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Lonthair JK, Wegner NC, Cheng BS, Fangue NA, O'Donnell MJ, Regish AM, Swenson JD, Argueta E, McCormick SD, Letcher BH, Komoroske LM. Smaller body size under warming is not due to gill-oxygen limitation in a cold-water salmonid. J Exp Biol 2024; 227:jeb246477. [PMID: 38380449 DOI: 10.1242/jeb.246477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Accepted: 01/10/2024] [Indexed: 02/22/2024]
Abstract
Declining body size in fishes and other aquatic ectotherms associated with anthropogenic climate warming has significant implications for future fisheries yields, stock assessments and aquatic ecosystem stability. One proposed mechanism seeking to explain such body-size reductions, known as the gill oxygen limitation (GOL) hypothesis, has recently been used to model future impacts of climate warming on fisheries but has not been robustly empirically tested. We used brook trout (Salvelinus fontinalis), a fast-growing, cold-water salmonid species of broad economic, conservation and ecological value, to examine the GOL hypothesis in a long-term experiment quantifying effects of temperature on growth, resting metabolic rate (RMR), maximum metabolic rate (MMR) and gill surface area (GSA). Despite significantly reduced growth and body size at an elevated temperature, allometric slopes of GSA were not significantly different than 1.0 and were above those for RMR and MMR at both temperature treatments (15°C and 20°C), contrary to GOL expectations. We also found that the effect of temperature on RMR was time-dependent, contradicting the prediction that heightened temperatures increase metabolic rates and reinforcing the importance of longer-term exposures (e.g. >6 months) to fully understand the influence of acclimation on temperature-metabolic rate relationships. Our results indicate that although oxygen limitation may be important in some aspects of temperature-body size relationships and constraints on metabolic supply may contribute to reduced growth in some cases, it is unlikely that GOL is a universal mechanism explaining temperature-body size relationships in aquatic ectotherms. We suggest future research focus on alternative mechanisms underlying temperature-body size relationships, and that projections of climate change impacts on fisheries yields using models based on GOL assumptions be interpreted with caution.
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Affiliation(s)
- Joshua K Lonthair
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- National Research Council under contract to Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla, CA 92037-1508, USA
| | - Nicholas C Wegner
- Fisheries Resources Division, Southwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, La Jolla 92037-1508, CA, USA
| | - Brian S Cheng
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Nann A Fangue
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, Davis, CA 95616, USA
| | - Matthew J O'Donnell
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Amy M Regish
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - John D Swenson
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Estefany Argueta
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
| | - Stephen D McCormick
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Benjamin H Letcher
- US Geological Survey, Eastern Ecological Science Center at the S. O. Conte Research Laboratory, Turners Falls, MA 01376-1000, USA
| | - Lisa M Komoroske
- Department of Environmental Conservation, University of Massachusetts Amherst, Amherst, MA 01003-9285, USA
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2
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Farrell AP. Getting to the heart of anatomical diversity and phenotypic plasticity: fish hearts are an optimal organ model in need of greater mechanistic study. J Exp Biol 2023; 226:jeb245582. [PMID: 37578108 DOI: 10.1242/jeb.245582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
Natural selection has produced many vertebrate 'solutions' for the cardiac life-support system, especially among the approximately 30,000 species of fishes. For example, across species, fish have the greatest range for central arterial blood pressure and relative ventricular mass of any vertebrate group. This enormous cardiac diversity is excellent ground material for mechanistic explorations. Added to this species diversity is the emerging field of population-specific diversity, which is revealing that cardiac design and function can be tailored to a fish population's local environmental conditions. Such information is important to conservation biologists and ecologists, as well as physiologists. Furthermore, the cardiac structure and function of an individual adult fish are extremely pliable (through phenotypic plasticity), which is typically beneficial to the heart's function when environmental conditions are variable. Consequently, exploring factors that trigger cardiac remodelling with acclimation to new environments represents a marvellous opportunity for performing mechanistic studies that minimize the genetic differences that accompany cross-species comparisons. What makes the heart an especially good system for the investigation of phenotypic plasticity and species diversity is that its function can be readily evaluated at the organ level using established methodologies, unlike most other organ systems. Although the fish heart has many merits as an organ-level model to provide a mechanistic understanding of phenotypic plasticity and species diversity, bringing this potential to fruition will require productive research collaborations among physiologists, geneticists, developmental biologists and ecologists.
