1
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Endress MGA, Penn JL, Boag TH, Burford BP, Sperling EA, Deutsch CA. Thermal optima in the hypoxia tolerance of marine ectotherms: Physiological causes and biogeographic consequences. PLoS Biol 2024; 22:e3002443. [PMID: 38227580 PMCID: PMC10790991 DOI: 10.1371/journal.pbio.3002443] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Accepted: 11/21/2023] [Indexed: 01/18/2024] Open
Abstract
The minimum O2 needed to fuel the demand of aquatic animals is commonly observed to increase with temperature, driven by accelerating metabolism. However, recent measurements of critical O2 thresholds ("Pcrit") reveal more complex patterns, including those with a minimum at an intermediate thermal "optimum". To discern the prevalence, physiological drivers, and biogeographic manifestations of such curves, we analyze new experimental and biogeographic data using a general dynamic model of aquatic water breathers. The model simulates the transfer of oxygen from ambient water through a boundary layer and into animal tissues driven by temperature-dependent rates of metabolism, diffusive gas exchange, and ventilatory and circulatory systems with O2-protein binding. We find that a thermal optimum in Pcrit can arise even when all physiological rates increase steadily with temperature. This occurs when O2 supply at low temperatures is limited by a process that is more temperature sensitive than metabolism, but becomes limited by a less sensitive process at warmer temperatures. Analysis of published species respiratory traits suggests that this scenario is not uncommon in marine biota, with ventilation and circulation limiting supply under cold conditions and diffusion limiting supply at high temperatures. Using occurrence data, we show that species with these physiological traits inhabit lowest O2 waters near the optimal temperature for hypoxia tolerance and are restricted to higher O2 at temperatures above and below this optimum. Our results imply that hypoxia tolerance can decline under both cold and warm conditions and thus may influence both poleward and equatorward species range limits.
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Affiliation(s)
- Martin-Georg A. Endress
- School of Oceanography, University of Washington, Seattle, Washington, United States of America
- Institute of Zoology, University of Cologne, Cologne, Germany
| | - Justin L. Penn
- School of Oceanography, University of Washington, Seattle, Washington, United States of America
- Department of Geosciences, Princeton University, Princeton, New Jersey, United States of America
| | - Thomas H. Boag
- Department of Geosciences, Princeton University, Princeton, New Jersey, United States of America
| | - Benjamin P. Burford
- Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, California, United States of America
- National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Southwest Fisheries Science Center, Santa Cruz, California, United States of America
| | - Erik A. Sperling
- Department of Earth and Planetary Sciences, Stanford University, Stanford, California, United States of America
| | - Curtis A. Deutsch
- School of Oceanography, University of Washington, Seattle, Washington, United States of America
- Department of Geosciences, Princeton University, Princeton, New Jersey, United States of America
- High Meadows Environmental Institute, Princeton University, Princeton, New Jersey, United States of America
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2
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Somo DA, Chu K, Richards JG. Gill surface area allometry does not constrain the body mass scaling of maximum oxygen uptake rate in the tidepool sculpin, Oligocottus maculosus. J Comp Physiol B 2023:10.1007/s00360-023-01490-9. [PMID: 37149515 DOI: 10.1007/s00360-023-01490-9] [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: 07/05/2022] [Revised: 03/03/2023] [Accepted: 04/14/2023] [Indexed: 05/08/2023]
Abstract
The gill oxygen limitation hypothesis (GOLH) suggests that hypometric scaling of metabolic rate in fishes is a consequence of oxygen supply constraints imposed by the mismatched growth rates of gill surface area (a two-dimensional surface) and body mass (a three-dimensional volume). GOLH may, therefore, explain the size-dependent spatial distribution of fish in temperature- and oxygen-variable environments through size-dependent respiratory capacity, but this question is unstudied. We tested GOLH in the tidepool sculpin, Oligocottus maculosus, a species in which body mass decreases with increasing temperature- and oxygen-variability in the intertidal, a pattern consistent with GOLH. We statistically evaluated support for GOLH versus distributed control of [Formula: see text] allometry by comparing scaling coefficients for gill surface area, standard and maximum [Formula: see text] ([Formula: see text],Standard and [Formula: see text],Max, respectively), ventricle mass, hematocrit, and metabolic enzyme activities in white muscle. To empirically evaluate whether there is a proximate constraint on oxygen supply capacity with increasing body mass, we measured [Formula: see text],Max across a range of Po2s from normoxia to Pcrit, calculated the regulation value (R), a measure of oxyregulatory capacity, and analyzed the R-body mass relationship. In contrast with GOLH, gill surface area scaling either matched or was more than sufficient to meet [Formula: see text] demands with increasing body mass and R did not change with body mass. Ventricle mass (b = 1.22) scaled similarly to [Formula: see text],Max (b = 1.18) suggesting a possible role for the heart in the scaling of [Formula: see text],Max. Together our results do not support GOLH as a mechanism structuring the distribution of O. maculosus and suggest distributed control of oxyregulatory capacity.
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Affiliation(s)
- Derek A Somo
- Department of Zoology, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
| | - Ken Chu
- Department of Zoology, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
| | - Jeffrey G Richards
- Department of Zoology, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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3
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Molina JM, Kunzmann A, Reis JP, Guerreiro PM. Metabolic Responses and Resilience to Environmental Challenges in the Sedentary Batrachoid Halobatrachus didactylus (Bloch & Schneider, 1801). Animals (Basel) 2023; 13:ani13040632. [PMID: 36830420 PMCID: PMC9951689 DOI: 10.3390/ani13040632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 02/06/2023] [Accepted: 02/10/2023] [Indexed: 02/16/2023] Open
Abstract
In the context of climate change, warming of the seas and expansion of hypoxic zones are challenges that most species of fish are, or will be subjected to. Understanding how different species cope with these changes in their environment at the individual level can shed light on how populations and ecosystems will be affected. We provide first-time estimates on the metabolic rates, thermal, and oxygen-related limits for Halobatrachus didactylus, a coastal sedentary fish that lives in intertidal environments of the Northeast Atlantic. Using respirometry in different experimental designs, we found that this species is highly resistant to acute thermal stress (CTmax: 34.82 ± 0.66 °C) and acute hypoxia (Pcrit: 0.59-1.97 mg O2 L-1). We found size-specific differences in this stress response, with smaller individuals being more sensitive. We also quantified its aerobic scope and daily activity patterns, finding this fish to be extremely sedentary, with one of the lowest standard metabolic rates found in temperate fish (SMR: 14.96 mg O2 kg-1h-1). H. didactylus activity increases at night, when its metabolic rate increases drastically (RMR: 36.01 mg O2 kg-1h-1). The maximum metabolic rate of H. didactylus was estimated to be 67.31 mg O2 kg-1h-1, producing an aerobic scope of 52.35 mg O2 kg-1h-1 (77.8% increase). The metrics obtained in this study prove that H. didactylus is remarkably resilient to acute environmental variations in temperature and oxygen content, which might enable it to adapt to the extreme abiotic conditions forecasted for the world's oceans in the near future.
