1
|
Vornanen M, Badr A, Haverinen J. Cardiac arrhythmias in fish induced by natural and anthropogenic changes in environmental conditions. J Exp Biol 2024; 227:jeb247446. [PMID: 39119881 DOI: 10.1242/jeb.247446] [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] [Indexed: 08/10/2024]
Abstract
A regular heartbeat is essential for maintaining the homeostasis of the vertebrate body. However, environmental pollutants, oxygen deficiency and extreme temperatures can impair heart function in fish. In this Review, we provide an integrative view of the molecular origins of cardiac arrhythmias and their functional consequences, from the level of ion channels to cardiac electrical activity in living fish. First, we describe the current knowledge of the cardiac excitation-contraction coupling of fish, as the electrical activity of the heart and intracellular Ca2+ regulation act as a platform for cardiac arrhythmias. Then, we compile findings on cardiac arrhythmias in fish. Although fish can experience several types of cardiac arrhythmia under stressful conditions, the most typical arrhythmia in fish - both under heat stress and in the presence of toxic substances - is atrioventricular block, which is the inability of the action potential to progress from the atrium to the ventricle. Early and delayed afterdepolarizations are less common in fish hearts than in the hearts of endotherms, perhaps owing to the excitation-contraction coupling properties of the fish heart. In fish hearts, Ca2+-induced Ca2+ release from the sarcoplasmic reticulum plays a smaller role than Ca2+ influx through the sarcolemma. Environmental changes and ion channel toxins can induce arrhythmias in fish and weaken their tolerance to environmental stresses. Although different from endotherm hearts in many respects, fish hearts can serve as a translational model for studying human cardiac arrhythmias, especially for human neonates.
Collapse
Affiliation(s)
- Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| | - Ahmed Badr
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
- Department of Zoology, Faculty of Science, Sohag University, 82524 Sohag, Egypt
| | - Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, PO Box 111, 80101 Joensuu, Finland
| |
Collapse
|
2
|
Badr A, Hassinen M, Vornanen M. Spatial uniformity of action potentials indicates base-to-apex depolarization and repolarization of rainbow trout (Oncorhynchus mykiss) ventricle. J Exp Biol 2022; 225:276292. [PMID: 35950359 DOI: 10.1242/jeb.244466] [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: 04/26/2022] [Accepted: 08/02/2022] [Indexed: 11/20/2022]
Abstract
The spatial pattern of electrical activation is crucial for a full understanding of fish heart function. However, it remains unclear whether there is regional variation in action potential (AP) morphologies and underlying ion currents. Because the direction of depolarization and spatial differences in the durations of ventricular APs set limits to potential patterns of ventricular repolarization, we determined AP morphologies, underlying ion currents, and ion channel expression in 4 different regions (spongy myocardium; and apex, base, and middle of the compact myocardium), and correlated them with in vivo electrocardiogram (ECG) in rainbow trout (Oncorhynchus mykiss). ECG recorded from 3 leads indicated that the depolarization and repolarization of AP propagate from base-to-apex, and the main depolarization axis of the ventricle is between +90° and +120°. AP shape was uniform across the whole ventricle, and little regional differences were found in density of repolarizing K+ currents or depolarizing Ca2+ and Na+ currents and the underlying transcripts of ion channels, providing compelling evidence for the suggested excitation pattern. The spatial uniformity of AP durations and base-to-apex propagation of activation with a relatively slow velocity of propagation indicates no special ventricular conduction pathway in the trout ventricle like the His-Purkinje system of mammalian hearts. The sequence of repolarization is solely determined by activation time without being affected by regional differences in AP duration.
Collapse
Affiliation(s)
- Ahmed Badr
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland.,Sohag University, Faculty of Science, Department of Zoology, 82524 Sohag, Egypt
| | - Minna Hassinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 111, 80101 Joensuu, Finland
| |
Collapse
|
3
|
Filice M, Cerra MC, Imbrogno S. The goldfish Carassius auratus: an emerging animal model for comparative cardiac research. J Comp Physiol B 2021; 192:27-48. [PMID: 34455483 PMCID: PMC8816371 DOI: 10.1007/s00360-021-01402-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2021] [Revised: 08/09/2021] [Accepted: 08/18/2021] [Indexed: 12/12/2022]
Abstract
The use of unconventional model organisms is significantly increasing in different fields of research, widely contributing to advance life sciences understanding. Among fishes, the cyprinid Carassius auratus (goldfish) is largely used for studies on comparative and evolutionary endocrinology, neurobiology, adaptive and conservation physiology, as well as for translational research aimed to explore mechanisms that may be useful in an applicative biomedical context. More recently, the research possibilities offered by the goldfish are further expanded to cardiac studies. A growing literature is available to illustrate the complex networks involved in the modulation of the goldfish cardiac performance, also in relation to the influence of environmental signals. However, an overview on the existing current knowledge is not yet available. By discussing the mechanisms that in C. auratus finely regulate the cardiac function under basal conditions and under environmental challenges, this review highlights the remarkable flexibility of the goldfish heart in relation not only to the basic morpho-functional design and complex neuro-humoral traits, but also to its extraordinary biochemical-metabolic plasticity and its adaptive potential. The purpose of this review is also to emphasize the power of the heart of C. auratus as an experimental tool useful to investigate mechanisms that could be difficult to explore using more conventional animal models and complex cardiac designs.
Collapse
Affiliation(s)
- Mariacristina Filice
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036, Arcavacata di Rende, CS, Italy.
| | - Maria Carmela Cerra
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036, Arcavacata di Rende, CS, Italy
| | - Sandra Imbrogno
- Department of Biology, Ecology and Earth Sciences, University of Calabria, 87036, Arcavacata di Rende, CS, Italy
| |
Collapse
|
4
|
Kibler NA, Nuzhny VP, Kharin SN, Shmakov DN. Effect of atrial artificial electrical stimulation on depolarization and repolarization and hemodynamics of the heart ventricle in rainbow trout Oncorhynchus mykiss. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1329-1339. [PMID: 34241764 DOI: 10.1007/s10695-021-00983-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 06/25/2021] [Indexed: 06/13/2023]
Abstract
The spatial-temporal organization of the activation, repolarization and hemodynamics of the heart ventricle in rainbow trout, Oncorhynchus mykiss, adapted to a temperature of 5-7 °C, were studied from the normal sinus rhythm (21.6 ± 4.9 bpm) to the highest possible heart rhythm (HR) (60 bpm), during which deterioration of the contractile activity of the myocardium occurred. Regardless of the HR, the main pattern of excitation of the heart ventricle was the movement of the depolarization wave from the dorsal areas of the base in the base-apical and ventral directions with the capture of the entire thickness of the walls, with a slight difference in the time of activation of the subendocardium compared to the subepicardium. The increase in HR above the sinus rhythm caused significant shortening of local repolarization durations in all areas and layers (endocardial, intramural and subepicardial) of the heart ventricle. Changes in local durations of repolarization led to an increase in the heterogeneity of repolarization of the ventricular myocardium; as a result, a deterioration of its contractility was observed. In relation to the sinus rhythm, the maximal systolic pressure in the heart ventricle decreased, the diastolic and end-diastolic pressure increased, and the maximum rates of pressure rise and fall decreased. In rainbow trout adapted to a temperature of 5-7 °C at sinus rhythm, the pumping function of the heart was probably within the upper limit of the physiological norm, and a further increase in the heart rate led to a decline in myocardial contractility.
Collapse
Affiliation(s)
- Natalya A Kibler
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia.
| | - Vladimir P Nuzhny
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
| | - Sergey N Kharin
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
| | - Dmitry N Shmakov
- Institute of Physiology, Federal Research Centre Komi Science Centre, Ural Branch, Russian Academy of Sciences, 50, Pervomayskaya str., Syktyvkar, 167982, Komi Republic, Russia
| |
Collapse
|
5
|
O'Brien KM, Joyce W, Crockett EL, Axelsson M, Egginton S, Farrell AP. Resilience of cardiac performance in Antarctic notothenioid fishes in a warming climate. J Exp Biol 2021; 224:268390. [PMID: 34042975 DOI: 10.1242/jeb.220129] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Warming in the region of the Western Antarctic Peninsula is occurring at an unprecedented rate, which may threaten the survival of Antarctic notothenioid fishes. Herein, we review studies characterizing thermal tolerance and cardiac performance in notothenioids - a group that includes both red-blooded species and the white-blooded, haemoglobinless icefishes - as well as the relevant biochemistry associated with cardiac failure during an acute temperature ramp. Because icefishes do not feed in captivity, making long-term acclimation studies unfeasible, we focus only on the responses of red-blooded notothenioids to warm acclimation. With acute warming, hearts of the white-blooded icefish Chaenocephalus aceratus display persistent arrhythmia at a lower temperature (8°C) compared with those of the red-blooded Notothenia coriiceps (14°C). When compared with the icefish, the enhanced cardiac performance of N. coriiceps during warming is associated with greater aerobic capacity, higher ATP levels, less oxidative damage and enhanced membrane integrity. Cardiac performance can be improved in N. coriiceps with warm acclimation to 5°C for 6-9 weeks, accompanied by an increase in the temperature at which cardiac failure occurs. Also, both cardiac mitochondrial and microsomal membranes are remodelled in response to warm acclimation in N. coriiceps, displaying homeoviscous adaptation. Overall, cardiac performance in N. coriiceps is malleable and resilient to warming, yet thermal tolerance and plasticity vary among different species of notothenioid fishes; disruptions to the Antarctic ecosystem driven by climate warming and other anthropogenic activities endanger the survival of notothenioids, warranting greater protection afforded by an expansion of marine protected areas.
