The three steroidal components of the goldfish preovulatory pheromone signal evoke different behaviors in males

Abstract

The goldfish sex pheromone system is the best understood among the teleost fishes. Pheromones in this species are unspecialized hormonal products, which are released in ratios that vary with reproductive status. This study examined behavioral responses of male goldfish to three steroidal components of the female preovulatory pheromone: 17,20β-dihydroxy-4-pregnen-3-one (1720βP); 17,20β-dihydroxy-4-pregnen-3-one-20-sulfate (1720βP-S); and androstenedione (AD). Males were observed during exposure to nanomolar concentrations of each steroid over a 2-h period. We observed chasing, nudging (courtship behaviors) and pushing (an aggressive behavior). Each steroid elicited a different set of behaviors. 1720βP, which is released by ovulatory females, elicited a low level of chasing and nudging that persisted throughout the experiment. Exposure to 1720βP-S, which is released primarily by ovulatory females, triggered a large increase in nudging and chasing that lasted for only 5 min. In contrast, AD, which is released by females early in the ovulatory cycle and by mature males, elicited increases in aggressive behavior. 1720βP and 1720βP-S both caused increases in GtH-II release while AD did not. These results demonstrate that goldfish can discriminate components found in the female pheromone blend, suggesting that goldfish, and likely other fish species, may employ blends of hormonal products as pheromones.