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The reproduction of organisms usually occurs sexually, with two individuals of different sex, carriers of complementary gametes or asexually. As a curious fact, we can say that there is around 1% of the planet's species in which a very peculiar type of asexual reproduction without previous fertilization can occur: parthenogenesis. From parthenogenesis in bees and moths, to parthenogenesis in cold-blooded vertebrates such as fish and reptiles, diverse organisms can reproduce as parthenogenetic species at some point in their life cycle.
Continue reading this interesting article by Ecologist Verde and discover in detail what is parthenogenesis and examples.
What is parthenogenesis
Parthenogenesis is one of the types of asexual reproduction most striking of the animal kingdom. It has been studied for more than 100 years, allowing researchers around the world to discover new features and causes of parthenogenesis. But, how parthenogenesis takes place exactly?
It is a strange asexual reproduction phenomenon that allows females of certain animal species to reproduce even when there are no males to reproduce sexually. Through the formation of haploid gametes by mitosis, females are able to develop new embryos exclusively from your maternal genetic material.
Surprising, right? Let's see in the next sections more characteristics and examples of this curious reproductive phenomenon.
Types of parthenogenesis
It is possible to differentiate between types of parthenogenesis attending to various classification criteria. On the one hand, within the animal kingdom, depending on the type of meiosis that occurs during the formation of gametes, parthenogenesis can be:
- Apomictic: only a mitosis-like division of the gametes occurs (without meiosis), so the descendants of these apomictic females are clones of their mothers.
- Automatic: complete meiosis occurs, counting on self-fertilization between the ovum and the polar body, so that the descendants are not total clones of their mothers.
On the other hand, within invertebrates and particularly insects, parthenogenesis can give rise to offspring of different sex. Depending on the proportion of each sex of these descendants, parthenogenesis can be:
- Telitochic parthenogenesis: the parents originate only female offspring.
- Arrenotochical parthenogenesis: the progenitors originate only males.
- Amphithochical parthenogenesis: descendants of both sexes originate.
In the same way, depending on the capacity of the species to be able to opt for parthenogenesis as an asexual reproduction process, it can be considered:
- Obligate parthenogenesis: females are forced to reproduce only and exclusively through parthenogenesis.
- Facultative parthenogenesis: Females can choose between this type of asexual reproduction or sexual reproduction, depending on the conditions of the environment and the guarantee of having individuals of the opposite sex that facilitate mating and reproduction.
Examples of parthenogenesis
Parthenogenesis has been verified in different organisms, being more common in invertebrates and in some vertebrates such as fish and reptiles. However, parthenogenesis in mammals has begun to occur artificially, under the intervention of humans in clinical research trials. Regarding parthenogenesis in plants, it should be noted that this is less common than in animals.
In the following list you will find examples of organisms that perform parthenogenesis, classified according to the group of living beings to which they belong and if their parthenogenesis occurs naturally (in the wild) or through the intervention of scientific trials (in captivity).
Vertebrates in captivity
- Komodo dragon (Varanus komodoensis).
- Rhesus macaques (Macaca mulatta).
- Sharks (superorder Selachimorpha).
Verberates in freedom
- Family fishes Poeciliidae.
- Family lizards Gekkonidae Y Teiidae.
- Asian viper (Gloydius halys).
Invertebrates in the wild
- European bee (Apis mellifera).
- Flatworms (flatworms).
- Cylindrical worms (nematodes).
- Earthworms (oligochaetes).
- Moths (order Lepidoptera).
- Flies and mosquitoes (order Diptera).
- Snails (order Gasteropoda).
- Weevils, weevils, and borers (order Coleoptera).
- Rotifers (family Bdelloidae).
- Water flea (Daphnia pulex).
Plants
- Family Asteraceae.
- Tobacco plant (Nicotiana tabacum).
- Wheat (genus Triticum).
- Ferns
On the other hand, it is interesting to highlight how scientific advances have managed to bring parthenogenesis to the human species. Several studies have managed to carry out clinical trials with human cells to develop the human parthenogenesis for applications for cell and tissue therapy.
What are the advantages of parthenogenesis
The main advantage of the parthenogenesis in biology is attributed to the species survival, allowing their evolution. Between the causes of parthenogenesis, scientific studies highlight the need for animals and plants to cope with drastic environmental conditions and the need to increase the number of individuals in their population, being able to survive before resuming sexual reproduction that usually continue under favorable conditions.
Thus, it is possible to affirm that species capable of reproducing through parthenogenesis benefit from different advantages, such as:
- Survival in habitats with extreme temperature conditions, lack of food and even lack of mates to reproduce.
- Greater speed and ease of reproduction in females, as they do not need to find male individuals to reproduce, also avoiding the energetic waste that the mating process sometimes supposes.
However, not all are advantages in parthenogenesis. Let's see in the next section some of its main disadvantages.
What are the disadvantages of parthenogenesis
From the point of view of genetic diversity, parthenogenesis, as a type of asexual reproduction, gives rise to the loss of information exchange and genetic variability, with the consequent cloning of genetic material in the descendants.
It would thus be a process of inbreeding that hinders genetic diversity between organisms, sometimes leading to parthenogenetic offspring having abnormalities and even suffering early death.
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Bibliography- Lanteri, A., Confalonieri, V. & Rodriguero, M. (2010) Curious forms of animal reproduction: parthenogenesis. Science Today Magazine (Argentina), Volume 20 (119), pp: 2-9.
- Writing team (11/20/2017) The strange reproduction of the Komodo dragon. National Geographic Science, Evolution theme. Recovered from: https://www.nationalgeographic.com.es/ciencia/actualidad/extrana-reproduccion-del-dragon-komodo_12082
- Cermak, K. (2011) Autogamy in the honey bee. Permanent Commission for Bee Biology, Beekeeping Research Institute, (Czech Republic), pp: 1-3.
