Ovoviviparous

About

Ovoviviparity, ovovivipary, or ovivipary, is a mode of reproduction in animals in which embryos develop inside eggs that are retained within the mother's body until they are ready to hatch. Ovoviviparous animals are similar to viviparous species in that there is internal fertilization and the young are born live, but differ in that there is no placental connection and the unborn young are nourished by egg yolk; the mother's body does provide gas exchange (respiration), but that is largely necessary for oviparous animals as well.

Ovoviviparity is employed by many aquatic life forms such as some fish, reptiles, and invertebrates. The young of ovoviviparous amphibians are sometimes born as larvae, and undergo metamorphosis outside the body of the mother. With more scientific rigor, five modes of reproduction can be differentiated based on relations between zygote and parents:

• Ovuliparity : fecundation is external (in arthropods and fishes, most of frogs)
• Oviparity : fecundation is internal, the female lays zygotes as eggs with important vitellus (typically birds)
• Ovo-viviparity : or oviparity with retention of zygotes in the female’s body or in the male’s body, but there are no trophic interactions between zygote and parents. (Anguis fragilis is an example of ovo-viviparity). In sea horse, zygotes are retained in the male’s ventral "marsupium". In the frog Rhinoderma darwinii, the zygotes developed in the vocal sac. In the frog Rheobatrachus, zygotes developed in the stomach.
• Histotrophic viviparity : the zygotes developed in the female’s oviducts, but find their nutriments by oophagy or adelphophagy (intrauterine cannibalism in some sharks or in the black salamander Salamandra atra).
• Hemotrophic viviparity : nutriments are provided by the female, often through placenta. In the frog Gastrotheca ovifera, embryos are fed by the mother through specialized gills. The lizard Pseudomoia pagenstecheri and most of mammals exhibit a hemotrophic viviparity.

Read more at Wikipedia