Vivipariæg

Vivipariæg is a term used in biology to describe a reproductive strategy where offspring develop inside the body of the parent and are born alive. This is in contrast to oviparity, where eggs are laid and hatch outside the parent's body, and ovoviviparity, where eggs develop inside the parent but hatch within the body before birth. In vivipariæg, the developing embryo receives nourishment directly from the parent, typically through a placenta or specialized yolk sac structures that facilitate nutrient and gas exchange.

This mode of reproduction is found across a wide range of animal groups, including mammals, some reptiles, amphibians, fish, and invertebrates. The specific mechanisms of parental nourishment and gestation vary significantly among these diverse species. For example, in placental mammals, a complex placenta allows for extensive nutrient transfer from mother to fetus. In some sharks, the developing pups may consume unfertilized eggs or even their siblings within the uterus.

Vivipariæg is considered an advanced reproductive strategy that can offer several advantages. These include increased protection for the developing young from external environmental hazards and predators, as well as a more consistent and regulated internal environment for growth. This often leads to a higher survival rate for offspring compared to oviparous strategies, though it typically involves a lower number of offspring produced at a time due to the energetic demands on the parent.