Influence of anoxia on adaptation of euryhaline polychaetes to hyposmotic conditions

The metabolic reactions ofArenicola marina andNereis diversicolor (both euryoxic and euryhaline polychaetes from the intertidal) to hyposmotic shock under anaerobic conditions were investigated in 1987–1988 using specimens from the East Frisian Wadden Sea. Although reductions in salinity were within the limits of tolerance under normoxic conditions, during anoxia they resulted in increased stress and a significant reduction in survival time. Both species were unable to sufficiently intensify anaerobic energy production to match the increased requirement for energy during adaptation to hyposmotic conditions. Moreover, as an adaptation to anoxic conditions, worms reduced their metabolic activity after the first 6 h. Thus, specimens remained more swollen than at the same reduction in salinity under normoxic conditions. InA. marina only the extracellular volume was reduced all be it to a limited extent.N. diversicolor probably reacted in the same or similar way. In both species, cells remained swollen. The concentrations of cellular free amino acids were not reduced; that means the main mechanism of cellular volume regulation was not activated under these conditions.