Female mudflat fiddlers can carry 5,000 to 30,000 eggs at one time, each with a volume of about 0.01 mm3 (Figueiredo et al. 2008, Greenspan 1980). Crabs release larvae into the water column once they are fully developed, usually during large nocturnal ebb tides (eg. Christy 1989). Unlike some other crabs, studies on U. rapax in Panama found that the species only released larvae at night (Morgan & Christy 1994). The purpose of this behavior is most likely to transport larvae offshore, away from abundant estuarine predators, while reducing predation risk under low light conditions. Planktonic larvae develop through a series of five zoeal stages (Christy 1989), feeding mostly on smaller zooplankton. The final larval stage (postlarva) is the demersal, or bottom-associated, megalopa. As the larvae travel back toward the estuary, they metamorphose into megalopae and look for settlement cues such as the presence of other members of the same species (conspecifics) and the appropriate sediment type, before settling to the bottom and undergoing their final metamorphosis to a juvenile crab (eg. O'Connor 1993).
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