There are around 400 different species of shark, each with unique systems of reproduction, growth patterns and behavioural traits. Each shark species has a different life span; broadly speaking, most sharks live for around 25 years. The spiny dogfish and some species of whale sharks have been known to live for over a century.
Although different shark species have different mating habits, all sharks reproduce sexually when the male shark's clasper inserts into the female shark's cloacal opening. The embryos gestate for between 9 months and 2 years, depending on the particular species. Some species of shark only give birth to one pup at a time; others can produce up to 100 pups.
The first stage of a shark's life cycle is the fertilisation of the female egg, which happens internally. The female shark carries her young in one of three different ways: oviparity, viviparity and ovoviviparity. Oviparity is the laying of eggs, which are often contained within a protective leathery case. Some female sharks have a placenta that nourishes and sustains the young inside her body before they are born at full term; this is viviparity. Finally, ovoviviparity is the laying and hatching of eggs within the body of the female shark, before the pups are born alive and fully developed.
Shark pups are around 5 feet long and weigh about 18.1 Kilogram when they are born. As soon as they are born, they swim away from their mother; there is no maternal care provided. If they do not leave the mother right away, there is a risk she will eat them. The pups are immediately ready to hunt and look after themselves. They begin to grow rapidly as soon as they are born.
Different species of shark reach sexual maturity at different times. The great white shark becomes sexually mature at around 15 years of age and has a lifespan of about 30 years, although some have been known to live for a century. The hammerhead shark also lives for around 30 years. At sexual maturity a shark's rate of growth slows down dramatically; however she will continue to grow until the end of her life. All sharks will reproduce as often as they can according to their gestation period.
Most species of shark migrate toward cooler water every year. Some sharks will travel for thousands of miles. In fact, some whale sharks tracked by satellite in U.S. waters were recorded as taking several years to complete their migratory journey. Sharks' migration can be influenced by weather patterns and the nutritional quality of certain water areas.
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