A possible epigenetic effect in rotifers:
Mrs. Allen in high school biology showed us a rotifer through a microscope. The name suggests that the creature carries something that rotates. It certainly looked like it to me. It looked like a little vase with wheels at the brim merrily spinning away. I was not surprised. The world then was full of the totally incomprehensible, and if the critter wanted to have wheels, then I saw no reason that it should not have wheels.
She explained that the motion had the effect of bringing little food particles into the tiny body cavity. But thinking about it later it did seem strange to me. How do you grow a wheel? And how to you power a wheel? I mean how do you do that if you are a tiny animal. There was no doubt in my mind that it has happening. I had seen it. Maybe you could grow a wheel by the usual means and then shear off the bearing, leaving the wheel free to rotate. But the wheel looked like it was as alive as the rest of the rotifer. That meant it needed nutrition. It is possible to supply material to a wheel. The old amphibious truck of WW II was able to inflate and deflate its tires while it was moving. That let it scramble up a soft sand beach and then harden up for a run along a road at a blistering 40 mph. Actually that was pretty fast compared with its speed in the water. I think I could engineer something that could do that although it probably wouldn’t work very well. But I didn’t see how the rotifer could.
Finally in college a professor said, “It doesn’t really rotate. Those are cilia that are moving that way.” A cilium is sort of like a little hair that is able to wave actively. That seemed far more accountable. The only mystery was how the organism had fooled me. But he did not show us one nor have I seen once since.
And now they are in the news. (Thanks, Mum! ECONMIST vol. 397 no. 8702 October 2, 2010 page 86) It turns out that a rotifer if starved lives longer than one that is fed to satiety. That is a known effect. But apparently rotifers can pass this longevity to their offspring according to a study done by Shugo Watabe of the University of Tokyo. This inheritance of an acquired characteristic is not so common.
The mechanism remains unclear, but one candidate is an epigenetic effect. My attention is duly grabbed. The Helgason study from Iceland, which I cite so often, demonstrated that if third cousins marry they will have higher fertility than less related couples and their children will also enjoy a higher fertility. (That’s third cousins by their reckoning, not the usual way.) Well that’s as close to being inheritance of acquired characteristics as makes no difference. And I suspect it is also an epigenetic effect.
When I first heard about epigenetic phenomena my reaction was, “Oh, no. I don’t want to think about that.” I guess I was older than when I learned about rotifers. At all events, I search eagerly for news from the epigenetic front and will try to pass it along.
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