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Desforges JE, Birnie-Gauvin K, Jutfelt F, Gilmour KM, Eliason EJ, Dressler TL, McKenzie DJ, Bates AE, Lawrence MJ, Fangue N, Cooke SJ. The ecological relevance of critical thermal maxima methodology for fishes. JOURNAL OF FISH BIOLOGY 2023; 102:1000-1016. [PMID: 36880500 DOI: 10.1111/jfb.15368] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Accepted: 02/28/2023] [Indexed: 05/13/2023]
Abstract
Critical thermal maxima methodology (CTM) has been used to infer acute upper thermal tolerance in fishes since the 1950s, yet its ecological relevance remains debated. In this study, the authors synthesize evidence to identify methodological concerns and common misconceptions that have limited the interpretation of critical thermal maximum (CTmax ; value for an individual fish during one trial) in ecological and evolutionary studies of fishes. They identified limitations of, and opportunities for, using CTmax as a metric in experiments, focusing on rates of thermal ramping, acclimation regimes, thermal safety margins, methodological endpoints, links to performance traits and repeatability. Care must be taken when interpreting CTM in ecological contexts, because the protocol was originally designed for ecotoxicological research with standardized methods to facilitate comparisons within study individuals, across species and contexts. CTM can, however, be used in ecological contexts to predict impacts of environmental warming, but only if parameters influencing thermal limits, such as acclimation temperature or rate of thermal ramping, are taken into account. Applications can include mitigating the effects of climate change, informing infrastructure planning or modelling species distribution, adaptation and/or performance in response to climate-related temperature change. The authors' synthesis points to several key directions for future research that will further aid the application and interpretation of CTM data in ecological contexts.
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Affiliation(s)
- Jessica E Desforges
- Department of Biology and Institute of Environmental and Interdisciplinary Science, Carleton University, Ottawa, Ontario, Canada
| | - Kim Birnie-Gauvin
- Department of Ecology, Evolution & Marine Biology, University of California Santa Barbara, Santa Barbara, California, USA
- Section for Freshwater Fisheries and Ecology, National Institute of Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark
| | - Fredrik Jutfelt
- Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
| | | | - Erika J Eliason
- Section for Freshwater Fisheries and Ecology, National Institute of Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark
| | - Terra L Dressler
- Section for Freshwater Fisheries and Ecology, National Institute of Aquatic Resources, Technical University of Denmark, Silkeborg, Denmark
| | | | - Amanda E Bates
- Department of Biology, University of Victoria, Victoria, British Columbia, Canada
| | - Michael J Lawrence
- Department of Biological Sciences, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Nann Fangue
- Department of Wildlife, Fish, and Conservation Biology, University of California Davis, Davis, California, USA
| | - Steven J Cooke
- Department of Biology and Institute of Environmental and Interdisciplinary Science, Carleton University, Ottawa, Ontario, Canada
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2
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Kuzmin V, Ushenin KS, Dzhumaniiazova IV, Abramochkin D, Vornanen M. High temperature and hyperkalemia cause exit block of action potentials at the atrioventricular junction of rainbow trout (Oncorhynchus mykiss) heart. J Therm Biol 2022; 110:103378. [PMID: 36462845 DOI: 10.1016/j.jtherbio.2022.103378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 10/13/2022] [Accepted: 10/21/2022] [Indexed: 11/07/2022]
Abstract
At critically high temperatures, atrioventricular (AV) block causes ventricular bradycardia and collapse of cardiac output in fish. Here, the possible role of the AV canal in high temperature-induced heart failure was examined. To this end, optical mapping was used to measure action potential (AP) conduction in isolated AV junction preparations of the rainbow trout (Oncorhynchus mykiss) heart during acute warming/cooling in the presence of 4 or 8 mM external K+ concentration. The preparation included the AV canal and some atrial and ventricular tissue at its edges, and it was paced either from atrial or ventricular side at a frequency of 0.67 Hz (40 beats min-1) to trigger forward (anterograde) and backward (retrograde) conduction, respectively. The propagation of AP was fast in atrial and ventricular tissues, but much slower in the AV canal, causing an AV delay. Acute warming from 15 °C to 27 °C or cooling from 15 °C to 5 °C did not impair AP conduction in the AV canal, as both anterograde and retrograde excitations propagated regularly through the AV canal. In contrast, anterograde conduction through the AV canal did not trigger ventricular excitation at the boundary zone between the AV canal and the ventricle when extracellular K+ concentration was raised from 4 mM to 8 mM at 27 °C. Also, the retrograde conduction was blocked at the border between the AV canal and the atrium in high K+ at 27 °C. These findings suggest that the AV canal is resistant against high temperatures (and high K+), but the ventricular muscle cannot be excited by APs coming from the AV canal when temperature and external K+ concentration are simultaneously elevated. Therefore, bradycardia at high temperatures in fish may occur due to inability of AP of the AV canal to trigger ventricular AP at the junctional zone between the AV canal and the proximal part of the ventricle.
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Affiliation(s)
- Vladislav Kuzmin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, building 12, Moscow, 119991, Russia.
