Very little is known about most shark mating rituals, and the same holds true for the Nurse shark. The Atlantic Nurse shark has been observed mating on the ocean floor. In general, the male inseminates the female with his claspers (these are located between the male's pelvic fins). During mating he turns his claspers foward and inserts one into the female and transfers his sperm. Nurse sharks can be either oviparous or ovoviparous. In oviparous organisms the eggs develop and hatch on the outside of the body. The pups, as baby sharks are called, hatch out of a leathery protective covering with the yolk attached and stay on the ocean floor until they fully mature. In ovoviparous creatures the eggs develop on the inside of the body and hatch within or immediately after extrusion by the parent. The yolk of these pups are hatched inside the uterus before the pups are developed, and they too have leathery eggs. These sharks have from 20-30 pups at a time. Nurse sharks grow about 13 centimeters in length and 2-3 kilograms a year. They do not reach sexually maturity until they are from 15 to 20 years old.