Oviparous animals are those that reproduce through eggs. In this way, the embryo develops inside the egg, but outside the maternal body, until, once, its development has finished, the egg hatches and the new individual is born. In viviparous animals , on the contrary, the embryo develops completely within its mother’s womb and there is a third group, the ovoviviparous ones , which keep the eggs inside during the development stage and once the embryo is already it has matured and is ready to hatch, the eggs hatch and the mother releases the young.
However, although all oviparous animals lay and hatch from an egg, the fertilization procedure, care and protection of the egg and the rearing varies enormously depending on the species in question. At AgroCorrn we explain what oviparous animals are and their different behaviors and techniques.
Fertilization in oviparous animals
Fertilization is the stage in which the genetic material of the female and the male, the ovary and the sperm, respectively, come into contact to give rise to the new individual. In oviparous animals, fertilization can be of two types :
- Internal fertilization: it is typical of all those animals that lay “dry” eggs, for example in the case of birds and reptiles. In this way, the eggs are fertilized by mating prior to laying.
- External fertilization: it is typical of animals that lay “soft” eggs, laid in a watery or humid environment as in the case of fish or amphibians. The female does the laying of the egg without fertilizing and it is, after laying or during it, when the male pours his sperm on the eggs to fertilize them.
All birds are oviparous, as are most insects, fish, amphibians, reptiles, and even some mammals.
Oviparous animals that are birds
While some birds make their nests exclusively for laying and caring for their eggs, others simply lay them between rocks, bushes or on the ground, as is the case with chickens.
After she has laid the egg, the female incubates it and provides it with heat for approximately two weeks, depending on the incubation time of the species in question, until they hatch and the chicks hatch. The female, and in some species of birds also the male, will continue to protect, care for and provide food for their chicks until they reach an adequate stage of maturity, as in the case of ducks or, the ability to fly, depending on their species, being an example of species that leave the nest, from storks, eagles, sparrows, etc.
Reptiles, oviparous animals
Reptile eggs are generally designed to be able to protect the young from arid or hostile conditions, so that their shell is more resistant and, in turn, has high reserves of water and nutrients. As reptiles are cold-blooded, they cannot hatch or provide heat to their eggs through their bodies, so they use sunlight or other natural heat sources to hatch them, although there are some species, such as the python, that they do have an adequate body temperature.
As for the care of the egg or the young, there are species that after laying do not even incubate the egg and leave it to their fate, such as turtles that lay their eggs on the beaches and bury them, while others, such as snakes and crocodiles take care of their young until they reach an adult stage.
Fish and amphibians, animals that lay eggs
Fish and amphibians can lay their eggs in a wide variety of places: between stones and vegetables, in holes dug in the bottoms of oceans and rivers, in nests made from foam, in water or even on other individuals. In addition, the appearance of the egg varies greatly depending on the species, being able to present red, yellow, transparent colors and very varied sizes and its fertilization is mainly external, although there are exceptions. In fact, not all fish are oviparous, rather some are viviparous or ovoviviparous, presenting internal fertilization.
Unlike birds, reptiles and mammals, both fish and amphibians that hatch from the egg are not fully formed, but must go through a larval period in which they develop until they reach the characteristics of the species. A well-known example of this type of development is that of some amphibians such as frogs.
Regarding the care of the young once it has been born, it should be noted that there are species that abandon their eggs to their fate, such as carpines and barbels and others that take care of both the egg and the fry after their birth, such as this is the case of some catfish or harlequins. There are also species that, after laying the egg, die, as for example in the case of piranhas.
Oviparous or egg-laying mammals
There are only two species of oviparous mammals :
- Platypus : fertilization occurs internally, so that, after mating, females build a tunnel-shaped nest / burrow in which they lay their eggs, usually between one and three eggs. It should be noted that before the egg is laid, it remains in the mother’s womb for about 28 days and after laying they are incubated for at least 10 days. During that period of time, the female is responsible for incubating and protecting them until they hatch. After birth, the female will continue to feed and care for her young in the burrow until she reaches the developmental stage necessary to get her own food.
- Echidnas : in this species of mammalian animals , fertilization takes place internally. After mating, the female gestates a single egg for about 22 days in her womb and then she lays and continues to incubate it in a kind of bag for 45–50 days.
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