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Chen Y, Pan Z, Bai Y, Xu S. Redox state and metabolic responses to severe heat stress in lenok Brachymystax lenok (Salmonidae). Front Mol Biosci 2023; 10:1156310. [PMID: 37293553 PMCID: PMC10244579 DOI: 10.3389/fmolb.2023.1156310] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 04/24/2023] [Indexed: 06/10/2023] Open
Abstract
In order to provide new insights into the physiological responses of lenok (Brachymystax lenok: Salmonidae) to acute and severe heat stress (25°C, 48 h), dynamic changes in redox state and metabolic responses are studied combined biochemical index and non-targeted metabolome. Nicotinamide adenine dinucleotide (NAD+) consumption causes significant increases in ratio of reduced NADH to NAD+ and ratio of reduced nicotinamide adenine dinucleotide phosphate (NADPH) to NADP+, which induced the redox imbalance in heat stressed lenok. Lowered reduced glutathione/oxidized glutathione (GSH/GSSG) ratios suggested that more oxidized conditions occurred in heat-stressed lenok, leading to membrane lipid oxidation. The first few hours of heat stress promoted the activity of enzymes involved in anaerobic glycolysis (hexokinase, pyruvate kinase, lactic dehydrogenase) and glutamicpyruvic transaminase and glutamic oxaloacetic transaminase, which might lead to consumption of many carbohydrates and amino acid catabolism. These enzyme activities decreased with time in a possible compensatory strategy to manage anabolic and catabolic metabolism, maintaining the redox homeostasis. After 48 h of recovery, NAD+, carbohydrate levels and enzyme activities had returned to control levels, whereas many amino acids were consumed for repair and new synthesis. GSH remained at levels lower than controls, and the more oxidized conditions had not recovered, aggravating oxidative damage. Glutamic acid, glutamine, lysine and arginine may play important roles in survival of heat-stressed lenok.
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Affiliation(s)
- Yan Chen
- National Engineering Research Center for Freshwaters (Beijing), Fisheries Science Institute, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
| | - Zhe Pan
- Ocean College of Hebei Agricultural University, Qinhuangdao, Hebei Province, China
| | - Yucen Bai
- China Rural Technology Development Center, Beijing, China
| | - Shaogang Xu
- National Engineering Research Center for Freshwaters (Beijing), Fisheries Science Institute, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China
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4
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Joyce W. Evolutionary loss of the ß1-adrenergic receptor in salmonids. Gen Comp Endocrinol 2023; 338:114279. [PMID: 37019291 DOI: 10.1016/j.ygcen.2023.114279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/21/2023] [Accepted: 03/30/2023] [Indexed: 04/07/2023]
Abstract
Whole-genome duplications (WGDs) have been at the heart of the diversification of ß-adrenergic receptors (ß-ARs) in vertebrates. Non-teleost jawed vertebrates typically possess three ß-AR genes: adrb1 (ß1-AR), adrb2 (ß2-AR), and adrb3 (ß3-AR), originating from the ancient 2R (two rounds) WGDs. Teleost fishes, owing to the teleost-specific WGD, have five ancestral adrb paralogs (adrb1, adrb2a, adrb2b, adrb3a and adrb3b). Salmonids are particularly intriguing from an evolutionary perspective as they experienced an additional WGD after separating from other teleosts. Moreover, adrenergic regulation in salmonids, especially rainbow trout, has been intensively studied for decades. However, the repertoire of adrb genes in salmonids has not been yet characterized. An exhaustive genome survey of diverse salmonids, spanning five genera, complemented by phylogenetic sequence analysis, revealed each species has seven adrb paralogs: two adrb2a, two adrb2b, two adrb3a and one adrb3b. Surprisingly, salmonids emerge as the first known jawed vertebrate lineage to lack adrb1. adrb1 is nevertheless highly expressed in the hearts of non-salmonid teleosts, indicating that the wealth of data on adrenergic regulation in salmonids should be generalised to other teleost fishes with caution. It is hypothesised that the loss of adrb1 could have been viable because of the evolutionary radiation of adrb2 and adrb3 genes attributable to the salmonid WGD.
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Affiliation(s)
- William Joyce
- Department of Biology - Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark; Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester M13 9PL, United Kingdom.
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Gilbert MJH, Middleton EK, Kanayok K, Harris LN, Moore JS, Farrell AP, Speers-Roesch B. Rapid cardiac thermal acclimation in wild anadromous Arctic char (Salvelinus alpinus). J Exp Biol 2022; 225:276421. [PMID: 36000268 DOI: 10.1242/jeb.244055] [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: 01/27/2022] [Accepted: 08/15/2022] [Indexed: 11/20/2022]
Abstract
Migratory fishes commonly encounter large and rapid thermal variation, which has the potential to disrupt essential physiological functions. Thus, we acclimated wild, migratory Arctic char to 13°C (∼7°C above a summer average) for an ecologically relevant period (3 days) and measured maximum heart rate (ƒHmax) during acute warming to determine their ability to rapidly improve cardiac function at high temperatures. Arctic char exhibited rapid compensatory cardiac plasticity similar to past observations following prolonged warm acclimation: They reduced ƒHmax over intermediate temperatures (-8%), improved their ability to increase ƒHmax during warming (+10%), and increased (+1.3°C) the temperature at the onset of an arrhythmic heartbeat, a sign of cardiac failure. Consequently, this rapid cardiac plasticity may help migrating fishes like Arctic char mitigate short-term thermal challenges. Furthermore, by using mobile Arctic research infrastructure in a remote field location, the present study illustrates the potential for field-based, experimental physiology in such locations.