Collapse
Affiliation(s)
- Kristin M O'Brien
- Institute of Arctic Biology , University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA
| | - William Joyce
- Department of Biology - Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | | | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, 40530 Gothenburg, Sweden
| | - Stuart Egginton
- School of Biomedical Sciences , University of Leeds, Leeds LS2 9JT, UK
| | - Anthony P Farrell
- Department of Zoology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| |
Collapse
|
6
|
Haverinen J, Dzhumaniiazova I, Abramochkin DV, Hassinen M, Vornanen M. Effects of Na+ channel isoforms and cellular environment on temperature tolerance of cardiac Na+ current in zebrafish (Danio rerio) and rainbow trout (Oncorhynchus mykiss). J Exp Biol 2021; 224:237812. [PMID: 33914031 DOI: 10.1242/jeb.241067] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 03/01/2021] [Indexed: 11/20/2022]
Abstract
Heat tolerance of heart rate in fish is suggested to be limited by impaired electrical excitation of the ventricle due to the antagonistic effects of high temperature on Na+ (INa) and K+ (IK1) ion currents (INa is depressed at high temperatures while IK1 is resistant to them). To examine the role of Na+ channel proteins in heat tolerance of INa, we compared temperature dependencies of zebrafish (Danio rerio, warm-dwelling subtropical species) and rainbow trout (Oncorhynchus mykiss, cold-active temperate species) ventricular INa, and INa generated by the cloned zebrafish and rainbow trout NaV1.4 and NaV1.5 Na+ channels in human embryonic kidney (HEK) cells. Whole-cell patch-clamp recordings showed that zebrafish ventricular INa has better heat tolerance and slower inactivation kinetics than rainbow trout ventricular INa. In contrast, heat tolerance and inactivation kinetics of zebrafish and rainbow trout NaV1.4 channels are similar when expressed in the identical cellular environment of HEK cells. The same applies to NaV1.5 channels. These findings indicate that thermal adaptation of ventricular INa is largely achieved by differential expression of Na+ channel alpha subunits: zebrafish that tolerate higher temperatures mainly express the slower NaV1.5 isoform, while rainbow trout that prefer cold waters mainly express the faster NaV1.4 isoform. Differences in elasticity (stiffness) of the lipid bilayer and/or accessory protein subunits of the channel assembly may also be involved in thermal adaptation of INa. The results are consistent with the hypothesis that slow Na+ channel kinetics are associated with increased heat tolerance of cardiac excitation.
Collapse
Affiliation(s)
- Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, 80101 Joensuu, Finland
| | - Irina Dzhumaniiazova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory 1-12, 119234 Moscow, Russia
| | - Denis V Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory 1-12, 119234 Moscow, Russia.,Laboratory of Cardiac Electrophysiology, National Medical Research Center for Cardiology, 3rd Cherepkovskaya 15a, 121552 Moscow, Russia.,Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova Str. 1, 117997 Moscow, Russia
| | - Minna Hassinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, 80101 Joensuu, Finland
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, 80101 Joensuu, Finland
| |
Collapse
|
7
|
Hassinen M, Dzhumaniiazova I, Abramochkin DV, Vornanen M. Ionic basis of atrioventricular conduction: ion channel expression and sarcolemmal ion currents of the atrioventricular canal of the rainbow trout (Oncorhynchus mykiss) heart. J Comp Physiol B 2021; 191:327-346. [PMID: 33575867 PMCID: PMC7895799 DOI: 10.1007/s00360-021-01344-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2020] [Revised: 12/15/2020] [Accepted: 01/18/2021] [Indexed: 12/17/2022]
Abstract
Atrioventricular (AV) nodal tissue synchronizes activities of atria and ventricles of the vertebrate heart and is also a potential site of cardiac arrhythmia, e.g., under acute heat stress. Since ion channel composition and ion currents of the fish AV canal have not been previously studied, we measured major cation currents and transcript expression of ion channels in rainbow trout (Oncorhynchus mykiss) AV tissue. Both ion current densities and expression of ion channel transcripts indicate that the fish AV canal has a characteristic electrophysiological phenotype that differs from those of sinoatrial tissue, atrium and ventricle. Two types of cardiomyocytes were distinguished electrophysiologically in trout AV nodal tissue: the one (transitional cell) is functionally intermediate between working atrial/ventricular myocytes and the other (AV nodal cell) has a less negative resting membrane potential than atrial and ventricular myocytes and is a more similar to the sinoatrial nodal cells in ion channel composition. The AV nodal cells are characterized by a small or non-existent inward rectifier potassium current (IK1), low density of fast sodium current (INa) and relatively high expression of T-type calcium channels (CACNA3.1). Pacemaker channel (HCN4 and HCN2) transcripts were expressed in the AV nodal tissue but If current was not found in enzymatically isolated nodal myocytes. The electrophysiological properties of the rainbow trout nodal cells are appropriate for a slow rate of action potential conduction (small INa) and a moderate propensity for pacemaking activity (absence of IK1).
Collapse
Affiliation(s)
- Minna Hassinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland
| | - Irina Dzhumaniiazova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia
| | - Denis V Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia.,Laboratory of Cardiac Electrophysiology, National Medical Research Center for Cardiology, Moscow, Russia.,Department of Physiology, Pirogov Russian National Research Medical University, Moscow, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland.
| |
Collapse
|
8
|
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.
Collapse
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
| |
Collapse
|
9
|
Mottola G, Kristensen T, Anttila K. Compromised thermal tolerance of cardiovascular capacity in upstream migrating Arctic char and brown trout-are hot summers threatening migrating salmonids? CONSERVATION PHYSIOLOGY 2020; 8:coaa101. [PMID: 34868596 PMCID: PMC7720086 DOI: 10.1093/conphys/coaa101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 09/14/2020] [Accepted: 10/08/2020] [Indexed: 06/13/2023]
Abstract
Heat waves are threatening fish around the world, leading sometimes to mass mortality events. One crucial function of fish failing in high temperatures is oxygen delivery capacity, i.e. cardiovascular function. For anadromous salmonids, increased temperature could be especially detrimental during upstream migration since they need efficiently working oxygen delivery system in order to cross the river rapids to reach upstream areas. The migration also occurs during summer and early autumn exposing salmonids to peak water temperatures, and in shallow rivers there is little availability for thermal refuges as compared to thermally stratified coastal and lake habitats. In order to shed light on the mechanisms underpinning the capacity of migrating fish to face high environmental temperatures, we applied a physiological and molecular approach measuring cardiovascular capacities of migrating and resident Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta) in Northern Norway. The maximum cardiovascular capacity of migrating fish was significantly lower compared to the resident conspecifics. The onset of cardiac impairment started only 2°C higher than river temperature, meaning that even a small increase in water temperature may already compromise cardiac function. The migrating fish were also under significant cellular stress, expressing increased level of cardiac heat shock proteins. We consider these findings highly valuable when addressing climate change effect on migrating fish and encourage taking action in riverine habitat conservation policies. The significant differences in upper thermal tolerance of resident and migrating fish could also lead changes in population dynamics, which should be taken into account in future conservation plans.
Collapse
Affiliation(s)
- Giovanna Mottola
- Department of Biology, University of Turku, Vesilinnantie 5, 20500, Turku, Finland
| | - Torstein Kristensen
- Faculty of Bioscience and Aquaculture, Nord University, Universitetsalléen 11, 8026, Bødo, Norway
| | - Katja Anttila
- Department of Biology, University of Turku, Vesilinnantie 5, 20500, Turku, Finland
| |
Collapse
|
10
|
Koene JP, Elmer KR, Adams CE. Intraspecific variation and structuring of phenotype in a lake-dwelling species are driven by lake size and elevation. Biol J Linn Soc Lond 2020. [DOI: 10.1093/biolinnean/blaa137] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
Abstract
The fragmented, heterogeneous and relatively depauperate ecosystems of recently glaciated lakes present contrasting ecological opportunities for resident fish. Across a species, local adaptation may induce diverse and distinct phenotypic responses to various selection pressures. We tested for intraspecific phenotypic structuring by population in a common native lake-dwelling fish species across a medium-scale geographic region with considerable variation in lake types. We investigated potential lake-characteristic drivers of trophic morphology. Using geometric morphometric techniques, we quantified the head shapes of 759 adult brown trout (Salmo trutta L.) from 28 lakes and reservoirs across Scotland. Multivariate statistical analyses showed that almost all populations differed from one another. Trout from larger and deeper lakes had deeper, but shorter heads, and smaller eyes. Higher elevation lakes were associated with fish with shorter heads and jaws. Within-population shape variation also differed by population, and was positively correlated with lake surface area and depth. Trout within reservoirs differed subtly from those in natural lakes, having larger eyes, shorter jaws and greater variability. This study documents an extraordinary morphological variation between and within populations of brown trout, and demonstrates the role of the extrinsic environment in driving phenotypic structuring over a medium-scale and varied geographic area.