| | - Konstantin S Ushenin
- Ural Federal University, Institute of Natural Sciences and Mathematics, Ekaterinburg, Kuybysheva Str., 48, Ekaterinburg, 620026, Russia
| | - Irina V Dzhumaniiazova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, building 12, Moscow, 119991, Russia
| | - Denis Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, building 12, Moscow, 119991, Russia; Laboratory of Cardiac Electrophysiology, National Medical Research Center for Cardiology, Moscow, Russia; Department of Physiology, Pirogov Russian National Research Medical University, Ostrovitjanova 1, Moscow, 117997, Russia
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O.Box 111, 80101, Joensuu, Finland
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3
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Huang T, Gu W, Liu E, Wang B, Wang G, Dong F, Guo F, Jiao W, Sun Y, Wang X, Li S, Xu G. miR-301b-5p and its target gene nfatc2ip regulate inflammatory responses in the liver of rainbow trout (Oncorhynchus mykiss) under high temperature stress. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2022; 242:113915. [PMID: 35901591 DOI: 10.1016/j.ecoenv.2022.113915] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2022] [Revised: 07/18/2022] [Accepted: 07/20/2022] [Indexed: 06/15/2023]
Abstract
Rainbow trout (Oncorhynchus mykiss) is a typical cold-water aquaculture fish and a high-end aquatic product. When water temperature exceeds its optimal range of 12-18 °C, the immune system of rainbow trout becomes weakened and unbalanced. High temperature in summer and global warming severely impact rainbow trout industry. The focus of this study was to explore the mechanisms regulating the immune response of rainbow trout under high temperature stress and identify molecular elements that account for resistance to high temperature. In this study, individual fish were screened in a high temperature stress experiment and divided into resistant (R) and sensitive (S) groups. The hepatic transcriptome sequencing and analysis of mRNAs and microRNAs of the R, S, and control groups showed that the number of the differentially expressed genes (DEGs) in the S group (9259) was higher than that in the R group (5313). Furthermore, the 1233 genes differentially expressed between S and R groups were mainly enriched in immune-related pathways, including cytokine-cytokine receptor interaction, TNF signaling and IL-17 signaling. Among these DEGs were miR-301b-5p and its target gene that encodes nuclear factor of activated T cells two interacting protein (nfatc2ip). The dual-luciferase reporter system and immunofluorescence experiments verified the relationship between miR-301b-5p and nfatc2ip. We also showed that expression levels of miR-301b-5p and nfatc2ip significantly negatively correlated in the liver of rainbow trout under high temperature stress. By performing functional experiments, we showed that activation of miR-301b-5p expression or inhibition of nfatc2ip expression stimulated the phosphorylation of p65, p38, and JNK in the classical nuclear factor kappa-B and mitogen-activated protein kinase pathways under high temperature stress. These manipulations initially promoted the secretion of the pro-inflammatory factor IL-1β and then increased the levels of IL-6, IL-12, and TNF-α. In addition, activation of miR-301b-5p expression or inhibition of nfatc2ip expression stimulated the repair of the hepatic ultrastructural damage caused by high temperature stress by activating the inflammatory response in rainbow trout liver.
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Affiliation(s)
- Tianqing Huang
- Cold Water Fish Industry Technology Innovation Strategic Alliance, Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin, PR China
| | - Wei Gu
- Cold Water Fish Industry Technology Innovation Strategic Alliance, Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin, PR China
| | - Enhui Liu
- Cold Water Fish Industry Technology Innovation Strategic Alliance, Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin, PR China
| | - Bingqian Wang
- Cold Water Fish Industry Technology Innovation Strategic Alliance, Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin, PR China
| | - Gaochao Wang
- Cold Water Fish Industry Technology Innovation Strategic Alliance, Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin, PR China
| | - Fulin Dong
- Cold Water Fish Industry Technology Innovation Strategic Alliance, Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin, PR China
| | - Fuyuan Guo
- Yantai Jinghai Marine Fishery Co Ltd, Yantai, PR China
| | - Wenlong Jiao
- Gansu Fisheries Research Institute, Lanzhou, PR China
| | - Yanchun Sun
- Cold Water Fish Industry Technology Innovation Strategic Alliance, Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin, PR China
| | - Xiance Wang
- Hangzhou Qiandaohu Xun Long Sci-tech CO., LTD, Hangzhou, PR China
| | - Shanwei Li
- Department of Food Science and Engineering, College of Food Science and Technology, Shanghai Ocean University, Shanghai, PR China
| | - Gefeng Xu
- Cold Water Fish Industry Technology Innovation Strategic Alliance, Heilongjiang River Fisheries Research Institute, Chinese Academy of Fishery Sciences, Harbin, PR China.
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4
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Thermal acclimation and acute temperature effects on cardiac barostatic reflexes in rainbow trout (Oncorhynchus mykiss). J Therm Biol 2022; 109:103315. [DOI: 10.1016/j.jtherbio.2022.103315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 07/26/2022] [Accepted: 08/24/2022] [Indexed: 11/17/2022]
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5
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Gamperl AK, Zrini ZA, Sandrelli RM. Atlantic Salmon ( Salmo salar) Cage-Site Distribution, Behavior, and Physiology During a Newfoundland Heat Wave. Front Physiol 2021; 12:719594. [PMID: 34504440 PMCID: PMC8421689 DOI: 10.3389/fphys.2021.719594] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 07/20/2021] [Indexed: 11/13/2022] Open
Abstract
Background: Climate change is leading to increased water temperatures and reduced oxygen levels at sea-cage sites, and this is a challenge that the Atlantic salmon aquaculture industry must adapt to it if it needs to grow sustainably. However, to do this, the industry must better understand how sea-cage conditions influence the physiology and behavior of the fish. Method: We fitted ~2.5 kg Atlantic salmon on the south coast of Newfoundland with Star-Oddi milli-HRT ACT and Milli-TD data loggers (data storage tags, DSTs) in the summer of 2019 that allowed us to simultaneously record the fish's 3D acceleration (i.e., activity/behavior), electrocardiograms (and thus, heart rate and heart rate variability), depth, and temperature from early July to mid-October. Results: Over the course of the summer/fall, surface water temperatures went from ~10–12 to 18–19.5°C, and then fell to 8°C. The data provide valuable information on how cage-site conditions affected the salmon and their determining factors. For example, although the fish typically selected a temperature of 14–18°C when available (i.e., this is their preferred temperature in culture), and thus were found deeper in the cage as surface water temperatures peaked, they continued to use the full range of depths available during the warmest part of the summer. The depth occupied by the fish and heart rate were greater during the day, but the latter effect was not temperature-related. Finally, while the fish generally swam at 0.4–1.0 body lengths per second (25–60 cm s−1), their activity and the proportion of time spent using non-steady swimming (i.e., burst-and-coast swimming) increased when feeding was stopped at high temperatures. Conclusion: Data storage tags that record multiple parameters are an effective tool to understand how cage-site conditions and management influence salmon (fish) behavior, physiology, and welfare in culture, and can even be used to provide fine-scale mapping of environmental conditions. The data collected here, and that in recent publications, strongly suggest that pathogen (biotic) challenges in combination with high temperatures, not high temperatures + moderate hypoxia (~70% air saturation) by themselves, are the biggest climate-related challenge facing the salmon aquaculture industry outside of Tasmania.
