The ovovivíparos are organisms that retain the fertilized eggs inside the body – either in the oviduct or uterus, after the reproductive event. The embryo remains in this location during its development and feeds on the nutritive material stored inside the egg. The fertilization of these individuals is internal.
This pattern of reproduction is widespread in the animal kingdom . There are ovoviviparous animals in the invertebrate lineage , such as annelids, brachiopods, insects, and gastropods.
In the same way, the pattern extends to vertebrates , being a common reproductive modality of fish, highlighting the groups Elasmobranchii, Teleostei; in amphibians and reptiles.
The reproductive alternatives are oviparous animals , those that “lay eggs”; and viviparous animals that have an intimate relationship with embryos and feed on their mother.
The ovoviviparous form has similarities both with the oviparous species – they also lay eggs – and with the viviparous species – the embryo develops inside the female.
From an evolutionary point of view, the modes of reproduction in an animal have profound consequences, since they directly affect the fitness of the species. In the animal kingdom, reproduction patterns are quite diverse.
Thus, the way and the physical space where the development of the embryo occurs in animals, allows them to be classified into three reproduction patterns: oviparous, viviparous and what seems to be an intermediate condition, ovoviviparous.
The first mode of reproduction is the most common in both invertebrates and vertebrates. These animals produce eggs, and their development occurs outside the mother’s body.
In oviparous animals, fertilization can be both internal and external; what happens next depends on the group studied.
Some simply abandon the fertilized eggs, while other groups spend a great deal of time and energy caring for the eggs – and also caring for the little one when the egg hatches.
Second we have the viviparous animals. The egg develops in the oviduct or in the mother’s uterus and the embryo takes the nutrients necessary for its growth directly from its mother. There is usually a very intimate physical connection between the two of you – the mother and the baby. Mothers give birth to a live calf.
This type of reproduction is confined to lizards, snakes, mammals, and some fish , although there are some viviparous invertebrates.
Finally, we have the third type of modality called ovoviviparous. In this case, the mother retains the egg in some cavity of her reproductive tract. In this article we will analyze in detail this reproductive pattern.
Ovoviviparous animals are mainly characterized by retaining the fertilized egg within their reproductive tract during their development. That is, they incubate it inside the body.
However, there is a debate between the authors between the time required for egg retention and the time that must pass from the time the animal lays the egg until it hatches to be considered ovoviviparous.
Depending on the species, hatching can occur just before parturition or just after egg laying.
During the evolution of pregnancy patterns, different ways of egg retention were obtained, both in fish and in amphibians and reptiles . Most of the eggs are retained at the level of the oviduct.
In the case of “organic” retention by parents using other structures such as skin, mouth or stomachs, it is probably a derivation of parental care.
Placenta and nutrition
Unlike viviparous animals, ovoviviparous animals do not form a placenta and the connection with the mother is not as deep. In some species, the developing fetus does not depend at any time on the mother for food, since the interior of the egg in which it is growing provides all the necessary nutrients.
In the literature, the type or manner of nutrition during gestation that does not depend on the mother is called lecithotrophy.
In other cases, the embryo exhausts all its reserves. In these cases, the mother must take a nutritional role in order to complete the development of the individual. The embryo can take nutrients from unfertilized eggs or secretions from the uterus.
In this type of reproduction, fertilization must occur internally and the mother gives birth to a young organism in a generally advanced stage of development.
In internal fertilization, sperm are introduced into the female’s body, and the union between the egg and the sperm takes place. Internal fertilization is believed to be an adaptation to life in the terrestrial environment, since sperm must remain in a liquid medium to reach the egg.
In fact, in animals that live in bodies of water, internal fertilization increases the probability of successful reproduction. If the sperm are introduced into the female’s body, the probability of an encounter is greater than if both parties “throw” their gametes into the water.
In some cases – but not all – internal fertilization requires copulation orchestrated by the sexual organs. In cases where there is no copulation and there is internal fertilization, the males leave a structure called spermatophore. When the female finds the spermatophore she can fertilize herself.