Collapse
Affiliation(s)
- J Peter Koene
- Scottish Centre for Ecology and the Natural Environment (SCENE), University of Glasgow, Rowardennan, Glasgow, UK
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Science, University of Glasgow, Glasgow, UK
| | - Kathryn R Elmer
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Science, University of Glasgow, Glasgow, UK
| | - Colin E Adams
- Scottish Centre for Ecology and the Natural Environment (SCENE), University of Glasgow, Rowardennan, Glasgow, UK
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Science, University of Glasgow, Glasgow, UK
| |
Collapse
|
11
|
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.
Collapse
Affiliation(s)
- Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland.
| |
Collapse
|
12
|
Gomez Isaza DF, Cramp RL, Franklin CE. Thermal acclimation offsets the negative effects of nitrate on aerobic scope and performance. J Exp Biol 2020; 223:jeb224444. [PMID: 32647016 DOI: 10.1242/jeb.224444] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2020] [Accepted: 07/06/2020] [Indexed: 08/26/2023]
Abstract
Rising temperatures are set to imperil freshwater fishes as climate change ensues unless compensatory strategies are employed. However, the presence of additional stressors, such as elevated nitrate concentrations, may affect the efficacy of compensatory responses. Here, juvenile silver perch (Bidyanus bidyanus) were exposed to current-day summer temperatures (28°C) or a future climate-warming scenario (32°C) and simultaneously exposed to one of three ecologically relevant nitrate concentrations (0, 50 or 100 mg l-1). We measured indicators of fish performance (growth, swimming), aerobic scope (AS) and upper thermal tolerance (CTmax) to test the hypothesis that nitrate exposure would increase susceptibility to elevated temperatures and limit thermal compensatory responses. After 8 weeks of acclimation, the thermal sensitivity and plasticity of AS and swimming performance were tested at three test temperatures (28, 32, 36°C). The AS of 28°C-acclimated fish declined with increasing temperature, and the effect was more pronounced in nitrate-exposed individuals. In these fish, declines in AS corresponded with poorer swimming performance and a 0.8°C decrease in CTmax compared with unexposed fish. In contrast, acclimation to 32°C masked the effects of nitrate; fish acclimated to 32°C displayed a thermally insensitive phenotype whereby locomotor performance remained unchanged, AS was maintained and CTmax was increased by ∼1°C irrespective of nitrate treatment compared with fish acclimated to 28°C. However, growth was markedly reduced in 32°C-acclimated compared with 28°C-acclimated fish. Our results indicate that nitrate exposure increases the susceptibility of fish to acute high temperatures, but thermal compensation can override some of these potentially detrimental effects.
Collapse
Affiliation(s)
- Daniel F Gomez Isaza
- School of Biological Science, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Rebecca L Cramp
- School of Biological Science, The University of Queensland, Brisbane, QLD 4072, Australia
| | - Craig E Franklin
- School of Biological Science, The University of Queensland, Brisbane, QLD 4072, Australia
| |
Collapse
|
13
|
Vornanen M. Feeling the heat: source–sink mismatch as a mechanism underlying the failure of thermal tolerance. J Exp Biol 2020; 223:223/16/jeb225680. [DOI: 10.1242/jeb.225680] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
ABSTRACT
A mechanistic explanation for the tolerance limits of animals at high temperatures is still missing, but one potential target for thermal failure is the electrical signaling off cells and tissues. With this in mind, here I review the effects of high temperature on the electrical excitability of heart, muscle and nerves, and refine a hypothesis regarding high temperature-induced failure of electrical excitation and signal transfer [the temperature-dependent deterioration of electrical excitability (TDEE) hypothesis]. A central tenet of the hypothesis is temperature-dependent mismatch between the depolarizing ion current (i.e. source) of the signaling cell and the repolarizing ion current (i.e. sink) of the receiving cell, which prevents the generation of action potentials (APs) in the latter. A source–sink mismatch can develop in heart, muscles and nerves at high temperatures owing to opposite effects of temperature on source and sink currents. AP propagation is more likely to fail at the sites of structural discontinuities, including electrically coupled cells, synapses and branching points of nerves and muscle, which impose an increased demand of inward current. At these sites, temperature-induced source–sink mismatch can reduce AP frequency, resulting in low-pass filtering or a complete block of signal transmission. In principle, this hypothesis can explain a number of heat-induced effects, including reduced heart rate, reduced synaptic transmission between neurons and reduced impulse transfer from neurons to muscles. The hypothesis is equally valid for ectothermic and endothermic animals, and for both aquatic and terrestrial species. Importantly, the hypothesis is strictly mechanistic and lends itself to experimental falsification.
Collapse
Affiliation(s)
- Matti Vornanen
- Department of Environmental and Biological Sciences , University of Eastern Finland, 80101 Joensuu, Finland
| |
Collapse
|
14
|
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.
Collapse
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
| |
Collapse
|
15
|
Filatova TS, Abramochkin DV, Shiels HA. Thermal acclimation and seasonal acclimatization: a comparative study of cardiac response to prolonged temperature change in shorthorn sculpin. ACTA ACUST UNITED AC 2019; 222:jeb.202242. [PMID: 31315933 DOI: 10.1242/jeb.202242] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 07/15/2019] [Indexed: 12/30/2022]
Abstract
Seasonal thermal remodelling (acclimatization) and laboratory thermal remodelling (acclimation) can induce different physiological changes in ectothermic animals. As global temperatures are changing at an increasing rate, there is urgency to understand the compensatory abilities of key organs such as the heart to adjust under natural conditions. Thus, the aim of the present study was to directly compare the acclimatization and acclimatory response within a single eurythermal fish species, the European shorthorn sculpin (Myoxocephalus scorpio). We used current- and voltage-clamp to measure ionic current densities in both isolated atrial and ventricular myocytes from three groups of fish: (1) summer-caught fish kept at 12°C ('summer-acclimated'); (2) summer-caught fish kept at 3°C ('cold acclimated'); and (3) fish caught in March ('winter-acclimatized'). At a common test temperature of 7.5°C, action potential (AP) was shortened by both winter acclimatization and cold acclimation compared with summer acclimation; however, winter acclimatization caused a greater shortening than did cold acclimation. Shortening of AP was achieved mostly by a significant increase in repolarizing current density (I Kr and I K1) following winter acclimatization, with cold acclimation having only minor effects. Compared with summer acclimation, the depolarizing L-type calcium current (I Ca) was larger following winter acclimatization, but again, there was no effect of cold acclimation on I Ca Interestingly, the other depolarizing current, I Na, was downregulated at low temperatures. Our further analysis shows that ionic current remodelling is primarily due to changes in ion channel density rather than current kinetics. In summary, acclimatization profoundly modified the electrical activity of the sculpin heart while acclimation to the same temperature for >1.5 months produced very limited remodelling effects.
Collapse
Affiliation(s)
- Tatiana S Filatova
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow, Russia 119234 .,Department of Physiology, Russian National Research Medical University, Ostrovityanova str., 1, Moscow, Russia 117997
| | - Denis V Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye gory, 1, 12, Moscow, Russia 119234.,Department of Physiology, Russian National Research Medical University, Ostrovityanova str., 1, Moscow, Russia 117997.,Ural Federal University, Mira 19, Ekaterinburg, Russia 620002
| | - Holly A Shiels
- Faculty of Life Sciences, Core Technology Facility, 46 Grafton Street, University of Manchester, Manchester M13 9NT, UK
| |
Collapse
|
16
|
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: 15] [Impact Index Per Article: 3.0] [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.
