How Are Sharks Born?

and an egg slash live birth combination. Plus in some shark species, you have to survive gestation without being eaten by your developing siblings. We'll get to that in a minute, but first let's look at how sharks get pregnant. As opposed to other fish. Sharks use internal fertilization in a process that can appear violent to humans. The male shark often bites the female's fins or back to keep her in place, then aligns their reproductive organs and inserts his

clasper into her cloaca. The clasper, which in some species is spiny and barbs that stays in place a transfers sperm into the female, some of which may fertilize eggs in her oviduct at that point, the male shark exits the story, never to be seen again. The female may mate with a few different males in order to produce a single litter. Gestation periods for sharks vary from about five to six months to two years. The spiny dogfish shark has the longest gestation period known not just of sharks,

but of all vertebrates, at twenty four months. Here's a rundown on those three different ways that sharks swim into the world. First up, we've got viviparity, or live berths. Viviparous sharks carry their embryos throughout the entire gestation period and give birth to live shark pups, similar to how mammals give birth. The embryos are attached inside the womb with a oak sack placenta, which is how they receive their nutrition. In some species, females also secrete uterine milk,

which provides more nutrients to the oak sac. Viviparity is practiced by bigger species, such as blue and hammerhead sharks. Then there's oviparity, or egg laying. Oviparous sharks lay eggs which are protected by a tough egg case. These egg cases are tubes sometimes called mermaids purses because they often look like flat pouches complete with stringy ends on their corners. They also look a little bit like ravioli or a

face mask. The female shark deposits the egg cases in the sea in spots that are hopefully safe from predators. For example, horn sharks leave the cases in rock crevices, where they harden into twisted spirals that are difficult to remove, although snails and seals have been known to break the shell. Port Jackson sharks do the same thing, carrying the egg cases in their mouth until they find a safe spot.

From there, the shark pup is on its own. The embryo is nourished by the yolk in the eggsack and choose itself out when it's fully developed. Oviparous sharks develop more embryos per litter than other sharks, but many won't survive due to predation. Finally, there's what's called ovoviviparity, which is a combination of the previous two. Ovoviviparous sharks produce eggs, but instead of laying them to hatch outside the body,

they carry the eggs inside themselves. When an egg hatches, the shark pup continues developing inside the female shark until it's born. For the first part of the gestation period, the embryos receive nourishment from their yolk sack, and once hatched, the lining of the uterus likely provides uterine milk or some other kind of nutritious fluid, but there's never a placenta directly connecting the embryo to its mother. In some ovoviviparous species, embryos get a dish nutrition from eating their

siblings in the womb. Yep. The eggs in ovoviviparous sharks hatch at different times, and the shark pups sometimes practice what's known as intrauterine cannibalism, or eating the other eggs fertilized or unfertilized in the womb. Only about fourteen species are known to do this, but the best known intrauterine cannibal is the sand tiger shark. Although the sand tiger shark has two uteri and produces many eggs, each litter

yields just two pups, one from each uterus. That's because as the sharks develop their embryonic teeth, they start to eat the other embryos and any unfertilized eggs. It's survival of the fittest until only one pup remains because of their pre birth diet. The sand tiger pups and to the world bigger than other pups. They measure approximately three feet or a meter long. The number of shark pups in a litter varies among species, even among the three

main categories. The viviparous blue shark has been known to give birth to one hundred and thirty four pups in one litter. The whale shark has given birth to three hundred, but such high numbers are rare. However, whether hatched from an egg or born live, shark pups emerge as miniature versions of the sharks they may become, which is a good thing because they receive no further assistance from their

parents after they're born or hatched. A shark pup's success in life is largely determined by its size of birth and whether the female shark has used a nursery area that is a shallow part of the sea with fewer predators than the open sea. A Some shark species grow very slowly, putting them in danger of being eaten by

bigger sharks for longer. If few pups survive to reach maturity and to reproduce themselves, whether due to natural predators, a lack of food, or other pressures like human interference, their species could become endangered. That's why scientists are researching how sharks reproduce and give birth, and are even experimenting

with artificial wombs four species of concern. The idea is that when fishers accidentally catch and kill pregnant sharks, the living embryos could be rescued and brought to term in these human made environments and then hopefully released into the wild, or, in the case of those sand tiger sharks, a few embryos could be rescued from the pup beat pop womb to develop in solitary safety. Today's episode is based on the article how are shark pops Born? On HowStuffWorks dot com,

written by Molly Edmunds. Brainstuff is production of iHeartRadio in partnership with how stuffworks dot Com and is produced by Tyler Klang. Four more podcasts from my heart Radio visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.