No Sex Please We're Rotifers
By Anne Pawsey
It seems fair to say that the human race is so obsessed with sex the idea of going without it seems nigh on impossible. Yet there are creatures who mange to do with out it for ages – in one case 40 million years.
This creature is the bdelloid rotifer, a tiny creature that lives in wet and wonderful environments such as ponds, lakes, mosses and lichens. They reproduce by cloning themselves, the mothers laying eggs that are genetically identical to them; this means that they have added bonus of being able to do with out males.
However, the surprising thing is that these creatures have evolved and adapted to their environment without resorting to sex.
Previously, many scientists had thought that sexual reproduction was necessary for speciation because of the importance of interbreeding in explaining speciation in sexual organisms. Asexual creatures like the bdelloid rotifers were known not to be all identical, but it had been argued that the differences might arise solely through the chance build-up of random mutations that occur in the 'cloning' process when a new rotifer is born.
But researchers at Imperial College London have found that the creatures have evolved into separate species ideally suited to their habitats.
"One remarkable example is of two species living in close proximity on the body of another animal, a water louse.” said Dr Tim Barraclough who led the study, “One lives around its legs, the other on its chest, yet they have diverged in body size and jaw shape to occupy these distinct ecological niches. Our results show that, over millions of years, natural selection has caused divergence into distinct entities equivalent to the species found in sexual organisms."
It makes us wonder quite how Dr Barraclough thinks organisms evolved in the billion or so years before sexual reproduction appeared on the scene.
The results have also surprised researchers as it was not thought that asexual species could survive this long; it might now be necessary for the mechanisms of evolution to be re-evaluated.
This creature is the bdelloid rotifer, a tiny creature that lives in wet and wonderful environments such as ponds, lakes, mosses and lichens. They reproduce by cloning themselves, the mothers laying eggs that are genetically identical to them; this means that they have added bonus of being able to do with out males.
However, the surprising thing is that these creatures have evolved and adapted to their environment without resorting to sex.
 |
| Bdelloid rotifers and their jaws. Is it any wonder they aren't getting any? (Credit: Diego Fontaneto / Courtesy of PLoS Biology) |
But researchers at Imperial College London have found that the creatures have evolved into separate species ideally suited to their habitats.
"One remarkable example is of two species living in close proximity on the body of another animal, a water louse.” said Dr Tim Barraclough who led the study, “One lives around its legs, the other on its chest, yet they have diverged in body size and jaw shape to occupy these distinct ecological niches. Our results show that, over millions of years, natural selection has caused divergence into distinct entities equivalent to the species found in sexual organisms."
It makes us wonder quite how Dr Barraclough thinks organisms evolved in the billion or so years before sexual reproduction appeared on the scene.
The results have also surprised researchers as it was not thought that asexual species could survive this long; it might now be necessary for the mechanisms of evolution to be re-evaluated.
Visit Anne's page for more fruity science.
 |
Age Ain't Important |
 |
Spandex Space Suits |
|
 |
The Blob from Outer Space |
 |
Health Food Makes Us Fat |
|
Image: Jenny Erickson