Collapse
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
| |
Collapse
|
17
|
Affiliation(s)
- Timothy D Clark
- University of Tasmania and CSIRO Agriculture and Food, Hobart, Tasmania, Australia 7000
| | - Felix C Mark
- Integrative Ecophysiology, Alfred Wegener Institute Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany
| |
Collapse
|
18
|
Kärcher O, Hering D, Frank K, Markovic D. Freshwater species distributions along thermal gradients. Ecol Evol 2019; 9:111-124. [PMID: 30680100 PMCID: PMC6342105 DOI: 10.1002/ece3.4659] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Accepted: 10/02/2018] [Indexed: 02/04/2023] Open
Abstract
The distribution of a species along a thermal gradient is commonly approximated by a unimodal response curve, with a characteristic single optimum near the temperature where a species is most likely to be found, and a decreasing probability of occurrence away from the optimum. We aimed at identifying thermal response curves (TRCs) of European freshwater species and evaluating the potential impact of climate warming across species, taxonomic groups, and latitude. We first applied generalized additive models using catchment-scale global data on distribution ranges of 577 freshwater species native to Europe and four different temperature variables (the current annual mean air/water temperature and the maximum air/water temperature of the warmest month) to describe species TRCs. We then classified TRCs into one of eight curve types and identified spatial patterns in thermal responses. Finally, we integrated empirical TRCs and the projected geographic distribution of climate warming to evaluate the effect of rising temperatures on species' distributions. For the different temperature variables, 390-463 of 577 species (67.6%-80.2%) were characterized by a unimodal TRC. The number of species with a unimodal TRC decreased from central toward northern and southern Europe. Warming tolerance (WT = maximum temperature of occurrence-preferred temperature) was higher at higher latitudes. Preferred temperature of many species is already exceeded. Rising temperatures will affect most Mediterranean species. We demonstrated that freshwater species' occurrence probabilities are most frequently unimodal. The impact of the global climate warming on species distributions is species and latitude dependent. Among the studied taxonomic groups, rising temperatures will be most detrimental to fish. Our findings support the efforts of catchment-based freshwater management and conservation in the face of global warming.
Collapse
Affiliation(s)
- Oskar Kärcher
- Faculty of Business Management and Social SciencesOsnabrück University of Applied SciencesOsnabrückGermany
| | - Daniel Hering
- Faculty of Biology, Aquatic EcologyUniversity of Duisburg‐EssenEssenGermany
| | - Karin Frank
- UFZ – Helmholtz Centre for Environmental Research LtdDepartment for Ecological ModellingLeipzigGermany
- Institute of Environmental Systems ResearchUniversity of OsnabrückOsnabrückGermany
- iDiv – German Centre for Integrative Biodiversity Research Halle‐Jena‐LeipzigLeipzigGermany
| | - Danijela Markovic
- Faculty of Business Management and Social SciencesOsnabrück University of Applied SciencesOsnabrückGermany
| |
Collapse
|
19
|
Abramochkin DV, Haverinen J, Mitenkov YA, Vornanen M. Temperature- and external K+-dependence of electrical excitation in ventricular myocytes of cod-like fishes. J Exp Biol 2019; 222:jeb.193607. [DOI: 10.1242/jeb.193607] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2018] [Accepted: 01/16/2019] [Indexed: 01/08/2023]
Abstract
Electrical excitability (EE) is vital for cardiac function and strongly modulated by temperature and external K+ concentration ([K+]o) as formulated in the hypothesis of temperature-dependent deterioration of electrical excitability (TDEE). Since little is known about EE of arctic stenothermic fishes, we tested the TDEE hypothesis on ventricular myocytes of polar cod (Boreogadus saida) and navaga cod (Eleginus navaga) of the Arctic Ocean and those of temperate freshwater burbot (Lota lota). Ventricular action potentials (APs) were elicited in current-clamp experiments at 3, 9 and 15°C, and AP characteristics and the current needed to elicit AP were examined. At 3°C, ventricular APs of polar and navaga cod were similar but differed from that of burbot in having lower rate of AP upstroke and higher rate of repolarization. EE of ventricular myocytes - defined as the ease with which all-or-none APs are triggered - was little affected by acute temperature changes between 3 and 15°C in any species. However, AP duration (APD50) was drastically reduced at higher temperatures. Elevation of [K+]o from 3 to 5.4 and further to 8 mM at 3, 9 and 15°C strongly affected EE and AP characteristics in polar and navaga cod, but less in burbot. In all species, ventricular excitation was resistant to acute temperature elevations, while small increases in [K+]o severely compromised EE, in particular in the marine stenotherms. This suggests that EE of the heart in these Gadiformes species is well equipped against acute warming, but less so against the simultaneous temperature and exercise stresses.
Collapse
Affiliation(s)
- Denis V. Abramochkin
- Department of human and animal physiology, Lomonosov Moscow State University, Leninskiye Gory, 1, 12, Moscow, Russia
- Department of Physiology, Pirogov Russian National Research Medical University, Moscow, Russia
- Laboratory of Cardiac Physiology, Institute of Physiology, Komi Science Center, Ural Branch, Russian Academy of Sciences, Syktyvkar, Russia
| | - Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Yuri A. Mitenkov
- VNIRO Russian Federal Research Institute of Fisheries and Oceanography, Moscow, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| |
Collapse
|
20
|
Joyce W, Egginton S, Farrell AP, Crockett EL, O'Brien KM, Axelsson M. Exploring nature's natural knockouts: in vivo cardiorespiratory performance of Antarctic fishes during acute warming. ACTA ACUST UNITED AC 2018; 221:jeb.183160. [PMID: 29967219 DOI: 10.1242/jeb.183160] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 06/25/2018] [Indexed: 01/09/2023]
Abstract
We tested the hypothesis that blackfin icefish (Chaenocephalus aceratus), one of the six species in the family Channichthyidae (the icefishes) that do not express haemoglobin and myoglobin, lack regulatory cardiovascular flexibility during acute warming and activity. The experimental protocols were designed to optimize the surgical protocol and minimize stress. First, minimally invasive heart rate (fH) measurements were made during a thermal ramp until cardiac failure in C. aceratus and compared with those from the closely related red-blooded black rockcod (Notothenia coriiceps). Then, integrative cardiovascular adjustments were more extensively studied using flow probes and intravascular catheters in C. aceratus during acute warming (from 0 to 8°C) at rest and after imposed activity. Chaenocephalus aceratus had a lower routine fH than N. coriiceps (9 beats min-1 versus 14 beats min-1) and a lower peak fH during acute warming (38 beats min-1 versus 55 beats min-1) with a similar cardiac breakpoint temperature (13 and 14°C, respectively). Routine cardiac output (Q̇) for C. aceratus at ∼0°C was much lower (26.6 ml min-1 kg-1) than previously reported, probably because fish in the present study had a low fH (12 beats min-1) indicative of a high routine vagal tone and low stress. Chaenocephalus aceratus increased oxygen consumption during acute warming and with activity. Correspondingly, Q̇ increased considerably (maximally 86.3 ml min-1 kg-1), as did vascular conductance (5-fold). Thus, unlike earlier suggestions, these data provide convincing evidence that icefish can mount a well-developed cardiovascular regulation of heart rate, cardiac output and vascular conductance, and this regulatory capacity provides flexibility during acute warming.
Collapse
Affiliation(s)
- William Joyce
- Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark
| | - Stuart Egginton
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, UK
| | - Anthony P Farrell
- Department of Zoology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC 45, Canada
| | | | - Kristin M O'Brien
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK 99775-7000, USA
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, 4139 90 Gothenburg, Sweden
| |
Collapse
|
21
|
Badr A, Abu-Amra ES, El-Sayed MF, Vornanen M. Electrical excitability of roach (Rutilus rutilus) ventricular myocytes: effects of extracellular K+, temperature, and pacing frequency. Am J Physiol Regul Integr Comp Physiol 2018; 315:R303-R311. [DOI: 10.1152/ajpregu.00436.2017] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Exercise, capture, and handling stress in fish can elevate extracellular K+ concentration ([K+]o) with potential impact on heart function in a temperature- and frequency-dependent manner. To this end, the effects of [K+]o on the excitability of ventricular myocytes of winter-acclimatized roach ( Rutilus rutilus) (4 ± 0.5°C) were examined at different test temperatures and varying pacing rates. Frequencies corresponding to in vivo heart rates at 4°C (0.37 Hz), 14°C (1.16 Hz), and 24°C (1.96 Hz) had no significant effect on the excitability of ventricular myocytes. Acute increase of temperature from 4 to 14°C did not affect excitability, but a further rise to 24 markedly decreased excitability: stimulus current and critical depolarization needed to elicit an action potential (AP) were ~25 and 14% higher, respectively, at 24°C than at 4°C and 14°C ( P < 0.05). This depression could be due to temperature-related mismatch between inward Na+ and outward K+ currents. In contrast, an increase of [K+]o from 3 to 5.4 or 8 mM at 24°C reduced the stimulus current needed to trigger AP. However, other aspects of excitability were strongly depressed by high [K+]o: maximum rate of AP upstroke and AP duration were drastically (89 and 50%, respectively) reduced at 8 mM [K+]o in comparison with 3 mM ( P < 0.05). As an extreme case, some myocytes completely failed to elicit all-or-none AP at 8 mM [K+]o at 24°C. Also, amplitude and overshoot of AP were reduced by elevation of [K+]o ( P < 0.05). Although high [K+]o antagonizes the negative effects of high temperature on excitation threshold, the precipitous depression of the rate of AP upstroke and complete loss of excitability in some myocytes suggest that the combination of high temperature and high [K+]o will severely impair ventricular excitability in roach.
