UPTAKE OF AMINO ACIDS BY MARINE POLYCHAETES UNDER ANOXIC CONDITIONS

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Abstract
Two species of marine polychaete annelids, Marphysa sanguinea and Pareurythoe californica, were used to investigate 2 features of transepidermal influx of free amino acids from dilute solution in the environment. Since polychaetes in the intertidal infauna may undergo relative or complete anoxia periodically, the response of transepidermal amino acid transport to these conditions was investigated. In both species, such transport continues during up to 4 h of anoxia but at reduced rates (roughly half of those under fully aerobic conditions). In conditions of relative anoxia, transport continues unabated in Pareurythoe until the ambient O2 falls below approximately 20% of air saturation values. Marphysa was not investigated. The other feature of transport which was studied concerns the relationship between influx of amino acid determined radiochemically, and net influx determined by fluorometric analysis. Influx as estimated by disappearance of 14C from the medium corresponds closely to net influx as estimated by the decrease in ambient primary amines determined fluorometrically. This is true both in aerobic and anoxic conditions. Influx is accompanied by a slow efflux of unidentified primary amines. Rate of this efflux appears independent of ambient concentration. Levels of free amino acid in the normal environment were also measured. This information, plus information concerning influx rates at the relevant concentrations, was used to estimate total reduced C entering by this pathway per unit time. This was compared with metabolic requirements as estimated from O2 consumption rates. Transepidermal transport of free amino acids from the environment is probably a major input for these worms. Sufficient C is acquired to account for O2 consumption under aerobic conditions. In anoxia, the contribution is smaller since both rates of transport decrease and metabolic requirements for reduced C increase.