reproduction is essential for all living organisms and is one of the three vital functions possessed by living beings. Without reproduction, all species would be doomed to extinction, although the presence of the female and male sex is not always necessary for reproduction to take place. There is a reproductive strategy called asexual reproduction that is indifferent (in almost all cases) to sex.
In this article on our site we will talk about asexual animals and their examples, beginning with the description of the term "asexual reproduction". In addition, we will show some very varied examples of asexually reproducing organisms.
What is asexual reproduction?
Asexual reproduction is a reproductive strategy carried out by certain animals and plants, in which the presence of two adult individuals of different sexes. This type of strategy occurs when an individual produces offspring genetically identical to them. Sometimes, we can find the term clonal reproduction, since it gives rise to individual clones of the parent.
Likewise, in this type of reproduction, germ cells (eggs or sperm) are not involved, with two exceptions, parthenogenesis and gynogenesis, which we will see below. Instead, they are somatic cells (those that make up all of the body's tissues) or body structures.
Types of asexual reproduction and examples
There are many types and subtypes of asexual reproduction in animals, and if we include plants and bacteria, the list gets even longer. Next, we show you the most studied asexual reproductive strategies of animals in the scientific world and, therefore, the best known.
1. Vegetative multiplication:
gemulation is the typical asexual reproduction of sea spongesOccurs when food particles accumulate in a specific cell type of sponges. These cells are insulated with a protective covering creating a gemmule which is later expelled, giving rise to a new sponge.
Another type of vegetative reproduction is buddingA group of cells on the surface of the animal begins to grow into a new individual that may eventually separate or remain united and form a colony. This type of reproduction occurs in hydras.
Some animals can reproduce by fragmentation In this type of reproduction, an animal can break into one or several pieces and, from each of those pieces a new complete individual develops. The most typical example can be seen in the life cycle of the starfish, because when they lose an arm, in addition to being able to regenerate it, another individual is formed from this arm, cloneof the original star.
two. Parthenogenesis:
As we said at the beginning, parthenogenesis requires an egg, but not a sperm. The unfertilized egg can develop into 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 uniparental reproduction. Ovules need a stimulus to develop an embryo, a sperm, but it does not donate its genome. So the offspring is a clone of the mother. The sperm used does not have to be of the same species as the mother, just a similar species. Occurs in amphibians and teleosts
Here is an example of reproduction by fragmentation in a starfish:
Asexual reproduction as a strategy for survival
Animals do not use this reproductive strategy as a normal method of reproduction, instead, they only carry it out at adverse times, such as changes in the environment, extreme temperatures, drought, absence of males, high predation, etc.
Asexual reproduction decreases genetic variability, which could result in the disappearance of a colony, group or population of animals if sudden changes in the environment continue.
Animals with asexual reproduction
Many organisms use asexual reproduction to perpetuate the species at inappropriate times. Here are some examples.
- Spongilla alba: is a type of freshwater sponge native to the American continent that can reproduce by gemulation when the temperature reaches -10 ºC.
- Planaria torva: belongs to the flatworm phylum or flatworms. They live in fresh water and are distributed throughout Europe. Plays by fragmentation. If cut into multiple pieces, each piece will produce a new individual.
- Ambystoma altamirani: The mountain stream salamander, like all other salamanders of the genus Ambystoma, can reproduce bygynogenesis . They are originally from Mexico.
- Ramphotyphlops braminus: The blind shingle is native to Asia and Africa, although it was introduced to other continents. It is a very small snake, less than 20 centimeters long and reproduces by parthenogenesis.
- Hydra oligactis: Hydras are a species of freshwater jellyfish that can reproduce by budding. They live in temperate zones of the northern hemisphere.
In the following video you can see the regeneration after amputation of a flatworm, specifically a Planaria torva:
