How do sharks and rays reproduce?


One of the main things in life for humans and animals is to reproduce, to secure that their genes make it to the next generation. There is a lot of different ways to do this. Mammals, like humans carry their young ones in the womb before giving birth. Reptiles and birds lay eggs. In most fish species females lay the eggs and the males fertilize them. Sharks and rays don’t reproduce like other fish. Males have two organs called claspers attached to their anal fins. When mating they will insert one of them into the females cloaca to transfer the sperm that will fertilize the eggs. Some sharks and rays are viviparous (will keep the eggs in their uterus) others oviparous (will lay the eggs).

Oviparous reproduction is used by about 30 % of sharks and rays in the world. After mating they will lay their eggs covered by a leathery case on the sea floor or attached to reefs. The baby will develop inside of this egg case and when the food supply (yolk) is finished the shark will escape through a slit in the case and swim away. These cases are often found on beaches worldwide and are referred to as mermaid purses.

Viviparous reproduction is when sharks and rays give birth to live young, just like mammals. In some species the eggs will be hatching inside the mother and the pups are born alive. In a few species the pups doesn’t only use the egg yolk for nourishment but also unfertilized eggs the mother produce to feed her young. About 30% of the viviparous species have a placenta. The yolk sac develops into a placenta attached to the wall of the uterus that nourishes the pups until birth.

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