Collapse
Affiliation(s)
- Ahmed Badr
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
- Department of Zoology, Faculty of Science, Sohag University, Sohag, Egypt
| | - El-Sabry Abu-Amra
- Department of Zoology, Faculty of Science, Sohag University, Sohag, Egypt
| | | | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| |
Collapse
|
22
|
Joyce W, Axelsson M, Egginton S, Farrell AP, Crockett EL, O’Brien KM. The effects of thermal acclimation on cardio-respiratory performance in an Antarctic fish ( Notothenia coriiceps). CONSERVATION PHYSIOLOGY 2018; 6:coy069. [PMID: 30568798 PMCID: PMC6291619 DOI: 10.1093/conphys/coy069] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 11/13/2018] [Accepted: 11/26/2018] [Indexed: 05/21/2023]
Abstract
The Southern Ocean has experienced stable, cold temperatures for over 10 million years, yet particular regions are currently undergoing rapid warming. To investigate the impacts of warming on cardiovascular oxygen transport, we compared the cardio-respiratory performance in an Antarctic notothenioid (Notothenia coriiceps) that was maintained at 0 or 5°C for 6.0-9.5 weeks. When compared at the fish's respective acclimation temperature, the oxygen consumption rate and cardiac output were significantly higher in 5°C-acclimated than 0°C-acclimated fish. The 2.7-fold elevation in cardiac output in 5°C-acclimated fish (17.4 vs. 6.5 ml min-1 kg-1) was predominantly due to a doubling of stroke volume, likely in response to increased cardiac preload, as measured by higher central venous pressure (0.15 vs. 0.08 kPa); tachycardia was minor (29.5 vs. 25.2 beats min-1). When fish were acutely warmed, oxygen consumption rate increased by similar amounts in 0°C- and 5°C-acclimated fish at equivalent test temperatures. In both acclimation groups, the increases in oxygen consumption rate during acute heating were supported by increased cardiac output achieved by elevating heart rate, while stroke volume changed relatively little. Cardiac output was similar between both acclimation groups until 12°C when cardiac output became significantly higher in 5°C-acclimated fish, driven largely by their higher stroke volume. Although cardiac arrhythmias developed at a similar temperature (~14.5°C) in both acclimation groups, the hearts of 5°C-acclimated fish continued to pump until significantly higher temperatures (CTmax for cardiac function 17.7 vs. 15.0°C for 0°C-acclimated fish). These results demonstrate that N. coriiceps is capable of increasing routine cardiac output during both acute and chronic warming, although the mechanisms are different (heart rate-dependent versus primarily stroke volume-dependent regulation, respectively). Cardiac performance was enhanced at higher temperatures following 5°C acclimation, suggesting cardiovascular function may not constrain the capacity of N. coriiceps to withstand a warming climate.
Collapse
Affiliation(s)
- William Joyce
- Department of Zoophysiology, Aarhus University, Aarhus C, Denmark
- Corresponding author: Department of Zoophysiology, Aarhus University, 8000 Aarhus C, Denmark.
| | - Michael Axelsson
- Department of Biological and Environmental Sciences, University of Gothenburg, Gothenburg, Sweden
| | - Stuart Egginton
- School of Biomedical Sciences, University of Leeds, Leeds, UK
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | | | - Kristin M O’Brien
- Institute of Arctic Biology, University of Alaska Fairbanks, Fairbanks, AK, USA
| |
Collapse
|
23
|
Badr A, Korajoki H, Abu-Amra ES, El-Sayed MF, Vornanen M. Effects of seasonal acclimatization on thermal tolerance of inward currents in roach (Rutilus rutilus) cardiac myocytes. J Comp Physiol B 2017; 188:255-269. [DOI: 10.1007/s00360-017-1126-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2017] [Revised: 08/23/2017] [Accepted: 09/15/2017] [Indexed: 02/06/2023]
|
24
|
Temperature-related parasite infection dynamics: the case of proliferative kidney disease of brown trout. Parasitology 2017; 145:281-291. [PMID: 28831940 DOI: 10.1017/s0031182017001482] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Climate change, in particular rising temperature, is suspected to be a major driver for the emergence of many wildlife diseases. Proliferative kidney disease of salmonids, caused by the myxozoan Tetracapsuloides bryosalmonae, was used to evaluate how temperature dependence of host-parasite interactions modulates disease emergence. Brown trout (Salmo trutta fario) kept at 12 and 15 °C, were experimentally infected with T. bryosalmonae. Parasite development in the fish host and release of spores were quantified simultaneously to unravel parasite transmission potential from the vertebrate to the invertebrate host. A change to a stable plateau in infection intensity of the kidney coincided with a threshold at which spore shedding commenced. This onset of parasite release was delayed at the low temperature in accordance with reaching this infection intensity threshold, but the amount of spores released was irrespective of temperature. The production of parasite transmission stages declined with time. In conclusion, elevated temperature modifies the parasite transmission opportunities by increasing the duration of transmission stage production, which may affect the spread and establishment of the parasite in a wider range of rivers.
Collapse
|
25
|
Messmer V, Pratchett MS, Hoey AS, Tobin AJ, Coker DJ, Cooke SJ, Clark TD. Global warming may disproportionately affect larger adults in a predatory coral reef fish. GLOBAL CHANGE BIOLOGY 2017; 23:2230-2240. [PMID: 27809393 DOI: 10.1111/gcb.13552] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Accepted: 09/22/2016] [Indexed: 06/06/2023]
Abstract
Global warming is expected to reduce body sizes of ectothermic animals. Although the underlying mechanisms of size reductions remain poorly understood, effects appear stronger at latitudinal extremes (poles and tropics) and in aquatic rather than terrestrial systems. To shed light on this phenomenon, we examined the size dependence of critical thermal maxima (CTmax) and aerobic metabolism in a commercially important tropical reef fish, the leopard coral grouper (Plectropomus leopardus) following acclimation to current-day (28.5 °C) vs. projected end-of-century (33 °C) summer temperatures for the northern Great Barrier Reef (GBR). CTmax declined from 38.3 to 37.5 °C with increasing body mass in adult fish (0.45-2.82 kg), indicating that larger individuals are more thermally sensitive than smaller conspecifics. This may be explained by a restricted capacity for large fish to increase mass-specific maximum metabolic rate (MMR) at 33 °C compared with 28.5 °C. Indeed, temperature influenced the relationship between metabolism and body mass (0.02-2.38 kg), whereby the scaling exponent for MMR increased from 0.74 ± 0.02 at 28.5 °C to 0.79 ± 0.01 at 33 °C, and the corresponding exponents for standard metabolic rate (SMR) were 0.75 ± 0.04 and 0.80 ± 0.03. The increase in metabolic scaling exponents at higher temperatures suggests that energy budgets may be disproportionately impacted in larger fish and contribute to reduced maximum adult size. Such climate-induced reductions in body size would have important ramifications for fisheries productivity, but are also likely to have knock-on effects for trophodynamics and functioning of ecosystems.
Collapse
Affiliation(s)
- Vanessa Messmer
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, 4811, Australia
| | - Morgan S Pratchett
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, 4811, Australia
| | - Andrew S Hoey
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, 4811, Australia
| | - Andrew J Tobin
- Centre for Sustainable Tropical Fisheries and Aquaculture, School of Earth and Environmental Sciences, James Cook University, Townsville, Queensland, 4811, Australia
| | - Darren J Coker
- Australian Research Council Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland, 4811, Australia
- Division of Biological and Environmental Science and Engineering, Red Sea Research Center, King Abdullah University of Science and Technology, Thuwal, Jeddah, 23955, Kingdom of Saudi Arabia
| | - Steven J Cooke
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental Science, Carleton University, Ottawa, Ontario, K1S 5B6, Canada
| | - Timothy D Clark
- Australian Institute of Marine Science, Townsville, Queensland, 4810, Australia
- University of Tasmania, and CSIRO Agriculture and Food, Hobart, Tasmania, 7000, Australia
| |
Collapse
|
26
|
Smirnova SL, Roshchevskaya IM. The cardiac electric field in psychrophilic and thermophilic fish during atrial depolarization. J EVOL BIOCHEM PHYS+ 2017. [DOI: 10.1134/s1234567817020057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
27
|
Badr A, Hassinen M, El-Sayed MF, Vornanen M. Effects of seasonal acclimatization on action potentials and sarcolemmal K+ currents in roach (Rutilus rutilus) cardiac myocytes. Comp Biochem Physiol A Mol Integr Physiol 2017; 205:15-27. [DOI: 10.1016/j.cbpa.2016.12.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2016] [Revised: 12/13/2016] [Accepted: 12/15/2016] [Indexed: 01/10/2023]
|
28
|
Haverinen J, Abramochkin DV, Kamkin A, Vornanen M. Maximum heart rate in brown trout (Salmo trutta fario) is not limited by firing rate of pacemaker cells. Am J Physiol Regul Integr Comp Physiol 2017; 312:R165-R171. [DOI: 10.1152/ajpregu.00403.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2016] [Revised: 11/23/2016] [Accepted: 11/23/2016] [Indexed: 01/17/2023]
Abstract
Temperature-induced changes in cardiac output (Q̇) in fish are largely dependent on thermal modulation of heart rate ( fH), and at high temperatures Q̇ collapses due to heat-dependent depression of fH. This study tests the hypothesis that firing rate of sinoatrial pacemaker cells sets the upper thermal limit of fH in vivo. To this end, temperature dependence of action potential (AP) frequency of enzymatically isolated pacemaker cells (pacemaker rate, fPM), spontaneous beating rate of isolated sinoatrial preparations ( fSA), and in vivo fH of the cold-acclimated (4°C) brown trout ( Salmo trutta fario) were compared under acute thermal challenges. With rising temperature, fPM steadily increased because of the acceleration of diastolic depolarization and shortening of AP duration up to the break point temperature (TBP) of 24.0 ± 0.37°C, at which point the electrical activity abruptly ceased. The maximum fPM at TBP was much higher [193 ± 21.0 beats per minute (bpm)] than the peak fSA (94.3 ± 6.0 bpm at 24.1°C) or peak fH (76.7 ± 2.4 at 15.7 ± 0.82°C) ( P < 0.05). These findings strongly suggest that the frequency generator of the sinoatrial pacemaker cells does not limit fH at high temperatures in the brown trout in vivo.