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Affiliation(s)
- Juan Manuel Molina
- Instituto Argentino de Oceanografía (CONICET), Bahía Blanca B8000, Argentina
- Leibniz-Zentrum für Marine Tropenforschung (ZMT), 28359 Bremen, Germany
- Centro de Ciências do Mar (CCMAR), Universidade do Algarve, 8005-139 Faro, Portugal
- Correspondence:
| | - Andreas Kunzmann
- Leibniz-Zentrum für Marine Tropenforschung (ZMT), 28359 Bremen, Germany
| | - João Pena Reis
- Centro de Ciências do Mar (CCMAR), Universidade do Algarve, 8005-139 Faro, Portugal
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4
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Castrillón-Cifuentes AL, Zapata FA, Giraldo A, Wild C. Spatiotemporal variability of oxygen concentration in coral reefs of Gorgona Island (Eastern Tropical Pacific) and its effect on the coral Pocillopora capitata. PeerJ 2023; 11:e14586. [PMID: 36721774 PMCID: PMC9884479 DOI: 10.7717/peerj.14586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 11/28/2022] [Indexed: 01/27/2023] Open
Abstract
Dissolved oxygen concentration (DO) is one of the main factors limiting benthic species distribution. Due to ocean warming and eutrophication, the ocean is deoxygenating. In the Eastern Tropical Pacific (ETP), deep waters with low DO (<1 mg L-1) may reach coral reefs, because upwelling will likely intensify due to climate change. To understand oxygen variability and its effects on corals, we characterize the Spatio-temporal changes of DO in coral reefs of Gorgona Island and calculate the critical oxygen tension (P crit) to identify the DO concentration that could represent a hypoxic condition for Pocillopora capitata, one of the main reef-building species in the ETP. The mean (±SD) DO concentration in the coral reefs of Gorgona Island was 4.6 ± 0.89 mg L-1. Low DO conditions were due to upwelling, but hypoxia (<3.71 mg L-1, defined as a DO value 1 SD lower than the Mean) down to 3.0 mg O2 L-1 sporadically occurred at 10 m depth. The P crit of P. capitata was 3.7 mg L-1 and lies close to the hypoxic condition recorded on coral reefs during the upwelling season at 10 m depth. At Gorgona Island oxygen conditions lower than 2.3 mg L-1 occur at >20 m depth and coincide with the deepest bathymetric distribution of scattered colonies of Pocillopora. Because DO concentrations in coral reefs of Gorgona Island were comparably low to other coral reefs in the Eastern Tropical Pacific, and the hypoxic threshold of P. capitata was close to the minimum DO record on reefs, hypoxic events could represent a threat if conditions that promote eutrophication (and consequently hypoxia) increase.
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Affiliation(s)
- Ana Lucia Castrillón-Cifuentes
- Department of Marine Ecology/Faculty of Biology and Chemistry, Universität Bremen, Bremen, Germany,Departamento de Biología/Facultad de Ciencias Naturales y Exactas/Grupo de Investigación en Ecología de Arrecifes Coralinos, Universidad del Valle, Cali, Valle del Cauca, Colombia
| | - Fernando A. Zapata
- Departamento de Biología/Facultad de Ciencias Naturales y Exactas/Grupo de Investigación en Ecología de Arrecifes Coralinos, Universidad del Valle, Cali, Valle del Cauca, Colombia
| | - Alan Giraldo
- Departamento de Biología/Facultad de Ciencias Naturales y Exactas/Grupo de Investigación en Ciencias Oceanográficas, Universidad del Valle, Cali, Valle del Cauca, Colombia
| | - Christian Wild
- Department of Marine Ecology/Faculty of Biology and Chemistry, Universität Bremen, Bremen, Germany
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5
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Somo DA, Chu K, Richards JG. Aerobic scope falls to nil at Pcrit and anaerobic ATP production increases below Pcrit in the tidepool sculpin, Oligocottus maculosus. Biol Lett 2022; 18:20220342. [PMID: 36475421 PMCID: PMC9727657 DOI: 10.1098/rsbl.2022.0342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The critical oxygen tension of whole-animal oxygen uptake rate, or Pcrit, has historically been defined as the oxygen partial pressure (PO2) at which aerobic scope falls to zero and further declines in PO2 require substrate-level phosphorylation to meet shortfalls in aerobic ATP production, thereby time-limiting survival. Despite the inclusion of aerobic scope and anaerobic ATP production in the definition, little effort has been made to verify that Pcrit measurements, the vast majority of which are obtained using respirometry in resting animals, actually reflect the predictions of zero aerobic scope and a transition to increasing reliance on anaerobic ATP production. To test these predictions, we compared aerobic scope and levels of whole-body lactate at oxygen partial pressures (PO2s) bracketing Pcrit obtained in resting fish during progressive hypoxia in the tidepool sculpin, Oligocottus maculosus. We found that aerobic scope falls to zero at Pcrit and, in resting fish exposed to PO2s < Pcrit, whole-body lactate accumulated pointing to an increased reliance on anaerobic ATP production. These results support the interpretation of Pcrit as a key oxygen threshold at which aerobic scope falls to nil and, below Pcrit, survival is time-limited based on anaerobic metabolic capacity.
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Affiliation(s)
- Derek A. Somo
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Ken Chu
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Jeffrey G. Richards
- Department of Zoology, The University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
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6
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Horne L, DeVries D, Stoeckel J. The Effects of Glochidia Infection on the Metabolic Rate and Hypoxia Tolerance of Bluegill Lepomis macrochirus and Largemouth Bass Micropterus salmoides. J Parasitol 2022; 108:467-475. [DOI: 10.1645/22-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Affiliation(s)
- Lindsay Horne
- School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, Alabama 36849
| | - Dennis DeVries
- School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, Alabama 36849
| | - James Stoeckel
- School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, Auburn, Alabama 36849
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7
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Hughes DJ, Alexander J, Cobbs G, Kühl M, Cooney C, Pernice M, Varkey D, Voolstra CR, Suggett DJ. Widespread oxyregulation in tropical corals under hypoxia. MARINE POLLUTION BULLETIN 2022; 179:113722. [PMID: 35537305 DOI: 10.1016/j.marpolbul.2022.113722] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/26/2021] [Revised: 04/12/2022] [Accepted: 04/30/2022] [Indexed: 06/14/2023]
Abstract
Hypoxia (low oxygen stress) is increasingly reported on coral reefs, caused by ocean deoxygenation linked to coastal nutrient pollution and ocean warming. While the ability to regulate respiration is a key driver of hypoxia tolerance in many other aquatic taxa, corals' oxyregulatory capabilities remain virtually unexplored. Here, we examine O2-consumption patterns across 17 coral species under declining O2 partial pressure (pO2). All corals showed ability to oxyregulate, but total positive regulation (Tpos) varied between species, ranging from 0.41 (Pocillopora damicornis) to 2.42 (P. acuta). On average, corals performed maximum regulation effort (Pcmax) at low pO2 (30% air saturation, corresponding to lower O2 levels measured on natural reef systems), and exhibited detectable regulation down to as low as <10% air saturation. Our study shows that corals are not oxyconformers as previously thought, suggesting oxyregulation is likely important for survival in dynamic O2 environments of shallow coral reefs subjected to hypoxic events.
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Affiliation(s)
- David J Hughes
- University of Technology Sydney, Climate Change Cluster, Ultimo, NSW 2007, Australia.
| | - James Alexander
- Department of Biology, University of Louisville, Louisville, KY 40292, USA
| | - Gary Cobbs
- Department of Biology, University of Louisville, Louisville, KY 40292, USA
| | - Michael Kühl
- Marine Biology Section, Department of Biology, University of Copenhagen, Strandpromenaden 5, DK 3000 Helsingør, Denmark
| | - Chris Cooney
- University of Technology Sydney, Climate Change Cluster, Ultimo, NSW 2007, Australia
| | - Mathieu Pernice
- University of Technology Sydney, Climate Change Cluster, Ultimo, NSW 2007, Australia
| | - Deepa Varkey
- Department of Molecular Sciences, Macquarie University, NSW 2109, Australia
| | | | - David J Suggett
- University of Technology Sydney, Climate Change Cluster, Ultimo, NSW 2007, Australia
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8
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Vazquez Roman KN, Burggren WW. Metabolic responses to crude oil during early life stages reveal critical developmental windows in the zebrafish (Danio rerio). Comp Biochem Physiol C Toxicol Pharmacol 2022; 254:109274. [PMID: 35051628 DOI: 10.1016/j.cbpc.2022.109274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 12/07/2021] [Accepted: 01/12/2022] [Indexed: 11/03/2022]
Abstract
Morphological effects of crude oil exposure on early development in fishes have been well documented, but crude oil's metabolic effects and when in early development these effects might be most prominent remains unclear. We hypothesized that zebrafish (Danio rerio) exposed to crude oil as a high energy water accommodated fraction (HEWAF) would show increased routine oxygen consumption (ṀO2) and critical oxygen tension (PCrit) and this effect would be dependent upon day of HEWAF exposure, revealing critical windows of development for exposure effects. Zebrafish were exposed to 0%, 10%, 25%, 50% or 100% HEWAF for 24 h during one of the first six days post-fertilization (dpf). Survival rate, body mass, routine ṀO2, and PCrit were then measured at 7 dpf. Survival rate and especially body mass were both decreased based on both exposure concentration and day of crude oil exposure, with the largest decrease when HEWAF exposure occurred at 3 dpf. HEWAF effects on routine ṀO2 also differed depending upon exposure day. The largest effect occurred at 3 dpf, when ṀO2 increased significantly by ~60% from 10.1 ± 0.8 μmol O2/g/h compared to control group value of 6.3 ± 0.4 μmol O2/g/h. No significant effects of HEWAF exposure on any day were evident for PCrit (85 ± 4 mmHg in the control population). Overall, the main effects on body mass and ṀO2 measured at 7 dpf occurred when HEWAF exposures occurred at ~3 dpf. This critical window for metabolism in zebrafish larvae coincides with time of hatching, which may represent an especially vulnerable period in development.
