^w^ Sharks grow slowly and most reach maturity very late. Some are not reproductively mature until they reach about 18 to 22 years of age.
^w^ Some behaviors that lead to mating include synchronized swimming movements that signal when the male and female are prepared for mating.
^w^ Males generally bite the pectoral fins of the females to secure a firm grasp for the mating event.
^w^ Sharks fertilize their eggs internally. During the mating, a male will place one of its claspers (its reproductive organs) inside the female so that sperm may pass to the female to fertilize the eggs.
^w^ The majority of species maintain their young within the uterus until the pups are fully developed, and therefore produce very few young at one time.
^w^ Pups of some species are nourished internally by nutrients in a large egg sac. The egg sac is attached to the digestive system of the mother shark, and nutrients are re-absorbed into the pup's developing system.
^w^ Other species feed upon eggs produced by the female during the pup's embryonic development. The pups consume the eggs, and obtain nutrition from this source as well as their own egg sac. In Sand Tiger Sharks, the more mature embryos eat their siblings before consuming the new eggs.
^w^ In Hammerheads and several other sharks, the yolk sacs of the embryos attach to the wall of the uterus and form a placental cord. As a rule, these sharks produce ten to fifteen young, but Blue Sharks have been known to bear forty-five pups at a time.
^w^ Pups nourished inside the uterus are born tail first. Their teeth are fully formed at birth and they are ready to fend for themselves.
^w^ Some sharks do not develop inside the female, but develop instead inside an egg case. These cases resemble leathery pouches with tendrils that attach the case to rocks or plants.
