viviparie

Viviparie is the reproductive mode in which embryos develop inside the parental body and are delivered as live offspring. The term, derived from Latin vivus, “live,” and parere, “to bear,” is used in biology to distinguish live birth from egg-laying and from ovoviviparity, where eggs hatch inside the parent.

There are different modes within viviparie. In placental viviparity, nutrients pass from parent to embryo through a placenta or placental analog. In histotrophic viviparity, nourishment comes from uterine secretions or specialized membranes without a full placenta. In most mammals, gestation is followed by birth, and lactation may provide postnatal nourishment and protection.

Viviparie is most conspicuously associated with mammals but occurs in other lineages as well. It is found in a number of reptiles, including several snakes and lizards, in several sharks and rays, and in a few other fishes and amphibians. The biology of gestation and nourishment varies across these groups, from placental connections to yolk-sac or histotrophic structures.

Evolutionarily, viviparie offers advantages such as protection of developing offspring and the ability to extend development in stable environments, but it imposes costs in gestational energy and often lowers reproductive frequency. The distribution of vivipary across taxa reflects diverse evolutionary histories and ecological trade-offs.

See also: oviparity, ovoviviparity, placentation.