How many types of sharks are there?
There are Around 440 Known Species of Sharks! There are many iconic species of sharks - the Great White in the film Jaws was burned into popular cutlure, for better and for worse - but they are still a very small subsection of the over 400 shark species that have been discovered by humans so far.
Do sharks lay eggs or give live birth?
Sharks exhibit a great diversity in reproductive modes.
There are oviparous (egg-laying) species in nature and viviparous (live-bearing) species. Oviparous species lay eggs that develop and hatch outside the mother's body with no parental care after the eggs are laid. The embryos are nourished by a yolk-sac inside the egg capsule.
Viviparous species can be separated into two categories: placental (having a placenta, or true connection between maternal and embryonic tissue), or aplacental (lacking a placenta). Among the aplacental species, there are those whose embryos rely primarily on a yolk-sac for nutrition during gestation and those that consume yolk-filled, unfertilized egg capsules (oophagy).
Types of Sharks That Lay Eggs
- Bamboo sharks
- Wobbegong sharks
- Carpet sharks
- Horn (bullhead) sharks
- Swell sharks
- Many catsharks
- Live-Bearing Sharks
About 60% of the shark species give birth to live young. This is called viviparity. In these sharks, the young remain in the mother's uterus until they are born.
The viviparous shark species can be further divided into the ways the young sharks are nourished while in the mother:
How Do Sharks Mate?
All sharks mate through internal fertilization. The male inserts one or both of his claspers into the female's reproductive tract and deposits sperm. During this time, the male may use his teeth to hold on to the female, so many females have scars and wounds from mating. You can check out shark facts for more information.
How do sharks give birth and reproduce?
After mating, the fertilized eggs may be laid by the mother, or they may develop either partially or fully inside the mother.
Viviparity
The eggs hatch inside the female's body and the babies are fed by a placenta which transfers nourishment from the mother to the babies (via an umbilical cord which is connected to the baby shark behind the between the pectoral fins). The placenta helps transfer nutrients and oxygen from the mother's bloodstream and transfers waste products from the baby to the mother for elimination. Viviparous sharks give birth to live young. The number of pups in a litter ranges from 2-20 or more. Examples of viviparous sharks include the Bull sharks, Whitetip reef shark, Lemon shark, Blue shark, Mako, Porbeagle, Salmon shark, the Silvertip shark, and Hammerheads. Although long thought to be oviparous (an egg 14 inches (36 cm) long was once found), Whale sharks are viviparous and pregnant females have been found containing hundreds of pups.
Oviparity
These sharks deposit eggs in the ocean which will hatch later if they are not eaten by predators. The eggs are not guarded by either parent. Shark eggs (sometimes called "mermaid's purses") are covered by a tough, leathery membrane. Their shape ranges from pouch-like to screw-shaped (like the California hornshark and the Port Jackson shark). Some eggs (like those of catsharks) have tendrils that attach the egg to objects on the sea bed. The egg has a yolk that feeds the embryo, very much like a chicken egg. Oviparous sharks include the Zebra shark, the catsharks, swellshark, the necklace carpetshark, some Epaulette sharks, and the Hornshark.
Aplacental Viviparity (Ovoviviparous)
In these animals, the eggs hatch and the babies develop inside the female's body but there is no placenta to nourish the pups. The pups eat any unfertilized eggs and each other (they are oviphagous). Very few pups in a litter survive until birth due to this form of sibling cannibalism. Great white sharks, sawsharks, Mako, crocodile sharks, Cookiecutter sharks, Pelagic thresher, Greenland shark, Gummy shark, Soupfin shark, Pacific Angelshark, Pygmy sharks, Nurse shark, Tiger shark, and Sand tiger sharks reproduce this way.
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