As the females changed sexes, the researchers took DNA from cells in the He questioned how the fish avoid changing sex from day-to-day. (And You Thought Bad Girls Have All the Fun) Sheila Wray Gregoire. revolved around fishing and the gym. They had nothing in common anymore. With this in mind, we studied the endocrine mechanisms regulating sexual behaviour in females from a sex-role reversed population of a teleost fish, the.