VITELLOGENIN INDUCTION IN THE CLAM TAPES PHYLIPPINARUM AFTER EXPOSURE TO 4-NONYLPHENOL

Nonylphenol (NP) is reported to exert estrogenic effects in marine organisms, being able to mimic the action of endogenous estrogens. As a consequence, NP can induce vitellogenin (Vg) synthesis, the major precursor of the egg-yolk proteins. In our previous study [Matozzo and Marin, 2005. Environ. Res., 97, 43-49], we found that exposure for 7 days of the clams Tapes philippinarum to NP caused a dose-related induction of Vg in both haemolymph and digestive gland of males. In the present study, Vg induction was evaluated in sexually undifferentiated clams exposed to NP: for 7 days to 0, 0 + acetone, 0.025, 0.05, 0.1, and 0.2 mg NP/L and for 14 days to 0, 0 + acetone, 0.025, 0.05, and 0.1 mg NP/L. Vg was determined in both haemolymph and digestive gland by the alkali-labile phosphate (ALP) assay. In the haemolymph Ca2+ levels were also measured. Exposure for 7 days to 0.2 mg NP/L resulted in significant increases (p < 0.05) in ALP in both aemolymph and digestive gland with respect to controls, whereas no difference was observed in Ca2+ levels. After 14 days exposure, ALP significantly (p < 0.05) increased in digestive gland from 0.05 and 0.1 mg NP/Lexposed clams. Increases (p < 0.05) in Ca2+ levels were recorded in haemolymph from clams exposed to 0.025 and 0.05 mg NP/L. Results obtained demonstrates that NP induces Vg synthesis in T. philippinarum also far from the reproductive period. As endocrine disruption may cause fertility reduction and alteration in sex ratio, a condition of potential risk for clam populations in estuarine areas is highlighted. This study was supported by grants from Co.Ri.La (Second Research Programme, 2004-2006).