Collapse
Affiliation(s)
- Jaakko Haverinen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| | - Denis V. Abramochkin
- Department of Human and Animal Physiology, Lomonosov Moscow State University, Leninskiye Gory, Moscow, Russia; and
- Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova, Moscow, Russia
| | - Andre Kamkin
- Department of Physiology, Pirogov Russian National Research Medical University, Ostrovityanova, Moscow, Russia
| | - Matti Vornanen
- Department of Environmental and Biological Sciences, University of Eastern Finland, Joensuu, Finland
| |
Collapse
|
29
|
|
30
|
Vornanen M. Electrical Excitability of the Fish Heart and Its Autonomic Regulation. FISH PHYSIOLOGY 2017. [DOI: 10.1016/bs.fp.2017.04.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
|
31
|
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.
Collapse
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
| |
Collapse
|
32
|
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.
Collapse
Affiliation(s)
- Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, PO Box 111, Joensuu 80101, Finland
| |
Collapse
|
33
|
Beers JM, Jayasundara N. Antarctic notothenioid fish: what are the future consequences of 'losses' and 'gains' acquired during long-term evolution at cold and stable temperatures? ACTA ACUST UNITED AC 2016; 218:1834-45. [PMID: 26085661 DOI: 10.1242/jeb.116129] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Antarctic notothenioids dominate the fish fauna of the Southern Ocean. Evolution for millions of years at cold and stable temperatures has led to the acquisition of numerous biochemical traits that allow these fishes to thrive in sub-zero waters. The gain of antifreeze glycoproteins has afforded notothenioids the ability to avert freezing and survive at temperatures often hovering near the freezing point of seawater. Additionally, possession of cold-adapted proteins and membranes permits them to sustain appropriate metabolic rates at exceptionally low body temperatures. The notothenioid genome is also distinguished by the disappearance of traits in some species, losses that might prove costly in a warmer environment. Perhaps the best-illustrated example is the lack of expression of hemoglobin in white-blooded icefishes from the family Channichthyidae. Loss of key elements of the cellular stress response, notably the heat shock response, has also been observed. Along with their attainment of cold tolerance, notothenioids have developed an extreme stenothermy and many species perish at temperatures only a few degrees above their habitat temperatures. Thus, in light of today's rapidly changing climate, it is critical to evaluate how these extreme stenotherms will respond to rising ocean temperatures. It is conceivable that the remarkable cold specialization of notothenioids may ultimately leave them vulnerable to future thermal increases and threaten their fitness and survival. Within this context, our review provides a current summary of the biochemical losses and gains that are known for notothenioids and examines these cold-adapted traits with a focus on processes underlying thermal tolerance and acclimation capacity.
Collapse
Affiliation(s)
- Jody M Beers
- Hopkins Marine Station, Stanford University, 120 Ocean View Boulevard, Pacific Grove, CA 93950, USA
| | - Nishad Jayasundara
- Nicholas School of the Environment, Duke University, 450 Research Drive, Durham, NC 27708, USA
| |
Collapse
|
34
|
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.
Collapse
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
| |
Collapse
|
35
|
Badr A, El-Sayed MF, Vornanen M. Effects of seasonal acclimatization on temperature dependence of cardiac excitability in the roach, Rutilus rutilus. ACTA ACUST UNITED AC 2016; 219:1495-504. [PMID: 26994185 DOI: 10.1242/jeb.138347] [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: 01/28/2016] [Accepted: 03/03/2016] [Indexed: 01/06/2023]
Abstract
Temperature sensitivity of electrical excitability is a potential limiting factor for performance level and thermal tolerance of excitable tissues in ectothermic animals. To test whether the rate and rhythm of the heart acclimatize to seasonal temperature changes, thermal sensitivity of cardiac excitation in a eurythermal teleost, the roach (Rutilus rutilus), was examined. Excitability of the heart was determined from in vivo electrocardiograms and in vitro microelectrode recordings of action potentials (APs) from winter and summer roach acclimatized to 4 and 18°C, respectively. Under heat ramps (3°C h(-1)), starting from the acclimatization temperatures of the fish, heart rate increased to maximum values of 78±5 beats min(-1) (at 19.8±0.5°C) and 150±7 beats min(-1) (at 28.1±0.5°C) for winter and summer roach, respectively, and then declined in both groups. Below 20°C, heart rate was significantly higher in winter than in summer roach (P<0.05), indicating positive thermal compensation. Cardiac arrhythmias appeared with rising temperature as missing QRS complexes, increase in variability of heart rate, episodes of atrial tachycardia, ventricular bradycardia and complete cessation of the heartbeat (asystole) in both winter and summer roach. Unlike winter roach, atrial APs of summer roach had a distinct early repolarization phase, which appeared as shorter durations of atrial AP at 10% and 20% repolarization levels in comparison to winter roach (P<0.05). In contrast, seasonal acclimatization had only subtle effects on ventricular AP characteristics. Plasticity of cardiac excitation appears to be necessary for seasonal improvements in performance level and thermal resilience of the roach heart.
Collapse
Affiliation(s)
- A Badr
- Department of Environmental and Biological Sciences, Faculty of Science and Forestry, University of Eastern Finland, 80101 Joensuu, Finland Department of Zoology, Faculty of Science, Sohag University, 82524 Sohag, Egypt
| | - M F El-Sayed
- Department of Zoology, Faculty of Science, Sohag University, 82524 Sohag, Egypt
| | - M Vornanen
- Department of Environmental and Biological Sciences, Faculty of Science and Forestry, University of Eastern Finland, 80101 Joensuu, Finland
| |
Collapse
|
36
|
Raby GD, Casselman MT, Cooke SJ, Hinch SG, Farrell AP, Clark TD. Aerobic scope increases throughout an ecologically relevant temperature range in coho salmon. J Exp Biol 2016; 219:1922-31. [DOI: 10.1242/jeb.137166] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 04/05/2016] [Indexed: 12/15/2022]
Abstract
Aerobic scope (AS) has been proposed as a functional measurement that can be used to make predictions about the thermal niche of aquatic ectotherms and hence potential fitness outcomes under future warming scenarios. Some salmonid species and populations, for example, have been reported to exhibit different thermal profiles for their AS curves such that AS peaks around the modal river temperature encountered during the upriver spawning migration, suggesting species- and population-level adaptations to river temperature regimes. Interestingly, some other salmonid species and populations have been reported to exhibit AS curves that maintain an upwards trajectory throughout the ecologically-relevant temperature range rather than peaking at a modal temperature. To shed further light on this apparent dichotomy, we used adult coho salmon (Onchorhynchus kisutch) to test the prediction that peak AS coincides with population-specific, historically experienced river temperatures. We assessed AS at 10°C and 15°C, which represent a typical river migration temperature and the upper limit of the historically experienced temperature range, respectively. We also examined published data on AS in juvenile coho salmon in relation to new temperature data measured from their freshwater rearing environments. In both cases, AS was either maintained or increased modestly throughout the range of ecologically relevant temperatures. In light of existing evidence and the new data presented here, we suggest that when attempting to understand thermal optima for Pacific salmon and other species across life stages, AS is a useful metric of oxygen transport capacity but other thermally-sensitive physiological indices of performance and fitness should be considered in concert.
