Ultraestrutura do espermatozóide de Ucides cordatus Linnaeus (Crustacea, Ocypodidae) do litoral norte do Brasil Ultrastructure of spermatozoon of the crab Ucides cordatus Linaeus (Crustacea, Decapoda) of the northern littoral of Brazil

Ultrastructure of spermatozoa of the crab Ucides cordatus Linnaeus, 1763 is described and illustrated. Three parts can be distinguished: 1. the elongate-ovoid acrosome located anteriorly; 2. the cytoplasmic region; and 3. the nuclear region. The acrosome is composed of a thick electron-dense wall and a less electron-dense subacrosomal space. The cytoplasm region connects the acrosome with the nucleus, and three arms filled with microtubules arise from this region. The nucleus is polymorphous. The spermatozoon of Ucides cordatus follows the general pattern described for other Decapods.