Within the large group of viviparous we are going to find different reproductive strategies, with their different names. In this article on our site we are going to explain them and discover certain curiosities that are worth knowing, making clear the difference between viviparous animals and mammals
In general terms we should know that the viviparous animals are those that develop the embryos of their offspring inside their parents. This reproductive strategy makes the embryos more likely to complete their development because they are constantly protected from predators, or from any incident that could spoil the offspring.
As we know, mammals also develop their embryos completely inside the mother, which is why they are included in the group of viviparous. Do you want to know more and clear all your doubts? Keep reading!
The least evolved: the oviparous
On the evolutionary scale we find that the first vertebrates were all oviparous In other words, after fertilization, which can be internal or external, the female deposits the eggs in a safe area and ignores them. Leaving the eggsalone at her mercy
This is the case of the sea turtles that lay thousands of eggs every year on the beaches. However, as there is a wide variety of predators, it is important to note that this method is not very safe for the hatchlings, as most of the eggs may not hatch.
As a solution to this problem, the evolution of different groups of animals led to viviparism. Which consists of housing the embryos inside the body of the adult parent until they complete their development.
Within viviparous we find ovoviviparous and mammals
The ovoviviparous harbor the eggs inside the adult. The fact that the eggs are stored internally causes the parent to protect them with its life. It costs a lot of energy as it has to feed itself and generate enough energy for the incubator bag to send food to the eggs.
In this group we have some
- Reptiles: some snakes such as pit vipers some lizards (family Xantusidae and Scincídae)
- Amphibians: newts and salamanders
- Fish: sharks, manta rays or various types of small fish such as guppies
The most famous example of ovoviviparous are our beloved Guppy fish so widely used in aquariums.
Egg development in ovoviviparous animals
In the parent's incubator bag, the embryos develop inside each egg. Once completed they can hatch inside the body or hatch at birth.
Once they are born, the parent rarely takes care of the offspring, as they are already prepared to have an independent life. They generally have internal fertilization and the parent that harbors them is the female. But this is not always the case.
Ovoviviparous curiosities
The sharks have cannibalism inside the mother. Individuals that develop first eat their siblings. The slowest specimens or those with malformations serve as food for the strongest.
The seahorsemale harbors the eggs that the female transfers to him in her brooding bag. The eggs are fertilized as they enter the bag. There are some insects, such as aphids, that also use this reproductive strategy.
The mammals
Of all the viviparous the most advanced type are the placental viviparous, this is the case of almost all mammals except monotremes and marsupials.
Being a mammal includes three mutually exclusive characteristics:
- They are vertebrates: they all have bony backbones
- Maman:females produce milk
- They are homeotherms: they maintain a constant temperature around 37ºC
In mammals, fertilization is always internal The pregnant female feeds the embryo directly through the umbilical cord that supplies the fetus nutrients and oxygen until delivery. From birth the baby remains dependent on the mother who feeds him milk.
Milk is exclusive to female mammals, it is a more or less greasy white liquid that provides all the necessary nutrients as well as antibodies and bacteria, necessary to complete the immune system of the new individual.
Exceptions in the group of mammals
- Monotremes: this is the case of platypuses that lay eggs outside the individual. Once hatched, the pups suckle milk.
- Marsupials: it does not have a placenta because it gives birth to an underdeveloped offspring that has to complete its development abroad. In a special bag called marsupio in which it feeds on the mother by sucking milk.
Curiosities
It is very curious the relationship between brain development of mammals and the number of offspringIt can be said that the more complex the animal is, the fewer offspring it has and the further a pregnancy is from another. This is because raising the baby takes more time and requires more dedication to learning feeding techniques, such as selecting edible plants or learning hunting techniques.
Another curiosity worth mentioning is the relationship between brain development and the position of the mammary glands The more developed the animal the closer the mother will have the breasts of the head. We can compare it between the elephants and killer whales that have them in the armpit with the sheep or antelopes that have them in the groin. This is because the care of the baby is more exhaustive in more developed cases and allows more visual contact.
