Respiratory exchange and transport of oxygen in Nautilus pompilius

Abstract

AbstractRespiratory exchange of oxygen and the role of the hemocyanin‐containing blood in gas transport have been studied in the cephalopod Nautilus pompilius.Nautilu has a blood O2 capacity of 2.30 ± 0.57 vol%. The oxygen affinity is high compared to that of other cephalopods, P50 being 16.9 mmHg at pH 7.45 and 18°C. The n‐value (Hill coefficient) is 2.7 under those conditions. The Bohr factor, Ø, is low (i.e. −0.20). The temperature sensitivity, expressed by Δ, = −9.8 Kcal·MolHCY−1.Average values for circulating blood Po2 are 99.2 (± 31.7 mmHg SD) for arterial and 20.4 (± 12.9 mmHg) for venous blood. Arterial blood is fully O2 saturated while the average venous O2 saturation is about 65%.Direct measurements of ventilation average 296 ml·kg−1·min−1 while breathing rates vary between 40–60 min−1 at 18–20°C. Breathing rates and ventilation increase during locomotor activity and exposure to hypoxic water.The results are compared and analysed with available data for other cephalopods. Nautilus, one species of Octopus and the squid Loligo show ascending transport efficiency for O2 correlated with increasing metabolic rates.