Pheromonal regulation of reproductive success in female zebrafish: female suppression and male enhancement

Competition among females represents an important but rather neglected variable in studies of sexual selection. Probably to avoid injury to self and offspring, competition among females is often displayed without much physical interaction and therefore remains harder to observe. Here, we show for the first time in a teleost fish, the zebrafish Danio rerio, that females can use waterborne pheromones to suppress reproduction by other females. Female zebrafish that had been exposed to another female's pheromones for 4 days prior to mating spawned significantly fewer viable eggs than females held in isolation or exposed to male pheromones. Male pheromones not only stimulated female reproduction but also increased the quality and viability of eggs. In grouped females, reproductive success correlated with dominance rank. These results indicate that fish pheromones function to control mates and competitors in addition to serving as reproductive timing signals. Differences in female reproductive success observed in many fish species might be explained by this mechanism.