What Are Ovoviviparous Animals?
Nature presents different types of embryonic development: oviparous, viviparous and ovoviviparous. Ovoviviparous animals are those that share characteristics of both oviparous and viviparous animals.
Definition of ovoviviparous animals
Ovoviviparous animals share traits of both oviparous and viviparous animals. Their reproduction can be defined as “the form of reproduction in which eggs develop inside the mother without her providing additional nutrition. They hatch inside her or immediately after leaving her body, so the chicks are born alive.”
The etymological origin of this word comes from Latin and is the union of: ovo (‘egg’), vivus (‘alive’) and parere (‘to give birth’).
Characteristics of ovoviviparous animals
Therefore, ovoviviparity consists in the fact that individuals lay eggs, but these remain inside the female. Once the embryo has finished developing, there are two options:
- The female lays the eggs and they hatch immediately after laying.
- Hatching occurs before delivery. Puppies are born directly from the mother.
Therefore, it is possible to say that animals that present this type of embryonic development carry out a process intermediate to the other two. Thus, ovoviviparity is a mixture between viviparity and oviparity.
The characteristics that identify ovoviviparity are as follows:
- There is internal fertilization.
- Puppies are born alive and fully developed.
- There is no placental connection between mother and offspring.
- In some cases, the nutritional support of the embryos can be provided only by the yolk sac of the egg (usually). In others, no.
Within ovoviviparity, two groups are differentiated according to the nutrition received by the embryos. Aplacental viviparity is the definition for ovoviviparous animals.
Applacental viviparity is one in which the embryos remain in the mother’s uterus, but do not receive any nutritional support or have a placental link with the mother. Two forms of embryonic development are differentiated: matrotrophy or lecytotrophy.
Matrotrophic species deplete their nutritional intake and, in order to continue to develop, they obtain nutrients from different sources. They can get them from other eggs (oophagy), from other embryos (intrauterine cannibalism), or they can show a specialization analogous to a placenta.
Examples of ovoviviparous animals
Most of the animals that make up the ovoviviparous list are invertebrate animals. However, some vertebrate animals, such as reptiles, fish or sharks, also have this type of embryonic development.
Invertebrates
Among invertebrates, there are different ovoviviparous species. One of the animal models par excellence in research laboratories is the Drosophila genus , which includes the fruit fly.
The Drosophila sechellia is an example of invertebrate ovoviviparous the order Diptera. Another group of invertebrates in which ovoviviparity can be found are the gastropods.
Fish: seahorses
Seahorses are ovoviviparous marine vertebrates. More specifically, they are fish belonging to the genus Hippocampus. These monogamous animals are known because it is the males that carry the fertilized eggs.
The gestation period lasts approximately between ten days and six weeks, depending on the species. Once finished, the male releases about 200 to 300 offspring over several hours.
Teleosts: sharks
Certain species of sharks, such as the bull shark ( Carcharias taurus ) , are ovoviviparous animals. Although the lecytotrophic strategy is the most observed in sharks, this species is an exception.
The bull shark is one of the three most dangerous species of shark, along with the tiger shark and the white shark. After all, they are all considered species most likely to attack humans.
Bull shark pups perform intrauterine cannibalism, so this species is matrotrophic. Inside the uterus, the larger embryo devours all of its siblings and leaves only one alive. So, in the end, only two puppies are born.
reptiles
Among reptiles, ovoviviparity manifests itself in different groups : some species of vipers and snakes, such as the anaconda, as well as the chameleon or the surinã toad, as the only species of toad.
Only a few species of the Chamaeleonidae family are ovoviviparous. Among them are the chameleon Trioceros hoehnelii and the chameleon Trioceros jacksonii.
It is possible to conclude that ovoviviparous animals are those whose embryonic development includes characteristics of both viviparous and oviparous animals. In nature, there are different examples of ovoviviparity, each with its own peculiarities.