Collapse
Affiliation(s)
- Graham D. Raby
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, Ottawa, ON, Canada, K1S 5B6
- Current affiliation: Great Lakes Institute for Environmental Research, University of Windsor, Windsor, ON, Canada, N9B 3P4
| | - Matthew T. Casselman
- Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Steven J. Cooke
- Fish Ecology and Conservation Physiology Laboratory, Department of Biology, Carleton University, Ottawa, ON, Canada, K1S 5B6
| | - Scott G. Hinch
- Department of Forest and Conservation Sciences, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Anthony P. Farrell
- Department of Zoology and Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Timothy D. Clark
- Australian Institute of Marine Science, PMB 3, Townsville MC, Townsville, Queensland, Australia 4810
- Current affiliation: University of Tasmania and CSIRO Agriculture Flagship, Hobart, Tasmania, Australia 7000
| |
Collapse
|
37
|
Tikkanen E, Haverinen J, Egginton S, Hassinen M, Vornanen M. Effects of prolonged anoxia on electrical activity of the heart in Crucian carp (Carassius carassius). J Exp Biol 2016; 220:445-454. [DOI: 10.1242/jeb.145177] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Accepted: 11/15/2016] [Indexed: 01/08/2023]
Abstract
The effects of sustained anoxia on cardiac electrical excitability were examined in the anoxia-tolerant Crucian carp (Carassius carassius). The electrocardiogram (ECG) and expression of excitation-contraction coupling genes were studied in fish acclimatised to normoxia in summer (+18°C) or winter (+2°C), and in winter fish after 1, 3 and 6 weeks of anoxia. Anoxia induced a sustained bradycardia from a heart rate of 10.3±0.77 to 4.1±0.29 bpm (P<0.05) after 5 weeks, and heart rate slowly recovered to control levels when oxygen was restored. Heart rate variability greatly increased under anoxia, and completely recovered under re-oxygenation. The RT interval increased from 2.8±0.34 s in normoxia to 5.8±0.44 s under anoxia (P<0.05), which reflects a doubling of the ventricular action potential (AP) duration. Acclimatisation to winter induced extensive changes in gene expression relative to summer-acclimatised fish, including depression in those coding for the sarcoplasmic reticulum calcium pump (Serca2-q2) and ATP-sensitive K+ channels (Kir6.2) (P<0.05). Genes of delayed rectifier K+ (kcnh6) and Ca2+ channels (cacna1c) were up-regulated in winter fish (P<0.05). In contrast, the additional challenge of anoxia caused only minor changes in gene expression, e.g. depressed expression of Kir2.2b K+ channel gene (kcnj12b), whereas expression of Ca2+ (cacna1a, -c and –g) and Na+ channel genes (scn4a and scn5a) were not affected. These data suggest that low temperature pre-conditions the Crucian carp heart for winter anoxia, whereas sustained anoxic bradycardia and prolongation of AP duration are directly induced by oxygen shortage without major changes in gene expression.
Collapse
Affiliation(s)
- Elisa Tikkanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | - Jaakko Haverinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | | | - Minna Hassinen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| | - Matti Vornanen
- University of Eastern Finland, Department of Environmental and Biological Sciences, Finland
| |
Collapse
|
38
|
Bjelde BE, Miller NA, Stillman JH, Todgham AE. The Role of Oxygen in Determining Upper Thermal Limits in Lottia digitalis under Air Exposure and Submersion. Physiol Biochem Zool 2015; 88:483-93. [PMID: 26658246 DOI: 10.1086/682220] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Oxygen limitation of aerobic metabolism is hypothesized to drive organismal thermal tolerance limits. Differences in oxygen availability in air and water may underlie observed differences in upper thermal tolerance of intertidal limpets if oxygen is limiting in submerged environments. We explored how cardiac performance (heart rate, breakpoint temperature [BPT], flat-line temperature [FLT], and temperature sensitivity) was affected by hyperoxia and hypoxia in the finger limpet, Lottia digitalis, under air exposure and submersion. Upper thermal tolerance limits were unchanged by increasing availability of oxygen, although air-exposed limpets were able to maintain cardiac function to higher temperatures than submerged limpets. Maximum heart rate did not increase with greater partial pressure of oxygen (Po2), suggesting that tissue Po2 levels are likely maximized during normoxia. Hypoxia reduced breakpoint BPTs and FLTs in air-exposed and submerged limpets and accentuated the difference in BPTs between the two groups through greater reductions in BPT in submerged limpets. Differences in respiratory structures and the degree to which thermal limits are already maximized may play significant roles in determining how oxygen availability influences upper temperature tolerance.
Collapse
Affiliation(s)
- Brittany E Bjelde
- Department of Biology, San Francisco State University, San Francisco, California 94132; 2Department of Animal Science, University of California, Davis, California 95616; 3Romberg Tiburon Center for Environmental Studies, San Francisco State University, Tiburon, California 94920; 4Department of Integrative Biology, University of California, Berkeley, California 94720
| | | | | | | |
Collapse
|
39
|
Devor DP, Kuhn DE, O'Brien KM, Crockett EL. Hyperoxia Does Not Extend Critical Thermal Maxima (CTmax) in White- or Red-Blooded Antarctic Notothenioid Fishes. Physiol Biochem Zool 2015; 89:1-9. [PMID: 27082520 DOI: 10.1086/684812] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Understanding what limits the capacity of organisms to tolerate increasing temperatures is a critical objective in comparative biology. Using an experimental system of Antarctic notothenioid fishes, we sought to determine whether a mismatch between oxygen demand and oxygen supply was responsible for setting thermal tolerance limits. Previous studies have shown that Antarctic icefishes (family Channichthyidae), which lack hemoglobin, have lower critical thermal maxima (CTmax) than red-blooded notothenioids collected from the same region of the Antarctic (Western Antarctic Peninsula). In addition, within the notothenioid fishes there exists a positive correlation between CTmax and hematocrit. We tested the hypothesis that the lower CTmax of icefishes is associated with reduced oxygen supply. We employed an experimental heat ramp (4°C h(-1)) to determine CTmax under both normoxic and hyperoxic conditions and quantified correlates of oxygen limitation (lactate levels and expression of hypoxia-inducible factor-1α) in white-blooded Chaenocephalus aceratus and red-blooded Notothenia coriiceps. Hyperoxia, corresponding to a three- to fourfold increase in seawater Po2, did not extend CTmax in either species despite an overall mitigation in the rise of plasma and muscle lactate compared with the normoxic treatment. Our results also indicate that cardiac HIF-1α mRNA levels were insensitive to changes in both temperature and oxygen treatments. The absence of a change in CTmax with hyperoxia is likely to represent the contribution of factors beyond oxygen supply to physiological failure at elevated temperatures.
Collapse
|
40
|
Hassinen M, Haverinen J, Hardy ME, Shiels HA, Vornanen M. Inward rectifier potassium current (I K1) and Kir2 composition of the zebrafish (Danio rerio) heart. Pflugers Arch 2015; 467:2437-46. [PMID: 25991088 DOI: 10.1007/s00424-015-1710-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2015] [Revised: 05/07/2015] [Accepted: 05/07/2015] [Indexed: 11/24/2022]
Abstract
Electrophysiological properties and molecular background of the zebrafish (Danio rerio) cardiac inward rectifier current (IK1) were examined. Ventricular myocytes of zebrafish have a robust (-6.7 ± 1.2 pA pF(-1) at -120 mV) strongly rectifying and Ba(2+)-sensitive (IC50 = 3.8 μM) IK1. Transcripts of six Kir2 channels (drKir2.1a, drKir2.1b, drKir2.2a, drKir2.2b, drKir2.3, and drKir2.4) were expressed in the zebrafish heart. drKir2.4 and drKir2.2a were the dominant isoforms in both the ventricle (92.9 ± 1.5 and 6.3 ± 1.5%) and the atrium (28.9 ± 2.9 and 64.7 ± 3.0%). The remaining four channels comprised together less than 1 and 7 % of the total transcripts in ventricle and atrium, respectively. The four main gene products (drKir2.1a, drKir2.2a, drKir2.2b, drKir2.4) were cloned, sequenced, and expressed in HEK cells for electrophysiological characterization. drKir2.1a was the most weakly rectifying (passed more outward current) and drKir2.2b the most strongly rectifying (passed less outward current) channel, whilst drKir2.2a and drKir2.4 were intermediate between the two. In regard to sensitivity to Ba(2+) block, drKir2.4 was the most sensitive (IC50 = 1.8 μM) and drKir2.1a the least sensitive channel (IC50 = 132 μM). These findings indicate that the Kir2 isoform composition of the zebrafish heart markedly differs from that of mammalian hearts. Furthermore orthologous Kir2 channels (Kir2.1 and Kir2.4) of zebrafish and mammals show striking differences in Ba(2+)-sensitivity. Structural and functional differences needs to be taken into account when zebrafish is used as a model for human cardiac electrophysiology, cardiac diseases, and in screening cardioactive substances.
Collapse
Affiliation(s)
- Minna Hassinen
- Department of Biology, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland.
| | - Jaakko Haverinen
- Department of Biology, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland
| | - Matt E Hardy
- Faculty of Life Sciences, University of Manchester, 46 Grafton Street, Manchester, M13 9NT, UK
| | - Holly A Shiels
- Faculty of Life Sciences, University of Manchester, 46 Grafton Street, Manchester, M13 9NT, UK
| | - Matti Vornanen
- Department of Biology, University of Eastern Finland, P.O. Box 111, 80101, Joensuu, Finland
| |
Collapse
|
41
|
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.
