VITELLOGENIN INDUCTION IN THE CLAM, TAPES PHILIPPINARUM, AND THE CRAB, CARCINUS AESTUARII, FROM THE LAGOON OF VENICE: A COMPARISON STUDY

Endocrine disrupting chemicals (EDCs) are a heterogeneous group of substances that may alter many endocrine functions in organisms. Among EDCs, xenoestrogens have been extensively studied owing to their capability to mimic natural estrogens. One of the best documented effects of xenoestrogens is the induction of vitellogenins (Vg), precursors of the egg-yolk proteins, which provide energy reserves for embryo development. It is documented that the Lagoon of Venice is characterised by inputs of xenoestrogens due to increased urban, agricultural and industrial development. In the present study, the possible effects of xenoestrogens were studied in two invertebrate species widespread in the Lagoon of Venice: the clam Tapes philippinarum, and the crab Carcinus aestuarii. Animals were collected in November 2008 in 4 sites of the Lagoon (Cà Roman, Valle di Brenta, Marghera and Palude del Monte). Vg-like protein levels were measured in digestive gland and haemolymph in both the species by the indirect alkali-labile phosphate assay. The survival-in-air test was also performed in clams, this stress indices being useful in detecting general stress conditions in bivalves. Bivalves collected at Marghera (a highly contaminated area) had higher Vg-like protein levels in digestive gland than animals from Valle di Brenta (close to the inner border of the Lagoon) and Palude del Monte (a licensed area for clam culture). Conversely, no statistically significant differences in Vg-like proteins were detected in haemolymph. Interestingly, in crabs, statistically significant higher Vg-like protein levels were observed in digestive gland of animals from Palude del Monte, with respect to crabs from Cà Roman (influenced by intense passage of ships and urban effluents from the city of Chioggia). Haemolymph Vg-like proteins were statistically higher in crabs from Marghera and Palude del Monte, with respect to crabs from Cà Roman. Significantly increased resistance to air exposure was observed in clams from Palude del Monte, when compared to those from the other sites. LT50 values fell from 15 days in clams from Palude del Monte to 5 days in animals collected at Cà Roman. The present study demonstrated a different responsiveness of the two invertebrate species to environmental xenoestrogens, probably owing to their different habits. Indications can be drawn for using crabs as sentinel species in biomonitoring wider geographical areas together with sessile species, such as clams, mainly suitable for more restricted areas. This work was funded by Regione Veneto (Italy) - Progetto di Ricerca Sanitaria Finalizzata (Bioindicatori di inquinamento ambientale come strumento di tutela del territorio e possibili ricadute di salute pubblica).