Living alone for 16 years, without mating, it gave birth to a child

After living alone for many years and never seeing a female of the opposite sex, they suddenly gave birth to children... Such things have happened to animals such as crocodiles, sharks, snakes and lizards .

In 2018, a female American alligator who hadn’t had any contact with her own kind in 16 years laid a clutch of 14 eggs at a zoo in Costa Rica. Seven of them looked fertile.

Fertilized crocodile eggs have a "belt" down the middle | Quetzal Dwyer

After three months of artificial incubation, the eggs had not successfully hatched, so the researchers opened the eggs and found a fully formed baby alligator inside one.

One egg contained a fully formed baby alligator, while six other eggs that appeared to be fertilized contained unidentifiable contents | Quetzal Dwyer

Parthenogenesis is the process by which female animals produce offspring without the need for males or mating. Since it is very difficult to observe parthenogenesis in the wild, many of the first discoveries in this area have occurred in animals raised by humans .

In August 2023, a baby epaulette shark was born in a zoo in Chicago, USA. The staff here were also surprised because they had never let its mother live with male sharks. Since last year, this adult female shark has laid several eggs every month, usually unfertilized eggs that cannot survive, until people discovered that one egg actually developed into an embryo. After 5 months of incubation, a baby shark broke out of the shell.

Before this, other aquariums have also recorded parthenogenesis in epaulette sharks. In 2016, a female leopard shark that had lived alone for many years in an Australian aquarium gave birth to three baby sharks. At first, researchers suspected that it might have stored sperm in its body, but when they used genetic identification technology to analyze it, they found that the genetic material of the baby sharks came only from the mother shark. Researchers believe that it may be the first shark ever observed to switch from sexual reproduction to asexual reproduction.

The colour and pattern of a juvenile leopard shark is different from that of an adult | Tourism and Events Queensland, Akhilesh KV

In 2012, a female reticulated python that had never seen the opposite sex laid some eggs at the Louisville Zoo in the United States. It is not uncommon for snakes to lay unfertilized eggs, but the staff found that these unfertilized eggs did not shrink or change color, but looked plump and healthy, so some of the eggs were artificially incubated, and as a result, 6 eggs developed into healthy little snakes.

Polar body and egg fusion

For most animals, reproduction is sexual, meaning that mating is required for reproduction, and involves the union of a female egg with a male sperm. Sperm and eggs are called sex cells, and both are produced through meiosis.

After meiosis, each egg ends up containing only half of the female's DNA, and each sperm ends up containing only half of the male's DNA . The resulting offspring will have half of their DNA from the mother and half from the father.

So, when parthenogenesis occurs, where does the other half of the offspring's genetic material come from?

In simple terms, the female body has found a unique way to fill in the gaps in genes that would normally be provided by sperm. In the female reproductive system, meiosis causes the egg cell to form a large egg and three smaller polar bodies . The polar bodies contain excess genetic material, which then degenerate and disappear to ensure that the egg has the correct number of chromosomes and to expel excess cytoplasm.

In the case of parthenogenesis, the polar body acts as sperm, combining with the egg to form an embryo.

Normally, the first polar body does not divide, but in some organisms, the first polar body will divide, and finally three polar bodies will be produced | Sciencia58
Because chromosomes reorganize during meiosis, offspring produced by parthenogenesis are genetically similar to the mother's, but slightly different. Therefore, parthenogenesis and cloning are different concepts , although they both involve asexual reproduction. The offspring produced by the former usually have a certain degree of genetic variation, while the offspring produced by the latter are genetic copies.

Most of the offspring are female, but some are male.

For most animals that can reproduce parthenogenetically, offspring usually receive two X chromosomes from their mothers, so they can only produce female offspring. In addition, scientists have found that this may be a genetic trait, that is, females who have experienced parthenogenesis may give birth to daughters who can reproduce parthenogenetically .

Sharks only give birth to daughters when they reproduce parthenogenetically, while some female animals give birth to sons. In 2006, a Komodo dragon in a British zoo also reproduced parthenogenetically. Female Komodo dragons carry WZ sex chromosomes, while males carry ZZ. When parthenogenesis occurs, females can only lay WW or ZZ eggs. Since WW eggs cannot survive, only ZZ eggs can successfully hatch, and the offspring are all male.

And once there are male individuals, Komodo dragons can then reproduce sexually...

A baby Komodo dragon is born via parthenogenesis at London's Chester Zoo in 2006 | Ian Stephen

Parthenogenesis is more common than people thought

From an evolutionary perspective, parthenogenesis doesn’t seem to be the best way to reproduce . Isolated populations that rely on parthenogenesis will have a smaller gene pool, and their offspring will be more susceptible to disease and less able to adapt to changing climate conditions or new predators.

