Affiliation: | (1) School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand;(2) Integrative Physiology, School of Biological Sciences A08, University of Sydney, NSW, 2006, Australia |
Abstract: | The Antarctic notothenioids are among the most stenothermal of fishes, well adapted to their stable, cold and icy environment. The current study set out to investigate the thermal sensitivity/insensitivity of heart rate and ventral aortic blood pressure of the Antarctic nototheniid fish Pagothenia borchgrevinki over a range of temperatures. The heart rate increased rapidly from –1 to 6°C (Q10=2.0–3.3), but was relatively insensitive to temperature above the ~6°C lethal limit of the species (Q10=1.2). The increase in heart rate from –1 to 6°C was the result of a 45% increase in excitatory adrenergic tone, masking a 37% increase in inhibitory cholinergic tone. Ventral aortic pressure was regulated well above the lethal limit, up to at least 10°C. With the return of the fish to environmental temperatures, the heart rate rapidly decreased back to control levels, while ventral aortic pressure increased and remained elevated for over an hour following a 6°C exposure. |