Crustaceans have two sets of copulatory organs: two penises and two vaginas. Male ostracods have specialized genitalia that can be half their body length. Some ostracods have a specialized organ that "pumps" the sperm into the female. It is called the Zenker's organ. The ostracod's sperm can be 10 milimeters long - impressive when you consider he is only about one milimeter long, which is why he needs his sperm pump.
The Zenker's organ consists of a chitinous tube wreathed by rings of chitinous spines connected by tiny muscles.