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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.,Department of Biological Sciences, University of New Brunswick - Saint John, 100 Tucker Park Rd., Saint John, NB, E2L 4L5, Canada
| | - Ella K Middleton
- Department of Biological Sciences, University of New Brunswick - Saint John, 100 Tucker Park Rd., Saint John, NB, E2L 4L5, Canada
| | - Kevin Kanayok
- Ekaluktutiak Hunters & Trappers Organization, Box 1270, Ekaluktutiak, NU, X0B 0C0, Canada
| | - Les N Harris
- Arctic and Aquatic Research Division, Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB, R3T 2N6, 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, 2357 Main Mall, Vancouver, BC, V6T 1Z4, Canada
| | - Ben Speers-Roesch
- Department of Biological Sciences, University of New Brunswick - Saint John, 100 Tucker Park Rd., Saint John, NB, E2L 4L5, Canada
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Adams OA, Zhang Y, Gilbert MH, Lawrence CS, Snow M, Farrell AP. An unusually high upper thermal acclimation potential for rainbow trout. CONSERVATION PHYSIOLOGY 2022; 10:coab101. [PMID: 35492409 PMCID: PMC9040278 DOI: 10.1093/conphys/coab101] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 12/01/2021] [Accepted: 12/11/2021] [Indexed: 06/02/2023]
Abstract
Thermal acclimation, a compensatory physiological response, is central to species survival especially during the current era of global warming. By providing the most comprehensive assessment to date for the cardiorespiratory phenotype of rainbow trout (Oncorhynchus mykiss) at six acclimation temperatures from 15°C to 25°C, we tested the hypothesis that, compared with other strains of rainbow trout, an Australian H-strain of rainbow trout has been selectively inbred to have an unusually high and broad thermal acclimation potential. Using a field setting at the breeding hatchery in Western Australia, thermal performance curves were generated for a warm-adapted H-strain by measuring growth, feed conversion efficiency, specific dynamic action, whole-animal oxygen uptake (ṀO2) during normoxia and hypoxia, the critical maximum temperature and the electrocardiographic response to acute warming. Appreciable growth and aerobic capacity were possible up to 23°C. However, growth fell off drastically at 25°C in concert with increases in the time required to digest a meal, its total oxygen cost and its peak ṀO2. The upper thermal tipping points for appetite and food conversion efficiency corresponded with a decrease in the ability to increase heart rate during warming and an increase in the cost to digest a meal. Also, comparison of upper thermal tipping points provides compelling evidence that limitations to increasing heart rate during acute warming occurred well below the critical thermal maximum (CTmax) and that the faltering ability of the heart to deliver oxygen at different acclimation temperatures is not reliably predicted by CTmax for the H-strain of rainbow trout. We, therefore, reasoned the remarkably high thermal acclimation potential revealed here for the Australian H-strain of rainbow trout reflected the existing genetic variation within the founder Californian population, which was then subjected to selective inbreeding in association with severe heat challenges. This is an encouraging discovery for those with conservation concerns for rainbow trout and other fish species. Indeed, those trying to predict the impact of global warming should more fully consider the possibility that the standing intra-specific genetic variation within a fish species could provide a high thermal acclimation potential, similar to that shown here for rainbow trout.
