Scientists have tricked male fish cells that were destined to become sperm into switching sex and becoming eggs instead. The technique could one day be used to quickly produce animals with desired traits, speed up breeding programs and help repopulate dwindling populations of endangered species or creating sushi on demand, the researchers said. The finding is detailed in the Feb. 7 issue of the journal for the Proceedings of the National Academy of Sciences. Sexually indifferent cells Scientists have long known that some fish are able to switch their sex, either spontaneously or when exposed to steroids. This led them...