Some animal species can survive successfully without sexual reproduction: study

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TORONTO – An international team of researchers has discovered that some animals can survive very long periods, perhaps millions of years, without sexual reproduction.

By studying a tiny species of beetle mite, barely a fifth of a millimeter in size, scientists have found that asexual reproduction can be successful in the long term.

The study authors note that until now, survival of an animal species over a geologically long period without sexual reproduction was considered highly unlikely, if not impossible.

Asexual reproduction involves one parent and produces offspring that are genetically identical to each other and the parent, while sexual reproduction involves two parents and produces genetically unique offspring.

Using the mite Oppiella nova, an entirely female species, researchers at the universities of Cologne and Göttingen, the University of Lausanne in Switzerland and the University of Montpellier in France have demonstrated for the first time the Meselson effect in animals.

According to the study, the Meselson effect is a characteristic trace in the genome of an organism that suggests “purely asexual reproduction”.

In the study, the researchers looked at different populations of Oppiella nova and the closely related but sexually reproducing species Oppiella subpectinata in Germany and sequenced their genomes. The study found that the sequencing of the genomes of Oppiella nova showed the Meselson effect.

The results were published Tuesday in PNAS peer-reviewed scientific journal.

Scientists had previously regarded the Oppiella nova species as an “ancient asexual scandal” because they could not determine how beetles managed to reproduce without having sex.

Initially, the study notes that biologists believed these beetles were hiding their reproductive acts.

“There could be, for example, some sort of ‘cryptic’ sexual exchange that is not known. Or not yet known,” said study lead author Alexander Brandt of the University of Lausanne in a report. Press release.

“For example, very rarely could a breeding male be produced after all – maybe even ‘by accident’,” he added.

However, the beetle mite Oppiella nova clones rather than reproduces, according to the study.

Researchers say the existence of ancient asexual animal species can be difficult to explain because asexual reproduction can seem “very disadvantageous” in the long run due to a lack of genetic diversity.

Biologists say there is generally an “evolutionary advantage” to having two different genomes that only a pair of parents can provide. Through sexual reproduction, this ensures a constant “mixing” of the two copies “of the genome in each of their cells.

This means that the two sets of genetic information remain very similar, but there are differences that allow organisms on earth to adapt over time, changing characteristics that best suit the changing environment.

Researchers have also discovered that it is possible for asexually reproducing species to introduce genetic variance into their genomes and thus adapt to their environment during evolution, despite producing genetic clones of them. themselves.

Scientists say that the lack of “genome mixing” with respect to sexual species causes the two copies of the genome of asexual animals to accumulate distinct mutations and evolve independently over time.

While the survival rate of a species without sexual reproduction is quite rare, scientists conclude that it is not impossible.

“Our results clearly show that O. nova reproduces exclusively asexually. When it comes to understanding how evolution works without sex, these beetle mites might still surprise,” said Jens Bast, group leader junior research fellow at the University of Cologne. in the press release.

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