Effects of in vivo exposure of Mya arenaria to organic and inorganic mercury on phagocytic activity of hemocytes

Abstract

Marine bivalves are aquatic invertebrate organisms which can be used as bioindicators in environmental monitoring. In vivo effects of mercuric chloride (HgCl 2) and methylmercury (CH 3HgCl) on phagocytic function of Mya arenaria hemocytes were evaluated in this study. Clams were exposed to single metal in water for up to 28 days at concentrations ranging from 10 −9 to 10 −5 M. Phagocytic activity of hemocytes was determined by uptake of fluorescent microspheres and flow cytometry. All clams exposed to 10 −5 M HgCl 2 died by day 7 of exposure. The viability of hemocytes was decreased only in clams exposed to 10 −6 M HgCl 2 for 28 days. A significant decrease in phagocytic activity of hemocytes was observed in clams exposed to 10 −6 M of HgCl 2 for 28 days. A similar pattern was observed with CH 3HgCl, but at an earlier time. Chemical analysis performed on the tissues of the animals clearly show a greater uptake of the organic form of mercury by clams. Furthermore, a clear correlation was established between body burden of mercury and effects on phagocytic activity of hemocytes. Overall, the results of this study show that both speciations of mercury inhibited phagocytic function of Mya arenaria hemocytes following in vivo exposures.