
Female shark learns to reproduce without males after years alone - perseusprime11
https://www.newscientist.com/article/2118052-female-shark-learns-to-reproduce-without-males-after-years-alone/
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irrational
How exactly did she _learn_ to do this? Is there a shark manual on asexual
reproduction that she has been boning up on?

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codazoda
She probably didn't and that makes the headline clickbait. At the end of the
article it points out that we probably just haven't observed this because we
aren't looking for it. Sharks are known to produce offspring asexually.

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phreenet
>One possibility was that Leonie had been storing sperm from her ex and using
it to fertilise her eggs. But genetic testing showed that the babies only
carried DNA from their mum, indicating they had been conceived via asexual
reproduction.

In this form of asexual reproduction are the babies genetic clones of the
mother?

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zaroth
From BBC via Google's infobox;

    
    
      Asexual reproduction needs only one parent, unlike sexual reproduction,
      which needs two parents. Since there is only one parent, there is no
      fusion of gametes and no mixing of genetic information. As a result, the
      offspring are genetically identical to the parent and to each other. They
      are clones.

~~~
maxerickson
I haven't figured out if it is all sharks or not, but apparently in many
previous observances the offspring have only been half clones of the mother.
The genes all come from the mother, the offspring just ends up with less
genetic diversity than the mother. The technical term is "automictic
parthenogenesis".
[https://en.wikipedia.org/wiki/Parthenogenesis#Automictic_par...](https://en.wikipedia.org/wiki/Parthenogenesis#Automictic_parthenogenesis)

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abandonliberty
>just ends up with less genetic diversity than the mother

"just"...

In humans, even a small loss in genetic variability such as cousin mating 1.5%
is bad enough that we have laws against it in nearly every society.

Charles II, the last Habsburg king of Spain, had lost 25% genetic diversity
and was mentally and physically disabled, and infertile. This genetic loss is
equivalent to parent-offspring or sibling mating.

Some animals, like lab mice, can survive without genetic diversity, but they
are much less fit and difficult to raise. Your half clone would have lost
nearly 100% of its genetic diversity. A near-full clone mechanism exists which
would preserves genetic diversity. We'd have to sequence this shark to find
out.

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tbirdz
>In humans, even a small loss in genetic variability such as cousin mating
1.5% is bad enough that we have laws against it in nearly every society.

I thought this sounded suspicious, so I looked it up, and it's not true.
Cousin marriage is legal in all of Europe, Australia and New Zealand, South
America, Canada, Mexico, the Middle East, Russia, and India.

In The USA, cousin marriage is allowed in 17 states. But 40 out of the 50
states allow cousin sexual relations and cohabitations.

The only places in the world that cousin marriage is illegal is in China,
Korea, Japan and some states in the US.

Whatever you think of cousin mating, it's just not true that "we have laws
against it in nearly every society." In fact, just the opposite, it is allowed
in nearly every society.

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shawndumas
Parthenogenesis...

[https://en.m.wikipedia.org/wiki/Parthenogenesis](https://en.m.wikipedia.org/wiki/Parthenogenesis)

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saycheese
Parthenogenesis is a natural form of asexual reproduction, though pretty sure
it is not the ONLY form asexual reproduction.

My guess is at this point it maybe unclear exactly what is going on.

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shawndumas
"Mum’s genes get passed down from female to female..."

That's the clue. Female to female === Parthenogenesis.

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roryrjb
Dr. Ian Malcolm: John, the kind of control you're attempting simply is... it's
not possible. If there is one thing the history of evolution has taught us
it's that life will not be contained. Life breaks free, it expands to new
territories and crashes through barriers, painfully, maybe even dangerously,
but, uh... well, there it is.

John Hammond: [sardonically] There it is.

Henry Wu: You're implying that a group composed entirely of female animals
will... breed?

Dr. Ian Malcolm: No. I'm, I'm simply saying that life, uh... finds a way.

~~~
elmar
Life imitates Art.

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maxerickson
The author wrote life into the art. Amphibian DNA was stuck into the dinosaurs
to make it harder for critics to criticize the parthenogenesis in the book.

Amphibian parthenogenesis is well documented:

[https://en.wikipedia.org/wiki/Parthenogenesis_in_amphibians](https://en.wikipedia.org/wiki/Parthenogenesis_in_amphibians)

~~~
logfromblammo
The book did not feature _parthenogenesis_. It featured _protogyny_. Some
individual females became male and bred with the individuals that remained
female.

This has been observed in West African common reed frogs ( _Hyperolius
viridiflavus_ ), as a result of population pressure. If the pond is a taco
fest, some of the frogs bring sausage.

This is actually more common in fish than in amphibians, but the book used
amphibian DNA.

