Comments on: Rotifers find answer to parasites by blowing on the wind

By: Brian Schmidt

Brian Schmidt — Tue, 02 Feb 2010 22:43:24 +0000

I’ll bet the “dry up and blow away” defense is less than perfect from the bdelloid’s viewpoint, because it seems likely that quite a few of them will die somewhere instead of finding a good home. So from the fungus viewpoint, it’s not a problem – why try to evolve the same capability when you should focus on reproducing in your current pond (and presumably sending spores out that will eventually found new populations elsewhere).

By: TerryDarc

TerryDarc — Sun, 31 Jan 2010 22:58:36 +0000

How do we know that the bdelloids are all “female”? I don’t what the sexual determination of rotifers is but apparently the bd’s don’t have that?
-Terry

By: Nathan Myers

Nathan Myers — Sun, 31 Jan 2010 08:25:53 +0000

Why don’t the fungus keep up? I think the global distribution of bdelloids might have something to do with it; there’s always a population in some place that is uncomfortable for any particular fungus. Also, since bdelloids don’t need to make contact with other bdelloids, a fungus that develops any dessication tolerance has to find a mate without help from the bdelloids. Furthermore, since each bdelloid is its own lineage, the ones we have now are all descended from billions of generations not successfully colonized by any fungus.
A more successful strategy would seem to be getting your genes adopted piecemeal directly into the bdelloid genome, retro-wise. This seems somehow less satisfying from a parasitical standpoint, but I would have a hard time expressing why. I doubt Nature would find any such argument persuasive.

By: amphiox

amphiox — Sun, 31 Jan 2010 02:38:18 +0000

With respect to Reviewer #3′s second question, how can we be certain that the fungi have also been co-evolving with the rotifers for 80 million years? These particular fungi could well have evolved to become rotifer parasites much more recently.
It seems to me that the desiccation strategy would work against almost any parasite, and could have first evolved as a defense against different parasites, possibly now extinct. Over the bdelloids’ 80 million year history, and entire sequence of different parasite species could have “had a go” at them, each failing in turn to evolve an adequate counter to the self-dessication strategy, and ultimately going extinct, eventually replaced by another new species of parasite, while the rotifers march on.

By: Ed Yong

Ed Yong — Sat, 30 Jan 2010 22:36:39 +0000

Reviewer 3 – the quick answer to the first one is that they’re really, really good at repairing their DNA. If I’m remembering correctly, their chromosomes are tetraploid, meaning they have four copies of each, rather than our two. This means that if anything breaks, they have multiple back-ups to copy the missing information from. Imagine that your computer had three back-up harddrives. It would be virtually impossible for you to lose your valuable data because you would always have a working spare.
The answer to the second question is less clear, but it’s not trivial to tolerate dessication. “Extremophiles” of this sort aren’t exactly common. You’ve got rotifers, tardigrades, Deinococcus, and maybe a few others.

By: Comrade PhysioProf

Comrade PhysioProf — Sat, 30 Jan 2010 22:25:19 +0000

Rotifers are the fucking best!

By: Reviewer 3

Reviewer 3 — Sat, 30 Jan 2010 19:04:53 +0000

Two questions, if you have time: if the bdelloids escape the parasitic fungi by dessicating themselves so the fungal cells and spores shatter, how do the bdelloids survive when their cell membranes and DNA also rupture?
And why haven’t the fungi evolved similarly to survive- 80 million years seems a long time to not develop tolerance to dessication.
Thanks Ed, returning to lurking mode now.

By: Lisa-Natalie Anjozian

Lisa-Natalie Anjozian — Fri, 29 Jan 2010 21:37:51 +0000

Love the post, love the personas of the posters. Regarding Nathan’s request for more bdelloid media, and Ed’s graphic “Ka-pow” response, I flashed on a Speed Racer-like cartoon featuring these self-desiccating asexual superheros.

By: MissPrism

MissPrism — Fri, 29 Jan 2010 12:19:40 +0000

Dang! Outpedanted.
Fantastic post.

By: Ed Yong

Ed Yong — Fri, 29 Jan 2010 12:14:56 +0000

Ah but I never claimed that Judson said it first, merely that she once said it. Ka-pow!