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Affiliation(s)
- Karem N Vazquez Roman
- Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, TX, USA.
| | - Warren W Burggren
- Developmental Integrative Biology Research Group, Department of Biological Sciences, University of North Texas, Denton, TX, USA
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9
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Harter TS, Damsgaard C, Regan MD. Linking environmental salinity to respiratory phenotypes and metabolic rate in fishes: a data mining and modelling approach. J Exp Biol 2022; 225:274262. [PMID: 35258603 DOI: 10.1242/jeb.243421] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The gill is the primary site of ionoregulation and gas exchange in adult teleost fishes. However, those characteristics that benefit diffusive gas exchange (large, thin gills) may also enhance the passive equilibration of ions and water that threaten osmotic homeostasis. Our literature review revealed that gill surface area and thickness were similar in freshwater (FW) and seawater (SW) species; however, the diffusive oxygen (O2) conductance (Gd) of the gill was lower in FW species. While a lower Gd may reduce ion losses, it also limits O2 uptake capacity and possibly aerobic performance in situations of high O2 demand (e.g. exercise) or low O2 availability (e.g. environmental hypoxia). We also found that FW fishes had significantly higher haemoglobin (Hb)-O2 binding affinities than SW species, which will increase the O2 diffusion gradient across the gills. Therefore, we hypothesized that the higher Hb-O2 affinity of FW fishes compensates, in part, for their lower Gd. Using a combined literature review and modelling approach, our results show that a higher Hb-O2 affinity in FW fishes increases the flux of O2 across their low-Gd gills. In addition, FW and SW teleosts can achieve similar maximal rates of O2 consumption (ṀO2,max) and hypoxia tolerance (Pcrit) through different combinations of Hb-O2 affinity and Gd. Our combined data identified novel patterns in gill and Hb characteristics between FW and SW fishes and our modelling approach provides mechanistic insight into the relationship between aerobic performance and species distribution ranges, generating novel hypotheses at the intersection of cardiorespiratory and ionoregulatory fish physiology.
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Affiliation(s)
- Till S Harter
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92093, USA
| | - Christian Damsgaard
- Zoophysiology, Department of Biology, Aarhus University, 8000 Aarhus, Denmark.,Aarhus Institute of Advanced Studies, Aarhus University, 8000 Aarhus, Denmark
| | - Matthew D Regan
- Département de sciences biologiques, Université de Montréal, Montreal, QC, Canada, H3T 1J4
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10
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Hvas M. Influence of photoperiod and protocol length on metabolic rate traits in ballan wrasse Labrus bergylta. JOURNAL OF FISH BIOLOGY 2022; 100:687-696. [PMID: 34928505 DOI: 10.1111/jfb.14981] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 12/15/2021] [Accepted: 12/16/2021] [Indexed: 06/14/2023]
Abstract
In this study, ballan wrasse Labrus bergylta were subjected to either a conventional 1-day or an extended 5-day respirometry protocol. Additionally, in the 5-day protocol the fish were subjected to a 12 h light-dark cycle to assess the effects of photoperiods on metabolic rates (ṀO2 ). Diurnal patterns in routine and resting ṀO2 were not observed, suggesting that circadian rhythms in metabolism largely are driven by activity patterns rather than being of endogenous origin. Moreover, lack of a detectable circadian ṀO2 may be an adaptation to lower costs of living in ballan wrasse. Protocol length influenced standard metabolic rates (SMR) where estimates decreased by 13% and 17% when using 48 h and 5 days, respectively, compared to 24 h. The maximum metabolic rate (MMR) and the derived absolute aerobic scope (MMR-SMR) were unaffected by protocol length. However, factorial scopes (MMR/SMR) were reduced from 8.5 to 6.4 in the 5-day protocol, showing that factorial scopes are more sensitive to how SMR are obtained. The critical oxygen tension (Pcrit ) was reduced from 15% PO2 in the 1-day group to 11% PO2 in the 5-day group. However, ṀO2 in response to decreasing PO2 was similar, which together with a similar oxygen extraction coefficient, α (ṀO2 /PO2 ), suggested that the higher Pcrit in the 1-day group was an artefact of overestimating SMR. Finally, α was 12% lower at MMR compared to at Pcrit , which either means that MMR was underestimated in proportion to this difference or that α is not constant in the entire PO2 range. In summary, this study found that a conventional 1-day respirometry protocol may overestimate SMR and thereby alter the derived Pcrit and aerobic scope, while α is unaffected by protocol length. Moreover, alternating light conditions in the absence of other stressors did not influence ṀO2 in ballan wrasse.
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Affiliation(s)
- Malthe Hvas
- Animal Welfare Research Group, Institute of Marine Research, Matre, Norway
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11
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Cochran JK, Orr SE, Buchwalter DB. Assessing the P crit in relation to temperature and the expression of hypoxia associated genes in the mayfly, Neocloeon triangulifer. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 808:151743. [PMID: 34826479 DOI: 10.1016/j.scitotenv.2021.151743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 11/08/2021] [Accepted: 11/13/2021] [Indexed: 06/13/2023]
Abstract
Hypoxia is a growing concern in aquatic ecosystems. Historically, scientists have used the Pcrit (the dissolved oxygen level below which an animal can no longer oxyregulate) to infer hypoxia tolerance across species. Here, we tested the hypothesis that the Pcrit is positively correlated with temperature in the mayfly, Neocloeon triangulifer. Cross-temperature comparisons showed a modest (r = 0.47), but significant (p < 0.0001) association between temperature and Pcrit despite relatively large interindividual variability (Coefficient of Variance (CV) = 39.9% at 18 °C). We used the expression of hypoxia-responsive genes EGL-9 (an oxygen sensing gene and modulator of HIF-1a activity) and LDH (a hypoxia indicator) to test whether oxygen partial pressure near the Pcrit stimulates expression of hypoxia-responsive genes. Neither gene was upregulated at oxygen levels above the estimated Pcrit, however, at or below the Pcrit estimates, expression of both genes was stimulated (~20- and ~3-fold change for EGL-9 and LDH, respectively). Finally, we evaluated the influence of hypoxic exposure time and pretreatment conditions on the mRNA expression levels of hypoxia-responsive genes. When larvae were exposed to a gradual reduction of DO, hypoxic gene expression was more robust than during instantaneous exposure to hypoxia. Our data provide modest support for traditional interpretation of the Pcrit as a physiologically meaningful shift from aerobic to anaerobic metabolism in N. triangulifer. However, we also discuss limitations of the Pcrit as a proxy measure of hypoxia tolerance at the species level.
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Affiliation(s)
- Jamie K Cochran
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, United States of America
| | - Sarah E Orr
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, United States of America
| | - David B Buchwalter
- Department of Biological Sciences, North Carolina State University, Raleigh, NC 27695, United States of America.
