Vascular Adaptations for a Low Pressure / High Flow Blood Supply to Locomotory Muscles of Antarctic Icefish

Abstract

The extremely stable Antarctic environment may be expected to have produced a number of cardiovascular adaptations to offset increased blood viscosity and/or decreased oxygen diffusion rates in the cold [1,2]. The ichthyofauna is dominated by Notothenioids which have a modest haematocrit and a reduced blood haemoglobin concentration [3], a situation taken to the extreme in the icefish (channichthyids) that possess only a few vestigial erythrocytes and no respiratory pigment. Low blood pressure and large venous return reported for icefish [4] would best be accommodated by a relatively low afterload on the heart [5]. Evidence for the origin of the assumed low peripheral resistance in icefish was sought in the morphology of the blood vascular system; preliminary results from this study were reported as abstracts [6,7].