THE ROLE OF HORMONES IN THE ACQUISITION OF SPERM MOTILITY IN SALMONID FISH

In salmonid fish, spermatozoa taken from the testes are immotile, but acquire motility during their passage through the sperm duct. Using male masu salmon (Oncorhynchus masou), we found that gonadotropin-induced testicular production of 17-alpha,20-beta-dihydroxy-4-pregnen-3-one (17-alpha,20-beta-DP), the oocyte maturation-inducing hormone of salmonid fish, is responsible for the acquisition of sperm motility. However, neither testosterone (T) nor 11-ketotestosterone (11-KT), the two major androgens in teleost fish, were effective. We also present evidence that 17-alpha,20-beta-DP action is mediated through an increase in sperm duct pH, which in turn increases the cAMP content of sperm allowing the acquisition of motility.