Oxygen consumption and sulfide detoxification in the lugworm Arenicola marina (L) at different ambient oxygen partial pressures and sulfide concentrations

The lugworm Arenicola marina is a typical inhabitant of intertidal flats. In its L-shaped burrow the animal is exposed to varying concentrations of O-2 and toxic sulfide depending on the tides. The lugworm is able to detoxify sulfide through its oxidation to thiosulfate. When exposed to declining O-2 tensions Arenicola marina reacted as an oxyconformer. In the presence of 25 mu mol.l(-1) sulfide the respiration was not affected. In contrast, the lugworm consumed significantly less O-2 at any Po-2 in the presence of 200 mu mol.l(-1) sulfide. Without sulfide anaerobic metabolism started al a Po-2 of approximately 10 kPa. Even at high O-2 tensions animals exposed to sulfide produced significantly more anaerobic metabolites compared with the controls. Accordingly the critical value Pc-M, the ambient Po-2 below which anaerobic metabolism starts, was shifted towards normoxia. Since O-2 supply was sufficient for aerobic metabolism, anaerobiosis was induced by sulfide. An influx of sulfide was observed at 25 as well as at 200 mu mol.l(-1) sulfide. The main product of sulfide detoxification in the lugworm was thiosulfate. Its synthesis increased with ambient Po-2 and depended on the sulfide concentration. Sulfide and thiosulfate were detected in the coelomic fluid, the blood, and the body wall of Arenicola marina. Only about 2% of the ambient O-2 was used for sulfide detoxification at 25 mu mol.l(-1) sulfide and about 50% at 200 mu mol.l(-1) sulfide, respectively. Even at the low sulfide concentration Arenicola marina's capacity to detoxify sulfide was too low to maintain a complete aerobic metabolism.