Effects of sex steroids on in vitro gamete release in the sea scallop, placopecten magellanicus

Effects of estradiol, testosterone and progesterone on 5-HT-induced gamete release were studied in vitro in both sexes of the sea scallop. The results showed that estradiol (10⁻⁵–10⁻⁸ M in females and 10⁻⁵–10⁻⁷ M in males) and progesterone (10⁻⁷–10⁻⁸ M in females and 10⁻⁵–10⁻⁷ M in males) potentiated gamete release in both sexes, whereas testosterone (10⁻⁵–10⁻⁷ M) had a facilitatory effect only in males. Pharmacological studies suggested that these effects may be achieved through activation of sex steroid receptors because they were abolished by receptor antagonists (tamoxifen, 1.25 μM; flutamine, 2.5 μM; RU486, 1 μM) and by RNA and protein synthesis inhibitors (actinomycin D, 8 μM; cycloheximide, 10 μM). These findings support a growing body of literature which suggests physiological roles of sex steroids in invertebrates. Furthermore, the results also suggest possible applications in the environmental monitoring of endocrine disrupting chemicals and in bivalve aquaculture.