Effect of selenium exposure on the freshwater bivalve Corbicula fluminea

Selenium is essential for most of living organisms. In normoxic to moderately hypoxic freshwaters, Se exists predominantly in the (+VI) and (+IV) oxidation states as selenate and selenite respectively, whereas in the biota it is incorporated as Se (-II) or Se (0). At low concentrations, it acts against oxidative damages, but it may be toxic at higher levels. In filter feeders, such as the freshwater bivalve Corbicula fluminea, the ventilatory activity is a primary limiting step that controls the water influx and therefore the delivery of contaminants. A number of different parameters such as algal food density or presence of contaminant can influence the ventilation and hence the bioaccumulation potential of the contaminant. We report here a set of short-term experiments performed to study the effects of different forms of dissolved Se (selenite, selenate, selenomethionine) and algal-bound Se on the ventilatory activity of Corbicula fluminea and to evaluate the Se bioaccumulation. All experiments were performed on a 3-day exposure period after acclimatizing the organisms during a 7-day period to the synthetic water, at a regulated algal density. Both bioaccumulation and ventilatory activity of Se exposed groups, in comparison to these of the reference group, varied greatly according to the form of Se used.