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12
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Heinrichs-Caldas W, de Almeida-Val VMF. Hypoxia tolerance in two amazon cichlids: mitochondrial respiration and cellular metabolism adjustments are result of species environmental preferences and distribution. FISH PHYSIOLOGY AND BIOCHEMISTRY 2021; 47:1759-1775. [PMID: 34480679 DOI: 10.1007/s10695-021-01000-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 08/08/2021] [Indexed: 06/13/2023]
Abstract
The amazon fishes' responses to hypoxia seem to be related to the Amazon basin diversity of aquatic environments, which present drastic daily and seasonal variations in the dissolved oxygen concentration. Among these fishes' adaptation to hypoxia, behavioral, metabolic, physiological, and biochemical responses are well known for some species. In this work, we aimed to identify how two different aquatic environments, normoxic forest streams and hypoxic lakes, dictate the responses to hypoxia for two cichlid species, Mesonauta festivus and Aequidens pallidus. In our results, we found that A. pallidus is less tolerant to hypoxia, which seems to be related to this animal's natural normoxic environment. Even though this species modulated the mitochondrial respiration in order to improve the oxygen use, it also showed a lower decrease in metabolic rate when exposed to hypoxia and no activation of the anaerobic metabolism. Instead, M. festivus showed a higher decrease in metabolic rate and an activation of the anaerobic metabolism. Our data reveal that the natural dissolved oxygen influences the hypoxia tolerance and the species' tolerance is related to its ability to perform metabolic depression. The interest results are the absence of mitochondrial respiration influences in these processes. The results observed with A. pallidus bring to light also the importance of preserving the forests, in which streams hold very specialized species acclimated to normoxia and lower temperature. The importance of hypoxia tolerance is, thus, important to keep fish assemblage and is thought to be a strong driver of fish biodiversity.
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Affiliation(s)
- Waldir Heinrichs-Caldas
- LEEM - Laboratório de Ecofisiologia e Evolução Molecular, Instituto Nacional de Pesquisas da Amazônia, Campus I, Manaus, Amazonas, Brazil.
| | - Vera Maria Fonseca de Almeida-Val
- LEEM - Laboratório de Ecofisiologia e Evolução Molecular, Instituto Nacional de Pesquisas da Amazônia, Campus I, Manaus, Amazonas, Brazil
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13
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Monteiro DA, Kalinin AL, Rantin FT, McKenzie DJ. Use of complex physiological traits as ecotoxicological biomarkers in tropical freshwater fishes. JOURNAL OF EXPERIMENTAL ZOOLOGY. PART A, ECOLOGICAL AND INTEGRATIVE PHYSIOLOGY 2021; 335:745-760. [PMID: 34529366 DOI: 10.1002/jez.2540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 07/21/2021] [Accepted: 08/02/2021] [Indexed: 06/13/2023]
Abstract
We review the use of complex physiological traits, of tolerance and performance, as biomarkers of the toxicological effects of contaminants in subtropical and tropical freshwater fishes. Such traits are growing in relevance due to climate change, as exposure to contaminants may influence the capacity of fishes to tolerate and perform in an increasingly stressful environment. We review the evidence that the critical oxygen level, a measure of hypoxia tolerance, provides a valuable biomarker of impacts of diverse classes of contaminants. When coupled with measures of cardiorespiratory variables, it can provide insight into mechanisms of toxicity. The critical thermal maximum, a simple measure of tolerance of acute warming, also provides a valuable biomarker despite a lack of understanding of its mechanistic basis. Its relative ease of application renders it useful in the rapid evaluation of multiple species, and in understanding how the severity of contaminant impacts depends upon prevailing environmental temperature. The critical swimming speed is a measure of exercise performance that is widely used as a biomarker in temperate species but very few studies have been performed on subtropical or tropical fishes. Overall, the review serves to highlight a critical lack of knowledge for subtropical and tropical freshwater fishes. There is a real need to expand the knowledge base and to use physiological biomarkers in support of decision making to manage tropical freshwater fish populations and their habitats, which sustain rich biodiversity but are under relentless anthropogenic pressure.
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Affiliation(s)
- Diana A Monteiro
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - Ana L Kalinin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - F Tadeu Rantin
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
| | - David J McKenzie
- Department of Physiological Sciences, Federal University of São Carlos (UFSCar), São Carlos, São Paulo, Brazil
- UMR Marbec, Univ. Montpellier, CNRS, IRD, Ifremer, Montpellier, France
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14
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Lau SC, Mehdi H, Bragg LM, Servos MR, Balshine S, Scott GR. Exposure to wastewater effluent disrupts hypoxia responses in killifish (Fundulus heteroclitus). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 284:117373. [PMID: 34077896 DOI: 10.1016/j.envpol.2021.117373] [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: 11/18/2020] [Revised: 05/05/2021] [Accepted: 05/12/2021] [Indexed: 06/12/2023]
Abstract
Hypoxia (low oxygen) often occurs in aquatic ecosystems that receive effluent from municipal wastewater treatment plants (WWTP). The combination of hypoxia and WWTP effluent could impair fish health, because WWTP effluent contains multiple contaminants that could disrupt the physiological pathways fish use to cope with hypoxia, but the interactive effects of these stressors on fish physiology are poorly understood. We have examined this issue by exposing mummichog killifish (Fundulus heteroclitus) to hypoxia (5 and 2 kPa O2) and/or 100% WWTP effluent for 21 days in a full factorial design. We then measured hypoxia tolerance, whole-animal metabolism, gill morphology, haematology, and tissue metabolites. In clean water, killifish responded to chronic hypoxia with improvements in hypoxia tolerance, as reflected by increases in time to loss of equilibrium at 0.5 kPa (tLOE). These improvements occurred in association with increases in the exposed surface of gill lamellae that resulted from a regression of interlamellar cell mass (ILCM). Concurrent exposure to wastewater attenuated the increases in tLOE and gill remodeling in chronic hypoxia, and nearly depleted brain glycogen stores. Therefore, exposure to WWTP effluent can disrupt the physiological mechanisms fish use to cope with chronic hypoxia and impair hypoxia tolerance. Our research suggests that the combination of stressors near WWTPs can have interactive effects on the physiology and health of fish.
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Affiliation(s)
- Samantha C Lau
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada
| | - Hossein Mehdi
- Department of Psychology, Neuroscience, and Behaviour, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada
| | - Leslie M Bragg
- Department of Biology, University of Waterloo, 200 University Ave. W, Waterloo, ON, N2L 3G1, Canada
| | - Mark R Servos
- Department of Biology, University of Waterloo, 200 University Ave. W, Waterloo, ON, N2L 3G1, Canada
| | - Sigal Balshine
- Department of Psychology, Neuroscience, and Behaviour, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada
| | - Graham R Scott
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4K1, Canada.
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15
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Braz-Mota S, Almeida-Val VMF. Ecological adaptations of Amazonian fishes acquired during evolution under environmental variations in dissolved oxygen: A review of responses to hypoxia in fishes, featuring the hypoxia-tolerant Astronotus spp. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2021; 335:771-786. [PMID: 34338442 DOI: 10.1002/jez.2531] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2021] [Revised: 06/25/2021] [Accepted: 07/12/2021] [Indexed: 11/06/2022]
Abstract
The Amazon Basin presents a dynamic regime of dissolved oxygen (DO) oscillations, which varies among habitats within the basin, including spatially, daily, and seasonally. Fish species inhabiting these environments have developed many physiological adaptations to deal with the frequent and periodic events of low (hypoxia), or no (anoxia) DO in the water. Cichlid fishes, especially the genus Astronotus (A. ocellatus and A. crassipinnis), are hypoxic-tolerant species that can survive in very low DO levels for long periods, while adults often inhabit places where DO is close to zero. The present review will focus on some metabolic adjustments that Amazonian fish use in response to hypoxic conditions, which include many strategies from behavioral, morphological, physiological, and biochemical strategies. These strategies include ASR (aerial surface respiration), lip expansion, branchial tissue remodeling, increases in glycolytic metabolism with the increase of blood glucose levels, and increases in anaerobic metabolism with increases of plasma lactate levels. Other groups over evolutionary time developed obligate aerial respiration with changes in pharyngeal and swim bladder vascularization as well as the development of a true lung. However, most species are water-breathing species, such as A. ocellatus and A. crassipinnis, which are detailed in this study because they are used as hypoxia-tolerant model fish. Herein, we draw together the literature data of the physiological mechanisms by which these species decrease aerobic metabolism and increase anaerobic metabolism to survive hypoxia. This is the first attempt to synthesize the physiological mechanisms of the hypoxia-tolerant Astronotus species.
