Slashdot Mirror
Female Shark Learns To Reproduce Without Males After Years Alone (newscientist.com)
An anonymous reader quotes a report from New Scientist: A female shark separated from her long-term mate has developed the ability to have babies on her own. Leonie the zebra shark (Stegostoma fasciatum) met her male partner at an aquarium in Townsville, Australia, in 1999. They had more than two dozen offspring together before he was moved to another tank in 2012. From then on, Leonie did not have any male contact. But in early 2016, she had three baby sharks. Intrigued, Christine Dudgeon at the University of Queensland in Brisbane, Australia, and her colleagues began fishing for answers. One possibility was that Leonie had been storing sperm from her ex and using it to fertilize her eggs. But genetic testing showed that the babies only carried DNA from their mum, indicating they had been conceived via asexual reproduction. Some vertebrate species have the ability to reproduce asexually even though they normally reproduce sexually. These include certain sharks, turkeys, Komodo dragons, snakes and rays. However, most reports have been in females who have never had male partners. In sharks, asexual reproduction can occur when a female's egg is fertilized by an adjacent cell known as a polar body, Dudgeon says. This also contains the female's genetic material, leading to "extreme inbreeding", she says. "It's not a strategy for surviving many generations because it reduces genetic diversity and adaptability." Nevertheless, it may be necessary at times when males are scarce. "It might be a holding-on mechanism," Dudgeon says. "Mum's genes get passed down from female to female until there are males available to mate with." It's possible that the switch from sexual to asexual reproduction is not that unusual; we just haven't known to look for it, Dudgeon says.
Life finds a way, life survives - any particular species may not. Life is resilient - but species are not. Indeed it could be argued that life is resilient BECAUSE species are not.
Unicode killed the ASCII-art *
The answer is (almost certainly) no. Parthenogeneses has never been observed in humans at all and has never been naturally observed in any mammal in fact. It does occur in some other species (fishes, reptiles and amphibians) but it is apparently impossible in mammals. The only cases in any mammals seen thus far were deliberately done by human intervention using the same types of techniques used for cloning.
Unicode killed the ASCII-art *
WTF? This has been known for decades.
I'm sure if you look at the WIkipedia article it has said this for at least several years...
Talk about Fake News.
Yes, perhaps it is better if you talk about fake news. This, however, is about science. I don't think I have read this particular article, but it has been mentioned in different places, and what is new, is the discovery that a female shark that has previously reproduced sexually, has been found to reproduce asexually several years later, which is a first. We had previously seen female sharks that grow up in captivity without males, can do this, but it was not obvious that this could also happen if they had mated in the past - it isn't unreasonable to think that mating might have triggered some mechanism - hormones or whatever - that would make asexual reproduction impossible.
Life, as a whole has survived every extinction level event that happened -but each has caused massive extinctions. Individual species come and go, as long as they don't all go at once, life persists.
Life could be reduced to a single species of extremeophile bacteria living around one volcanic vent in the pacific ocean tomorrow... and in a million years the world would, once again, be crawling with many different creatures.
In fact, the immediate aftermath of mass extinctions tend to be the time when the greatest biodiversity is found. With all the old species gone, practically *anything* can survive - so some really weird creatures evolve and thrive for a while. Then the numbers get big enough for resources to stop being abundant and natural selection kicks in. The worst species start failing and die out.
After a while you get into an equilibrium state - where every breeding pair of every species only produce, on average, two offspring the go on to breed again. That state lasts until the next major extinction level event.
The reason life can survive whatever the universe throws at it is because life doesn't rely on any particular species, any of them can be lost - it just needs SOMETHING to survive.
Unicode killed the ASCII-art *