Asexual Reproduction

Asexual Reproduction


Some snakes, komodo dragons, sharks, and turkeys are capable of "virgin births", meaning, asexual reproduction.


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Thelma the snake confused then astounded her keepers.

This 6m long (20 ft) 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.

Perhaps she'd managed to secretively mate with a male many years before, and store his sperm all this time?

Genetic tests soon revealed the answer.

Thelma had become the first reticulated python in the world known to have had a real-life virgin birth.

She'd made eggs that contained all the genetic information required to make a daughter; without the need for a father, his sperm or DNA. She'd done it 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, triggering the egg to develop into an embryo. Each of her offspring contained two copies of half her chromosomes. They were half-clones of Thelma.

Scientists are discovering that virgin births occur in many different species; amphibians, reptiles, cartilaginous and bony fish and birds and it happens for reasons we don't quite understand.

Initially, a virgin birth, also known as parthenogenesis, was thought to be triggered by extreme situations; it was only documented among captive animals, for example, perhaps by the stress, or isolation. A way to continue the bloodline when all other options had gone, when there was no other choice.

Not necessarily. It now appears that some virgin females produce offspring even in the presence of males.

What's more, they do so in the wild, and may have been doing it for hundreds of millions of years. It may carry advantages, even more so in a modern world where populations of many species are rapidly dwindling, but it raises fundamental questions about the importance of sex.

And other uncertainties remain. Why among vertebrates, can fish, reptiles and birds have virgin births, but mammals, including humans, seemingly cannot? Even here, things aren't straightforward…


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