The thermal acclimation potential of maximum heart rate and cardiac heat tolerance in Arctic char (Salvelinus alpinus), a northern cold-water specialist. (January 2021)

• Record Type: Journal Article
• Authors: Gilbert, Matthew J.H.; Farrell, Anthony P.
• Is Part Of: Journal of thermal biology. Volume 95(2021)
• Publication Date: 2021-01
• Subjects: Heat tolerance -- Arctic climate change -- Cardiorespiratory -- Arctic char -- Thermal acclimation -- Environmental physiology; Thermobiology -- Periodicals; Temperature -- Periodicals; Biology -- Periodicals; Thermobiologie -- Périodiques; Thermobiology; Periodicals; 571.46
• DOI: 10.1016/j.jtherbio.2020.102816
• Languages: English
• ISSNs: 0306-4565

Abstract

Abstract: Increasing heart rate (ƒH ) is a central, if not primary mechanism used by fishes to support their elevated tissue oxygen consumption during acute warming. Thermal acclimation can adjust this acute response to improve cardiac performance and heat tolerance under the prevailing temperatures. We predict that such acclimation will be particularly important in regions undergoing rapid environmental change such as the Arctic. Therefore, we acclimated Arctic char ( Salvelinus alpinus ), a high latitude, cold-adapted salmonid, to ecologically relevant temperatures (2, 6, 10, 14 and 18 °C) and examined how thermal acclimation influenced their cardiac heat tolerance by measuring the maximum heart rate (ƒHmax ) response to acute warming. As expected, acute warming increased ƒHmax in all Arctic char before ƒHmax reached a peak and then became arrhythmic. The peak ƒHmax, and the temperature at which peak ƒHmax (Tpeak ) and that at which arrhythmia first occurred (Tarr ) all increased progressively (+33%, 49% and 35%, respectively) with acclimation temperature from 2 to 14 °C. When compared at the same test temperature ƒHmax also decreased by as much as 29% with increasing acclimation temperature, indicating significant thermal compensation. The upper temperature at which fish first lost their equilibrium (critical thermal maximum: CTmax ) also increased with acclimation temperature, albeit to a lesser extent (+11%). Importantly, Arctic char experienced mortality after several weeks of acclimation at 18 °C and survivors did not have elevated cardiac thermal tolerance. Collectively, these findings suggest that if wild Arctic char have access to suitable temperatures (<18 °C) for a sufficient duration, warm acclimation can potentially mitigate some of the cardiorespiratory impairments previously documented during acute heat exposure. Graphical abstract: Image 1 Highlights: We acclimated Arctic char to ecologically relevant temperatures (2, 6, 10, 14 & 18 °C). Acclimation from 2 to 14 °C increased cardiac thermal tolerance by 35–49%. Acclimation to 18 °C did not improve thermal tolerance and caused mortality. Warm acclimation decreased max heart rate by up to 29% at similar temperatures. Warm acclimation may help wild Arctic char cope with extreme heat events.