develop within eggs
that remain within the mother's body up until they hatch or are about to hatch. This strategy of birth
is known as ovoviviparity
. It is similar to vivipary
in that the embryo develops within the mother's body. Unlike the embryos of viviparous species, ovoviviparous embryos
are nourished by the egg yolk
rather than by the mother's body. However, the mother's body does provide gas exchange
Ovoviviparity is employed by many aquatic life forms such as fish and some sharks, reptiles, and invertebrates. The young of ovoviviparous amphibians are sometimes born as larvae, and undergo metamorphosis outside the body of the mother.