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Cartilaginous fish - Sharks

Shark Reproduction

Sharks reproduce using internal fertilization and produce a small number of well-developed young. Male sharks have claspers as part of their pelvic fins. These are placed into an opening in the female's body and sperm passes along grooves in the clasper into the female's uterus. The female may be biten by the male shark during courtship.

There are three ways in which different sharks produce young:

Claspers on a male shark
Oviparous Ovoviviparous Viviparous
A shell or case is formed around the egg which protects it while it is developing. The female deposits the egg cases in the sea. Different sharks have differently shaped egg cases.

A thin tissue covers an egg or group of eggs (called a candle) and this stays inside the mother's body. After a while, the tissue is shed and the young sharks continue to develop inside the mother's uterus (womb). The young develop inside the mother's uterus and are born live. In some kinds of shark, the young eat each other before birth and the strongest one is the only one to be born.

Examples of all three reproduction methods are found in sharks living in Australian waters. The Port Jackson Shark (Heterodontus portusjacksoni) lays spiral shaped eggs that young hatch from (oviparous), the Smooth Hammerhead Shark (Hphyrna zygaena) gives birth to live young (viviparous) and the Grey Nurse Shark (Carcharias taurus) gives birth to pups after they have hatched from eggs within the uterus (ovoviviparous).

Most sharks are ovoviviparous, meaning that the eggs hatch in the oviduct within the mother's body and that the egg's yolk and fluids secreted by glands in the walls of the oviduct nourishes the embryos. The young continue to be nourished by the remnants of the yolk and the oviduct's fluids. The young are born alive and fully functional.

Most ovoviviparous sharks give birth in sheltered areas, including bays, river mouths and shallow reefs. They choose such areas for protection from predators (mainly other sharks) and the abundance of food. Dogfish have the longest known gestation period of any shark, at 18 to 24 months.

Stages of development in a Gummy shark

Port Jackson shark - an oviparous species

Port Jackson shark egg case

Port Jackson shark embryo



Mating Port Jackson sharks
Image © Roland Bircher Flickr


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