~~~
arcticfox
I'm confused why you are downvoted - you appear to be correct.

~~~
bryanrasmussen
the taco fest sausage thing might have upset some people, I didn't downvote
but does seem somewhat gross.

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agentgt
While this is fascinating I still can't believe we still have never observed
many shark species giving birth particularly Great Whites.

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EdHominem
Learns how? Horrible title. As if the shark tried many times but finally
discovered this one simple trick...

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aclissold
(serious question) Do any genetic algorithms take something like this into
account? Seems like it could be a good way to increase the odds of furthering
successful generations.

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dragonwriter
IIRC, it's common for GAs to have variability as the only source of variation,
not crossbreeding. And those that do use crossbreeding usually don't have a
concept of the "sex" of an individual algorithm. So, crossbreeding of what are
effectively two haploid gametes (a polar body isn't exactly a gamete, but...)
from the same diploid individual when mates of the opposite sex are in short
supply isn't something that would be directly applicable to most genetic
algorithms.

You _could_ build a framework for evolving genetic algorithms where this would
be relevant and meaningful, but I'm not sure there is any good reason to
bother with all the complexity that would be necessary.

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aclissold
Gotcha. It's not that genetic algorithms are meant to emulate the real-world,
but rather that they're inspired by it.

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JumpCrisscross
> _A female shark separated from her long-term mate..._

Aw. Do most sharks exhibit long-term pair bonding?

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sndean
Some possibly do
([http://rsbl.royalsocietypublishing.org/content/9/3/20130003](http://rsbl.royalsocietypublishing.org/content/9/3/20130003)),
but many of the animals that are said to be monogamous are only ever proven to
be 'genetically monogamous'.

It's hard to prove whether one male's sperm simply outcompetes other sperm.

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dekhn
Parthenogenesis. A word I first saw in a Canned Heat album
([https://www.youtube.com/watch?v=YEaIiB4UV20](https://www.youtube.com/watch?v=YEaIiB4UV20)
love the jaw harp solo!). Then I asked my bio teacher about it and she
explained it. I figured it was something that only happened in "really simple
organisms" but then learned it was not uncommon amongst some animals.

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david-given
e.g. the New Mexico Whiptail Lizard, a.k.a. the 'Leaping Lesbian Lizards':

[http://guardianlv.com/2015/06/lesbian-lizards-a-hybrid-
speci...](http://guardianlv.com/2015/06/lesbian-lizards-a-hybrid-species-out-
of-new-mexico/)

They get the nickname because despite every member of the species being female
(and, except for minor mutational differences, clones of each other), they
still engage in faux-mating behaviour with each other --- they need the
stimulation to ovulate.

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greens231
this was reported first in 2011: [https://www.jumeirah.com/en/jumeirah-
group/press-centre/pres...](https://www.jumeirah.com/en/jumeirah-group/press-
centre/press-releases/press-releases-for-2011/jumeirahs-zebra-shark-is-first-
of-its-species-to-reproduce-through-parthenogenesis/)

~~~
nekopa
The main point in this article was that the shark did this after having had
babies with a mate before. That hadn't been observed in this species.

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joeskyyy
Probably stupid question, but I'll ask since others may have the same
question: Would all the offspring in this case be female?

I'm blanking on my old biology knowledge that's stored somewhere in the cold
storage of my brain haha

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ubernostrum
Like the other comment said, depends on the sex determination system. Which in
fish can get complicated -- there are quite a few types of fish which undergo
sex changes as a result of the environment they find themselves in. Anglerfish
(which become male if they find an adult female early in life, otherwise
female) are one well-known example. Clownfish are another: they live in
hierarchical groups where the dominant fish becomes the lone female and breeds
with the top male. If the female leaves or dies, the previous top male then
becomes female and breeds with the previous #2 male.

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pvaldes
Sequential hermaphroditism (sex changing) is in a different category. Sex
changing fishes still need a partner to have babies. Not the case here.

Another posibilities could be that sperm where provided by other shark species
in the same tank (The male DNA being discarded later) or that some chemical
compounds where released in the closed water system, triggering the ovocite
growth.

Finally, we could hypothesize that some old stored sperm could act as stimulus
for oocyte division, even if the male cells were too old and damaged to be
functional.

If you want to read some more about sex changing in fishes you can take a look
to this article, for example:

 _P.Valdes, A.Garcia-Alcazar, I.Abdel, M.Arizcun, C.Suarez & E.Abellan.
Aquaculture International. 2004, Vol 12(4). Seasonal Changes on Gonadosomatic
Index and Maturation Stages in Common Pandora Pagellus erythrinus_

(Yes, I'm the same P.Valdes)

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BadassFractal
Recommend reading
[https://en.wikipedia.org/wiki/The_Red_Queen:_Sex_and_the_Evo...](https://en.wikipedia.org/wiki/The_Red_Queen:_Sex_and_the_Evolution_of_Human_Nature)
if you are interesting in the topic. It goes way in depth into this and many
other common reproduction strategies.

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DoodleBuggy
Fascinating, some reptiles and plants do the same.

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sperm
Well I'll be damned.

