After the walking legs come paired appendages called swimmerets. Depending on the sex of the individual, the swimmerets may be variously modified. In males, the first pair of swimmerets (14) are called gonopods because they have been modified for sperm transfer. In females, the first pair of swimmerets (which are rudimentary) are used for carrying the eggs and young. The remaining swimmerets (15-18) in both males and females can be used for creating currents for water circulation over the gills. The last paired appendages are called uropods (19) that along with the terminal, un-paired telson (20) form the tail fan, which is used for locomotion and egg protection.