Redescription of the megalopa of the fiddler crab Uca uruguayensis (Decapoda, Brachyura, Ocypodidae) with special emphasis on its setae

The megalopa stage of the fiddler crab endemic to the Neotropical region, Uca uruguayensis, is redescribed, measured and illustrated from 216 specimens collected at Channel 1, Samborombón Bay, Argentina, the southernmost permanent population of the species. Special attention is given to the description of the types of setae, which are compared to those cited for U. uruguayensis and other fiddler crab megalopae reared in the laboratory.

The differences are given in the outline of the carapace, the plumose spines of the telson, and also in the following appendages: antennule, antenna, mandible, maxillule, maxilla, first, second and third maxillipeds. These cited differences could be due to: the origin of the organisms, caught in the field from their settlement area versus reared in the laboratory, and/or the sampling locality. The purpose of the present paper is to provide a detailed description of the megalopa that may allow resolution of taxonomic and phylogenetic relationships within this complex genus.