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Affiliation(s)
- Olivia A Adams
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Yangfan Zhang
- Corresponding author: Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia, Canada and Museum of Comparative Zoology, Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States
| | - Matthew H Gilbert
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, Canada
| | - Craig S Lawrence
- Faculty of Science, School of Agriculture and Environment, The University of Western Australia, Perth, Western Australia, Australia
| | - Michael Snow
- Aquatic Life Industries, Perth, Western Australia, Australia
| | - Anthony P Farrell
- Faculty of Land and Food Systems, The University of British Columbia, Vancouver, British Columbia, Canada
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7
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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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8
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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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9
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Leeuwis RHJ, Zanuzzo FS, Peroni EFC, Gamperl AK. Research on sablefish ( Anoplopoma fimbria) suggests that limited capacity to increase heart function leaves hypoxic fish susceptible to heat waves. Proc Biol Sci 2021; 288:20202340. [PMID: 33715435 PMCID: PMC7944113 DOI: 10.1098/rspb.2020.2340] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 02/11/2021] [Indexed: 01/19/2023] Open
Abstract
Studies of heart function and metabolism have been used to predict the impact of global warming on fish survival and distribution, and their susceptibility to acute and chronic temperature increases. Yet, despite the fact that hypoxia and high temperatures often co-occur, only one study has examined the effects of hypoxia on fish thermal tolerance, and the consequences of hypoxia for fish cardiac responses to acute warming have not been investigated. We report that sablefish (Anoplopoma fimbria) did not increase heart rate or cardiac output when warmed while hypoxic, and that this response was associated with reductions in maximum O2 consumption and thermal tolerance (CTmax) of 66% and approximately 3°C, respectively. Further, acclimation to hypoxia for four to six months did not substantially alter the sablefish's temperature-dependent physiological responses or improve its CTmax. These results provide novel, and compelling, evidence that hypoxia can impair the cardiac and metabolic response to increased temperatures in fish, and suggest that some coastal species may be more vulnerable to climate change-related heat waves than previously thought. Further, they support research showing that cross-tolerance and physiological plasticity in fish following hypoxia acclimation are limited.
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Affiliation(s)
- Robine H. J. Leeuwis
- Department of Ocean Sciences, Memorial University of Newfoundland, St John's, NL, Canada A1C 5S7
| | - Fábio S. Zanuzzo
- Department of Ocean Sciences, Memorial University of Newfoundland, St John's, NL, Canada A1C 5S7
| | - Ellen F. C. Peroni
- Department of Ocean Sciences, Memorial University of Newfoundland, St John's, NL, Canada A1C 5S7
| | - A. Kurt Gamperl
- Department of Ocean Sciences, Memorial University of Newfoundland, St John's, NL, Canada A1C 5S7
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10
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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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11
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Gilbert MJH, Farrell AP. The thermal acclimation potential of maximum heart rate and cardiac heat tolerance in Arctic char (Salvelinus alpinus), a northern cold-water specialist. J Therm Biol 2020; 95:102816. [PMID: 33454044 DOI: 10.1016/j.jtherbio.2020.102816] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Revised: 10/30/2020] [Accepted: 12/12/2020] [Indexed: 10/22/2022]
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.
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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.
| | - 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, 2357 Main Mall, Vancouver, BC, V6T 1Z4, Canada
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12
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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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13
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Sutcliffe RL, Li S, Gilbert MJH, Schulte PM, Miller KM, Farrell AP. A rapid intrinsic heart rate resetting response with thermal acclimation in rainbow trout, Oncorhynchus mykiss. J Exp Biol 2020; 223:jeb215210. [PMID: 32345705 PMCID: PMC7328139 DOI: 10.1242/jeb.215210] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2019] [Accepted: 04/17/2020] [Indexed: 01/01/2023]
Abstract
We examined cardiac pacemaker rate resetting in rainbow trout following a reciprocal temperature transfer. In the original experiment, performed in winter, 4°C-acclimated fish transferred to 12°C reset intrinsic heart rate after just 1 h (from 56.8±1.2 to 50.8±1.5 beats min-1); 12°C-acclimated fish transferred to 4°C reset intrinsic heart rate after 8 h (from 33.4±0.7 to 37.7±1.2 beats min-1). However, in a replicate experiment, performed in the summer using a different brood year, intrinsic heart rate was not reset, even after 10 weeks at a new temperature. Using this serendipitous opportunity, we compared mRNA expression changes of a suite of proteins in sinoatrial node (SAN), atrial and ventricular tissues after both 1 h and longer than 3 weeks for both experimental acclimation groups to identify those changes only associated with pacemaker rate resetting. Of the changes in mRNA expression occurring after more than 3 weeks of warm acclimation and associated with pacemaker rate resetting, we observed downregulation of NKA α1c in the atrium and ventricle, and upregulation of HCN1 in the ventricle. However, in the SAN there were no mRNA expression changes unique to the fish with pacemaker rate resetting after either 1 h or 3 weeks of warm acclimation. Thus, despite identifying changes in mRNA expression of contractile cardiac tissues, there was an absence of changes in mRNA expression directly involved with the initial, rapid pacemaker rate resetting with warm acclimation. Importantly, pacemaker rate resetting with thermal acclimation does not always occur in rainbow trout.
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Affiliation(s)
- Rachel L Sutcliffe
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Shaorong Li
- Pacific Biological Station, Fisheries and Oceans, Nanaimo, BC, Canada, V9T 6N7
| | - Matthew J H Gilbert
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Patricia M Schulte
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Kristi M Miller
- Pacific Biological Station, Fisheries and Oceans, Nanaimo, BC, Canada, V9T 6N7
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
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14
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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: 11] [Impact Index Per Article: 2.8] [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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15
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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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