Sulfide detoxification and tolerance in Nereis (Hediste) diversicolor and Nereis (Neanthes) virens (Annelida. Polychaeta)

Sulfide oxidation activity was quantified for different tissues of the polychaetes Nereis diversicolor and N virens. Blood, intestinal wall and intestinal fluid of both species catalyzed sulfide oxidahon. N. dvers~color showed a sign~flcantly higher activity than did N. virens. Sulfide oxidation activity in the blood correlated with the concentration of 'brown pigment' N. diversicolor was more tolerant to long-term exposure to hypoxia and to hypoxia in the presence of sulfide than N. virens, and was twice as tolerant as N. virens to short-term exposure to high concentrations of sulfide. Results are discussed in terms of habitat preferences and competitive interactions.