Acute olfactory sensitivity of wild common carp, Cyprinus carpio, to goldfish hormonal sex pheromones is influenced by gonadal maturity

To determine whether wild common carp (Cyprinus carpio) employ as pheromones the same gonadal hormones as goldfish, and whether their olfactory sensitivity is influenced by gonadal condition, the olfactory responsiveness of Mississippi River carp to gonadal steroids was measured by electro-olfactogram recording during two spawning seasons. Thirty-three gonadal steroids and two prostaglandins were tested. Of the steroids, only 17α,20β-dihydroxy-4-pregnen-3-one (17α,20βP), 17α,20βP-sulfate (17α,20βP-S), and androstenedione (A) were specifically detected with high sensitivity. 17α,20βP was the most potent compound, with a threshold concentration of 10−13 M, while 17α,20βP-S, and A had thresholds of approximately 10−10 M. This pattern of sensitivity matches that of the goldfish, which strongly suggests that these species share steroidal pheromone systems. The olfactory sensitivities and specificities of adult male and female carp to steroids were similar to each other and did not vary with season. However, juvenile fish were less sensitive than adults to 17α,20βP, 17α,20βP-S, prostaglandin F2α, and 15-ketoprostaglandin F2α, and more sensitive to both A and L-serine: the sensitivity of the carp olfactory epithelium to putative pheromones was apparently influenced by gonadal maturity and likely also by hormonal condition.