How microscopic creatures survive without sex for 50 million years

February 2nd, 2010 - 1:54 pm ICT by ANI  

Washington, Feb 2 (ANI): Reports have it that there is one creature in the world that can survive without sex for 50 million years, by simply drying up.

For most animals, sex is not only a way of producing the next generation, but a means of keeping enemies at bay.

“If an organism stops having sex and crystallizes its genome, all of (its enemies) catch up with it evolutionarily and can quickly overwhelm it,” explained Paul Sherman, a neurobiologist at Cornell University in New York.

This idea, known as the Red Queen Hypothesis, helps explain why most animals go to great lengths to find mates and have sex.

But according to a report in National Geographic News, the bdelloid rotifers, microscopic asexual freshwater invertebrates, have survived by abstaining from sex for the last 30 to 50 million years.

In that time the rotifer has proliferated into more than 450 species found around the globe.

In contrast, other creatures that reproduce without sex - such as the nematode worm - are expected to die out after several hundred thousand years.

When faced with the threat of parasitic fungi, the rotifers dry up and allow themselves to be blown away by the wind.

They come back to life when exposed to freshwater. Scientists estimate that nearly 100 rotifers can fit into a single drop of water.

So while most animals are locked in evolutionary arms races with their foes, bdelloid rotifers escape them altogether simply by being carried on the wind.

To figure out the bdelloids’ trick, Sherman and his colleague Chris Wilson, also at Cornell, infected populations of rotifers in freshwater with deadly fungi and found they all died within a few weeks.

The team then dried out other infected populations for various lengths of time before re-hydrating them.

They found that the rotifers could live longer without water than their fungi enemies.

The longer the infected populations remained dried out, the more likely they were to survive.

In a second experiment, the scientists placed the desiccated, fungus-exposed rotifers in a wind chamber.

They observed that the rotifers were able to blow away and leave the fungi behind.

The scientists think that by drying out and drifting - sometimes for thousands of miles - the rotifers can continually establish new, uninfected populations.

“The bdelloids are playing this never-ending game of hide-and-seek,” said Sherman. (ANI)

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