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Affiliation(s)
- Anthony K Gamperl
- Department of Ocean Sciences, Memorial University, St. John's, NL, Canada
| | - Zoe A Zrini
- Department of Ocean Sciences, Memorial University, St. John's, NL, Canada
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6
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McKenzie DJ, Zhang Y, Eliason EJ, Schulte PM, Claireaux G, Blasco FR, Nati JJH, Farrell AP. Intraspecific variation in tolerance of warming in fishes. JOURNAL OF FISH BIOLOGY 2021; 98:1536-1555. [PMID: 33216368 DOI: 10.1111/jfb.14620] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Revised: 10/09/2020] [Accepted: 11/17/2020] [Indexed: 05/12/2023]
Abstract
Intraspecific variation in key traits such as tolerance of warming can have profound effects on ecological and evolutionary processes, notably responses to climate change. The empirical evidence for three primary elements of intraspecific variation in tolerance of warming in fishes is reviewed. The first is purely mechanistic that tolerance varies across life stages and as fishes become mature. The limited evidence indicates strongly that this is the case, possibly because of universal physiological principles. The second is intraspecific variation that is because of phenotypic plasticity, also a mechanistic phenomenon that buffers individuals' sensitivity to negative impacts of global warming in their lifetime, or to some extent through epigenetic effects over successive generations. Although the evidence for plasticity in tolerance to warming is extensive, more work is required to understand underlying mechanisms and to reveal whether there are general patterns. The third element is intraspecific variation based on heritable genetic differences in tolerance, which underlies local adaptation and may define long-term adaptability of a species in the face of ongoing global change. There is clear evidence of local adaptation and some evidence of heritability of tolerance to warming, but the knowledge base is limited with detailed information for only a few model or emblematic species. There is also strong evidence of structured variation in tolerance of warming within species, which may have ecological and evolutionary significance irrespective of whether it reflects plasticity or adaptation. Although the overwhelming consensus is that having broader intraspecific variation in tolerance should reduce species vulnerability to impacts of global warming, there are no sufficient data on fishes to provide insights into particular mechanisms by which this may occur.
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Affiliation(s)
- David J McKenzie
- MARBEC, University of Montpellier, CNRS, IFREMER, IRD, Montpellier, France
| | - Yangfan Zhang
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | | | - Patricia M Schulte
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Guy Claireaux
- Université de Bretagne Occidentale, LEMAR (UMR 6539), Centre Ifremer de Bretagne, Plouzané, France
| | - Felipe R Blasco
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
- Joint Graduate Program in Physiological Sciences, Federal University of São Carlos - UFSCar/São Paulo State University, UNESP Campus Araraquara, Araraquara, Brazil
| | - Julie J H Nati
- MARBEC, University of Montpellier, CNRS, IFREMER, IRD, Montpellier, France
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
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7
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Adrenergic tone benefits cardiac performance and warming tolerance in two teleost fishes that lack a coronary circulation. J Comp Physiol B 2021; 191:701-709. [PMID: 33738526 PMCID: PMC8241749 DOI: 10.1007/s00360-021-01359-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 02/04/2021] [Accepted: 02/22/2021] [Indexed: 01/14/2023]
Abstract
Tolerance to acute environmental warming in fish is partly governed by the functional capacity of the heart to increase systemic oxygen delivery at high temperatures. However, cardiac function typically deteriorates at high temperatures, due to declining heart rate and an impaired capacity to maintain or increase cardiac stroke volume, which in turn has been attributed to a deterioration of the electrical conductivity of cardiac tissues and/or an impaired cardiac oxygen supply. While autonomic regulation of the heart may benefit cardiac function during warming by improving myocardial oxygenation, contractility and conductivity, the role of these processes for determining whole animal thermal tolerance is not clear. This is in part because interpretations of previous pharmacological in vivo experiments in salmonids are ambiguous and were confounded by potential compensatory increases in coronary oxygen delivery to the myocardium. Here, we tested the previously advanced hypothesis that cardiac autonomic control benefits heart function and acute warming tolerance in perch (Perca fluviatilis) and roach (Rutilus rutilus); two species that lack coronary arteries and rely entirely on luminal venous oxygen supplies for cardiac oxygenation. Pharmacological blockade of β-adrenergic tone lowered the upper temperature where heart rate started to decline in both species, marking the onset of cardiac failure, and reduced the critical thermal maximum (CTmax) in perch. Cholinergic (muscarinic) blockade had no effect on these thermal tolerance indices. Our findings are consistent with the hypothesis that adrenergic stimulation improves cardiac performance during acute warming, which, at least in perch, increases acute thermal tolerance.
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8
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Lefevre S, Wang T, McKenzie DJ. The role of mechanistic physiology in investigating impacts of global warming on fishes. J Exp Biol 2021; 224:224/Suppl_1/jeb238840. [PMID: 33627469 DOI: 10.1242/jeb.238840] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Warming of aquatic environments as a result of climate change is already having measurable impacts on fishes, manifested as changes in phenology, range shifts and reductions in body size. Understanding the physiological mechanisms underlying these seemingly universal patterns is crucial if we are to reliably predict the fate of fish populations with future warming. This includes an understanding of mechanisms for acute thermal tolerance, as extreme heatwaves may be a major driver of observed effects. The hypothesis of gill oxygen limitation (GOL) is claimed to explain asymptotic fish growth, and why some fish species are decreasing in size with warming; but its underlying assumptions conflict with established knowledge and direct mechanistic evidence is lacking. The hypothesis of oxygen- and capacity-limited thermal tolerance (OCLTT) has stimulated a wave of research into the role of oxygen supply capacity and thermal performance curves for aerobic scope, but results vary greatly between species, indicating that it is unlikely to be a universal mechanism. As thermal performance curves remain important for incorporating physiological tolerance into models, we discuss potentially fruitful alternatives to aerobic scope, notably specific dynamic action and growth rate. We consider the limitations of estimating acute thermal tolerance by a single rapid measure whose mechanism of action is not known. We emphasise the continued importance of experimental physiology, particularly in advancing our understanding of underlying mechanisms, but also the challenge of making this knowledge relevant to the more complex reality.
