Female freshwater ostracods (a group of small crustaceans) store the giant sperm in two so-called seminal receptacles until they use the sperm cells to fertilize their eggs. When filled, these receptacles make up more than a third of the female's body length. This picture shows an artificially stained receptacle of the ostracod Eucypris virens, filled to about half of its maximum capacity with sperm cells (sperm length about 1.8 mm). Credit: Renate Matzke-Karasz