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Most animals reproduce sexually, a process which shuffles genes from parent to offspring. This makes natural selection more efficient and allows animals to evolve defences against changing environmental conditions more rapidly, especially new diseases.
Bdelloid rotifers however appear to be an exception to this rule: they are all female, and their offspring are clones of their mothers. Bdelloids are microscopic animals that live in freshwater and damp habitats across the world. Despite their apparent lack of sex, we know they have evolved for tens of millions of years into more than 500 species.
Genomes - Set - Genes - Animal - Characteristics
By studying their genomes -- the set of all the genes that define an animal's characteristics -- researchers thought they had identified an explanation for how bdelloids had 'gotten away' with no sex for millions of years.
However, a new study, published today in PLOS Biology and led by Imperial College London researchers, reveals this mechanism may not be the main explanation for the bdelloids' success.
Species - Endure - Periods - Desiccation - Desiccation
Many species of bdelloid endure periods of drying out, called desiccation. Although they survive desiccation, the process damages their DNA, which they need to repair when rehydrated.
Based on a previous study of the genome of a species that survives desiccation, researchers had proposed that the repair of DNA might remove some of the problems of being asexual, for example by removing harmful mutations and possibly allowing occasional recombination of genes to occur.
Theory - Predictions - Genomes - Number - Species
This theory made key predictions about what the genomes of the small number of bdelloid species that cannot survive desiccation should look like. The new study looked at the genomes of three further species, including some that do not undergo desiccation.
The researchers found that the predicted differences between species that can and cannot survive desiccation were not observed. This suggests that DNA repair following desiccation may not be as important as previously thought, and...
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