Is vitellogenin-like protein induction responsive to 17-b estradiol? The clam Tapes philippinarum as a case study.

Estrogenic potency of 17ß-estradiol (E2) was evaluated in both sexually undifferentiated (resting phase) and differentiated (pre-spawning phase) clams (Tapes philippinarum) by exposing them for 7 and 14 days to various E2 concentrations (0, 0+acetone, 5, 25, 50, 100 and 1000 ng/L). Vitellogenin (Vg)-like protein levels were then evaluated in both haemolymph and digestive glands. In the resting phase, increased Vg-like protein levels were observed in haemolymph from clams exposed for 7 and 14 days to E2. Interestingly, significant decreases in Vg-like protein content were recorded in haemolymph from females exposed in the pre-spawning phase for 7 days to 50, 100, and 1000 ng E2/L. Conversely, 14 days E2 exposure was shown to increase Vg-like protein levels in haemolymph from both females (at 50 ng E2/L) and males (at 100 ng E2/L). Results obtained are difficult to explain, and suggest that further studies are needed to elucidate the role of E2 in promoting Vg induction in Tapes philippinarum.