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Affiliation(s)
- Sjannie Lefevre
- Section for Physiology and Cell Biology, Department of Biosciences, University of Oslo, 0316 Oslo, Norway
| | - Tobias Wang
- Department of Biology - Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | - David J McKenzie
- Marine Biodiversity, Exploitation and Conservation (MARBEC), Université de Montpellier, CNRS, Ifremer, IRD, 34000 Montpellier, France
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9
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Vornanen M. Effects of acute warming on cardiac and myotomal sarco(endo)plasmic reticulum ATPase (SERCA) of thermally acclimated brown trout (Salmo trutta). J Comp Physiol B 2020; 191:43-53. [PMID: 32980918 PMCID: PMC7819936 DOI: 10.1007/s00360-020-01313-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 08/21/2020] [Accepted: 09/09/2020] [Indexed: 11/24/2022]
Abstract
At high temperatures, ventricular beating rate collapses and depresses cardiac output in fish. The role of sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) in thermal tolerance of ventricular function was examined in brown trout (Salmo trutta) by measuring heart SERCA and comparing it to that of the dorsolateral myotomal muscle. Activity of SERCA was measured from crude homogenates of cold-acclimated (+ 3 °C, c.a.) and warm-acclimated (+ 13 °C, w.a.) brown trout as cyclopiazonic acid (20 µM) sensitive Ca2+-ATPase between + 3 and + 33 °C. Activity of the heart SERCA was significantly higher in c.a. than w.a. trout and increased strongly between + 3 and + 23 °C with linear Arrhenius plots but started to plateau between + 23 and + 33 °C in both acclimation groups. The rate of thermal inactivation of the heart SERCA at + 35 °C was similar in c.a. and w.a. fish. Activity of the muscle SERCA was less temperature dependent and more heat resistant than that of the heart SERCA and showed linear Arrhenius plots between + 3 and + 33 °C in both c.a. and w.a. fish. SERCA activity of the c.a. muscle was slightly higher than that of w.a. muscle. The rate of thermal inactivation at + 40 °C was similar for both c.a. and w.a. muscle SERCA at + 40 °C. Although the heart SERCA is more sensitive to high temperatures than the muscle SERCA, it is unlikely to be a limiting factor for heart rate, because its heat tolerance, unlike that of the ventricular beating rate, was not changed by temperature acclimation.
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Affiliation(s)
- Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland.
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10
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Haverinen J, Vornanen M. Reduced ventricular excitability causes atrioventricular block and depression of heart rate in fish at critically high temperatures. J Exp Biol 2020; 223:jeb225227. [PMID: 32434803 DOI: 10.1242/jeb.225227] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 05/13/2020] [Indexed: 01/08/2023]
Abstract
At critically high temperature, cardiac output in fish collapses as a result of depression of heart rate (bradycardia). However, the cause of bradycardia remains unresolved. To investigate this, rainbow trout (Oncorhynchus mykiss; acclimated at 12°C) were exposed to acute warming while electrocardiograms were recorded. From 12°C to 25.3°C, electrical excitation between different parts of the heart was coordinated, but above 25.3°C, atrial and ventricular beating rates became partly dissociated because of 2:1 atrioventricular (AV) block. With further warming, atrial rate increased to a peak value of 188±22 beats min-1 at 27°C, whereas the ventricle rate peaked at 124±10 beats min-1 at 25.3°C and thereafter dropped to 111±15 beats min-1 at 27°C. In single ventricular myocytes, warming from 12°C to 25°C attenuated electrical excitability as evidenced by increases in rheobase current and the size of critical depolarization required to trigger action potential. Depression of excitability was caused by temperature-induced decrease in input resistance (sarcolemmal K+ leak via the outward IK1 current) of resting myocytes and decrease in inward charge transfer by the Na+ current (INa) of active myocytes. Collectively, these findings show that at critically high temperatures AV block causes ventricular bradycardia owing to the increased excitation threshold of the ventricle, which is due to changes in the passive (resting ion leak) and active (inward charge movement) electrical properties of ventricular myocytes. The sequence of events from the level of ion channels to cardiac function in vivo provides a mechanistic explanation for the depression of cardiac output in fish at critically high temperature.
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Affiliation(s)
- Jaakko Haverinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, 80101 Joensuu, Finland
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, 80101 Joensuu, Finland
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11
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Gilbert MJH, Harris LN, Malley BK, Schimnowski A, Moore JS, Farrell AP. The thermal limits of cardiorespiratory performance in anadromous Arctic char ( Salvelinus alpinus): a field-based investigation using a remote mobile laboratory. CONSERVATION PHYSIOLOGY 2020; 8:coaa036. [PMID: 32346481 PMCID: PMC7176916 DOI: 10.1093/conphys/coaa036] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2019] [Revised: 03/17/2020] [Accepted: 03/24/2020] [Indexed: 05/31/2023]
Abstract
Despite immense concern over amplified warming in the Arctic, physiological research to address related conservation issues for valuable cold-adapted fish, such as the Arctic char (Salvelinus alpinus), is lacking. This crucial knowledge gap is largely attributable to the practical and logistical challenges of conducting sensitive physiological investigations in remote field settings. Here, we used an innovative, mobile aquatic-research laboratory to assess the effects of temperature on aerobic metabolism and maximum heart rate (f Hmax) of upriver migrating Arctic char in the Kitikmeot region of Nunavut in the central Canadian Arctic. Absolute aerobic scope was unchanged at temperatures from 4 to 16°C, while f Hmax increased with temperature (Q 10 = 2.1), as expected. However, f Hmax fell precipitously below 4°C and it began to plateau above ~ 16°C, reaching a maximum at ~ 19°C before declining and becoming arrhythmic at ~ 21°C. Furthermore, recovery from exhaustive exercise appeared to be critically impaired above 16°C. The broad thermal range (~4-16°C) for increasing f Hmax and maintaining absolute aerobic scope matches river temperatures commonly encountered by migrating Arctic char in this region. Nevertheless, river temperatures can exceed 20°C during warm events and our results confirm that such temperatures would limit exercise performance and thus impair migration in this species. Thus, unless Arctic char can rapidly acclimatize or alter its migration timing or location, which are both open questions, these impairments would likely impact population persistence and reduce lifetime fitness. As such, future conservation efforts should work towards quantifying and accounting for the impacts of warming, variable river temperatures on migration and reproductive success.
