Respiratory exchange and transport of oxygen in <i>Nautilus pompilius</i>

Abstract

Abstract Respiratory 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 O 2 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 Po 2 are 99.2 (± 31.7 mmHg SD) for arterial and 20.4 (± 12.9 mmHg) for venous blood. Arterial blood is fully O 2 saturated while the average venous O 2 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 O 2 correlated with increasing metabolic rates.