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Affiliation(s)
- Susana Braz-Mota
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research in the Amazon, Manaus, Amazonas, Brazil
| | - Vera M F Almeida-Val
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research in the Amazon, Manaus, Amazonas, Brazil
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16
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Dubuc A, Collins GM, Coleman L, Waltham NJ, Rummer JL, Sheaves M. Association between physiological performance and short temporal changes in habitat utilisation modulated by environmental factors. MARINE ENVIRONMENTAL RESEARCH 2021; 170:105448. [PMID: 34438217 DOI: 10.1016/j.marenvres.2021.105448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/29/2021] [Revised: 08/12/2021] [Accepted: 08/13/2021] [Indexed: 06/13/2023]
Abstract
Temporal environmental variability causes behavioural and physiological responses in organisms that can affect their spatial location in time, and ultimately drive changes in population and community dynamics. Linking ecological changes with underlying environmental drivers is a complex task that can however be facilitated through the integration of physiology. Our overarching aim was to investigate the association between physiological performance and habitat utilisation patterns modulated by short temporal fluctuations in environmental factors. We used in situ monitoring data from a system experiencing extreme environmental fluctuations over a few hours and we selected four fish species with different habitat utilisation patterns across dissolved oxygen (DO) fluctuations: two commonly observed species (Siganus lineatus and Acanthopagrus pacificus), including at low DO (40 and 50% saturation, respectively), and two reef species (Heniochus acuminatus and Chaetodon vagabundus) never recorded below 70% saturation. We hypothesised that these patterns were associated to species' physiological performance in hypoxia. Therefore, we measured different metabolic variables (O2crit, incipient lethal oxygen (ILO), time to ILO, index of cumulative ambient oxygen deficit (O2deficit), maximum oxygen supply capacity (α)) using respirometry. Physiological performance differed among species and was intrinsically associated to habitat use patterns. S. lineatus had a lower O2crit than H. acuminatus, A. pacificus and C. vagabundus (13, 18.7, 20 and 20.2% saturation respectively). Additionally, S. lineatus and A. pacificus displayed better capacity for survival below O2crit than C. vagabundus and H. acuminatus (lower ILO, higher O2deficit and longer time to ILO) and higher α. Field monitoring data revealed that DO temporarily falls below species' O2crit and even ILO on most days, suggesting that short temporal variability in DO likely forces species to temporarily avoid harmful conditions, driving important changes in ecosystem structure over a few hours. Our results support the hypothesis that organismal physiology can provide insights into ecological changes occurring over a few hours as a result of environmental variability. Consequently, integrating physiology with ecological data at relevant temporal scales may help predict temporal shifts in ecosystems structure and functions to account for ecological patterns often overlooked and difficult to identify.
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Affiliation(s)
- Alexia Dubuc
- College of Science and Engineering, James Cook University, Townsville, Qld, Australia.
| | | | - Laura Coleman
- College of Science and Engineering, James Cook University, Townsville, Qld, Australia
| | - Nathan J Waltham
- College of Science and Engineering, James Cook University, Townsville, Qld, Australia; TropWATER, Townsville, Qld, Australia
| | - Jodie L Rummer
- College of Science and Engineering, James Cook University, Townsville, Qld, Australia; ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Qld, Australia
| | - Marcus Sheaves
- College of Science and Engineering, James Cook University, Townsville, Qld, Australia; TropWATER, Townsville, Qld, Australia
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17
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Hughes MC, Perry SF. Does blood flow limit acute hypoxia performance in larval zebrafish (Danio rerio)? J Comp Physiol B 2021; 191:469-478. [PMID: 33580284 DOI: 10.1007/s00360-020-01331-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 10/22/2020] [Accepted: 11/18/2020] [Indexed: 01/21/2023]
Abstract
Oxygen uptake (ṀO2) in larval zebrafish prior to maturation of the gill relies on cutaneous O2 transfer. Under normoxic conditions, rates of cutaneous O2 transfer are unaffected by haemoglobin availability but are diminished in fish lacking a functional circulatory system, suggesting that internal convection is critically involved in setting the resting ṀO2 in zebrafish larvae, even when relying on cutaneous O2 transfer. The reliance of ṀO2 on blood circulation led to the first objective of the current study, to determine whether loss of internal convection would reduce acute hypoxia performance (as determined by measuring critical PO2; Pcrit) in larval zebrafish under conditions of moderate hypoxia (PO2 = 55 mmHg) at 28.5 and 34 °C. Internal convection was eliminated by preventing development of blood vessels using morpholino knockdown of vascular endothelial growth factor (VEGF); these fish are termed VEGF morphants. Breathing frequency (fV) and heart rate (fH) also were measured (at 28.5 °C) to determine whether any detriment in performance might be linked to cardiorespiratory dysfunction. Although ṀO2 was reduced in the VEGF morphants, there was no significant effect on Pcrit at 28.5 °C. Raising temperature to 34 °C resulted in the VEGF morphants exhibiting a higher Pcrit than the shams, suggesting an impairment of hypoxia tolerance in the morphants at the higher temperature. The usual robust increase in fV during hypoxia was absent or attenuated in VEGF morphants at 4 and 5 days post fertilization (dpf), respectively. Resting fH was reduced in the VEGF morphants and unlike the sham fish, the morphants did not exhibit hypoxic tachycardia at 4 or 5 dpf. The number of cutaneous neuroepithelial cells (presumptive O2 chemoreceptors) was significantly higher in the VEGF morphants and thus the cardiorespiratory impairment in the morphants during hypoxia was unlikely related to inadequate peripheral O2 sensing.
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Affiliation(s)
- M C Hughes
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, K1N6N5, Canada
| | - S F Perry
- Department of Biology, University of Ottawa, 30 Marie Curie, Ottawa, ON, K1N6N5, Canada.
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18
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Seibel BA, Andres A, Birk MA, Burns AL, Shaw CT, Timpe AW, Welsh CJ. Oxygen supply capacity breathes new life into critical oxygen partial pressure (Pcrit). J Exp Biol 2021; 224:jeb.242210. [PMID: 33692079 DOI: 10.1242/jeb.242210] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2021] [Accepted: 03/01/2021] [Indexed: 12/11/2022]
Abstract
The critical oxygen partial pressure (Pcrit), typically defined as the PO2 below which an animal's metabolic rate (MR) is unsustainable, is widely interpreted as a measure of hypoxia tolerance. Here, Pcrit is defined as the PO2 at which physiological oxygen supply (α0) reaches its maximum capacity (α; µmol O2 g-1 h-1 kPa-1). α is a species- and temperature-specific constant describing the oxygen dependency of the maximum metabolic rate (MMR=PO2×α) or, equivalently, the MR dependence of Pcrit (Pcrit=MR/α). We describe the α-method, in which the MR is monitored as oxygen declines and, for each measurement period, is divided by the corresponding PO2 to provide the concurrent oxygen supply (α0=MR/PO2). The highest α0 value (or, more conservatively, the mean of the three highest values) is designated as α. The same value of α is reached at Pcrit for any MR regardless of previous or subsequent metabolic activity. The MR need not be constant (regulated), standardized or exhibit a clear breakpoint at Pcrit for accurate determination of α. The α-method has several advantages over Pcrit determination and non-linear analyses, including: (1) less ambiguity and greater accuracy, (2) fewer constraints in respirometry methodology and analysis, and (3) greater predictive power and ecological and physiological insight. Across the species evaluated here, α values are correlated with MR, but not Pcrit. Rather than an index of hypoxia tolerance, Pcrit is a reflection of α, which evolves to support maximum energy demands and aerobic scope at the prevailing temperature and oxygen level.