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Affiliation(s)
- Matthew J H Gilbert
- Department of Zoology, University of British Columbia, #4200-6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
| | - Les N Harris
- Freshwater Institute, Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB, R3T 2N6, Canada
| | - Brendan K Malley
- Freshwater Institute, Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB, R3T 2N6, Canada
| | - Adrian Schimnowski
- Arctic Research Foundation, 1505 Charleswood Road, Winnipeg, MB, R3S 1C2, Canada
| | - Jean-Sébastien Moore
- Institut de Biologie Intégrative et des Systèmes and Département de Biologie, Université Laval, 1030 Avenue de la Médecine, Quebec City, QC, Québec G1V 0A6, Canada
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, #4200-6270 University Blvd, Vancouver, BC, V6T 1Z4, Canada
- Faculty of Land and Food Systems, University of British Columbia, #4200-6270 University Blvd, Vancouver, BC, V6T 1Z4
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12
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Safi H, Zhang Y, Schulte PM, Farrell AP. The effect of acute warming and thermal acclimation on maximum heart rate of the common killifish Fundulus heteroclitus. JOURNAL OF FISH BIOLOGY 2019; 95:1441-1446. [PMID: 31613985 DOI: 10.1111/jfb.14159] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2019] [Accepted: 10/14/2019] [Indexed: 06/10/2023]
Abstract
Common killifish Fundulus heteroclitus were acclimated to ecologically relevant temperatures (5, 15 and 33°C) and their maximum heart rate (fHmax ) was measured at each acclimation temperature during an acute warming protocol. Acclimation to 33°C increased peak fHmax by up to 32% and allowed the heart to beat rhythmically at a temperature 10°C higher when compared with acclimation to 5°C. Independent of acclimation temperature, peak fHmax occurred about 3°C cooler than the temperature that first produced cardiac arrhythmias. Thus, when compared with previously published values for the critical thermal maximum of F. heteroclitus, the temperature for peak fHmax was cooler and the temperature that first produced cardiac arrhythmias was similar to these critical thermal maxima. The considerable thermal plasticity of fHmax demonstrated in the present study is entirely consistent with eurythermal ecology of killifish, as shown previously for another eurythermal fish Gillichthys mirabilis.
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Affiliation(s)
- Hamid Safi
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Yangfan Zhang
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
| | - Patricia M Schulte
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
- Faculty of Land and Food Systems, University of British Columbia, Vancouver, British Columbia, Canada
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13
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Ekström A, Gräns A, Sandblom E. Can´t beat the heat? Importance of cardiac control and coronary perfusion for heat tolerance in rainbow trout. J Comp Physiol B 2019; 189:10.1007/s00360-019-01243-7. [PMID: 31707423 DOI: 10.1007/s00360-019-01243-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2019] [Revised: 10/11/2019] [Accepted: 10/24/2019] [Indexed: 12/11/2022]
Abstract
Coronary perfusion and cardiac autonomic regulation may benefit myocardial oxygen delivery and thermal performance of the teleost heart, and thus influence whole animal heat tolerance. Yet, no study has examined how coronary perfusion affects cardiac output during warming in vivo. Moreover, while β-adrenergic stimulation could protect cardiac contractility, and cholinergic decrease in heart rate may enhance myocardial oxygen diffusion at critically high temperatures, previous studies in rainbow trout (Oncorhynchus mykiss) using pharmacological antagonists to block cholinergic and β-adrenergic regulation showed contradictory results with regard to cardiac performance and heat tolerance. This could reflect intra-specific differences in the extent to which altered coronary perfusion buffered potential negative effects of the pharmacological blockade. Here, we first tested how cardiac performance and the critical thermal maximum (CTmax) were affected following a coronary ligation. We then assessed how these performances were influenced by pharmacological cholinergic or β-adrenergic blockade, hypothesising that the effects of the pharmacological treatment would be more pronounced in coronary ligated trout compared to trout with intact coronaries. Coronary blockade reduced CTmax by 1.5 °C, constrained stroke volume and cardiac output across temperatures, led to earlier cardiac failure and was associated with reduced blood oxygen-carrying capacity. Nonetheless, CTmax and the temperatures for cardiac failure were not affected by autonomic blockade. Collectively, our data show that coronary perfusion improves heat tolerance and cardiac performance in trout, while evidence for beneficial effects of altered cardiac autonomic tone during warming remains inconclusive.
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Affiliation(s)
- Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30, Göteborg, Sweden.
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Göteborg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30, Göteborg, Sweden
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14
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Morgenroth D, Ekström A, Hjelmstedt P, Gräns A, Axelsson M, Sandblom E. Hemodynamic responses to warming in euryhaline rainbow trout: implications of the osmo-respiratory compromise. ACTA ACUST UNITED AC 2019; 222:jeb.207522. [PMID: 31395678 DOI: 10.1242/jeb.207522] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 07/31/2019] [Indexed: 12/19/2022]
Abstract
In seawater, rainbow trout (Oncorhynchus mykiss) drink and absorb water through the gastrointestinal tract to compensate for water passively lost to the hyperosmotic environment. Concomitantly, they exhibit elevated cardiac output and a doubling of gastrointestinal blood flow to provide additional O2 to the gut and increase convective flux of absorbed ions and water. Yet, it is unknown how warming waters, which elevate tissue O2 demand and the rate of diffusion of ions and water across the gills (i.e. the osmo-respiratory compromise), affects these processes. We measured cardiovascular and blood variables of rainbow trout acclimated to freshwater and seawater during acute warming from 11 to 17°C. Relative to freshwater-acclimated trout, cardiac output was 34% and 55% higher in seawater-acclimated trout at 11 and 17°C, respectively, which allowed them to increase gastrointestinal blood flow significantly more during warming (increases of 75% in seawater vs. 31% in freshwater). These adjustments likely served to mitigate the impact of warming on osmotic balance, as changes in ionic and osmotic blood composition were minor. Furthermore, seawater-acclimated trout seemingly had a lower tissue O2 extraction, explaining why trout acclimated to freshwater and seawater often exhibit similar metabolic rates, despite a higher cardiac output in seawater. Our results highlight a novel role of gastrointestinal blood perfusion in the osmo-respiratory compromise in fish, and improve our understanding of the physiological changes euryhaline fishes must undergo when faced with interacting environmental challenges such as transient warming events.
