On the role of strombine formation in the energy metabolism of adductor muscle of a sessile bivalve

Abstract

1. Intertidal rocky shore mussels (Mytilus edulis) were subjected for 24 h to aerial exposure and after returing them to aerated sea water, the adductor muscle was excised at various time intervals up to 50 h and analysed for alanine, aspartate, glutamate, ammonia, succinate, malate, pyruvate, octopine, strombine and malate. In addition pH,PO2 and ammonia of the blood taken from the adductor sinus were estimated at time intervals both during aerial exposure and recovery. 2. It was observed that during the first 4 h of reimmersion the anaerobic end products were still formed, notably strombine (Fig. 1 a). It is argued that this is due to the fact that the energy demand in this period is too high to be met by respiration alone. 3. Within the first 2 h after reimmersion there was full restoration ofPO2, an overshoot in pH (Figs. 2a, b) and the clearance of blood ammonia (Fig. 3) and of succinate in the adductor muscle. At the same time glutamate, alanine and aspartate levels increased. From 2 h onwards glutamate and alanine levels started to decrease. 4. Within the first 4 h after reimmersion there was a much faster rate of formation of the pyruvate derivatives strombine, octopine and lactate when compared to the period of aerial exposure. Also pyruvate itself increased. 5. In the first hours of reimmersion the adductor muscle fixes considerable amounts of free ammonia. This is regarded as an auxiliary mechanism for blood ammonia clearance, which complements excretion into the medium. 6. It appears that anaerobic metabolism in the habitat of the sea mussel is involved not only in situations where oxygen uptake is blocked (natural anaerobiosis), but also when the energy demand is strongly increased (first hours of recovery). In the former condition alanine and succinate are the main end products, in the latter condition pyruvate derivatives accumulate.