A viviparous animal gives birth to fully formed live young. Embryos are nurtured with unique organs in the parents that feed nourishment to the expanding embryos as they develop. Matrotrophy is a condition in which the embryo takes nutrients directly from the mother rather than the yolk.
The distinction between ovoviviparity and viviparity is that viviparous animals provide nutrition to their embryos from the mother. There is no substantial yolk sac for the embryo to live in without a huge egg. Various groups of viviparous creatures have developed through time, each weighing in on the advantages and disadvantages of being viviparous.
There are viviparous creatures in practically every vertebrate taxon, but few, if any, in the invertebrate taxon (though many invertebrates are ovoviviparous). Only the birds do not exhibit any type of viviparity among the identifiable animal groupings. Viviparous members may be found in fish, amphibians, reptiles, and mammals, although none of them are entirely viviparous. Viviparous development of the young seems to be a derived feature from oviparous animals. According to the notion, some oviparous species take longer to mature eggs internally than others.
In certain species, this results in ovoviviparity, where the young are hatched inside the mother. In ovoviviparous species, the young often feed on each other for nutrition after hatching but while still in the womb. Some of these ovoviviparous animals started feeding nutrients released by the oviducts or other portions of the reproductive system to their babies. Although the yolk sac gets additional nutrition from specific tissues in the oviduct, it nonetheless serves a function in certain primitive viviparous mammals.
Other viviparous animals have young larvae that grow within the mother and feed on unique secretions from her reproductive system. Mammalian mothers have taken this notion a step further by giving birth to their offspring sooner and feeding them a nutritious food product produced by the mammary glands. This combines the advantages of viviparous animals with the capacity to reduce gestation duration and maternal demand.
Internal fertilisation is required for viviparous animals to procreate sexually, since this is where their fertilised eggs develop. To fertilise the female, males must have some structure. This may be a penis in mammals, claspers in sharks, or the weird gel-like structure that male salamanders leave for their partners to discover and deposit inside. It’s noteworthy to note that birds are the only animal group without any viviparous species.
This is assumed to be due to the evolution of birds. Birds become endothermic early in their development. This suggests they could just brood their eggs like viviparous creatures and have identical outcomes. In colder regions, certain snakes and reptiles evolved viviparity and ovoviviparity in order to transport their eggs to the sun to warm them up. While the types of viviparous animals differ, there are some similar benefits and drawbacks.
All viviparous animals have the ability to transfer their growing young, which is critical in places where predators are abundant. The capacity to reproduce at any time of year is another significant advantage of viviparity. Unlike oviparous animals, which must form yolk sacs when their food intake is at its peak, viviparous species may feed their young from fat stores. This permits viviparous creatures to mate whenever they have the opportunity. Being viviparous, on the other hand, comes at a high cost to the female mother.
The young children might seriously injure the female’s organs and reproductive system, depending on the particular method of viviparity. Carrying and nourishing progeny consumes far more energy than merely laying an egg. Furthermore, carrying a brood of embryos slows females down, making them more vulnerable to predators. Viviparous animals are not the most common creatures because of these and other benefits and downsides. Viviparity has evolved several times in response to a variety of environmental situations that favoured viviparity’s advantages above its drawbacks.
Examples of Viviparous
Humans, like the majority of mammals, are viviparous. Internal fertilisation is how humans reproduce. In all higher animals, the egg implants in the uterine wall as it matures. The placenta is a blood vessel-filled structure that grows from the uterine wall. This tissue protects the embryo by supplying it with nutrition and removing waste. The embryo becomes a tiny foetus, which then becomes a baby. Humans are born before they are completely mature, unlike other viviparous species.
Milk offers a rich and nourishing meal for newborns, which is observed in many animals. It also relieves the mother’s burden by removing the need for her to carry the baby for the many years it would take for it to completely mature. This allows mom to obtain sustenance for the baby and re-establish her pregnancy. While most mammals exhibit high levels of parental care, viviparous species are not required to do so.
Sharks are an example of a viviparous species that provides little to no parental care. While sharks have a broad variety of reproductive systems, a few have acquired sophisticated viviparity techniques similar to those used by humans. Sharks, such as the Great White, have tissues that act similarly to a mammalian placenta. These tissues grow from the oviducts and deliver spaghetti-like strands into each growing shark’s gills. In the form of a secreted milky liquid, the tissues exchange oxygen and give nutrition to the newborn sharks.
When the sharks have evolved to the point where they can live on their own, they leave the oviduct and make their way to the cloaca. Sharks need relatively minimal parental care after they are born into the environment, since they may immediately begin feeding on fish and other prey species.
During their viviparous reproductive cycles, amphibians, like sharks, have multiple derived groups that generate placenta-like structures. This is how many salamanders and some frogs reproduce. The oviducts are designed in such a manner that they not only convey eggs to the cloaca, but also feed them along the route. Young embryos connect to the oviduct and use specific embryonic teeth to scrape its surface.
The scrape causes the oviduct to create a nutritive material, which the young consume until they are mature enough to be born. Many amphibians are still in the larval stage when they are born, and they must grow and undergo metamorphosis before becoming adults.
Related Biology Terms
- Oviparous – A species of animal that reproduces by depositing eggs in a nest or releasing them into the wild.
- Ovoviviparous – An animal that broods a batch of eggs internally, using just the yolk sac of the egg as a source of maternal nutrition.
Question and Answer
1.Which of the following represents a viviparous species?
- A blue whale is fertilized internally, develops its young, gives live birth, and nurtures is young on milk.
- A female seahorse lays her eggs in a special sac on the male’s belly, where they develop until they hatch.
- A species of snake broods its eggs internally, and births the young immediately after they hatch.
A is correct. Neither B or C is an example of a viviparous animal. Whales, like most mammals, use a placenta to nourish their young internally, which is the defining characteristic of viviparous animals. Answer B is a strange example of oviparity, where the male’s sac is simply a good external environment that serves the purpose of a nest. Answer C represents an ovoviviparous species.
2, A species of shark develops eggs in its reproductive tract. The eggs hatch, with a large yolk still attached to the embryo. The yolk is highly vascularized, and exchanges nutrients with a special tissue in the shark’s oviduct. Which of the following describes the shark?
A is correct. This shark is viviparous because it supplies nutrients to its offspring in a form other than a yolk sac. Other sharks that do not form vascular connects with their embryos are still ovoviviparous sharks, and the sharks are often born right away or eat each other for continued nourishment during development. Still other shark lay their eggs, and do not develop them internally at all. These are called oviparous sharks.
3. Monotremes are mammals that lay eggs. Which of the following describe monotremes?
C is correct. While monotremes still use milk to nourish their young, they retain the ancestral form of laying eggs to develop young. Based on this, it is assumed that viviparity is a derived trait in the rest of the mammals, and that it arose after mammals evolved mammary glands. It is thought that mammary glands and viviparity are highly successful in conjunction, although not required.