Tubificoides benedii (Tubificidae, Oligochaeta) - a pioneer in hypoxic andsulfidic environments. An overview of adaptive pathways

Eutrophic tidal flats and polluted coastal sites are the predominant habita t of the marine oligochaete Tubificoides benedii. The worms live in dense p opulations in these stressed habitats which are often characterized by high levels of hydrogen sulfide. This indicates that they have a high capacity to tolerate anoxic (and sulfidic) conditions. Respiration rates of T. bened ii measured at various oxygen concentrations showed that aerobic respiratio n is maintained even at very low oxygen concentrations. This ability is com bined with a high regulatory capacity of oxygen uptake. Addition of sulfide considerably reduced this capacity of maintaining aerobic metabolic pathwa ys at low oxygen concentrations. The present work in relation to earlier ph ysiological and structural studies (Giere et al., 1988; Dubilier et al., 19 94, 1995, 1997) suggests adaptive strategies that make T. benedii one of th e most successful inhabitants of ecologically stressed, sulfidic benthic en vironments. This is corroborated by comparison with other typical 'sulfide annelids' such as the polychaetes Capitella capitata and Arenicola marina.