Mermaids purses, no, not handbag
Many sharks lay eggs, called mermaids purses, which attach to marine vegetation or rocks, while others hatch inside the female and are live born. Species in which the eggs hatch inside the female often exhibit what is called intrauterine cannibalism, where shark pups still in the womb eat their siblings and other unfertilized eggs. Others species, such as the great white shark, have pups that grow inside the female attached to the uterus, as in mammals, with gestation lasting anywhere from five months to two years. However sharks as a class of animals will never win a parent of the year award as baby sharks once born or hatched are left to fend completely for themselves.
You can often find empty shark egg cases at the beach and you can usually tell which species it is from because different species produce different shaped egg cases. The baby sharks inside chew their way out of the egg case and emerge into fully formed and ready to explore their new environment. Surprisingly the biggest threat to baby sharks is other sharks as larger sharks often eat smaller sharks. Shark embryos still in their egg cases are able to sense the electrical current given off by potential predators and freeze to stop themselves becoming lunch. Sharks with the best chance of survival are those born big and those that grow fast. It also helps if their mom chooses a spot that isn’t swimming with potential predators.
The sharks that hold the records for having the most pups are the blue shark that may produce over 100 pups per litter and the whale shark that can produce up to 300 pups. Unfortunately large predatory sharks such as the great white only produce one or two pups at a time and as a slow growing and late maturing species they are at serious risk of going extinct.
