BIOENERGETICS OF A HIGHLY ADAPTABLE BRACKISH-WATER POLYCHAETE

The metabolic activities of different developmental stages of the poly chaete Marenzelleria viridis (Verrill 1873), which has successfully po pulated Baltic coastal waters since the 1980s, were determined under d ifferent temperatures, salinities and oxygen partial pressures by simu ltaneous calorimetry and respirometry. Larvae of M. viridis maintained their metabolic activity and met this fully aerobically down to sever e hypoxia. Adult individuals gradually reduced their metabolic activit y with decreasing oxygen partial pressures. An additional hyposmotic s tress of 0.5 parts per thousand, salinity, referring to low salinities in the biotope, led to an approach of the response of M. viridis to t he oxyconformer model. The results for adults were compared to those o f the common indigenous polychaete Nereis (Hediste) diversicolor (O.F. Muller), which responded with maintained metabolic activities to hypo xia. The ecological efficiency of the different adaptation strategies to hypoxia are discussed.