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Affiliation(s)
- Brad A Seibel
- College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
| | - Alyssa Andres
- College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
| | - Matthew A Birk
- College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
| | - Alexandra L Burns
- College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
| | - C Tracy Shaw
- College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
| | - Alexander W Timpe
- College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
| | - Christina J Welsh
- College of Marine Science, University of South Florida, St Petersburg, FL 33701, USA
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19
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Ackerly KL, Esbaugh AJ. The effects of temperature on oil-induced respiratory impairment in red drum (Sciaenops ocellatus). AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2021; 233:105773. [PMID: 33610857 DOI: 10.1016/j.aquatox.2021.105773] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 02/03/2021] [Accepted: 02/05/2021] [Indexed: 06/12/2023]
Abstract
The 2010 Deepwater Horizon (DWH) crude oil spill, among the largest environmental disasters in U.S. history, affected numerous economically important fishes. Exposure to crude oil can lead to reduced cardiac function, limiting oxygen transport, ATP production, and aerobic performance. However, crude oil exposure is not the only stressor that affects aerobic performance, and increasing environmental temperatures are known to significantly increase metabolic demands in fishes. As the DWH spill was active during warm summer months in the Gulf of Mexico, it is important to understand the combined effects of oil and temperature on a suite of metabolic parameters. Therefore, we investigated the effects of 24h crude oil exposure on the aerobic metabolism and hypoxia tolerance of red drum (Sciaenops ocellatus) following 3 week chronic exposure to four ecologically relevant temperatures (18 °C, 22 °C, 25 °C, 28 °C). Our results show that individuals acclimated to higher temperatures had significantly higher standard metabolic rate than individuals at lower temperatures, which resulted in significantly decreased critical oxygen threshold and reduced recovery from exercise. As predicted, crude oil exposure resulted in lower maximum metabolic rates (MMR) across the temperature range, and a significantly reduced ability to recover from exercise. The lowest temperature acclimation showed the smallest effect of oil on MMR, while the highest temperature showed the smallest effect on exercise recovery. Reduced respiratory performance and hypoxia tolerance are likely to have meaningful impacts on the fitness of red drum, especially with climate-induced temperature increases and continued oil exploration in the Gulf of Mexico.
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Affiliation(s)
- Kerri Lynn Ackerly
- The University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78373, United States.
| | - Andrew J Esbaugh
- The University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas, TX 78373, United States.
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20
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Does hypoxia-inducible factor 1α play a role in regulating cutaneous oxygen flux in larval zebrafish (Danio rerio)? J Comp Physiol B 2021; 191:645-655. [PMID: 33774721 DOI: 10.1007/s00360-021-01361-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 02/12/2021] [Accepted: 03/10/2021] [Indexed: 10/21/2022]
Abstract
Previous studies have demonstrated that hypoxia tolerance is improved in zebrafish (Danio rerio) larvae after prior exposure to lowered ambient O2 levels. Such improved hypoxia performance was attributed in part, to increased levels of hypoxia-inducible factor 1α (Hif-1α) exerting downstream effects on various physiological processes including promotion of trunk skin angiogenesis. Since O2 uptake ([Formula: see text]) in larvae is facilitated largely by O2 diffusion across the skin, enhanced cutaneous vascularization is expected to enhance [Formula: see text] during hypoxia and thus contribute to improved hypoxia tolerance. In this study, we used the scanning micro-optrode technique together with quantification of cutaneous vascularity in wild types (WT) and Hif-1α knockouts (hif1aa-/-ab-/-) to test the hypothesis that improved hypoxia tolerance after hypoxia acclimation in larvae at 4 or 7 days post-fertilization (dpf) was associated with Hif-1α-dependent increases in skin vascularity and regional cutaneous O2 fluxes (JO2). Hypoxia tolerance, as determined by measurements of critical PO2 (Pcrit), was unaltered by hypoxia pre-exposure in larvae at 4 dpf and there were no significant differences in Pcrit between WT and hif1aa-/-ab-/- larvae at this developmental stage. However, at 7 dpf there was a significant effect of genotype with WT larvae showing a lower Pcrit than hif1aa-/-ab-/- larvae, an effect that was being driven by a reduced Pcrit in the WT larvae after hypoxia pre-exposure (19.2 ± 1.9 mmHg) compared to hif1aa-/-ab-/- fish (35.5 ± 3.5 mmHg). Regardless of genotype, pre-exposure status or developmental age, JO2 decreased along the body in the anterior-to-posterior direction. Neither hypoxia pre-exposure nor genotype affected JO2 at any region along the body. The lack of any effect of hypoxia pre-exposure or genotype on JO2 was consistent with the lack of any effect on skin vascularity as measured in Tg(fli1:EGFP)yl transgenic larvae. Thus, the decreased hypoxia performance (increased Pcrit) at 7 dpf in the hif1aa-/-ab-/- larvae did not appear to be reliant on changes in trunk vascularity or cutaneous O2 diffusion.
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21
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Collins M, Truebano M, Verberk WCEP, Spicer JI. Do aquatic ectotherms perform better under hypoxia after warm acclimation? J Exp Biol 2021; 224:224/3/jeb232512. [PMID: 33542094 DOI: 10.1242/jeb.232512] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Aquatic animals increasingly encounter environmental hypoxia due to climate-related warming and/or eutrophication. Although acute warming typically reduces performance under hypoxia, the ability of organisms to modulate hypoxic performance via thermal acclimation is less understood. Here, we review the literature and ask whether hypoxic performance of aquatic ectotherms improves following warm acclimation. Interpretation of thermal acclimation effects is limited by reliance on data from experiments that are not designed to directly test for beneficial or detrimental effects on hypoxic performance. Most studies have tested hypoxic responses exclusively at test temperatures matching organisms' acclimation temperatures, precluding the possibility of distinguishing between acclimation and acute thermal effects. Only a few studies have applied appropriate methodology to identify beneficial thermal acclimation effects on hypoxic performance, i.e. acclimation to different temperatures prior to determining hypoxic responses at standardised test temperatures. These studies reveal that acute warming predominantly impairs hypoxic performance, whereas warm acclimation tends to be either beneficial or have no effect. If this generalises, we predict that warm-acclimated individuals in some species should outperform non-acclimated individuals under hypoxia. However, acclimation seems to only partially offset acute warming effects; therefore, aquatic ectotherms will probably display overall reduced hypoxic performance in the long term. Drawing on the appropriate methodology, future studies can quantify the ability of organisms to modulate hypoxic performance via (reversible) thermal acclimation and unravel the underlying mechanisms. Testing whether developmental acclimation and multigenerational effects allow for a more complete compensation is essential to allow us to predict species' resilience to chronically warmer, hypoxic environments.
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Affiliation(s)
- Michael Collins
- Marine Biology and Ecology Research Centre, Plymouth University, Drake Circus, PL4 8AA, UK
| | - Manuela Truebano
- Marine Biology and Ecology Research Centre, Plymouth University, Drake Circus, PL4 8AA, UK
| | - Wilco C E P Verberk
- Department of Animal Ecology and Physiology, Institute for Water and Wetland Research, Radboud University, 6500 GL Nijmegen, The Netherlands
| | - John I Spicer
- Marine Biology and Ecology Research Centre, Plymouth University, Drake Circus, PL4 8AA, UK
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22
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Reemeyer JE, Rees BB. Plasticity, repeatability and phenotypic correlations of aerobic metabolic traits in a small estuarine fish. J Exp Biol 2020; 223:jeb.228098. [PMID: 32587069 DOI: 10.1101/2020.05.01.072587] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 06/10/2020] [Indexed: 05/21/2023]
Abstract
Standard metabolic rate (SMR), maximum metabolic rate (MMR), absolute aerobic scope (AAS) and critical oxygen tension (Pcrit) were determined for the Gulf killifish, Fundulus grandis, an ecologically dominant estuarine fish, acclimated to lowered salinity, elevated temperature and lowered oxygen concentration. Acclimation to low salinity resulted in a small, but significant, elevation of Pcrit (suggesting lower tolerance of hypoxia); acclimation to elevated temperature increased SMR, MMR, AAS and Pcrit; acclimation to low oxygen led to a small increase in SMR, but substantial decreases in MMR, AAS and Pcrit Variation in these metabolic traits among individuals was consistent and repeatable when measured during multiple control exposures over 7 months. Trait repeatability was unaffected by acclimation condition, suggesting that repeatability of these traits is not context dependent. There were significant phenotypic correlations between specific metabolic traits: SMR was positively correlated with MMR and Pcrit; MMR was positively correlated with AAS; and AAS was negatively correlated with Pcrit In general, within-individual variation contributed more than among-individual variation to these phenotypic correlations. The effects of acclimation on these traits demonstrate that aerobic metabolism is plastic and influenced by the conditions experienced by these fish in the dynamic habitats in which they occur; however, the repeatability of these traits and the correlations among them suggest that these traits change in ways that maintain the rank order of performance among individuals across a range of environmental variation.
