The Eﬀects of Thermal Acclimation on Cardio-Respiratory Performance in an Antarctic Fish (Notothenia Coriiceps)
© The Author(s) 2018. Published by Oxford University Press and the Society for Experimental Biology. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. The Southern Ocean has experienced stable, cold temperatures for over 10 million years, yet particular regions are currently undergoing rapid warming. To investigate the impacts of warming on cardiovascular oxygen transport, we compared the cardiorespiratory performance in an Antarctic notothenioid (Notothenia coriiceps) that was maintained at 0 or 5°C for 6.0-9.5 weeks. When compared at the ﬁsh's respective acclimation temperature, the oxygen consumption rate and cardiac output were signiﬁcantly higher in 5°C-acclimated than 0°C-acclimated ﬁsh. The 2.7-fold elevation in cardiac output in 5°C-acclimated ﬁsh (17.4 vs. 6.5 ml min−1 kg−1) was predominantly due to a doubling of stroke volume, likely in response to increased cardiac preload, as measured by higher central venous pressure (0.15 vs. 0.08 kPa); tachycardia was minor (29.5 vs. 25.2 beats min−1). When ﬁsh were acutely warmed, oxygen consumption rate increased by similar amounts in 0°C- and 5°C-acclimated ﬁsh at equivalent test temperatures. In both acclimation groups, the increases in oxygen consumption rate during acute heating were supported by increased cardiac output achieved by elevating heart rate, while stroke volume changed relatively little. Cardiac output was similar between both acclimation groups until 12°C when cardiac output became signiﬁcantly higher in 5°C-acclimated ﬁsh, driven largely by their higher stroke volume. Although cardiac arrhythmias developed at a similar temperature (~14.5°C) in both acclimation groups, the hearts of 5°C-acclimated ﬁsh continued to pump until signiﬁcantly higher temperatures (CTmax for cardiac function 17.7 vs. 15.0°C for 0°C-acclimated ﬁsh). These results demonstrate that N. coriiceps is capable of increasing routine cardiac output during both acute and chronic warming, although the mechanisms are diﬀerent (heart rate-dependent versus primarily stroke volume-dependent regulation, respectively). Cardiac performance was enhanced at higher temperatures following 5°C acclimation, suggesting cardiovascular function may not constrain the capacity of N. coriiceps to withstand a warming climate.
Joyce, William; Axelsson, Michael; Egginton, Stuart; Farrell, Anthony P.; Crockett, Elizabeth L.; and O'Brien, Kristin M., "The Eﬀects of Thermal Acclimation on Cardio-Respiratory Performance in an Antarctic Fish (Notothenia Coriiceps)" (2018). Biological Sciences Open Access Publications. 30.