Evolutionary Hide & Seek: Species Avoids Extinction By Abstaining from Sex for 30 Million Years

They haven't had sex in some 30 million years, but some very small invertebrates named bdelloid rotifers should have gone extinct long ago. Cornell researchers have discovered the secret to their evolutionary longevity: they are microscopic escape artists.

"These animals have evolved a way to avoid parasites and pathogens by drying up and blowing away," said Paul Sherman, Cornell professor of neurobiology and behavior.

"These animals are essentially playing an evolutionary game of hide and seek," said Sherman. "They can drift on the wind to colonize parasite-free habitat patches where they reproduce rapidly and depart again before their enemies catch up. This effectively enables them to evade biotic enemies without sex, using mechanisms that no other known animals can duplicate."

After drying up, bdelloids come back to life when re-exposed to fresh water. The Cornell study is featured on the cover of the Jan. 29 issue of Science.

Bdelloid rotifers (pronounced DELL -- oyd ROW-tiff-ers) are tiny, freshwater invertebrates that have long puzzled scientists because, as completely asexual animals, they should have been extinguished by parasites and pathogens long ago in evolutionary time. Instead, the bdelloids have proliferated into more than 450 species. Asexual animals like rotifers reproduce by cloning and this makes for a fixed gene pool.

Many scientists believe that the function of sex itself is to shuffle genes around. They theorize that the fresh genetic combinations that which sex provides allow sexual animals to fend off relentlessly evolving parasites and pathogens.

The discovery that bdelloids can desiccate and wisp away with the wind helps resolve the mystery of their ancient asexuality and success. "It also helps answer one of the deepest puzzles in evolutionary biology -- why sex is nearly ubiquitous," said Chris Wilson, a Cornell doctoral candidate in Sherman's lab..

To study the bdelloids' adaptations, Wilson infected populations of rotifers with deadly fungi and found that they all died within a few weeks.

He then tried drying out other infected populations for varying lengths of time before rehydrating them. He found that the fungi were far more sensitive to dehydration than the rotifers. The longer the infected populations remained dried out, the more successful they were at completely ridding themselves of fungi and eluding death.

In a second wave of experiments, Wilson placed dried, fungus-infected rotifers in a wind chamber. The scientists observed that the rotifers were able to disperse without the fungi and establish parasite-free populations. After just seven days of blowing around, there were as many fungus-free rotifer populations as there were after three weeks of dehydration without wind. So, by drying and drifting passively on the wind -- sometimes for hundreds of miles -- bdelloids can continually establish new, uninfected populations.

Casey Kazan Via Cornell University, via EurekAlert

Comments

[Raj Aryan]

Biology rocks !

[anon]

Lots of organisms can reproduce asexually... i don't get why this one is such a big deal.

[Emma]

Because they're animals.

[Bill]

It is also an anomaly because they've survived effectively without developing pathogens, something quite amazing.

[fajita]

talk about badasses

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i don't get why this one is such a big deal.

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It's a big deal because there are BARELY any surviving animals that reproduce asexually(this might actually be the first example).

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It's a big deal because there are BARELY any surviving animals that reproduce asexually(this might actually be the first example).

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other than bacteria, this can be big

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You say this can be big, but i'm confused. Its great that we've found an animal that has avoided extinction, but how does this change anything? Its not going to cure the problem that a lot of species of animals are near extinction. Am I missing something here??

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surviving animals that reproduce asexually(this might actually be the first example).

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Bdelloid rotifers (pronounced DELL -- oyd ROW-tiff-ers) are tiny, freshwater invertebrates that have long puzzled scientists because, as completely asexual animals, they should have been extinguished by parasites and pathogens long ago in evolutionary time. Instead, the bdelloids have proliferated into more than 450 species. Asexual animals like rotifers reproduce by cloning and this makes for a fixed gene pool.

[Peter]

My wife has a similar attitude!

[Tristan]

"It also helps answer one of the deepest puzzles in evolutionary biology -- why sex is nearly ubiquitous," that's why it's important

[Ashley]

This article is deceptively titled.

This species hasn't survived extinction BY abstaining from sex, they've avoided it DESPITE lacking sexual reproduction.

I read the article and I fail to see how their abstinence has anything to do with their remarkable survival mechanisms. For the love of crap, can we stop with the sensationalist article titling, already? First NASA's "alien life" discovery, now this bullsh*t ...

[Paul]

I agree with Ashley the title is deceptive. They seemed to have survived with the dry and blowing strategy.

@fajita "i don't get why this one is such a big deal."
These seem to be the only known organism using this strategy would qualify as interesting or "big deal" to me. Or maybe you are like Raj who is going to start a discussion not based on the contents, but headline - "Lots of organisms can reproduce asexually"

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These animals really survived even in thousands of years amazing!

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