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Affiliation(s)
- Daniel Morgenroth
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Per Hjelmstedt
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, 532 23 Skara, Sweden
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, 532 23 Skara, Sweden
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, PO Box 463, 405 30 Gothenburg, Sweden
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15
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Gilbert MJH, Rani V, McKenzie SM, Farrell AP. Autonomic cardiac regulation facilitates acute heat tolerance in rainbow trout: in situ and in vivo support. ACTA ACUST UNITED AC 2019; 222:jeb.194365. [PMID: 31015284 DOI: 10.1242/jeb.194365] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Accepted: 04/10/2019] [Indexed: 12/27/2022]
Abstract
Acute warming in fish increases heart rate (f H) and cardiac output to peak values, after which performance plateaus or declines and arrhythmia may occur. This cardiac response can place a convective limitation on systemic oxygen delivery at high temperatures. To test the hypothesis that autonomic cardiac regulation protects cardiac performance in rainbow trout during acute warming, we investigated adrenergic and cholinergic regulation during the onset and progression of cardiac limitations. We explored the direct effects of adrenergic stimulation by acutely warming an in situ working perfused heart until arrhythmia occurred, cooling the heart to restore rhythmicity and rewarming with increasing adrenergic stimulation. Adrenergic stimulation produced a clear, dose-dependent increase in the temperature and peak f H achieved prior to the onset of arrhythmia. To examine how this adrenergic protection functions in conjunction with cholinergic vagal inhibition in vivo, rainbow trout fitted with ECG electrodes were acutely warmed in a respirometer until they lost equilibrium (CTmax) with and without muscarinic (atropine) and β-adrenergic (sotalol) antagonists. Trout exhibited roughly equal and opposing cholinergic and adrenergic tone on f H that persisted up to critical temperatures. β-Adrenergic blockade significantly lowered peak f H by 14-17%, while muscarinic blockade significantly lowered the temperature for peak f H by 2.0°C. Moreover, muscarinic and β-adrenergic blockers injected individually or together significantly reduced CTmax by up to 3°C, indicating for the first time that cardiac adrenergic stimulation and cholinergic inhibition can enhance acute heat tolerance in rainbow trout at the level of the heart and the whole animal.
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Affiliation(s)
- Matthew J H Gilbert
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4
| | - Varsha Rani
- Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, BC, Canada V6T 1Z4
| | - Sean M McKenzie
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4.,Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, BC, Canada V6T 1Z4
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16
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17
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18
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Brijs J, Sandblom E, Dekens E, Näslund J, Ekström A, Axelsson M. Cardiac remodeling and increased central venous pressure underlie elevated stroke volume and cardiac output of seawater-acclimated rainbow trout. Am J Physiol Regul Integr Comp Physiol 2017; 312:R31-R39. [DOI: 10.1152/ajpregu.00374.2016] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 10/11/2016] [Accepted: 11/23/2016] [Indexed: 11/22/2022]
Abstract
Substantial increases in cardiac output (CO), stroke volume (SV), and gastrointestinal blood flow are essential for euryhaline rainbow trout ( Oncorhyncus mykiss) osmoregulation in seawater. However, the underlying hemodynamic mechanisms responsible for these changes are unknown. By examining a range of circulatory and cardiac morphological variables of seawater- and freshwater-acclimated rainbow trout, the present study revealed a significantly higher central venous pressure (CVP) in seawater-acclimated trout (~0.09 vs. −0.02 kPa). This serves to increase cardiac end-diastolic volume in seawater and explains the elevations in SV (~0.41 vs. 0.27 ml/kg) and CO (~21.5 vs. 14.2 ml·min−1·kg−1) when compared with trout in freshwater. Furthermore, these hemodynamic modifications coincided with a significant increase in the proportion of compact myocardium, which may be necessary to compensate for the increased wall tension associated with a larger stroke volume. Following a temperature increase from 10 to 16.5°C, both acclimation groups exhibited similar increases in heart rate (Q10 of ~2), but SV tended to decrease in seawater-acclimated trout despite the fact that CVP was maintained in both groups. This resulted in CO of seawater- and freshwater-acclimated trout stabilizing at a similar level after warming (~26 ml·min−1·kg−1). The consistently higher CVP of seawater-acclimated trout suggests that factors other than compromised cardiac filling constrained the SV and CO of these individuals at high temperatures. The present study highlights, for the first time, the complex interacting effects of temperature and water salinity on cardiovascular responses in a euryhaline fish species.
