Female shark learns to reproduce without males

after years alone

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Female shark learns to reproduce without males

#1  Postby Papa Smurf » Jan 17, 2017 2:39 pm

https://www.newscientist.com/article/21 ... ars-alone/

New Scientist wrote:Who needs men? 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.


Apparently the switch from sexual to a-sexual reproduction is what's most special here. Long-term storage of sperm was ruled out as the babies only carried DNA from their mum.
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Re: Female shark learns to reproduce without males

#2  Postby DavidMcC » Jan 17, 2017 4:08 pm

I'm not sure the NS used the appropriate term when it said that the shark LEARNED to reproduce asexually. It's surely better to say that its asexual mode was turned on by an extended absence of males to mate with.

EDIT: The shark does not even have to think about switching to asexual mode - it just happens, presumably as a result of chemical changes in its reproductive system.
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Re: Female shark learns to reproduce without males

#3  Postby Alan B » Jan 17, 2017 5:04 pm

And, of course, any offspring under these circumstances would always be female.
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Re: Female shark learns to reproduce without males

#4  Postby DavidMcC » Jan 17, 2017 5:36 pm

Alan B wrote:And, of course, any offspring under these circumstances would always be female.

That would make evolutionary sense, because it means that natural selection favours females when males aren't around in any case. However, it could be catastrophic if it goes on indefinitely, because it would lead to too much genetic uniformity, and therefore vulnerability to existential threats to the population.
Last edited by DavidMcC on Jan 17, 2017 5:37 pm, edited 1 time in total.
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Re: Female shark learns to reproduce without males

#5  Postby Animavore » Jan 17, 2017 5:37 pm

Alan B wrote:And, of course, any offspring under these circumstances would always be female.

Evidence that Jesus was a woman.
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Re: Female shark learns to reproduce without males

#6  Postby Evolving » Jan 17, 2017 5:42 pm

No, he had Holy Ghost DNA, with a Holy Ghost Y chromosome, and more Holy Ghost genes that gave him his super powers, like the Time Traveller's Wife.

EDIT I mean the time traveller himself, obviously.
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Re: Female shark learns to reproduce without males

#7  Postby scott1328 » Jan 17, 2017 11:24 pm

Alan B wrote:And, of course, any offspring under these circumstances would always be female.

Sharks use ZW sex determination system. the shark pups were likely male.
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Re: Female shark learns to reproduce without males

#8  Postby Alan B » Jan 18, 2017 10:44 am

scott1328 wrote:
Alan B wrote:And, of course, any offspring under these circumstances would always be female.

Sharks use ZW sex determination system. the shark pups were likely male.

Ah! Didn't know that.

Might not be a wise evolutionary move... :think:
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Re: Female shark learns to reproduce without males

#9  Postby DavidMcC » Jan 18, 2017 11:44 am

Alan B wrote:
scott1328 wrote:
Alan B wrote:And, of course, any offspring under these circumstances would always be female.

Sharks use ZW sex determination system. the shark pups were likely male.

Ah! Didn't know that.

Might not be a wise evolutionary move... :think:

Depends on the relative importance of sexual reproduction to the shark population. In the long term, it is obviously important, but the sharks wouldn't "know" that, would they?
Also, I would like to have a more definitive answer than "the shark pups were likely male".
It is unfortunate that Alice didn't mention the gender, but IIRC, sharks only give birth to one live animal at a time - two develop initially, but the first to develop eats the other one, and then there is one!

EDIT: Ah, maybe this only applies to great whites? :dunno:
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Re: Female shark learns to reproduce without males

#10  Postby Calilasseia » Feb 07, 2017 8:26 pm

In the case of the ZW chromosome system, the homogametic individuals (ZZ) are male, whilst the heterogametic individuals (ZW) are female.

in the case of this shark, if the ability to produce viable diploid eggs was present, then the obvious choice is for the eggs to be heterogametic like their mother (ZW). It's a bit difficult to see how a Z and W chromosome could be swapped between eggs in order to facilitate the emergence of ZZ eggs, because [1] this would require a mechanism that as far as I'm aware, isn't known to exist by biologists, and [2] would have as a side effect producing non-viable WW eggs. That is, unless there are known instances of WW individuals being viable in species with this determination system.
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