Viviparity


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Related to Viviparity: territoriality, ovoviviparity
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Viviparity

 

a means of reproducing offspring in which the embryo develops in the mother’s body, is nourished directly by the mother through a placenta, and is born more or less developed and free of any egg covering.

Viviparity is counterposed to oviparity, in which the development of the embryo and its release from the egg covering occur outside the mother’s body (after the eggs are laid). The historical connection between viviparity and oviparity is indicated by rare cases of ovoviviparity, in which the embryo develops from an egg in the mother’s body and is nourished chiefly on substances stored in the egg itself, but also is secreted by the mother’s body and is freed of the egg covering, usually after the egg is laid.

Among invertebrates, viviparity is characteristic of some coelenterates, arthropods, mollusks, worms, and echinoderms. Among chordates, it is characteristic of salpas, many sharks and rays, some cyprinodonts, frogs, Caeciliidae, salamanders, tortoises, lizards, and snakes, and of the majority of mammals (except Echidna, Proechidna, and the platypus), including man. Development of the embryo in viviparity may occur in the ovary, the oviducts or dilations of them converted into a uterus, or in the vagina. In many viviparous animals embryonic membranes are formed around the embryo.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Viviparity: the maternal-fetal relationships in fishes.
Remarkably, however, once these species evolve viviparity, the process is mostly irreversible and they remain restricted to such cold climates.
Materno-fetal immunotolerance: is Interleukin-1 a fundamental mediator in placental viviparity? Dev Comp Immunol 2005; 29(5):409-415.
Reproduction in the lizard Mabuya heathi (Scincidae), a comemntary on viviparity in new world Mabuya.
While the phenomenon has not been given the attention it deserves there are a number of cases that have recently appeared in the literature including bilateral shift to asymmetry in the animal kingdom, the shell shape in freshwater snails, viviparity in reptiles, sex determination in turtles, leaf form in buttercups, and ant attracting extra-floral nectar secretion in Acacia trees (Palmer, A.R., 2004).
A cost of viviparity and parental care in scorpions: reduced sprint speed and behavioural compensation.
Reproductive biology and phylogeny of fishes (agnathans and bony fishes); phylogeny, reproductive system, viviparity, spermatozoa.
The yolkless egg and the evolution of eutherian viviparity. Biology of Reproduction 68:337-357.
Key words: polychaeta, Syllidae, Coiba, Pacific, Panama, viviparity.
Makos exhibit a placental viviparity: the eggs are retained in the uterus throughout development and fetuses obtain nourishment from their yolk sacs and also by feeding on the unfertilized eggs produced by the mother (oophagy).
Beyond the relatively simple question of when a crop will flower, there are a number of problems in reproductive development, including pollen incompatibility in both self and cross species situations, apomixis, parthenocarpic fruit set, embryo abortion, viviparity, dormancy, and quality of seed.