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| Bdelloid Rotifer. Photo by Michael Sribak and Irina Arkhipova |
Animals appear to be pretty keen on sex as a form of reproduction. It makes perfect sense,
having offspring in this manner introduces genetic variability to the younger
generations which allows them to survive in a changing environment. Any species
in the animal kingdom reproducing asexually is expected to eventually become
extinct. The bdelloids, tiny freshwater inhabitants, are defying this rule, as
they have gone for the past 80 million year without intercourse of any kind.
All bdelloids are female and they lay eggs that require no fertilisation by
sperm. They also have the curious property of being able to withstand
staggeringly high levels of radiation and survive for years when the water that
they call home suddenly evaporates.
This bizarre asexual
and resilient lifestyle prompted an investigation into the genes this creature
expresses. The findings, published this month in PLoS Genetics, only add to the uniqueness of this critter. It
turns out that 10% of the bdelloids’ active genes come from other organisms
like bacteria, fungi and algae. They appear to have acquired these genes from
more than 500 different species making them by far the most adept thieves in
the animal kingdom.
It is likely that
this foreign genetic material originates from the bdelloids’ everyday food.
They are known to eat any organic debris smaller than their head, and the DNA
in these particles seems to somehow end up in their own genomes. The alien
genes make a huge contribution to the bdelloids’ biochemical repertoire, making
up 40% of all the enzymes they possess. This lets them break down toxins in the
environment akin to certain bacteria and produce antioxidants that are never found in
animals. Thus it would appear that the bdelloids have foregone sex and focused
on eating and thieving instead; so far it
seems to be working out for them.