However, parthenogenesis seems to provide an emergency measure. Take the Komodo dragon, for example. As an islander on many deserted islands in Indonesia, when a female Komodo dragon is stranded on an island without its own kind, it can still maintain the continuation of the species through parthenogenesis . When one day, when the same kind from another island is washed ashore, the diversity of the gene pool here will increase. But strangely, even in mixed-sex populations, some Komodo dragons still use parthenogenesis.

In 2021, researchers discovered that two California condors also reproduce parthenogenetically, and that they had successfully reproduced with males many times before | Joseph Brandt

There is still a lot we don’t know about parthenogenesis. In the past, parthenogenesis was thought to be rare, but more and more discoveries are showing that it may be much more common than we thought.

References

[1] Chappell, B. (2023). No Daddy Shark in sight: Zoo greets a cute shark pup after apparent parthenogenesis. NPR. Retrieved from https://www.npr.org/2023/11/07/1211178209/shark-pup-parthenogenes

[2] Wetzel, C. (2021). How some animals have 'virgin births': Parthenogenesis explained. Animals. Retrieved from https://www.nationalgeographic.com/animals/article/parthenogenesis-how-animals-have-virgin-births

[3] Yarber, A. (2023). In a first, scientists find genetic cause for 'virgin birth' in animals. Washington Post. Retrieved from https://www.washingtonpost.com/science/2023/07/28/animals-asexual-reproduction-genetic-discovery

[4] Bittel, J. (2023). American crocodiles can have 'virgin births'—here's what that means. Animals. Retrieved from https://www.nationalgeographic.com/animals/article/american-crocodiles-virgin-birth-parthenogenesis

[5] Sperling, AL, Fabian, DK, Garrison, E., & Glover, DM (2023). A genetic basis for facultative parthenogenesis in Drosophila. Curr. Biol., 33(17), 3545–3560.e13. doi: 10.1016/j.cub.2023.07.006

[6] Booth, W., Levine, BA, Corush, JB, Davis, MA, Dwyer, Q., De Plecker, R., & Schuett, GW (2023). Discovery of facultative parthenogenesis in a new world crocodile. Biol. Lett., 19(6), 20230129. doi: 10.1098/rsbl.2023.0129

[7] Qiu, L. (2021). World's Longest Snake Has Virgin Birth—First Recorded in Species. Animals. Retrieved from https://www.nationalgeographic.com/animals/article/141023-virgin-birth-pythons-snakes-animals-science

[8] Burns, M. (2020). Virgin births from parthenogenesis: How females from some species can reproduce without males. Conversation. Retrieved from https://theconversation.com/virgin-births-from-parthenogenesis-how-females-from-some-species-can-reproduce-without-males-150496

[9] Yirka, B. (2023). Some stick insects that normally reproduce through parthenogenesis found to mate on occasion. Phys.org. Retrieved from https://phys.org/news/2023-09-insects-parthenogenesis-occasion.html

[10] Shibata, H., Sakata, S., Hirano, Y., Nitasaka, E., & Sakabe, A. (2017). Facultative parthenogenesis validated by DNA analyzes in the green anaconda (Eunectes murinus). PLoS One, 12(12). doi: 10.1371/journal.pone.0189654

[11] No sex please, we're parthenogenetic. (2023, December 20). Retrieved from https://www.nzgeo.com/stories/no-sex-please-were-parthenogenetic

[12] A Virgin Snake Birth. (2014, December 18). Retrieved from https://louisvillezoo.org/virginsnakebirth

[13]Are baby Komodo dragons clones of their mom? - The Tech Interactive. (2023, December 21). Retrieved from https://www.thetech.org/ask-a-geneticist/articles/2016/komodo-dragon-parthenogenesis-not-clone

[14] https://www.annualreviews.org/doi/full/10.1146/annurev-ecolsys-011720-114900#_i2

[15] Chicago Zoological Society - Brookfield Zoo Press Room. (2023, December 21). Retrieved from https://czs.org/Epaulette-Shark-Hatches-at-Brookfield-Zoo

[16] Booth, W., Levine, BA, Corush, JB, Davis, MA, Dwyer, Q., De Plecker, R., & Schuett, GW (2023). Discovery of facultative parthenogenesis in a new world crocodile. Biol. Lett., 19(6), 20230129. doi: 10.1098/rsbl.2023.0129

Planning and production

Source: Bringing Science Home (id: steamforkids)

Author | Editor of Cloud Magazine

Reviewer | Editor of Ziv's Everything Magazine

Editor: Yinuo