Ovoviviparous animals are characterized by presenting an egg that is larger than viviparous ones, and is similar to those found in oviparous ones. The egg yolk is also of a significant size.
A pattern has been found between the thinning of the shell and the increase in the retention period of the egg. In many species of ovoviviparous animals – such as the lizard of the species Scleropus scalaris – after a period of internal incubation, the fine and delicate shell of the egg is destroyed at the moment in which the female expels the egg.
One of the most important model animals for biology laboratories are the Diptera of the genus Drosophila. In Diptera, the three described reproduction patterns are recognized. For example, the species Drosophila sechellia and D. yakuba are ovoviviparous – just to mention a few specific species.
In gastropods there are also species that retain their eggs in the female tract, such as the species Pupa umbilicata and Helix rupestris .
As fish are such a large and diverse group, the patterns of reproduction correspond to the heterogeneity of their species. Most species are dioecious and exhibit external fertilization and external embryo development – that is, they are oviparous. However, there are exceptions.
Some species of tropical fish, such as “guppies” are popular ovoviviparous and highly colorful species that normally inhabit home aquariums. These specimens give birth to their live young after development in the mother’s ovarian cavity.
However, within groups of bony fishes, both ovoviviparous and viviparous species are rare.
Sharks are characterized by exhibiting a wide range of reproductive patterns. Although in all species the fertilization is internal, the way of retention of the embryo by the female varies. This group of fish present the three reproductive modalities that we discussed in the previous section: viviparous, oviparous and ovoviviparous.
The ovoviviparous condition in shark species could represent an adaptation, offering a series of advantages such as protection against unfavorable environmental agents and potential predators of the eggs. In summary, the chances of survival of the animal are much higher if it develops inside the mother.
There is a very particular ovoviviparous species belonging to the Squalidae family: Squalus acanthias. This little shark has the longest known gestation periods. Of the 2 to 12 embryos that it can present, it takes 20 to 22 months.
In order to meet the nutritional demands during this enormous period of time, the egg of this species has a considerable yolk sac and is believed to be sufficient for it to complete 22 months without the need for an external food supply.
The Phallichthys is a petiole of which four species are known ( Phallichthys amates, Phallichthys fairweatheri , Phallichthys quadripunctatus and Phallichthys tico ) whose females are larger than the males.
This genus of ovoviviparous aquatic vertebrate lives in Central America, but is widely found in Costa Rica, Mexico, and Guatemala. Its favorite habitat is fresh water, that is, rivers, river currents where there is abundant vegetation.
The million fish ( Poecilia reticulata ) is also known as guppy or guppies. It is one of the most abundant tropical fish and it is also one of the most sought after in aquariums for its rainbow colors.
This ovoviviparous is found on the Caribbean coasts of Venezuela, Antigua and Barbuda, Trinidad and Tobago, Jamaica, Guyana, Brazil and the Netherlands Antilles. As in other petioles, female guppies are larger than males.
The Girardinus is a petiole that belongs to the order of the Cyprinodontiformes . This ovoviviparous lives in the fresh waters of Cuba, so it is a river animal with a tropical climate with temperatures ranging from 22º to 25ºC.
It does not have migratory habits. Females, which are up to 9.3 centimeters long, are often larger than males, reaching 3.3 centimeters in length. So far 7 species are known, including the Girardinus mettallicus .
The Phalloceros is a fish that inhabits various areas of Argentina, Brazil and Uruguay, hence it receives the common name of guarú-guarú, madrecita, madrecita de una spot, pikí and barigudinho.
This ovoviviparous aquatic vertebrate is freshwater (that is, it is a freshwater fish). The measurements of their specimens are different between the sexes, and the females (which are up to 6 centimeters in length) are always larger than the males (which are up to 3.5 centimeters long).
The Belonesox is a Cyprinodontiformes fish that tolerates low levels of oxygen in the water, in addition to alkaline waters and high salinity. They are essentially carnivorous and roam the shallower aquatic areas.
