinae, there is still phylogenetic and taxonomical debate as to whether the movement from the overall genus of ‘’Uca’’ to these subfamilies and the separate 11 genera

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 major claw is lost, males will regenerate one on the same 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.

In a controlled laboratory setting, fiddler crabs exhibit a constant circadian rhythm that mimics the ebb and flow of the tides: they turn dark during the day and light at night. Provided by Wikipedia