Shark Gives Virgin Birth
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Scientists confirm that female hammerhead sharks can reproduce without having sex. The evidence comes from a shark at Henry Doorly Zoo in Nebraska which gave birth to a pup in 2001 despite having had no contact with a male.
Genetic tests by a team from Belfast, Nebraska and Florida prove conclusively the young animal possessed no paternal DNA, Biology Letters journal reports.
Parthenogenesis (out of the Greek for “virgin birth”), as this type of reproduction is known, occurs when an egg cell is triggered to develop as an embryo without the addition of any genetic material from a male sperm cell.
The puzzle over the bonnethead birth — a species of the hammerhead group — was widely reported in 2001, but it is only with the new DNA profiling techniques that scientists have now been able to show irrefutably what happened.
The investigation of the birth was conducted by the research team from Queen’s University Belfast, Nova Southeastern University in Florida, and Henry Doorly Zoo itself.
In the wild, these animals have come under extreme pressure through overfishing and many species have experienced sharp declines.
If dwindling shark groups resort to parthenogenesis to reproduce because females have difficulty finding mates, this is likely to weaken populations still further, the researchers warn.
The reason is that asexual reproduction reduces genetic diversity and this makes it harder for organisms to adapt — to changed environmental conditions or the emergence of a new disease.
With normal sex, the mixing of maternal and paternal DNA introduces genetic novelty which can give animals new traits that might be advantageous in their new circumstances.
Dr Paulo Prodohl, a co-author on the Biology Letters paper from Queen’s School of Biological Sciences, said: “Vertebrates in general have evolved away from parthenogenesis to boost genetic diversity and enhance evolutionary potential.”
“The concern for sharks is that not only could we be reducing their numbers but we could be making them less fit as well.”
“Our findings will now have to be taken into consideration for any conservation management strategy, especially for overexploited species.”
The birth of the hammerhead (of the bonnethead species, Sphyrna tiburo) at Henry Doorly was as tragic as it was puzzling.
The new pup was soon killed by a stingray before keepers could remove it from its tank.
Some theorized that a male tiger shark kept at the zoo could have been the father — but the institution’s three bonnethead females had none of the bite marks that are usually inflicted on their gender during shark sex. Wow, how’s that for rough sex.
Some even suggested that one of the females could have had sex in the wild and stored the sperm in her body — but the three-year period in captivity made this explanation highly unlikely.
The new tests on the dead pup’s tissues now show the newborn’s DNA only matched up with one of the females — and there was none of any male origin.
Hammerhead Sharks
Hammerhead sharks off Cocos Island.
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I would never have know this was possible. Have there been any other species that have been able to do this?
Mark, yes, apparently “virgin birth” occurs naturally in a number of lower plants and animals, invertebrates such as water fleas, aphids, some bees and parasitic wasps, and vertebrates — some reptiles, fish, and very rarely, birds.
Parthenogenesis is sometimes also used to describe reproduction modes in hermaphroditic species which can self-fertilize.
That’s pretty amazing. we’re just finding this out?
Ron, it doesn’t appear to be very broadly touched on, but I did come across an article today about a Komodo Dragon over a year ago that had a ‘virgin birth’. So it isn’t a very recent discovery.
It’s pretty amazing what nature can do to maintain a species’ existence.
[...] Stories: Shark Gives Virgin Birth Albino Alligator Kept in the Dark Octopus Octi Performs Bottle Tricks Chimps Play Computer Games [...]
[...] Komodos are capable of parthenogenesis — out of the Greek for “virgin birthâ€? — which occurs naturally in a number of lower plants and animals, invertebrates such as water fleas, aphids, some bees and parasitic wasps, and vertebrates — some reptiles, fish, and very rarely, birds. See our article for a shark that recently gave a virgin birth. [...]
[...] stories: Shark Gives Virgin Birth Albino Alligator Kept in the Dark Octopus Octi Performs Bottle Tricks Tags:animals Boto Botos [...]
Please check out the excellent documentary Sharkwater. It will change your mind (as it did mine) about buying another shark-related item. Please spread the word about the slaughter of sharks and the danger sharkmeat poses to children and pregnant women (as it is extremely high in mercury). Even if you don’t care about the animal, you owe it to yourself and future generations to protect the sharks. When they get wiped out (and they are being killed at a dangerously high rate), our oxygen supply (and obviously, health) will be messed up, as well. There are plenty of other things for us to eat without threatening our environment and future.
Thanks for your wonderful input Mika. I have seen excerpts of the film, which is truly amazing. You can see a brief clip of it, along with more information on sharks for an article here for 7 Incredible and Bizarre Underwater Inventions and Feats
Wow – I never would have imagined that they could do that! Great post.
This is intriguing. I know smaller animals reproduce asexually , but a shark? Very strange. Although I’m sure this would only happen infrequently and if the female was in isolation. Maybe one day humans shall evolve similarly!
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