Stingrays are ovoviparous, meaning that the eggs develop and hatch inside the mother, who then give birth to live young. They have between 5 and 13 offspring at a time. Before birth, the female holds the embryos in the womb without a placenta. Instead, the embryos absorb nutrients from a yolk sac, and after the sac is depleted, the mother provides uterine "milk".
Two female stingrays at the London Aquarium have given birth to young in spite of the fact that they haven't been near a male in more than two years. Therefore, it stands to reason that female stingrays have the ability to store sperm in some way.
