Reproduction is essential for all living organisms and one of the three vital functions that living beings possess. Without reproduction, all species would be doomed to extinction, however, the presence of both the female and male sex is not necessarily necessary to complete the reproductive process. There is a reproductive strategy called asexual reproduction, which is indifferent, in almost all cases, to sex.

In this article Asexual Reproduction in Animals, we will talk about asexual animals and some of their characteristics, we will start by defining asexual reproduction and we will continue by illustrating this definition with various examples of animals that reproduce on their own.

Asexual reproduction in animals

Reproduction is essential for all living organisms and one of the three vital functions that living beings possess. Without reproduction, all species would be doomed to extinction, however, the presence of both the female and male sex is not necessarily necessary to complete the reproductive process. There is a reproductive strategy called asexual reproduction, which is indifferent, in almost all cases, to sex.

In this article Asexual Reproduction in Animals, we will talk about asexual animals and some of their characteristics, we will start by defining asexual reproduction and we will continue by illustrating this definition with various examples of animals that reproduce on their own.

What is asexual reproduction?

Asexual reproduction is a reproductive strategy, which is carried out by certain animals that reproduce alone and certain plants that do not require the presence of two adult individuals of different sexes to reproduce. This type of strategy occurs when an individual produces genetically identical offspring. Sometimes you may come across the term clonal reproduction, as it gives rise to individuals that are cloned to the progenitor.

Thus, during this type of reproduction, germ cells (ova or sperm) are not involved, with two exceptions, parthenogenesis and gynogenesis, which we will discuss in more detail below. Instead, they are somatic cells (those that makeup all the tissues of the body) or body structures.

Types of asexual reproduction and examples
There are many types and subtypes of asexual reproduction in animals, and if plants and bacteria are included, the list gets even longer. In the following, we will present the most studied asexual reproduction strategies in animals in the scientific world.

1. Vegetative multiplication :
Gemmulation is the typical asexual reproduction of sea sponges. It occurs when food particles accumulate in a specific cell type of sponges. These cells isolate themselves with covered protection creating what is called a gemmule, which will be expelled a posteriori, giving birth to a new sponge.

Another type of vegetative reproduction is germination. A group of cells on the surface of an animal begins to grow until it forms a new individual that can eventually separate or stay together and form a colony. This type of reproduction can be observed in hydrants.

Some animals can also reproduce by fragmentation. During this type of reproduction, an animal may separate and divide into one or more pieces, and each of these pieces develops into a completely new individual. The most glaring example of this type of reproduction is found in the life cycle of the starfish when the starfish loses an arm, in addition to being able to regenerate it, another individual, a clone of the original starfish, is formed.

2. Parthenogenesis:
As we said at the beginning, parthenogenesis requires an egg, but not sperm. The unfertilized egg can become a whole new organism. This type of asexual reproduction was first described in aphids, a type of insect.

3. Gynogenesis:
Gynogenesis is another type of single-parent reproduction. Egg cells need a stimulus to develop an embryo, a sperm, but the sperm does not provide any of its genomes. As far as the offspring are concerned, it will be a true clone of the mother. The sperm used does not necessarily have to be a member of the same species as the mother, but it must be a species close to that of the mother. This type of asexual reproduction occurs in amphibians and teleosts.

Asexual reproduction as a survival strategy

Animals do not use this breeding strategy as a usual method of reproduction, in fact, they only use it in difficult times, such as during changes in their environment, extreme temperatures, droughts, when there are no males, high depredation, etc…

Asexual reproduction reduces genetic variability, which can result in the disappearance of a colony, group, or population of animals if abrupt changes in the environment continue.

List of animals that follow asexual reproduction
Many organisms use asexual reproduction to perpetuate the species during times of crisis. In the following some examples are presented:

*Spongilla alba: it is a type of freshwater sponge native to the American continent that can reproduce by gemmulation when the temperature reaches -10ÂșC.
*Planaria torva: it belongs to the flatworm family. It lives in freshwater and is distributed throughout Europe. It reproduces by fragmentation. If it is cut into several pieces, each piece will produce a new individual.
*Ambystoma altamirani: This salamander, like the rest of the salamanders belonging to the genus Ambystoma, can reproduce by gynogenesis. They are native to Mexico.
*Ramphotyphlops braminus: this species of snake is native to Asia and Africa, although it has been introduced to other continents. It is a very small snake, less than 20 cm, which reproduces by parthenogenesis.
Hydra oligarchies: Hydras are a species of freshwater jellyfish that can reproduce by germination. They live in temperate zones of the northern hemisphere.

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