For decades, asexual reproduction in animals, known as parthenogenesis, has been thought to be the key to protecting endangered species. Artificial insemination is emerging as a viable means to aid the survival of some endangered animals. But what is parthenogenesis exactly, how does it work, and is it really going to save animals from extinction?
What Is Parthenogenesis?
Parthenogenesis, which derives from Greek and translates to “virgin birth”, is a type of asexual reproduction in which the offspring of some species develops from the egg or female gamete without first being fertilised by the male gamete.
Generally, an egg cell and a sperm cell are required for sexual reproduction. Each contains half of the genetic information required for a living creature to develop. However, in parthenogenesis, the body devises a novel method of replacing the genes normally delivered by the sperm.
Ovaries generate eggs via a complicated process known as meiosis, in which cells reproduce, rearrange, and then separate. These eggs have just half of the mother’s chromosomes, with one copy of each. These are known as haploid cells, and cells with two chromosomal copies are known as diploid cells.
Tiny cells known as polar bodies are a byproduct of meiosis and they differ from the viable egg. An animal can create offspring by merging a polar body with an egg in a kind of parthenogenesis known as Automixis. This mechanism, which has been observed mostly in sharks, slightly shuffles the mother’s DNA to produce children who are close to but not identical clones of the mother.
Another example of parthenogenesis is Apomixis, a process in which reproductive cells multiply by mitosis. To put it in simple words, it is a type of genetic copy-and-paste. Because these cells do not go through the gene-jumbling process of meiosis, the offspring generated are genetically identical clones of their parents. Plants are more prone to this type of parthenogenesis.
In the past, natural parthenogenesis has been witnessed on several occasions, which sent shockwaves across the scientific community. In 2017, a female zebra shark from Australia called Leonie was able to successfully produce three pups despite never having direct contact with a male zebra. At the Louisville Zoo in 2015, a male reticulated python called Thelma laid six eggs on its own in a caged environment. And in 2006, Flora, a female Komono dragon living in the Chester Zoo in England, was able to procreate despite never having had penetrative sex.
Since animals such as bees and some species of fish do not have sex chromosomes, parthenogenesis is a huge component of their reproduction. Parthenogenetic development of fertilised eggs can also occur through a variety of chemical and physical methods, also referred to as artificial parthenogenesis.
In egg cells, the physical means of parthenogenesis can be induced by temperature, ultraviolet, electrical shocks, or sometimes even through the prickling of a needle. Chemically, the process can be mainly stimulated by chloroform, urea, sucrose, strychnine, fat solvents, acids, and chlorides.
Artificial insemination is crucial in that it can maximise the survival probabilities and longevity of wildlife species. In the absence of a male, parthenogenesis is a mechanism of self-reproduction in which egg cells grow into progeny (i.e. offspring). As a result, artificially parthenogenetic animals and plants may still reproduce without having to spend time and effort hunting for a suitable counterpart. This can allow the parents to utilise this time to look for food and shelter. Aphids, for example, reproduce asexually through parthenogenesis during summer when green leaves are plentiful and the days are longer.
Parthenogenesis enables a population to expand twice as rapidly as a sexually reproducing population. It allows for fast reproduction and population growth without the requirement for fertilisation. In fact, females who reproduce via parthenogenesis can generate the same number of children as sexually reproduced females while using half the resources.
Some parthenogenetic species can build a colony without mating, generating female offspring that can develop and reproduce again to generate a huge number of offspring in a short amount of time. Furthermore, certain genes can retain the potential to integrate additional ones during the sexual reproduction cycle. As a result, they can continue to evolve while generating more progeny.
Parthenogenesis also has less genetic variation than sexual reproduction. It may be advantageous in that it generates clones with the same genes for desirable features as their parents. In other words, if the mother lives in an environment to which she has adapted, her kids will also have the same genes to ensure their survival in that environment.
How Can Parthenogenesis Help With Dwindling Numbers of Endangered Species?
Parthenogenesis can undoubtedly help protect endangered species. As a type of adaptive strategy, this process allows animals to reproduce even in improper environmental conditions, or when the male population is scarce. It also permits organisms’ cells to have more than two sets of chromosomes, a condition known as polyploidy. This, in turn, allows the possibility of mutation, which may result in the development of advantageous mutant characteristics.
In 2004, the first ever viable parthenogenetic animal was found. Dr. Tomohino Kono and colleagues developed Kaguya, an artificially inseminated mouse. This study pushed the limits of what is feasible with artificial reproduction and has important implications for understanding embryonic development and gene regulation.
More recently, new research has been conducted on the whitespotted bamboo shark regarding their parthenogenetic potential. The research collected elasmobranch sperm from the sharks to better understand their reproductive mechanisms, the results had then led to significant progress in artificial insemination technology. In the same year, the South-East Zoo Alliance for Reproduction & Conservation, a nonprofit based in Florida, bred almost 100 shark pups using artificial insemination.
The artificial induction of some reptiles and animals was famously described in sea urchins in 1899 by the late German-American scientist Jacques Loeb. He pioneered the embryonic growth in sea urchins without fertilisation by immersing them in adequate salt solutions. Despite offering a method of reducing ethical barriers to regenerative medicine utilising human stem cells, Loeb’s discovery received an extraordinarily unfavourable public response at the time.
Long Term Concerns
This brings us to consider some of the ethical concerns regarding this type of reproduction in endangered species. History demonstrates that scientists and the general population may have quite different perspectives on life. These basic disparities are at the root of current unfavourable reactions to scientific results, such as the recent controversy over human stem cell research and therapeutic cloning.
Some of us crave the natural development of the world, but some of us also characterise change as issues that need fixing. Scientists do not always have the same, unified ideals. Is it within our moral conscience to interfere with human and animal reproduction? Should life forms be curated in a test tube? There is an implication between alleviating the issue of falling populations of endangered animals and deliberately increasing their numbers through insemination. Too frequently, the existence of several moral notions within this realm of research is overlooked.
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There should also be a consideration of long-term repercussions. As discussed previously, the necessity of parthenogenetic reproduction is characterised by passing on identical genetic information, since the offspring receives all its genetic material from a single parent. Due to this lack of genetic variety, offspring are often predisposed to the same illnesses and ailments as their parents. Furthermore, deleterious mutations and poor features will remain for many generations; and because parthenogenesis produces genetic clones of the parents, the children will consequently not adapt or survive when the conditions change and become unfavourable. As a result, parthenogenesis may result in a huge number of creatures that cannot survive even minor changes in their environment.
So, Is Parthenogenesis Good or Bad?
So, should parthenogenesis be considered a feasible technique for assisting in the survival of endangered animals?
Much like anything else, this is something that should be decided on a case-by-case basis. The importance of restoring balance to the food chain and protecting endangered species should not be underestimated. However, because artificial parthenogenetic technology is still in its early stages, there should be a limit on which species are to be artificially inseminated. And the existence of such technology should not hinder the public’s future preservation efforts. Science continues to present us with new and fascinating approaches to tackle new environmental conundrums, but we, the public, must continue to do our best to protect existing wildlife and their habitats.
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