The female Amazon Molly fish has been using the "I have a head ache" excuse for 700 centuries*, baffling evolutionary scientists and frustrating blue-balled male Molly's. So why is this cold fish, which should have become extinct 70,000 years ago, still flapping around? Scientists think it's the "occasional sex with strangers," "tricks" and "something special going on."
The Telegraph has the story
A female fish which hasn't had full sex for at least 70,000 years is baffling scientists.
Amazon Molly fish defies evolution by reproducing without a male
The Amazon Molly fish defies evolutionary rules by reproducing without the help of a male Molly.
In fact there aren't any male Molly fish and the female relies on a dalliance with males of other species.
This triggers her reproductive cycle but she doesn't seem to use any of the sperm passed by her partner.
And when her young are born they inherit only her genes and nothing from the male.
Scientists at Edinburgh University have been studying the Molly in an effort to discover how the species has managed to survive.
Sex is usually crucial because it enriches the genetic complement, or genome. It mixes genes much more quickly than random DNA mutations and helps new species to evolve and change with their environment.
Normally a creature that reproduces asexually misses out on this opportunity, fails to adapt to changes and eventually succumbs to extinction.
The scientists used powerful computing systems to calculate complex genetic changes over many thousands of generations which should have brought the Molly's tenure on Earth to an end.
They were able to show for the first time that it should have died out 70,000 years ago but in fact it still thrives in rivers in south-east Texas and north-east Mexico.
The researchers suspect it may be using special genetic survival "tricks" which keeps the species going including taking some of the male's DNA to revitalise its gene pool.
Dr Laurence Loewe, of the university's School of Biological Sciences, said: "What we have shown now is that this fish really has something special going on and that some special tricks exist to help this fish survive.
"Maybe there is still occasional sex with strangers that keeps the species alive. Future research may give us some answers."
"I think one of the interesting things is that we are learning more about how other species might use these tricks as well and might have a more general importance."
The Edinburgh-led study was carried out in collaboration with the Austrian Academy of Sciences and the findings are published in the journal BMC Evolutionary Biology.
*CORRECTION (thanks to solstice2005): Scanner Katie originally wrote "Lady Fish Goes Without Sex For 7,000 Years" and for "7 centuries." The correct numbers are, of course, 70,000 and 700 centuries. Scanner Katie just couldn't fathom going without sex for 70,000 years so subconsciously replaced it with the more palatable 7,000-year-long dry spell.