London, Apr 23 : It doesn’t have sex and should be extinct by now, but
the tiny fish, Amazon Molly – that has survived for 70,000 years – is
still swimming against the evolutionary tide, say researchers.

Scientists have shown that the Amazon Molly is defying some laws of evolution by avoiding extinction.

Researchers believe that the fish may be employing special genetic
survival “tricks”, and they are now trying to understand more about how
the species has managed to stay alive.

Amazon Molly fish, all of which are female, interact sexually with males of other species to trigger their reproduction process.

The males' sperm sparks the development of an embryo, but none of the
male DNA is actually passed on to the offspring. Only the mother's
genes are inherited.

Typically, when creatures reproduce asexually, harmful changes creep into their genes over many generations.

The species will eventually have problems reproducing and can often fall victim to extinction.

University of Edinburgh researchers have been studying complex
mathematical models on a highly powerful computing system to look at
the case of the Amazon Molly.

Researchers calculated the time to extinction for the fish, based on
modelling genetic changes over many thousands of generations.

They are now able to say conclusively, for the first time, that the
fish ought to have become extinct within the last 70,000 years, based
on the current simple models.

Scientists believe the fish, which are still thriving in rivers in
south-east Texas and in north-east Mexico, are using special genetic
survival "tricks" to help them stay alive.

One theory is that the fish may occasionally be taking some of the DNA
from the males that trigger reproduction, in order to refresh their
gene pool.

"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 to
survive. Maybe there is still occasional sex with strangers that keeps
the species alive. Future research may give us some answers,” The
Scotsman quoted Dr Laurence Loewe, of the university's School of
Biological Sciences, as saying.

The study is published in the journal BMC Evolutionary Biology. (ANI)