viviparity is a form of reproduction present in most mammals, commonly called viviparous animals. However, there are also other classes of animals that carry out reproduction based on viviparity, such as certain amphibians, reptiles and fish.
In this article on our site we will explain everything about viviparous animals, starting with the definition, showing you how embryonic development occurs in animals, the characteristics of viviparous animals and, finally, you will also find a complete list with names and examples of viviparous animals that you will be surprised to discover.
What are viviparous animals?
To really know what viviparous animals are, we will begin by reviewing the definition provided by the R. A. E (Royal Spanish Academy), which defines the adjective "viviparous, ra" as follows:
Said of an animal: Give birth to children in the well-developed fetus phase.
Therefore, viviparous animals are those that carry out their embryonic development in the mother's uterus, receiving through her the necessary oxygen and nutrients until the moment of birth, when they are considered fully formed and developed.
Embryonic development in animals
But to really understand what viviparous animals are, it is essential to talk about embryonic development, which is the period that elapses from fertilization to the birth of a new individual. Thus, in the sexual reproduction of animals, we can distinguish three types of embryonic development:
- Viviparous Animals: After internal fertilization, the embryos develop within a specialized structure of the mother's body, which protects and protects them. nurture until they are fully formed and ready for calving.
- Oviparous animals: in this case internal fertilization also occurs, however, the development of the embryo takes place outside of the mother's body, inside an egg.
- Ovoviviparous animals: also through internal fertilization, the embryos of ovoviviparous animals develop inside an egg, although in this case the egg also resides within the body of the parent, until hatching occurs and, therefore, the birth of the young.
Discover characteristics and examples of oviparous animals and ovoviviparous animals on our site.
Types of reproduction of viviparous animals
However, in addition to differentiating between the different types of embryonic development, we must know that there are different types of reproduction within viviparous animals:
- Placental viviparous: are those that develop within the placenta, an organ attached to the uterus that extends during pregnancy to leave room for fetuses. An example would be the human being.
- Marsupial viviparous: unlike other mammals, marsupials are born undeveloped and finish forming inside the marsupial, an external pouch It performs a function similar to the placenta. The best known example would be the kangaroo.
- Ovoviviparous: as we have already told you, it is a mix between viviparism and oviparism. In this case, the parent lays the eggs inside her body, where they will develop until they are fully formed. The young can be born inside the mother's body or outside.
Characteristics of viviparous animals
Placental viviparity, which is carried out by most mammals, is a more evolved and developed gestation system than the one that oviparous animals present, since their fetus is gestated within a specialized structure called the placenta. In addition to receiving oxygen and nutrients, embryonic development within the parent offers greater protection compared to oviparous animals.
Another important feature is that developing viviparous animals lack a hard outer shell. The placenta is a membranous organ containing a rich and powerful blood supply that surrounds the uterus of pregnant females. The fetus is nourished through a supply line called the umbilical cord The time between fertilization and birth of viviparous is called the gestation period or pregnancy and varies depending on each species.
One of the most important aspects among mammals as viviparous animals is the important transition that females undergo after an ovule is fertilized and the period of gestation or pregnancy begins. At this stage, the uterus increases in size in proportion to the growth of the zygote, and the female begins to undergo a series of changes, both internal and external in perfect natural preparation of this whole process.
The vast majority of viviparous animals are quadrupedal, which means that they need four legs to stand, walk and move.
Most mammalian mothers have a strong and narrow maternal instinct to nurture and protect their young until it can fend for itself. herself. The female will know exactly when it will be time. In the animal world there is also another form of viviparism, this being the least common. We are talking about marsupials, such as the kangaroo.
Marsupials are creatures that give birth to their young in an immature state and then carry and nurse them in bags on their abdomenThe newborns remain in this place until they are fully formed and do not need any more of their mother's milk to survive.
Examples of viviparous animals - Viviparous mammals
What are viviparous animals? Almost all mammalian animals are viviparous, there are only a few exceptions of oviparous mammals, calledmonotremes whose main representatives are the echidna and the platypus. In this group we must also include marine species such as dolphins, whales and narwhals, as well as the only species of flying mammal: the bat.
Examples of viviparous animals terrestrial mammals:
- Dog
- Cat
- Rabbit
- Horse
- Cow
- Pork
- Giraffe
- Lion
- Chimpanzee
- Elephant
Examples of viviparous aquatic mammals:
- Dolphin
- Whale
- Sperm Whale
- Killer whale
- Narwhal
Examples of viviparous animals - Viviparous fish
Continuing with the article on viviparous animals, we must learn about some of the most common viviparous fish, although technically they are ovoviviparous animals. We are talking about the species of guppies, platys or mollies:
- Poecilia reticulata
- Poecilia sphenops
- Poecilia wingei
- Xiphophorus maculatus
- Xiphophorus helleri
- Dermogenys pusillus
- Nomorhamphus liemi
Examples of viviparous animals - Viviparous amphibians
As in the previous case, the viviparous amphibians are not particularly common, however, we find in theorder Caudata two representative animals:
- Triton
- Salamander
Examples of viviparous animals - Viviparous reptiles
To finish our list of viviparous animals we must mention some viviparous reptiles. Although most reptiles are oviparous, we also find specific species that carry out viviparism:
- Boa (Boidae)
- Sea Serpent (Hydrophiinae)
- Rattlesnake (Crotalus)
