Seasonal variations of exposure biomarkers, oxidative stress responses and cell damage in the clams, Tapes philippinarum, and mussels, Mytilus galloprovincialis, from Adriatic sea.

This work investigated the natural variability of several biomarkers in Tapes philippinarum and Mytilus galloprovincialis, sampled from Northern Adriatic where these organisms are important sentinel species for future environmental impact assessment. Levels of metallothioneins, peroxisomal enzymes and acetylcholinesterase, showed a significant seasonality and marked differences between clams and mussels. Among antioxidant enzymes, catalase and GST decreased during the warmer period, the latter enzyme activity resulting particularly high in clams. The total oxyradical scavenging capacity toward peroxyl radicals decreased in mussels from winter to summer, indicating a prooxidant challenge due to higher seawater temperature and intensity of light irradiance. Lysosomal membrane stability did not exhibit significant seasonal variations, while some variations were observed for DNA damages. Overall results indicated a significant influence of seasonal variability on several biomarkers and species-specific differences which should be considered to discriminate the appearance of anthropogenic disturbance.

Bioaccumulation and biotransformation of arsenic in the Mediterranean polychaete Sabella spallanzanii: experimental observations.

The Mediterranean fan worm Sabella spallanzanii is characterized by elevated basal levels of arsenic in branchial crowns (>1000 microg/g) and an unusual prevalence of dimethylarsinic acid (DMA), a relatively toxic compound with a possible antipredatory role. The aim of this work was to obtain further insights on the capability of this polychaete to accumulate arsenic from different compounds and to operate biotransformation reactions. Laboratory exposures to arsenate (As(V)), dimethylarsinic acid (DMA), trimethylarsine (TMA), and arsenobetaine (AsB) revealed significant differences among tissues and kind of experiments. The highest increases of arsenic content were observed in branchial crowns of organisms treated with arsenate, which can enter the cell through the phosphate carrier system; lower variations were measured with DMA and TMA, while not-significant changes of total As occurred after treatments with AsB. In body tissues, exposure to As(V), DMA, and TMA confirmed a progressively lower accumulation of total arsenic, while a marked increase was caused by AsB. Obtained results suggested that accumulated arsenic could be chemically transformed, thus explaining the elevated basal levels of DMA typical of S. spallanzanii; during all the experiments, DMA was the most accumulated molecule, suggesting that this species possesses the enzymatic pathways for methylation and demethylation reactions of inorganic and trimethylated arsenicals. Only arsenobetaine was not converted into DMA, which would confirm a microbial pathway for degradation for this molecule, particularly important in body tissues of S. spallanzanii for the presence of bacteria associated to digestive tracts. Overall, the present study suggests future investigations on the biological role of arsenic and DMA in S. spallanzanii as a potential adaptive mechanism against predation in more vulnerable tissues.