Proceedings of The Physiological Society

University of Central Lancashire (2002) J Physiol 543P, S234


How seals may cool their brains during prolonged diving

A.S. Blix, L.P. Folkow and L. Walloe

Department of Arctic Biology, University of Troms

When seals dive for prolonged periods, their arterial oxygen tension may decrease to values as low as 2.0 kPa. The time it takes to reach such extreme values is mainly determined by the extent of a selective peripheral vasoconstriction which distributes most of a much reduced cardiac output to the brain, while the rest of the body has to rely on local stores of oxygen and anaerobic metabolism (e.g. Blix & Folkow, 1983). In this situation brain oxygen demand would be much reduced, and hence dive duration further extended, if brain temperature was reduced. We have shown that that is indeed the case (Odden et al. 1999). In the present study we have used six harp seals (Pagophilus groenlandicus) and measured brain temperature (Tb), carotid blood temperature (Tc), muscle (m. latissimus dorsi) temperature (Tm) and rectal temperature (Tr) during experimental dives of 10 min duration. The details of the methodology followed Odden et al. (1999), the experiments being approved by the Norwegian Committee on Ethics in Animal Experimentation. We found that heart rate always fell promptly from about 100 to 8

Where applicable, experiments conform with Society ethical requirements