Ventilation and circulation during exercise inOctopus vulgaris

Abstract

Ventilation frequency, volume, oxygen uptake, and oxygen transport by the blood have been studied in unrestrained octopus,Octopus vulgaris before, during and after recovery from 20 min of enforced activity. Exercise increased oxygen consumption 2.8 fold. The percentage utilisation of oxygen from the branchial water is maintained or increased at around 35% during activity and the calculated ventilation volume increases by 3 times. Prior to exercise the hemocyanin in arterial blood is 98% saturated and there is 83% utilisation of the oxygen in the blood. During activity there is remarkably little change in blood parameters so that the hemocyanin in the arterial blood remains at 96% saturation and oxygen utilisation is 90%. Cardiac output was calculated to have risen 2.5 fold during activity. As theP O 2 gradients across the gill do not change significantly during exercise the major adaptation which can account for an increase in oxygen consumption must be a 3 fold increase in the transfer factor. At rest 22% of the total CO2 present in the blood is excreted during its passage through the gills and this rises to 32% during activity. There is no accumulation of CO2 and only a slight acidification of the blood during activity. A significant respiratory and metabolic acidosis is avoided and the hemocyanin continues to function normally.