External features of an intersex fiddler crab, Uca pugilator (Bosc, 1802) (Decapoda, Brachyura)

The external features of an intersex fiddler crab, Uca pugilator, are descr ibed. Both male- and female-type sexual characteristics occur on the specim en. This sexually abnormal individual exhibits reduced bilateral asymmetry in its chelipeds. Its abdomen is intermediate between those of a typical ma le and a typical female. The first and second pairs of pleopods closely res emble those found in a typical male. One female-type pleopod occurs on the right side of the third abdominal segment, while on the fifth segment of th e abdomen there exist two female-type pleopods, one on each side. No male g enital apertures were found, but two female gonopores occur, one on each si de of the midline of the thoracic segment that bears the third pair of walk ing legs. Possible causes for the sexual aberrations found in this specimen are discussed.