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Affiliation(s)
- Jeroen Brijs
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Esmée Dekens
- Institute for Life Sciences and Chemistry, University of Applied Sciences, Utrecht, The Netherlands; and
| | - Joacim Näslund
- Faculty of Science, Department of Ecosystem Biology, University of South Bohemia, České Budějovice, Czech Republic
| | - Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
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19
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Ekström A, Sandblom E, Blier PU, Dupont Cyr BA, Brijs J, Pichaud N. Thermal sensitivity and phenotypic plasticity of cardiac mitochondrial metabolism in European perch, Perca fluviatilis. ACTA ACUST UNITED AC 2016; 220:386-396. [PMID: 27852753 DOI: 10.1242/jeb.150698] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2016] [Accepted: 11/11/2016] [Indexed: 01/06/2023]
Abstract
Cellular and mitochondrial metabolic capacity of the heart has been suggested to limit performance of fish at warm temperatures. We investigated this hypothesis by studying the effects of acute temperature increases (16, 23, 30, 32.5 and 36°C) on the thermal sensitivity of 10 key enzymes governing cardiac oxidative and glycolytic metabolism in two populations of European perch (Perca fluviatilis) field-acclimated to 15.5 and 22.5°C, as well as the effects of acclimation on cardiac lipid composition. In both populations of perch, the activity of glycolytic (pyruvate kinase and lactate dehydrogenase) and tricarboxylic acid cycle (pyruvate dehydrogenase and citrate synthase) enzymes increased with acute warming. However, at temperatures exceeding 30°C, a drastic thermally induced decline in citrate synthase activity was observed in the cold- and warm-acclimated populations, respectively, indicating a bottleneck for producing the reducing equivalents required for oxidative phosphorylation. Yet, the increase in aspartate aminotransferase and malate dehydrogenase activities occurring in both populations at temperatures exceeding 30°C suggests that the malate-aspartate shuttle may help to maintain cardiac oxidative capacities at high temperatures. Warm acclimation resulted in a reorganization of the lipid profile, a general depression of enzymatic activity and an increased fatty acid metabolism and oxidative capacity. Although these compensatory mechanisms may help to maintain cardiac energy production at high temperatures, the activity of the electron transport system enzymes, such as complexes I and IV, declined at 36°C in both populations, indicating a thermal limit of oxidative phosphorylation capacity in the heart of European perch.
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Affiliation(s)
- Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, 41390 Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, 41390 Gothenburg, Sweden
| | - Pierre U Blier
- Department of Biology, University of Québec, Rimouski, Québec, Canada G5L 3A1
| | | | - Jeroen Brijs
- Department of Biological and Environmental Sciences, University of Gothenburg, 41390 Gothenburg, Sweden
| | - Nicolas Pichaud
- Department of Biological and Environmental Sciences, University of Gothenburg, 41390 Gothenburg, Sweden.,Department of Biology, University of Québec, Rimouski, Québec, Canada G5L 3A1.,Department of Chemistry and Biochemistry, University of Moncton, Moncton, NB, Canada E1A 3E9
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20
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Vornanen M. The temperature dependence of electrical excitability in fish hearts. J Exp Biol 2016; 219:1941-52. [DOI: 10.1242/jeb.128439] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Accepted: 05/17/2016] [Indexed: 01/08/2023]
Abstract
ABSTRACT
Environmental temperature has pervasive effects on the rate of life processes in ectothermic animals. Animal performance is affected by temperature, but there are finite thermal limits for vital body functions, including contraction of the heart. This Review discusses the electrical excitation that initiates and controls the rate and rhythm of fish cardiac contraction and is therefore a central factor in the temperature-dependent modulation of fish cardiac function. The control of cardiac electrical excitability should be sensitive enough to respond to temperature changes but simultaneously robust enough to protect against cardiac arrhythmia; therefore, the thermal resilience and plasticity of electrical excitation are physiological qualities that may affect the ability of fishes to adjust to climate change. Acute changes in temperature alter the frequency of the heartbeat and the duration of atrial and ventricular action potentials (APs). Prolonged exposure to new thermal conditions induces compensatory changes in ion channel expression and function, which usually partially alleviate the direct effects of temperature on cardiac APs and heart rate. The most heat-sensitive molecular components contributing to the electrical excitation of the fish heart seem to be Na+ channels, which may set the upper thermal limit for the cardiac excitability by compromising the initiation of the cardiac AP at high temperatures. In cardiac and other excitable cells, the different temperature dependencies of the outward K+ current and inward Na+ current may compromise electrical excitability at temperature extremes, a hypothesis termed the temperature-dependent depression of electrical excitation.
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Affiliation(s)
- Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, PO Box 111, Joensuu 80101, Finland
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21
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Ekström A, Brijs J, Clark TD, Gräns A, Jutfelt F, Sandblom E. Cardiac oxygen limitation during an acute thermal challenge in the European perch: effects of chronic environmental warming and experimental hyperoxia. Am J Physiol Regul Integr Comp Physiol 2016; 311:R440-9. [PMID: 27280433 DOI: 10.1152/ajpregu.00530.2015] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 06/07/2016] [Indexed: 11/22/2022]
Abstract
Oxygen supply to the heart has been hypothesized to limit cardiac performance and whole animal acute thermal tolerance (CTmax) in fish. We tested these hypotheses by continuously measuring venous oxygen tension (Pvo2) and cardiovascular variables in vivo during acute warming in European perch (Perca fluviatilis) from a reference area during summer (18°C) and a chronically heated area (Biotest enclosure) that receives warm effluent water from a nuclear power plant and is normally 5-10°C above ambient (24°C at the time of experiments). While CTmax was 2.2°C higher in Biotest compared with reference perch, the peaks in cardiac output and heart rate prior to CTmax occurred at statistically similar Pvo2 values (2.3-4.0 kPa), suggesting that cardiac failure occurred at a common critical Pvo2 threshold. Environmental hyperoxia (200% air saturation) increased Pvo2 across temperatures in reference fish, but heart rate still declined at a similar temperature. CTmax of reference fish increased slightly (by 0.9°C) in hyperoxia, but remained significantly lower than in Biotest fish despite an improved cardiac output due to an elevated stroke volume. Thus, while cardiac oxygen supply appears critical to elevate stroke volume at high temperatures, oxygen limitation may not explain the bradycardia and arrhythmia that occur prior to CTmax Acute thermal tolerance and its thermal plasticity can, therefore, only be partially attributed to cardiac failure from myocardial oxygen limitations, and likely involves limiting factors on multiple organizational levels.