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Affiliation(s)
- Jessica E Reemeyer
- University of New Orleans, Department of Biological Sciences, 2000 Lakeshore Drive, New Orleans, LA 70148, USA
| | - Bernard B Rees
- University of New Orleans, Department of Biological Sciences, 2000 Lakeshore Drive, New Orleans, LA 70148, USA
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23
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Reemeyer JE, Rees BB. Plasticity, repeatability and phenotypic correlations of aerobic metabolic traits in a small estuarine fish. J Exp Biol 2020; 223:jeb228098. [PMID: 32587069 DOI: 10.1242/jeb.228098] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2020] [Accepted: 06/10/2020] [Indexed: 12/14/2022]
Abstract
Standard metabolic rate (SMR), maximum metabolic rate (MMR), absolute aerobic scope (AAS) and critical oxygen tension (Pcrit) were determined for the Gulf killifish, Fundulus grandis, an ecologically dominant estuarine fish, acclimated to lowered salinity, elevated temperature and lowered oxygen concentration. Acclimation to low salinity resulted in a small, but significant, elevation of Pcrit (suggesting lower tolerance of hypoxia); acclimation to elevated temperature increased SMR, MMR, AAS and Pcrit; acclimation to low oxygen led to a small increase in SMR, but substantial decreases in MMR, AAS and Pcrit Variation in these metabolic traits among individuals was consistent and repeatable when measured during multiple control exposures over 7 months. Trait repeatability was unaffected by acclimation condition, suggesting that repeatability of these traits is not context dependent. There were significant phenotypic correlations between specific metabolic traits: SMR was positively correlated with MMR and Pcrit; MMR was positively correlated with AAS; and AAS was negatively correlated with Pcrit In general, within-individual variation contributed more than among-individual variation to these phenotypic correlations. The effects of acclimation on these traits demonstrate that aerobic metabolism is plastic and influenced by the conditions experienced by these fish in the dynamic habitats in which they occur; however, the repeatability of these traits and the correlations among them suggest that these traits change in ways that maintain the rank order of performance among individuals across a range of environmental variation.
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Affiliation(s)
- Jessica E Reemeyer
- University of New Orleans, Department of Biological Sciences, 2000 Lakeshore Drive, New Orleans, LA 70148, USA
| | - Bernard B Rees
- University of New Orleans, Department of Biological Sciences, 2000 Lakeshore Drive, New Orleans, LA 70148, USA
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24
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Gamperl AK. Experimentally addressing and evaluating the impact of human activities on marine organisms. CAN J ZOOL 2020. [DOI: 10.1139/cjz-2020-0044] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- A. Kurt Gamperl
- Department of Ocean Sciences, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
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25
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Borowiec BG, Hoffman RD, Hess CD, Galvez F, Scott GR. Interspecific variation in hypoxia tolerance and hypoxia acclimation responses in killifish from the family Fundulidae. J Exp Biol 2020; 223:jeb209692. [PMID: 31988166 PMCID: PMC7044458 DOI: 10.1242/jeb.209692] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 01/20/2020] [Indexed: 01/25/2023]
Abstract
Hypoxia is a pervasive stressor in aquatic environments, and both phenotypic plasticity and evolutionary adaptation could shape the ability to cope with hypoxia. We investigated evolved variation in hypoxia tolerance and the hypoxia acclimation response across fundulid killifishes that naturally experience different patterns of hypoxia exposure. We compared resting O2 consumption rate (ṀO2 ), and various indices of hypoxia tolerance [critical O2 tension (Pcrit), regulation index (RI), O2 tension (PO2 ) at loss of equilibrium (PLOE) and time to LOE (tLOE) at 0.6 kPa O2] in Fundulus confluentus, Fundulus diaphanus, Fundulus heteroclitus, Fundulus rathbuni, Lucania goodei and Lucania parva We examined the effects of chronic (28 days) exposure to constant hypoxia (2 kPa) or nocturnal intermittent hypoxia (12 h normoxia:12 h hypoxia) in a subset of species. Some species exhibited a two-breakpoint model in ṀO2 caused by early, modest declines in ṀO2 in moderate hypoxia. We found that hypoxia tolerance varied appreciably across species: F. confluentus was the most tolerant (lowest PLOE and Pcrit, longest tLOE), whereas F. rathbuni and F. diaphanus were the least tolerant. However, there was not a consistent pattern of interspecific variation for different indices of hypoxia tolerance, with or without taking phylogenetic relatedness into account, probably because these different indices are underlain by partially distinct mechanisms. Hypoxia acclimation generally improved hypoxia tolerance, but the magnitude of plasticity and responsiveness to different hypoxia patterns varied interspecifically. Our results therefore suggest that hypoxia tolerance is a complex trait that is best appreciated by considering multiple indices of tolerance.
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Affiliation(s)
| | - Ryan D Hoffman
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Chelsea D Hess
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Fernando Galvez
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Graham R Scott
- Department of Biology, McMaster University, Hamilton, ON, Canada, L8S 4K1
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26
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Moulton TL, Chapman LJ, Krahe R. Effects of hypoxia on aerobic metabolism and active electrosensory acquisition in the African weakly electric fish Marcusenius victoriae. JOURNAL OF FISH BIOLOGY 2020; 96:496-505. [PMID: 31845335 DOI: 10.1111/jfb.14234] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2019] [Accepted: 12/13/2019] [Indexed: 06/10/2023]
Abstract
Environmental hypoxia has effected numerous and well-documented anatomical, physiological and behavioural adaptations in fishes. Comparatively little is known about hypoxia's impacts on sensing because it is difficult to quantify sensory acquisition in vivo. Weakly electric fishes, however, rely heavily on an easily-measurable sensory modality-active electric sensing-whereby individuals emit and detect electric organ discharges (EODs). In this study, hypoxia tolerance of a mormyrid weakly electric fish, Marcusenius victoriae, was assessed by examining both its metabolic and EOD rates using a critical threshold (pcrit ) paradigm. The routine metabolic rate was 1.42 mg O2 h-1 , and the associated critical oxygen tension was 14.34 mmHg. Routine EOD rate was 5.68 Hz with an associated critical tension of 15.14 mmHg. These metabolic indicators of hypoxia tolerance measured in this study were consistent with those in previous studies on M. victoriae and other weakly electric fishes. Furthermore, our results suggest that some aerobic processes may be reduced in favour of maintaining the EOD rate under extreme hypoxia. These findings underscore the importance of the active electrosensory modality to these hypoxia-tolerant fish.
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Affiliation(s)
- Tyler L Moulton
- Department of Biology, McGill University, Montreal, Quebec, Canada
- Department of Biology, Hamilton College, Clinton, New York, USA
| | - Lauren J Chapman
- Department of Biology, McGill University, Montreal, Quebec, Canada
| | - Rüdiger Krahe
- Department of Biology, McGill University, Montreal, Quebec, Canada
- Institut für Biologie, Humboldt-Universität zu Berlin, Berlin, Germany
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27
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Ultsch GR, Regan MD. The utility and determination of P crit in fishes. ACTA ACUST UNITED AC 2019; 222:222/22/jeb203646. [PMID: 31722971 DOI: 10.1242/jeb.203646] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The critical O2 tension (P crit) is the lowest P O2 at which an animal can maintain some benchmark rate of O2 uptake (Ṁ O2 ). This P O2 has long served as a comparator of hypoxia tolerance in fishes and aquatic invertebrates, but its usefulness in this role, particularly when applied to fishes, has recently been questioned. We believe that P crit remains a useful comparator of hypoxia tolerance provided it is determined using the proper methods and hypoxia tolerance is clearly defined. Here, we review the available methods for each of the three steps of P crit determination: (1) measuring the most appropriate benchmark Ṁ O2 state for P crit determination (Ṁ O2,std, the Ṁ O2 required to support standard metabolic rate); (2) reducing water P O2 ; and (3) calculating P crit from the Ṁ O2 versus P O2 curve. We make suggestions on best practices for each step and for how to report P crit results to maximize their comparative value. We also discuss the concept of hypoxia tolerance and how P crit relates to a fish's overall hypoxia tolerance. When appropriate methods are used, P crit provides useful comparative physiological and ecological information about the aerobic contributions to a fish's hypoxic survival. When paired with other hypoxia-related physiological measurements (e.g. lactate accumulation, calorimetry-based measurements of metabolic depression, loss-of-equilibrium experiments), P crit contributes to a comprehensive understanding of how a fish combines aerobic metabolism, anaerobic metabolism and metabolic depression in an overall strategy for hypoxia tolerance.
