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A species of beetle mite survived for thousands of years without having sex

They are called "ancient asexual scandals".

A species of beetle mite survived for thousands of years without having sex
The beetle mite, Oppiella nova. M. Maraun, K. Wehner

Nature has figured out the recipe for success. However, success can manifest itself in an infinite number of ways.

That seems to be the case in a new study demonstrating for the first time that asexual reproduction can be successful in the long term. Until today, the survival of an animal species over a geologically long period of time was thought to be extremely implausible — if not impossible. The new findings, which were published in the journal PNAS, paint a quite different narrative.

A team of zoologists and evolutionary biologists from the Universities of Cologne and Göttingen, the University of Lausanne, and the University of Montpellier demonstrated for the first time in animals of the ancient asexual beetle mite species, Oppiella nova, the so-called Meselson effect, which describes a characteristic trace in an organism's genome that suggests purely asexual reproduction. The Meselson effect had never been proven conclusively in animals — until now.

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The survival of a species without sexual reproduction

The genetic variety produced in offspring by the encounter of two different genomes that a pair of parents can supply is a significant evolutionary advantage of sexual reproduction. This is one of the reasons why the existence of ancient asexual animal species such as O. nova are tough for evolutionary biologists to explain.

After all, asexual reproduction appears to be exceedingly unfavorable in the long run. Or else, why would practically all animal species reproduce entirely sexually?

Animal species that are all female, such as O. nova, are thus referred to as "ancient asexual scandals", according to the press release. For some animals, the mating game can be so inconvenient that doing it alone and reproducing asexually is sometimes the best option. In fact, these beetle mites have been quite all right living a chaste lifestyle for millions of years.

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However, proving that the ancient asexual organisms do, in fact, reproduce purely asexually and that have done so for a very long time has been an extremely difficult task.

Analyzing the genetic information of mites: "A Sisyphean task"

In order to prove that the species is entirely asexual, the researchers sequenced and analyzed the genetic information of several populations of O. nova and the nearly similar, but sexually reproducing species Oppiella subpectinata in Germany. However, this wasn't an easy job.

"These mites are only one-fifth of a millimetre in size and difficult to identify," explained Jens Bast, Emmy Noether junior research group leader at the University of Cologne’s Institute of Zoology. Analyzing the genome data was a tedious task and necessitated the use of computer programs that were specifically created for this purpose.

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At the end, the team came out on top and was able to prove the Meselson effect, showing that the O. nova beetle mite clones itself rather than reproducing.

"Our results clearly show that O. nova reproduces exclusively asexually. When it comes to understanding how evolution works without sex, these beetle mites could still provide a surprise or two," Bast said.

This demonstrates that, while a species' survival without sexual reproduction is extremely rare, it's not impossible. While asexual reproduction is not without issues, the beetle mite appears to be an exception to an otherwise pretty consistent biological rule, which is why the team's next step will be to figure out what makes them so unique.

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