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Affiliation(s)
- Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden;
| | - Jeroen Brijs
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Timothy D Clark
- Australian Institute of Marine Science, Townsville, Queensland, Australia; and
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Skara, Sweden
| | - Fredrik Jutfelt
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
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Sandblom E, Ekström A, Brijs J, Sundström LF, Jutfelt F, Clark TD, Adill A, Aho T, Gräns A. Cardiac reflexes in a warming world: Thermal plasticity of barostatic control and autonomic tones in a temperate fish. J Exp Biol 2016; 219:2880-2887. [DOI: 10.1242/jeb.140319] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 07/04/2016] [Indexed: 12/24/2022]
Abstract
Thermal plasticity of cardiorespiratory function allows ectotherms like fish to cope with seasonal temperature changes and is critical for resilience to climate change. Yet, the chronic thermal effects on cardiovascular homeostatic reflexes in fish are little understood although this may have important implications for physiological performance and overall resilience to climate warming. We compared cardiac autonomic control and baroreflex regulation of heart rate in perch (Perca fluviatilis L.) from a reference area in the Baltic Sea at 18–19°C with conspecifics from the ‘Biotest enclosure’, a chronically heated ecosystem receiving warmed effluent water (24–25°C) from a nuclear power plant. Resting heart rates of Biotest fish displayed clear thermal compensation and were 58.3±2.3 beats min−1 compared with 52.4±2.6 beats min−1 in reference fish at their respective environmental temperatures (Q10: 1.2). The thermally-compensated heart rate of Biotest fish was a combined effect of elevated inhibitory cholinergic tone (105% in Biotest fish versus 70% in reference fish) and reduced intrinsic cardiac pacemaker rate. A barostatic response was evident in both groups, as pharmacologically-induced increases and decreases in blood pressure resulted in atropine-sensitive bradycardia and tachycardia, respectively. Yet, the tachycardia in Biotest fish was significantly greater, presumably due to the larger scope for vagal release. Acclimation of Biotest fish to 18°C for 3 weeks abolished differences in intrinsic heart rate and autonomic tones, suggesting considerable short-term thermal plasticity of cardiovascular control in this species. The heightened hypotensive tachycardia in Biotest perch may represent an important mechanism of ectothermic vertebrates that safeguards tissue perfusion pressure when tissue oxygen demand is elevated by environmental warming.
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Affiliation(s)
- E. Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - A. Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - J. Brijs
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - L. F. Sundström
- Department of Animal Ecology/Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden
| | - F. Jutfelt
- Department of Biology, Norwegian University of Science and Technology, Trondheim, Norway
| | - T. D. Clark
- Australian Institute of Marine Science, Townsville, Queensland, Australia (current affiliation: University of Tasmania and CSIRO Agriculture Flagship, Hobart, Tasmania, Australia)
| | - A. Adill
- Institute of Coastal Research, Swedish University of Agricultural Sciences, Öregrund, Sweden
| | - T. Aho
- Institute of Coastal Research, Swedish University of Agricultural Sciences, Öregrund, Sweden
| | - A. Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Skara, Sweden
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Ekström A, Hellgren K, Gräns A, Pichaud N, Sandblom E. Dynamic changes in scope for heart rate and cardiac autonomic control during warm acclimation in rainbow trout. J Exp Biol 2016; 219:1106-9. [DOI: 10.1242/jeb.134312] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 02/04/2016] [Indexed: 11/20/2022]
Abstract
Time course studies are critical to understand regulatory mechanisms and temporal constraints in ectothermic animals acclimating to warmer temperatures. Therefore, we investigated the dynamics of heart rate and its neuro-humoral control in rainbow trout (Onchorhynchus mykiss L.) acclimating to 16°C for 39 days after being acutely warmed from 9°C. Resting heart rate was 39 bpm at 9°C, and increased significantly when acutely warmed to 16°C (Q10: 1.9), but then declined during acclimation (Q10 of 1.2 at day 39); mainly due to increased cholinergic inhibition while the intrinsic heart rate and adrenergic tone were little affected. Maximum heart rate also increased with warming, although a partial modest decrease occurred during the acclimation period. Consequently, heart rate scope exhibited a complex pattern with an initial increase with acute warming, followed by a steep decline and then a subsequent increase, which was primarily explained by cholinergic inhibition of resting heart rate.
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Affiliation(s)
- Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Kim Hellgren
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Skara, Sweden
| | - Nicolas Pichaud
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
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Brijs J, Jutfelt F, Clark TD, Gräns A, Ekström A, Sandblom E. Experimental manipulations of tissue oxygen supply do not affect warming tolerance of European perch. J Exp Biol 2015; 218:2448-54. [DOI: 10.1242/jeb.121889] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2015] [Accepted: 05/21/2015] [Indexed: 01/18/2023]
Abstract
A progressive inability of the cardiorespiratory system to maintain systemic oxygen supply at elevated temperatures has been suggested to reduce aerobic scope and the upper thermal limit of aquatic ectotherms. However, few studies have directly investigated the dependence of thermal limits on oxygen transport capacity. By manipulating oxygen availability (via environmental hyperoxia) and blood oxygen carrying capacity (via experimentally-induced anemia) in European perch (Perca fluviatilis, Linneaus), we investigated the effects of oxygen transport capacity on aerobic scope and the critical thermal maximum (CTmax). Hyperoxia resulted in a two-fold increase in aerobic scope at the control temperature of 23°C, but this did not translate to an elevated CTmax in comparison with control fish (34.6±0.1°C vs. 34.0±0.5°C, respectively). Anemia (∼43% reduction in haemoglobin concentration) did not cause a reduction in aerobic scope nor CTmax (33.8±0.3°C) compared with control fish. Additionally, oxygen consumption rates of anemic perch during thermal ramping increased in a similar exponential manner as in control fish, highlighting that perch have an impressive capacity to compensate for a substantial reduction in blood oxygen carrying capacity. Taken together, these results indicate that oxygen limitation is not a universal mechanism determining the CTmax of fishes.
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Affiliation(s)
- Jeroen Brijs
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Fredrik Jutfelt
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Timothy D. Clark
- University of Tasmania and CSIRO Agriculture Flagship, Hobart, Tasmania, Australia (formerly at the Australian Institute of Marine Science, Townsville, Queensland Australia)
| | - Albin Gräns
- Department of Animal Environment and Health, Swedish University of Agricultural Sciences, Skara, Sweden
| | - Andreas Ekström
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Erik Sandblom
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
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