Marenzelleria cf. wireni (Polychaeta: Spionidae) from the Tay estuary. Metabolic response to severe hypoxia and hydrogen sulphide

Abstract

The appearance of the spionid polychaete Marenzelleria spp. in the Tay estuary (Scotland) was first reported in 1984. Since estuaries are known as environments where abiotic conditions fluctuate widely, a laboratory study was conducted aimed to elucidate how this introduced species deals with low oxygen concentrations and exposure to hydrogen sulphide. Experimental evidence reveals that during severe hypoxia Marenzelleria cf. wireni switched to anaerobic pathways known from other marine invertebrates. Under the influence of sulphide (1 mmol l-1) accumulation of anaerobic end products is more pronounced. It is assumed that in the presence of sulphide, due to its inhibition of aerobic respiration, the worms have to switch to anaerobic energy production directly after the onset of hypoxia. Seasonal differences in the metabolic reaction were found. It was shown that in specimens that were filled with gametes (winter), accumulation of end products of anaerobic metabolism was more pronounced than in immature worms (summer). The amount of succinate, an indicator for anaerobic energy production for instance, was nearly twice as high in the ‘winter specimens’. Since the amount of thiosulphate (a typical sulphide detoxification product) in the tissues is relatively low, it is suggested that Marenzelleria cf. wireni also accumulates other detoxification products. Sulphite, however, also known as a detoxification product, was found only in traces. Field measurements provide evidence that the potential of Marenzelleria cf. wireni to survive low oxygen and high sulphide concentrations is clearly higher than that normally needed in the Tay estuary.