Sulphide-induced metal precipitation in the mantle edge of Macoma balthica(Bivalvia, Tellinidae) - a means of detoxification

The blackening of tissues or mucus of benthic animals from sulphidic enviro nments is a remarkable phenomenon whose ecological interpretation is disput ed. In the Baltic clam Macoma balthica the mantle edge turned black after s ulphide exposure owing to numerous precipitates in the extracellular matrix underneath the epidermal cells. In the apical parts of these cells, simila r precipitates were found, albeit in lower abundance. Elemental analyses sh owed that copper (214.7 mu g g(-1) ww [wet weight]) and sulphur (1328.6 mu g g(-1) ww) were the main components, with iron (311.2 mu g g(-1) ww) and z inc (112.7 mu g g(-1) ww) in lower concentration Apparently, these precipit ates become phagocytosed by amoebocytes and concentrated in haemocytic gran ules. This is interpreted as a pathway of removal from the mantle edge. On the basis of calculated diffusion rates (D-HS(-) = 1.9 X 10(-6) cm(2) S-1), there is a sulphide influx of 61 nmol h(-1) into the body of M, balthica. Even under conservative assumptions, this would lead to the binding of all the copper present in about 30 min. It is concluded that the process of sul phide precipitation can represent a temporarily effective pathway attenuati ng sulphide toxification.