Rotifers are interesting in their own way. They are an example of an animal where their sex is determined by what environmental conditions their parents were in. We normally think of sex determination as something that happens at conception, but with rotifers it is much before that.
There's actually some evidence and theory to suggest that sex of human children is determined by their mother's stress level: http://www.economist.com/node/10130882
To be clear, in humans that's a 5-10% shift in probability, and no evidence to suggest that the effect is determined post-conception (an extraordinary conjecture) and not statistical miscarriage pressure.
