Viviparous Definition
A viviparous animal gives birth to live young. Growing embryos are nourished by special organs in the parents as they develop. Matrotrophy is the condition in which the embryo receives nutrients directly from the mother, rather than from the yolk. The difference between ovoviviparity and viviparity is that viviparous animals feed their embryos nutrients from their mothers.
A large yolk sac is necessary for the embryo to survive without a large egg. Over time, different groups of viviparous animals have evolved, weighing in on the pros and cons of being viviparous.
There are viviparous animals in almost every vertebrate taxon, but few, if any, invertebrates (although many are ovoviviparous). Only birds are the only recognizable groups of animals that do not exhibit viviparity. A number of fish, amphibians, reptiles, and mammals are viviparous, but none are exclusively so. From oviparous animals, viviparous animals seem to develop their young viviparously.
There is a theory that some oviparous animals develop their eggs internally more slowly than others. The young are often hatched within the mother, or ovoviviparity, in some species. The young of ovoviviparous animals often feed each other after hatching, but while in the womb. These ovoviviparous species supplemented their offspring with nutrients secreted by their oviducts or reproductive tracts.
Although the yolk sac receives extra nutrients from the oviduct in some primitive viviparous animals, it still plays an important role. Other viviparous animals develop into young larvae inside the mother, feeding on her reproductive secretions.
This concept has been taken one step further by mammals, who birth their young earlier and feed them nutritive substances from their mammary glands. With this method, viviparous animals are combined with the ability to shorten gestation time and mother’s workload.
In order for viviparous animals to reproduce sexually, they must undergo internal fertilization. It is necessary for males to have some structure in order to fertilize females. A penis in mammals, a clasper in sharks, or even the strange gel-like structure that male salamanders leave behind for their mates to find, which the females deposit internally, can all be examples of this.
Birds are the only group of animals without any viviparous species. As a result of the way birds evolved, this is thought to be the case. Birds evolved into endothermic creatures early in their evolution. In other words, they would receive the same results as viviparous animals if they brooded their eggs.
In colder climates, however, some snakes and reptiles developed viviparity and ovoviviparity to move their eggs to the sun to warm them. Viviparous animals come in a wide variety of forms, but they all have certain advantages and disadvantages.
It is of the utmost importance for viviparous animals to be able to move their developing young when predators are present. The ability to reproduce at any time of the year is another important benefit of viviparity. In contrast to oviparous animals, which must produce yolk sacs when their food intake is at its highest, viviparous animals can nourish their young with fat reserves.
Viviparous animals can mate at any time when they get a suitable interaction. Viviparity is expensive for female mothers on the downside. Young offspring can severely damage the female’s organs and reproductive structure depending on the exact mode of viviparity. The process of carrying and feeding offspring is much more energy-intensive than simply laying an egg.
Additionally, carrying a brood of embryos makes females slower, making them easier prey for predators. Due to these and other advantages and disadvantages, viviparous animals are not the most widespread. As a result of very different environmental conditions, viviparity has developed many times, favored by its benefits over its disadvantages.
Examples of Viviparous
Humans
We are viviparous animals, as are most mammals. Internal fertilization is the method by which humans reproduce. In all higher mammals, the egg implants in the uterine wall during development. An organ containing many blood vessels develops within the uterine wall called the placenta. Embryos are surrounded by this tissue, which provides them with nutrients and removes waste products. Fetuses develop into babies as embryos become fetuses.
As opposed to some viviparous animals, humans are born well before they are fully developed. In many mammals, milk provides a rich and nutritive substance for babies. Moreover, the mother does not have to carry the baby for the many years that it would take for it to fully develop, which lessens her burden. As a result, she has more time to gather food for the baby and become pregnant again. While most mammals show high levels of parental care, viviparous animals do not.
Higher Sharks
The shark is a viviparous animal that exhibits very little parental care. Many shark species use a variety of reproductive strategies, but some have evolved viviparity methods similar to mammals. The tissues of sharks such as the Great White behave much like the placenta in mammals. As these tissues grow, they send spaghetti-like strands into the shark’s gills as outgrowths of the oviducts.
As a secreted milky substance, the tissues exchange oxygen and nutrients with the young sharks. In order to survive on their own, sharks detach from the oviduct and find their way to the cloaca. Since sharks can eat fish and other prey species as soon as they are born, they require very little parental care.
Amphibians
During their viviparous reproduction cycles, amphibians have several derived groups that form placenta-like structures. It is a method used by many salamanders and some frogs to reproduce. Aside from transporting eggs to the cloaca, the oviducts also nourish them in the process. Special embryonic teeth scrape the surface of the oviduct when young embryos attach to it.
In response to scraping, the oviduct produces a nutritive substance, which the young consume until they are able to be born. Amphibians are still in their larval stage when they are born, and must develop further and undergo metamorphosis before they become adults.
Related Biology Terms
- Oviparous – An animal that reproduces by laying eggs in a nest or releasing them into the environment.
- Ovoviviparous – An animals that broods a batch of eggs internally, with no maternal nutrients provided other than the yolk sac of the egg.
FAQ’s
Viviparous refers to the reproductive strategy in animals where offspring develop inside the mother’s body and are born alive, rather than hatching from eggs. This process involves the direct transfer of nutrients and oxygen from the mother to the developing embryos.
Yes, all mammals are viviparous. Viviparity is a defining characteristic of mammals, and it distinguishes them from other vertebrates, such as reptiles and birds, which are mostly oviparous (laying eggs).
While viviparity is most commonly associated with mammals, there are some non-mammalian examples as well. Certain species of sharks, some reptiles (like some species of snakes and lizards), and a few fish species exhibit viviparity. However, this reproductive strategy is relatively rare outside of the mammalian class.
Viviparity offers several advantages to animals. First, it allows for greater parental care as the developing embryos receive direct nourishment and protection from the mother’s body. This increases the survival chances of offspring. Additionally, viviparity enables species to colonize diverse habitats and adapt to changing environmental conditions.
Viviparity and ovoviviparity are both reproductive strategies involving live birth, but they differ in the way the embryos receive nourishment. In viviparity, the mother directly provides nutrients to the developing embryos, while in ovoviviparity, the embryos obtain nutrients from the yolk sac within eggs retained inside the mother’s body until hatching.