A sexual pheromone in the guppy, Poecilia reticulata (Peters)

Male guppies, Poecilia reticulata, were attracted to water which had previously held con-specific females and not to control water or water in which males or ovariectomized females had been maintained. Males expressed a preference for water which had held females in the first few days of their gestation cycles over water which held midcycle (gravid) or ovariectomized females. When males were placed with an unresponsive ovariectomized female, addition of water which had contained intact females resulted in a marked increase in courtship directed towards the ovariectomized female. It is hypothesized that the female guppy releases a sexual pheromone which attracts males and stimulates increased male courtship activity. The pheromone appears to be produced in the ovary and secreted by the female at the period of maximum receptivity following parturition.