Ventilatory and metabolic responses to hypoxia and sulphide in the lugworm Arenicola marina (L.).

We examined the effects of hypoxia and sulphide levels on the ventilatory activity of Arenicola marina and determined whether ventilation compensates for oxygen deficiency and affects the mode of energy provision. A. marina ventilated intermittently, irrespective of ambient P(O2) and sulphide concentration. The ventilation rate was 28.5+/-16 ml h(-1) g(-1) wet mass during normoxia, but increased to 175+/-60% of this value during moderate hypoxia, during which aerobic energy metabolism was maintained. Below a P(O2) of 6.2 kPa, A. marina reduced the ventilated volume to 54+/-16% of the normoxic value and became anaerobic, as indicated by the accumulation of succinate and strombine. Incubation with 27 micromol l(-1) ambient sulphide had no effect on the normoxic and hypoxic ventilation rates or on the P(O2) below which anaerobiosis started (P(cM)). Increased sulphide concentrations reduced the ventilation rate and shifted the P(cM) towards a higher P(O2) below 10.7 kPa. Sulphide diffused into the body and was at least partially detoxified to thiosulphate when oxygen was present. Under normoxia, sulphide accumulated in the body wall tissue and coelomic fluid when ambient sulphide levels exceeded 117 micromol l(-1) and 216 micromol l(-1), respectively. A decrease in P(O2) in the presence of 27 or 117 micromol l(-1) ambient sulphide had no significant effect on sulphide accumulation.