vivipar

Vivipar is a term used in biology to describe organisms that give birth to live young rather than laying eggs. In formal usage, the adjective viviparous is more common, but vivipar can appear as a shorthand or root form in some texts and discussions about reproductive strategies.

In contrast to oviparous species, which lay eggs that develop and hatch outside the body, and ovoviviparous species, in which eggs hatch inside the mother with no direct placental connection, viviparous animals rely on internal gestation. During gestation, the developing offspring typically receive nutrients through a placenta or placenta-like structures, allowing continuous nourishment and protection until birth. The specifics of nourishment and exchange can vary widely across groups.

Viviparity occurs in a range of animal groups, though it is most prominent among mammals, where all members of the group are born live and fed via a persistent placental connection. Some fishes, such as certain sharks and rays, as well as a few reptiles, also display live birth with internal nourishment. In other species, such as seahorses, a unique form of viviparity exists in which the male carries and nourishes the developing embryos. It is important to distinguish viviparity from ovoviviparity, where embryos develop inside eggs that hatch within the mother, and from plant vivipary, where seeds germinate while still on the parent plant.

Etymology traces vivipar to Latin roots meaning “living-bearing.” The concept helps explain a broad spectrum of reproductive strategies across the animal kingdom and highlights the diversity of life-history adaptations.