Excretion of thiosulphate, the main detoxification product of sulphide, bythe lugworm Arenicola marina L.

Thiosulphate, the main sulphide detoxification product, is accumulated in t he body fluids of the lugworm Arenicola marina. The aim of this study was t o elucidate the fate of thiosulphate. Electrophysiological measurements rev ealed that the transepithelial resistance of body wall sections was 76 +/- 34 Omega cm(2) (mean +/- S.D., N = 14), indicating that the body wall of th e lugworm is a leaky tissue in which mainly paracellular transport along ce ll junctions takes place. The body wall was equally permeable from both sid es to thiosulphate, the permeability coefficient of which was 1.31 x 10(-3) +/- 0.37 x 10(-3) cm h(-1) (mean +/- S.D., N = 30), No evidence was found for a significant contribution of the gills or the nephridia to thiosulphat e permeation, Thiosulphate flux followed the concentration gradient, showin g a linear correlation (r = 0.997) between permeated and supplied (10-100 m mol l(-1)) thiosulphate. The permeability of thiosulphate was not sensitive to the presence of various metabolic inhibitors, implicating a permeation process independent of membrane proteins and showing that the lugworm does not need to use energy to dispose of the sulphide detoxification product, T he present data suggest a passive permeation of thiosulphate across the bod y wall of A, marina. In live lugworms, thiosulphate levels in the coelomic fluid and body wall tissue decreased slowly and at similar rates during rec overy from sulphide exposure. The decline in thiosulphate levels followed a decreasing double-exponential function, Thiosulphate was not further oxidi zed to sulphite or sulphate but was excreted into the sea water.