An investigation on the anaerobic metabolism of Nephtys hombergii (Annelida: Polychaeta)

Abstract

In Nephtys hombergii Savigny (Annelida: Polychaeta: Errantia), succinate and less pronounced L-alanine are accumulated as endproducts during an initial phase of anaerobiosis. In this phase aspartate is utilized as substrate for anaerobic energy production in addition to glycogen. Prolonged anaerobiosis results in the formation of propionate and acetate which, to a large extent, are excreted into the water. The concentrations of aspartate and succinate were found to remain unchanged down to a Pw_{O 2}(oxygen partial pressure in incubation water) of approximately 20 torr, indicating a fully aerobic metabolism. At a Pw_{O 2}of 15 torr characteristic changes can be observed: energy production becomes partially anaerobic. At a Pw_{O 2}of 7 torr the level of aspartate is largely reduced, but the accumulation of succinate is still significantly less than at anoxia. [In the habitat of N. hombergii, the intertidal mud flats, a Pw_{O 2}in the range from 0 torr (Pamatmat, 1968) to 12 torr (Wells and Warren, 1975) was measured.] The activities of some important enzymes involved in anaerobic energy production (among them pyruvate kinase, phosphoenolpyruvate carboxykinase and lactate dehydrogenase) were measured. Although N. hombergii has a high glycolytic capacity, no lactate dehydrogenase was detected. Instead strombine and alanopine dehydrogenases were present in comparatively high activities.