Does the title of the headline wonder you? It sure sounds almost impossible that new offspring can be brought forth without a fusion of male and female gametes.
Initially, a virgin birth, also known as parthenogenesis was thought to be triggered by extreme situations since it was only documented among captive animals – perhaps as a result of stress, isolation, or when there are no other options to reproduce. It now appears though, that some virgin females produce offspring even in the presence of males.
Consider the facts yourself.
1. Reticulated pythons
Thelma, a 6m long (20 ft) reticulated python had spent four years alone in Louisville zoo in the US without ever having met a male of her species. But somehow, she laid over 61 eggs, producing six healthy babies, thus becoming the first reticulated python in the world known to have had a real-life virgin birth.
But had she managed to mate with a male many years before, and store his sperm all this time? Genetic tests soon revealed that she had made eggs that contained all the genetic information required to make a daughter; without the need of a male’s sperm or DNA.
This she did by fusing her eggs with a by-product of her dividing cells, called a polar body. This object played the same role as sperm would normally do, triggering the egg to develop into an embryo. Each of her offspring contained two copies of half her chromosomes, and her babies became half-clones of her – all daughters!
2. Bonnethead Shark
On 14 December 2001, one of three captive adult female bonnethead sharks gave birth to a healthy female pup. Each of the prospective mothers had been caught as immature fish from the wild waters off Florida in the United States. None had met a male shark, and all were virgins.
Later genetic tests confirmed that no males had been involved, and since then, the same has been discovered in four other shark species.
3. Wild Pit Vipers
In 2012, two litters of wild pit vipers were discovered to have been born via parthenogenesis. It was the first time parthenogenesis had been documented in wild-caught snakes, which presumably had access to males. So why didn’t they mate with them?
Scientists believe females may choose to reproduce alone because the act of sexual reproduction can be costly. In the sense that, females have to put up with males competing and fighting over them, which may make it hard to find the ideal male partner. They also suggest that it could be triggered by some outside factor – a hormone, hormonal imbalance, a virus, or parasite or other pathogens.
For a fact, it has been observed that a species of wasps produce asexually when infected with a certain bacteria. But if no such trigger is found, it could be that the ability to have virgin births is retained in species as some kind of back-up mechanism, to be utilised when sexual reproduction is too unlikely or costly, as when populations of many wild species dwindle
4. Smalltooth Sawfish
This discovery came about by chance when ecologists were studying sawfish genes to understand how their declining population in the oceans was affecting them. Though the reason why female smalltooth sawfish chose to undergo a virgin birth is not clearly known, they believe that it could be a survival strategy when population levels are low.
They suggest that it may be a survival strategy that kicks in when they can’t find a mate, as something of a last-minute effort for these females to pass on their genes. What’s more, the young sawfish were healthy and thriving despite being inbred, but this is not always the case when parthenogenesis happens, as a lot of mortality or lack of development due to in-breeding has also been observed.
The benefits of parthenogenesis are that if any of these animals were left stranded, they could continue to reproduce; but at the cost of genetic diversity. Animals that clone themselves leave their lineages vulnerable to disease and other threats due to a lack of genetic variety.
