June 04, 2008

Interesting Evolution

Bdelloid Rotifers - It sounds greek to me...But these species seem to have achieved something that no creature in this world has achieved.

The bdelloid rotifers are ancient asexuals: they appear to have been living entirely without sex for more than 85 million years.

NYTimes - Olivia Judson's blog - Wild life - The Weird Sisters, has more such startling revelations.

"..evolving asexuality isn’t the hard part. The hard part is making an evolutionary success of it.....asexuality evolves often, but rarely persists for long: asexuals typically go extinct soon after they appear. The swift extinction of asexuals, and the absence of big asexual groups, suggests that sex is essential for long-term evolutionary success: giving up sex is a Bad Idea, a kind of evolutionary suicide.
How are they managing to flourish despite this epic period of abstinence? For they do flourish: bdelloids are everywhere
It now looks as though the bdelloids do acquire new genes from time to time — that mutation isn’t their only source of genetic novelty. Yet their means of getting new genes is unlike anything previously known for an animal. Namely: they seem to pick up genes from the environment, and add them into their genomes.
No one knows how the bdelloids pick up these genes. One idea is that it may be due to another oddity of their lifestyle: their ability to dry up and blow away. When the piece of moss they are living in dries up, these animals often dry up, too. It’s a state of suspended animation — add water and, all being well, they come back to life as frisky, or even friskier, than before. (This isn’t unique to bdelloids — some other small animals have evolved to endure dessication. But most of these others can only do it at particular stages of their lives. The bdelloids can do it at any time. They can also — probably as a consequence of their dessication abilities — survive high levels of radiation. Much higher than other animals can.) During the drying and rehydration, cell membranes may become disrupted, and their DNA fragmented. Perhaps all this makes it easier for stray bits of foreign DNA to get into the cells that will become eggs.

What to say...Nature has more than its share of surprises!!

1 comment:

Krishnan said...

Wow ! that was quite interesting.