Evidence of endocrine alterations in the clam Tapes philippinarum and in the cockle Cerastoderma glaucum from the Lagoon of Venice.

Endocrine disrupting chemicals (EDCs) are a heterogeneous group of substances that can alter many endocrine functions in organisms. Among EDCs, xenoestrogens, are extensively studied owing to their capability to mimic natural estrogens. Xenoestrogens may activate estrogen receptor or prevent hormonal binding to hormone receptor. The main sources of these contaminants are untreated municipal and industrial effluents, agricultural practices, livestock wastes and sewage treatment plants (STP). One of the most documented effects of xenoestrogens is the induction of vitellogenins (Vg), precursors of the egg-yolk proteins, vitellins, which provide energy reserves for embryonic development in oviparous organisms. In the present study, Vg-like protein induction was investigated, for the first time, in the clam, Tapes philippinarum, and the cockle, Cerastoderma glaucum, from 6 sites of the Lagoon of Venice. Bivalves were collected far from the reproductive phase (January) and in pre-spawning period (June). Vg-like proteins were measured by the alkali labile phosphate method (ALP), in both haemolymph and digestive gland from males and females (when it was possible to distinguish sex by microscopic observation of gonadal tissue). Haemolymph calcium concentrations and bivalve condition index (CI) were also measured. In both seasons, bivalves collected at Campalto (nearby a STP) and Marghera (highly contaminated area) had higher Vg-like proteins levels (particularly in haemolymph) than animals from other sampling sites. Interestingly, the CI did not show the same pattern of variation. In June only, Vg-like proteins and Ca levels in haemolymph exhibited similar trend in both bivalve species at all sampling sites, except for Campalto. Responsiveness of bivalves to environmental xenoestrogens was higher in June, allowing a better discrimination among sites. Acknowledgements: This work was supported by CO.RI.LA (Research Programme 2004-2007).