Collapse
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
| |
Collapse
|
42
|
The beat goes on: Cardiac pacemaking in extreme conditions. Comp Biochem Physiol A Mol Integr Physiol 2014; 186:52-60. [PMID: 25178563 DOI: 10.1016/j.cbpa.2014.08.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2014] [Revised: 08/17/2014] [Accepted: 08/20/2014] [Indexed: 11/21/2022]
Abstract
In order for an animal to survive, the heart beat must go on in all environmental conditions, or at least restart its beat. This review is about maintaining a rhythmic heartbeat under the extreme conditions of anoxia (or very severe hypoxia) and high temperatures. It starts by considering the primitive versions of the protein channels that are responsible for initiating the heartbeat, HCN channels, divulging recent findings from the ancestral craniate, the Pacific hagfish (Eptatretus stoutii). It then explores how a heartbeat can maintain a rhythm, albeit slower, for hours without any oxygen, and sometimes without autonomic innervation. It closes with a discussion of recent work on fishes, where the cardiac rhythm can become arrhythmic when a fish experiences extreme heat.
Collapse
|
43
|
Ferreira EO, Anttila K, Farrell AP. Thermal optima and tolerance in the eurythermic goldfish (Carassius auratus): relationships between whole-animal aerobic capacity and maximum heart rate. Physiol Biochem Zool 2014; 87:599-611. [PMID: 25244373 DOI: 10.1086/677317] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
The wide thermal tolerance range of a eurythermic fish (goldfish, Carassius auratus) was used to evaluate how temperature performance curves derived from maximum heart rate (fH) related to those for aerobic scope. For acclimation temperatures of 12°, 20°, and 28°C, optimum temperatures derived from aerobic scope curves (Topt) were 19.9° ± 0.4°, 19.3° ± 0.8°, and 28.7° ± 0.8°C, respectively. The Arrhenius breakpoint temperatures (TAB) for maximum fH were 21.5° ± 0.6°, 23.8° ± 0.9°, and 24.6° ± 0.5°C, respectively. The TQB (temperature where the incremental Q10 of maximum fH decreased abruptly below 1.9) was 24.0° ± 0.7° and 29.8° ± 0.6°C for the 12° and 28°C acclimation temperatures, respectively, and was within the Topt window (11.5°-30.3° and 26.9°-30.5°C, respectively), but TQB for the 20°C acclimation temperature (27.3° ± 0.6°C) was higher than the Topt window (15.4°-23.2°C). Warm acclimation increased the upper critical temperature (Tcrit; from 37.2° ± 0.7° to 44.7° ± 11.8°C) as well as the temperature that triggered a cardiac arrhythmia (Tarr; from 31.1° ± 0.7° to 39.3° ± 0.4°C). In conclusion, we propose that maximum fH and its associated rate transition temperatures (TAB, TQB, and Tarr) can be used to estimate the upper thermal tolerance of eurythermic as well as stenothermic fish independent of acclimation temperature. All the same, great care is needed with such evaluations. For the goldfish, while TAB and TQB were always within the Topt window for 90% of maximum aerobic scope and Topt was closely associated with TAB for 12°C-acclimated fish, TQB had the closest association after 28°C acclimation, and both TAB and TQB were above the Topt window after 20°C acclimation.
Collapse
Affiliation(s)
- Elizabeth O Ferreira
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada; 2Faculty of Land and Food Systems, University of British Columbia, 2357 Main Mall, Vancouver, British Columbia V6T 1Z4, Canada
| | | | | |
Collapse
|
44
|
Ekström A, Jutfelt F, Sandblom E. Effects of autonomic blockade on acute thermal tolerance and cardioventilatory performance in rainbow trout, Oncorhynchus mykiss. J Therm Biol 2014; 44:47-54. [PMID: 25086973 DOI: 10.1016/j.jtherbio.2014.06.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2014] [Revised: 05/30/2014] [Accepted: 06/02/2014] [Indexed: 10/25/2022]
Abstract
Predicted future increases in global temperature may impose challenges for ectothermic animals like fish, but the physiological mechanisms determining the critical thermal maximum (CTmax) are not well understood. One hypothesis suggests that impaired cardiac performance, limited by oxygen supply, is an important underlying mechanism. Since vagal bradycardia is suggested to improve cardiac oxygenation and adrenergic stimulation may improve cardiac contractility and protect cardiac function at high temperatures, we predicted that pharmacological blockade of cardiac autonomic control would lower CTmax. Rainbow trout was instrumented with a flow probe and a ventilation catheter for cardioventilatory recordings and exposed to an acute thermal challenge until CTmax following selective pharmacological blockade of muscarinic or β-adrenergic receptors. Contrary to our prediction, CTmax (~26°C) was unchanged between treatments. While β-adrenergic blockade reduced heart rate it did not impair cardiac stroke volume across temperatures suggesting that compensatory increases in cardiac filling pressure may serve to maintain cardiac output. While warming resulted in significant tachycardia and increased cardiac output, a high cholinergic tone on the heart was observed at temperatures approaching CTmax. This may represent a mechanism to maintain scope for heart rate and possibly to improve myocardial contractility and oxygen supply at high temperatures. This is the first study evaluating the importance of autonomic cardiac control on thermal tolerance in fish. While no effects on CTmax were observed, this study raises important questions about the underlying mechanisms determining thermal tolerance limits in ectothermic animals.
Collapse
Affiliation(s)
- Andreas Ekström
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden.
| | - Fredrik Jutfelt
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden; The Sven Lovén Centre for Marine Sciences, Kristineberg, Fiskebäckskil, Sweden
| | - Erik Sandblom
- Department of Biology and Environmental Sciences, University of Gothenburg, Gothenburg Sweden
| |
Collapse
|
45
|
Lin E, Ribeiro A, Ding W, Hove-Madsen L, Sarunic MV, Beg MF, Tibbits GF. Optical mapping of the electrical activity of isolated adult zebrafish hearts: acute effects of temperature. Am J Physiol Regul Integr Comp Physiol 2014; 306:R823-36. [PMID: 24671241 DOI: 10.1152/ajpregu.00002.2014] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The zebrafish (Danio rerio) has emerged as an important model for developmental cardiovascular (CV) biology; however, little is known about the cardiac function of the adult zebrafish enabling it to be used as a model of teleost CV biology. Here, we describe electrophysiological parameters, such as heart rate (HR), action potential duration (APD), and atrioventricular (AV) delay, in the zebrafish heart over a range of physiological temperatures (18-28°C). Hearts were isolated and incubated in a potentiometric dye, RH-237, enabling electrical activity assessment in several distinct regions of the heart simultaneously. Integration of a rapid thermoelectric cooling system facilitated the investigation of acute changes in temperature on critical electrophysiological parameters in the zebrafish heart. While intrinsic HR varied considerably between fish, the ex vivo preparation exhibited impressively stable HRs and sinus rhythm for more than 5 h, with a mean HR of 158 ± 9 bpm (means ± SE; n = 20) at 28°C. Atrial and ventricular APDs at 50% repolarization (APD50) were 33 ± 1 ms and 98 ± 2 ms, respectively. Excitation originated in the atrium, and there was an AV delay of 61 ± 3 ms prior to activation of the ventricle at 28°C. APD and AV delay varied between hearts beating at unique HRs; however, APD and AV delay did not appear to be statistically dependent on intrinsic basal HR, likely due to the innate beat-to-beat variability within each heart. As hearts were cooled to 18°C (by 1°C increments), HR decreased by ~40%, and atrial and ventricular APD50 increased by a factor of ~3 and 2, respectively. The increase in APD with cooling was disproportionate at different levels of repolarization, indicating unique temperature sensitivities for ion currents at different phases of the action potential. The effect of temperature was more apparent at lower levels of repolarization and, as a whole, the atrial APD was the cardiac parameter most affected by acute temperature change. In conclusion, this study describes a preparation enabling the in-depth analysis of transmembrane potential dynamics in whole zebrafish hearts. Because the zebrafish offers some critical advantages over the murine model for cardiac electrophysiology, optical mapping studies utilizing zebrafish offer insightful information into the understanding and treatment of human cardiac arrhythmias, as well as serving as a model for other teleosts.
Collapse
Affiliation(s)
- Eric Lin
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Amanda Ribeiro
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada
| | - Weiguang Ding
- Medical Image Analysis Laboratory, School of Engineering Science, Simon Fraser University, Burnaby, Canada
| | - Leif Hove-Madsen
- Cardiovascular Research Centre, CSIC-ICCC, Hospital de Sant Pau, Barcelona, Spain
| | - Marinko V Sarunic
- Biomedical Optics Research Group, School of Engineering Science, Simon Fraser University, Burnaby, Canada; and
| | - Mirza Faisal Beg
- Medical Image Analysis Laboratory, School of Engineering Science, Simon Fraser University, Burnaby, Canada
| | - Glen F Tibbits
- Molecular Cardiac Physiology Group, Biomedical Physiology and Kinesiology, Simon Fraser University, Burnaby, Canada; Cardiovascular Sciences, Child and Family Research Institute, Vancouver, Canada
| |
Collapse
|