OXYGEN-CONSUMPTION AND SULFIDE DETOXIFICATION IN THE LUGWORM ARENICOLA-MARINA (L) AT DIFFERENT AMBIENT OXYGEN PARTIAL PRESSURES AND SULFIDECONCENTRATIONS

The lugworm Arenicola marina is a typical inhabitant of intertidal fla ts. In its L-shaped burrow the animal is exposed to varying concentrat ions of O-2 and toxic sulfide depending on the tides. The lugworm is a ble to detoxify sulfide through its oxidation to thiosulfate. When exp osed to declining O-2 tensions Arenicola marina reacted as an oxyconfo rmer. In the presence of 25 mu mol.l(-1) sulfide the respiration was n ot 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 sulfi de anaerobic metabolism started al a Po-2 of approximately 10 kPa. Eve n at high O-2 tensions animals exposed to sulfide produced significant ly more anaerobic metabolites compared with the controls. Accordingly the critical value Pc-M, the ambient Po-2 below which anaerobic metabo lism starts, was shifted towards normoxia. Since O-2 supply was suffic ient for aerobic metabolism, anaerobiosis was induced by sulfide. An i nflux of sulfide was observed at 25 as well as at 200 mu mol.l(-1) sul fide. The main product of sulfide detoxification in the lugworm was th iosulfate. Its synthesis increased with ambient Po-2 and depended on t he sulfide concentration. Sulfide and thiosulfate were detected in the coelomic fluid, the blood, and the body wall of Arenicola marina. Onl y about 2% of the ambient O-2 was used for sulfide detoxification at 2 5 mu mol.l(-1) sulfide and about 50% at 200 mu mol.l(-1) sulfide, resp ectively. Even at the low sulfide concentration Arenicola marina's cap acity to detoxify sulfide was too low to maintain a complete aerobic m etabolism.