This study directly tested the hypothesis that 17α,20β-dihydroxy-4-pregnen-3-one (17,20β-P) is a goldfish preovulatory pheromone (pheromone released at peak levels during oocyte final maturation) which increases blood gonadotropin (GtH) and milt volume in males. During spontaneous ovulation, GtH and 17,20β-P in female blood and 17,20β-P released to the water increased dramatically 7-10 hr prior to ovulation, peaked 1-4 hr prior to ovulation, and then rapidly declined. Males held with these females, or exposed to their odors, had increased GtH levels and milt volumes at approximately the time when increased 17,20β-P release by ovulatory females commenced. Although these findings strongly support the hypothesis that 17,20β-P is a preovulatory female sex pheromone in goldfish which stimulates male GtH levels and milt production prior to spawning, the milt increases occurred earlier than predicted, suggesting either that preovulatory 17,20β-P release begins earlier than the data indicate or that other steroids known to have pheromonal activity are released before 17,20β-P.
Bibliographical noteFunding Information:
This study was supported by the Natural Sciences and Engineering Research Council of Canada (Grant A2903 to N.E.S.) and the Alberta Heritage Foundation for Medical Research.