Effects of sex steroids on spawning in the sea scallop, Placopecten magellanicus

Sex steroids have long been known to exist in molluscs, but few studies have focused on the roles of these substances in molluscan reproduction. In this study, we demonstrate that injections of estradiol into ripe sea scallops induced spawning in both sexes, testosterone injections induced spawning in males only and progesterone blocked spawning in both sexes. We also show that injections of sex steroids significantly affected subsequent 5-HT-induced spawning. Injection of estradiol promoted 5-HT-induced spawning in both sexes and testosterone potentiated spawning in males only. In addition, progesterone inhibited 5-HT-induced spawning in females while potentiating the spawning in males. These findings are consistent with a hormonal role for steroids in molluscan reproduction and also suggest the possible development of more efficient methods for spawning induction in molluscan aquaculture.