Virgin Shark Gives Birth

27 May 2007


Back in 2001, a rather far-fetched story hit the headlines declaring that a baby shark had been born in an aquarium tank to a virgin female shark. And it turns out, the immaculate conception did actually happen.

The miraculous birth of the bonnethead shark - a close relative of hammerhead sharks with their peculiar-shaped heads - took place in Henry Doorly Zoo, in Nebraska in the United States.Bonnethead shark

Until now scientists thought that the unlikely sex-free birth was probably a consequence of the females storing sperm from their time in the wild.

But now, 6 years later a genetic study carried out by a team of American and Irish scientists, has confirmed that it was indeed an immaculate conception - a process known scientifically as parthenogenesis.  Instead of needing sperm from a male to fertilise their eggs, some females can produce embryos without having sex. In fact, parthenogenesis has been observed in birds, reptiles, amphibians and bony fish - but it has so far never been seen in mammals, and this is the first time its been observed in sharks.

This is certainly an incredible discovery to find that this form of asexual reproduction can take place in such a ancient group of animals - sharks in one form or another have been around on the planet for 450 million years.

But there is also a worrying side to this story.  Baby sharks produced by this particular form of asexual reproduction, have much lower genetic diversity than their mothers which means they are much less well equipped to survive in the wild.  So if male sharks become scarce in the oceans due to the heavy fishing pressure from us humans, it is possible that females will increasingly rely on this form of asexual reproduction, and ultimately shark populations could quickly loose vital genetic diversity.


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