Burrowing behaviour and anaerobiosis in the bivalveArctica islandica(L.)

In laboratory tanks as well as in the seaArctica islandicashows a pattern of intermittent burrowing activity. Periods spent at the surface of the deposit alternate with periods buried several centimetres beneath the surface of the sand, during which the animals respire anaerobically. There is no obvious rhythmicity to this behaviour; the duration of periods spent beneath the surface is very variable even in the same animal, but normally lasts between 1 and 7 days. On the return to aerobic conditions both the heart rate and oxygen consumption areincreased but decline gradually during the following 20–25 h. This increased oxygen uptake is caused primarily by an increase in oxygen utilization but there is little change in ventilation rate. Both the initial rate of oxygen consumption and the duration of the recovery period show a correlation with the duration of the period of anaerobiosis. The concentration of alaninc in the blood ofArcticais high immediately after the return to aerobic conditions but declines during the recovery period. The similarity in the time taken for the concentration of alanine in the blood and the oxygen consumption ofArcticato return to normal levels suggests that at least part of this increased oxygen demand is associated with the metabolism of end-products of anaerobiosis.