This image shows a ventral view of a male preserved crayfish. The male is easily distinguished from the female by the presence of a pair of modified first swimmerets called gonopods (1), stiff structures that are enlarged and directed forward. The gonopods are used by the male to transfer sperm to the female. Also observe the small openings (which have been expanded to make them more visible) to each vas deferens (2) at the bases of the fifth pairs of walking legs. The vasa deferentia conduct sperm from the testes to the outside of the crayfish. Although portions of the third (3), fourth (4) and fifth (5) walking legs can be seen, the remaining swimmerets and most of the abdominal segments have been removed for clarity.