A viviparous animal is an animal employing vivipary: the embryo develops inside the body of the mother, as opposed to outside in an egg (ovipary). The mother then gives live birth. The less developed form of vivipary is called ovoviviparity, which, for instance, occurs in most vipers. The more developed form of vivipary is called placental viviparity; placental mammals are the best example, but other animals^{[citation needed]} have also adapted by incorporating this behavior, such as in scorpions, some sharks, some snakes, and in velvet worms. Certain lizards also employ this method such as the genera Tiliqua and Corucia. The placenta is attached directly to the mother in these lizards which is called viviparous matrotrophy. Viviparous offspring live independently and require an external food supply from birth. There are numerous advantages and disadvantages to being viviparous.

There is a relationship between sex-determining mechanism and whether a species bears live young or lays eggs. Temperature-dependent sex determination does not work in the sea, so marine viviparous species use genotypic sex determination (sex chromosomes)^[1].

Poa alpina, a grass which shows vivipary: the seeds germinate while still attached to the mother plant.

Viviparous plants produce seeds that germinate before they detach from the parent. In many Mangroves, for instance, the seedling germinates and grows under its own energy while still attached to its parent before dropping into the water in order to transport away.^[2]

[edit] References

[edit] See also

• Oviparity
• Ovoviviparity
• Placental mammals
• Marsupials
• Live-bearing aquarium fish
• False vivipary

This developmental biology article is a stub. You can help Wikipedia by expanding it. v • d • e