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Riddle of the sexless rotifer solved, biologists say
Jan. 28, 2010
Courtesy Science
and World Science staff
An enduring mystery of biology has been solved, according to scientists. One that didn't make it:
This bdelloid rotifer was killed by a fungal parasite,
Rotiferophthora
angustispora, researchers say. Spore-bearing elongations or
hyphae formed
by the parasite sprout out from the digested corpse. Although this one
failed to dry up in time to kill off its tormentor, the other members the
clonal rotiifer population can still find time to dry up and escape,
scientists say. (Image courtesy Kent Loeffler, Kathie T. Hodge and C.G.
Wilson)
Researchers had wondered why the bdelloid rotifer, a microscopic freshwater animal, hasn’t died off after reproducing without sex for millions of years.
By relying exclusively on asexual or sexless reproduction, each rotifer creates genetically identical offspring, clones of itself. This would seem to shut off most possibilities of change or adaptation over generations, compared to sexual reproduction, in which each offspring recombines its parents’ genes in new ways.
Therefore, an entirely sexless creature would presumably lose the “arms race” that is the struggle for survival. Adaptable creatures such as parasites, known to afflict bdelloid rotifers in particular, would eventually finish them off.
Researchers have now come up with a solution. It seems that the bdelloid rotifer has already evolved an anti-parasite defense so ruthlessly effective that it has closed off any room for a viable counter-maneuver by the parasites, at least so far.
Christopher G. Wilson of Cornell University in New York and colleagues raised populations of the rotifers in a laboratory, and noticed that the asexual invertebrates could rid themselves of a deadly fungal parasite by drying themselves up completely and blowing away with the wind to new territory.
The rotifers became so dry that their parasites couldn’t survive the punishing conditions. They were then able to ride the breeze and start afresh in new, presumably parasite-free pastures.
The research appears in the Jan. 29 issue of the research journal
Science.
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An enduring mystery of biology has been solved, according to scientists. Researchers had wondered why the bdelloid rotifer, a microscopic freshwater animal, hasn’t died off after reproducing without sex for millions of years. By relying exclusively on asexual or sexless reproduction, each rotifer creates genetically identical offspring, clones of itself. This would seem to shut off most possibilities of change or adaptation over generations, compared to sexual reproduction, in which each offspring recombines its parents’ genes in new ways. Therefore, an entirely sexless creature would presumably lose the “arms race” that is the struggle for survival. Adaptable creatures such as parasites, known to afflict bdelloid rotifers in particular, would eventually finish them off. Researchers have now come up with a solution. It seems that the bdelloid rotifer has already evolved an anti-parasite defense so ruthlessly effective that it has closed off any room for a viable counter-maneuver by the parasites, at least so far. Christopher G. Wilson of Cornell University in New York and colleagues raised populations of the rotifers in a laboratory, and noticed that the asexual invertebrates could rid themselves of a deadly fungal parasite by drying themselves up completely and blowing away with the wind to new territory. The rotifers became so dry that their parasites couldn’t survive the punishing conditions. They were then able to ride the breeze and start afresh in new, presumably parasite-free pastures. This research appears in the Jan. 29 issue of the research journal Science.