I'm not sure how it works, either. It was interesting, although I only worked on the study, I didn't analyze the results. Mosquitofish are actually pretty cool, because they give birth to live young. The males have an intromittent organ to insert sperm into the female. That would be how we could tell if it is a Kevin or Kevina.
We also had coral snakes, water moccasins and rattlesnakes in Texas. We only get rattlers here in California. I have a recent blog post about almost running over one with my mountain bike.