Its color is usually yellowish, grayish and even with orange tones. Females have a gestation of 5 months until they give birth to up to a hundred fry (which can measure 2 centimeters in length), which feed on zooplankton.
Amphibians and reptiles
Amphibians are made up of caecilians, salamanders, and frogs. Some salamanders have the ovoviviparous reproductive pattern. However, since internal fertilization is not common in frogs, there are few species that retain their eggs.
This modality has been described in the anuran of the Eleutherodactylus jasperi species , it is endemic to Puerto Rico and unfortunately it is already extinct. African jesters also retain their eggs.
In reptiles, although most species of snakes are oviparous, a significant number – including species of American vipers – are ovoviviparous. Snakes have the peculiarity of keeping sperm inside the female.
The puffing viper ( Bitis arietans ) has a sexual maturity of about 2 years, after which it can reproduce between the months of October and December. Once the female is fertilized, the incubation of the young lasts 5 months.
Afterwards, the young, 30-80 individuals, are about 20 centimeters long and do not take long to hunt all kinds of prey, ranging from amphibians to rodents of various sizes.
The anaconda (of the genus Eunectes ) is par excellence one of the best known snakes in the world. Their young, which can number up to 40 per litter, are 60 centimeters long and can hunt their prey and swim within just a few hours of being born.
The lucion ( Anguis fragilis ) is known as the legless lizard; for that reason it is easy for this reptile to be taken as a snake both in appearance and in its mode of movement.
The mating of this animal, which takes place between the months of April and May, causes the female to become pregnant and to adapt to the climate to ensure that her young are born as soon as possible; at birth (the litter reaches up to 12) they have immediate independence to feed.
The boa constrictor is an ovoviviparous snake whose sexual maturity is reached after about 2 or 3 years. Their mating is in the rainy season, and after the development of the young, they are lit by the female; the gestation of the same can last months.
The young can be up to 50 centimeters in length, but they do not start feeding until two weeks after they are born.
The garter snake ( Thamnophis sirtalis ) is also baptized as the striped snake. After their sexual maturity (which may take 2 to 3 years), their mating occurs in the spring season, after hibernation.
Later, the female is fertilized and the eggs are kept in her body for three months until they hatch; From there, up to 70 young per litter come out, which at birth are detached from all maternal assistance.
The mapanare ( Bothrops atrox ) is the most dangerous snake in South America and is seen a lot in the savannas of Venezuela. Their gestation lasts between 3 and 4 months, although their mating can occur throughout the year.
The young that are born are up to 30 centimeters in length and their number can reach 70 per litter. The mapanare is a specialist in climbing trees, but also in camouflaging itself in the terrain, which is why it is often difficult to see with the naked eye.
The skink ( Scincidae ) is a fairly common lizard. The biological variety of these reptiles is as vast as it is diverse in terms of reproduction. However, it should be noted that not all animals in this family are ovoviviparous, as some are oviparous.
Its feeding habit is herbivorous and the female gives birth to a maximum of two young, which can have a size equivalent to one third of the adult skink.
The limnonectes larvaepartus is one of the very few cases of ovovivíparos amphibians, as almost everyone in this category consists of egg – laying animals.
That is, while amphibians (ie, frogs, toads) usually lay eggs from which tadpoles later develop, Limnonectes larvaepartus has the peculiarity of giving birth to its young.
The Gabon viper ( Bitis gabonica ) is a snake that inhabits sub-Saharan Africa, specifically in countries such as Gabon, Ghana, Nigeria and the Congo, among others. Its habitat is centered in rain forests, in low altitude areas and in places with abundant wood.
Their habits are nocturnal and males tend to be aggressive when seeking to mate with females. This viper, by the way, is very poisonous and represents a greater danger in agricultural areas.
Birds and mammals
In general, all species of birds and prototeric mammals are oviparous (they lay eggs, they do not retain them in the body of the female), while the terian mammals are viviparous. However, the prototerial mammal Echidna is considered ovoviviparous.
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