Girl-only fish species survives by cloning Researchers are pondering how an exclusively-female fish species has survived without genetically self-destructing itself into extinction, the BBC reports. The Amazon Molly, found in Mexico and Texas, reproduces by cloning, and while it does "interact" with chaps from other species to "trigger its reproduction process", doesn' …
So they get together with males of other species to trigger reproduction? Sounds just like the Asari in Mass Effect to me. Though they apparently do use the partner's DNA (I wonder if that's what the Amazon Molly is somehow doing)?
Sigh... I'll never forget my brief liaison with Liara... possibly the funniest moment in any computer game ever, and as sexually charged as a late night Channel 5 movie, yet it somehow still managed to irk the censors!
Actually they do use males... of other species, just to get excited and expell the eggs.
Anyhow there's been some recent research also on some other asexual complex animals (rotifers) and it seems they have other tricks to keep their genome healthy and variegated (http://www.sciencedaily.com/releases/2008/04/080402145746.htm): they repair their broken DNA, causing random changes. This seems to be an adaptation to dehidratation but it also protects them from radiation.
The Amazon Molly parthenogen species complex is know for many years as just that; the females need to be stimulated in some sense by the presence of male sperm but then go on with the standard split-my-own-cells-and-stick-them-back-together way of sexless reproduction. So that's not news.
Many models try to explain why this is bad, and really so bad that it's even worse than sex(*). It goes all the way back to famous brit RA Fisher, pointing out that if a mother makes 2 daughters per generation (as will those) then your population doubles every generation; if a mother has to make 1 son and 1 daughter per generation (to mate with another mother's offspring) at the same cost, then the population stays at the same level. (If both make 4 children, it's "doubles" versus "quadruples", etc.) This is the famous "2-fold cost of sex". So any heritable trait that lets you avoid this cost will be very advantageous.
So what they in the BBC article claim to have done, is make a model along these lines, run the numbers and find out the outcome didn't fit. Thus only pointing out some assumption somewhere is wrong? I don't get it, are peer review standards slipping?
The most typical arguments contra parthenogenesis are M"uller's Ratchet and similar, that the recombination in sex allows you to combine good, or less-damaged, genes with other good ones and maintain your population's health; without recombination you will eventually have bad mutations in each gene and no way to improve this. [One way to repair this is recombination-with-yourself, so that the daughter is not an identical copy of you, but in each locus has either both alleles that the mother had or two copies of one of the two --- drawback is that you lose a lot of variation until everybody has 2 copies of the same allele in each locus anyway; but after that it's a good way to repair your genome.]
But these not-working models or not-fitting numbers are old news; a working one would be good news. Hm.
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*No it didn't surprise anyone that it was an (very very late-victorian) englishman that tried to convince the world what a pointless and costly distraction sex is.
The current Focus magazine has a big article about this (in fact it's the cover story), looks like it's reasonably common in fish, sharks if kept in all female tanks may "clone" themselves without males triggering it, mind you it's the exception rather than the rule, it's a very interesting thing, but what sets this fish apart is the fact it (a much 'higher' animal than a rotifier) does it as a rule without genetically killing itself, maybe other species have done this and died out because of it?
> Many models try to explain why this is bad ...
Sounds like the guy who came up with this theory has anthropomorphised it a bit. For most species, the more offspring, the better, unless of course they consume all the available food supply and eat themselves into extinction. But that's got nothing to do with whether they're all the same gender or not - many (most?) species produce multiple offspring in a single litter. Not all the offspring will survive to maturity - the greater the number you produce in a hostile environment, the greater the number that will survive to reproduce, since fish aren't known for their nuturing skills.
I just want to know: without any males, what do they spend their time complaining about?
When I read the tagline, I was thinking more on the lines of "village bicycle"...
"Quite how it has survived remains a mystery, although one theory suggests occasional liaisons with males in which DNA is taken on board to "refresh" the species' genetic make-up."
There must be so few of these males... so perhaps "village bicycle" is the correct term after all.
If the females self-replicate, I assume they all have identical DNA, and come from a single ancestor (from a Darwinian perspective). If that's so, where do the males come from?
The extraterrestrial explination would, of course, be Intelligent Design, since Darwin was, in fact, terrestrial. Or a terrist?
All sounds a bit unfair to me.....male fish, minding his own business, female comes up to him and rubs against him a few times and then buggers off. He's left wondering what the hell just happened (and frustrated) until x weeks later when the demand for child support payments comes through the door!
Hang on....I know marriages like that.....
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