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Affiliation(s)
- Gordon R Ultsch
- Department of Biology, University of Florida, Gainesville, FL 32611, USA
| | - Matthew D Regan
- Department of Comparative Biosciences, University of Wisconsin-Madison, Madison, WI 53706, USA
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28
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Negrete B, Esbaugh AJ. A methodological evaluation of the determination of critical oxygen threshold in an estuarine teleost. Biol Open 2019; 8:bio.045310. [PMID: 31649119 PMCID: PMC6899028 DOI: 10.1242/bio.045310] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
One measure of hypoxia tolerance is the critical oxygen threshold, Pcrit, which is the point where standard metabolism can no longer be maintained through aerobic processes. Traditionally, Pcrit was determined using closed respirometry, whereby the fish's respiration naturally lowered O2. More recently, intermittent flow techniques have been adopted, where N2 is used to displace O2, which ostensibly reduces end-product build-up. This study used a paired design on the marine teleost, red drum. Pcrit is comparable between closed (4.6±0.2 kPa; mean±s.e.m.) and intermittent flow (4.4±0.2 kPa; mean±s.e.m.) respirometry. pCO2, ammonia and pH changes within the chamber were measured prior to the onset of Pcrit and at the end of a typical Pcrit trial and revealed changes in water chemistry in both closed and intermittent flow. Pcrit values were similar in both methods of hypoxia induction regardless of subsequent water chemistry changes that occurred in both methods. Summary: The two leading methods of measuring the critical oxygen threshold in fishes are similar in their estimations, regardless of changes to water chemistry.
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Affiliation(s)
- Benjamin Negrete
- Department of Marine Science, Marine Science Institute, The University of Texas at Austin, Port Aransas, TX 78373, USA
| | - Andrew J Esbaugh
- Department of Marine Science, Marine Science Institute, The University of Texas at Austin, Port Aransas, TX 78373, USA
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29
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Clarke SB, Chapman LJ, Krahe R. The effect of normoxia exposure on hypoxia tolerance and sensory sampling in a swamp-dwelling mormyrid fish. Comp Biochem Physiol A Mol Integr Physiol 2019; 240:110586. [PMID: 31648062 DOI: 10.1016/j.cbpa.2019.110586] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2019] [Revised: 09/22/2019] [Accepted: 09/23/2019] [Indexed: 11/27/2022]
Abstract
Effects of energetic limitations on the performance of sensory systems are generally difficult to quantify. Weakly electric fishes provide an ideal model system to quantify the effects of metabolic stressors on sensory information acquisition, because they use an active-sensing strategy that permits easy measurement of the sensing effort. These fishes discharge an electric signal and sense perturbations of the resulting electric field. We used the mormyrid Petrocephalus degeni to quantify the relationship between routine metabolic rate and the rate of sensory sampling (rate of electric organ discharge, EOD) while under progressive hypoxia by quantifying the critical oxygen tension (PC-MR) and the critical electric organ discharge threshold (PC-EOD). PC-MR was significantly higher in fish acclimated to normoxia for over 40 days compared to animals tested within 1-5 days of capture from a hypoxic swamp, which suggests high costs of maintaining hypoxia tolerance; however, there was no acclimation effect on PC-EOD. All P. degeni reached their PC-EOD prior to their PC-MR. However, below the respective critical tension value, EOD rate decreased more gradually than the metabolic rate suggesting that the fish were increasing the proportion of their energy budget allocated to acquiring sensory information as dissolved-oxygen levels dropped. Trade-offs between sensory sampling and other physiological functions are also suggested by the increase in routine EOD rate with long-term normoxia acclimation, in contrast to metabolic rate, which showed no significant changes. These results highlight the relationship between sensory sampling and metabolic rate in response to progressive hypoxia and the plasticity of hypoxia tolerance.
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Affiliation(s)
- Shelby B Clarke
- Department of Biology, McGill University, 1205 Ave du Docteur-Penfield, Montreal, QC H3A1B1, Canada.
| | - Lauren J Chapman
- Department of Biology, McGill University, 1205 Ave du Docteur-Penfield, Montreal, QC H3A1B1, Canada.
| | - Rüdiger Krahe
- Department of Biology, McGill University, 1205 Ave du Docteur-Penfield, Montreal, QC H3A1B1, Canada; Humboldt-Universität zu Berlin, Institute of Biology, Unter den Linden 6, 10099 Berlin, Germany.
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30
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Montgomery DW, Simpson SD, Engelhard GH, Birchenough SNR, Wilson RW. Rising CO 2 enhances hypoxia tolerance in a marine fish. Sci Rep 2019; 9:15152. [PMID: 31641181 PMCID: PMC6805886 DOI: 10.1038/s41598-019-51572-4] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2019] [Accepted: 09/25/2019] [Indexed: 11/09/2022] Open
Abstract
Global environmental change is increasing hypoxia in aquatic ecosystems. During hypoxic events, bacterial respiration causes an increase in carbon dioxide (CO2) while oxygen (O2) declines. This is rarely accounted for when assessing hypoxia tolerances of aquatic organisms. We investigated the impact of environmentally realistic increases in CO2 on responses to hypoxia in European sea bass (Dicentrarchus labrax). We conducted a critical oxygen (O2crit) test, a common measure of hypoxia tolerance, using two treatments in which O2 levels were reduced with constant ambient CO2 levels (~530 µatm), or with reciprocal increases in CO2 (rising to ~2,500 µatm). We also assessed blood acid-base chemistry and haemoglobin-O2 binding affinity of sea bass in hypoxic conditions with ambient (~650 μatm) or raised CO2 (~1770 μatm) levels. Sea bass exhibited greater hypoxia tolerance (~20% reduced O2crit), associated with increased haemoglobin-O2 affinity (~32% fall in P50) of red blood cells, when exposed to reciprocal changes in O2 and CO2. This indicates that rising CO2 which accompanies environmental hypoxia facilitates increased O2 uptake by the blood in low O2 conditions, enhancing hypoxia tolerance. We recommend that when impacts of hypoxia on aquatic organisms are assessed, due consideration is given to associated environmental increases in CO2.
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Affiliation(s)
- Daniel W Montgomery
- Bioscience Department, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
| | - Stephen D Simpson
- Bioscience Department, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Georg H Engelhard
- Centre for Environment, Fisheries & Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT, UK
- School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Silvana N R Birchenough
- Centre for Environment, Fisheries & Aquaculture Science (Cefas), Pakefield Road, Lowestoft, NR33 0HT, UK
| | - Rod W Wilson
- Bioscience Department, College of Life and Environmental Sciences, University of Exeter, Exeter, UK.
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31
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Reemeyer JE, Rees BB. Standardizing the determination and interpretation of P crit in fishes. ACTA ACUST UNITED AC 2019; 222:jeb.210633. [PMID: 31511343 DOI: 10.1242/jeb.210633] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2019] [Accepted: 09/06/2019] [Indexed: 12/30/2022]
Abstract
The critical oxygen tension (P crit) for fishes is the oxygen level below which the rate of oxygen consumption (Ṁ O2 ) becomes dependent upon ambient oxygen partial pressure (P O2 ). We compare multiple curve-fitting approaches to estimate P crit of the Gulf killifish, Fundulus grandis, during closed and intermittent-flow respirometry. Fitting two line segments of Ṁ O2 versus P O2 produced high and variable estimates of P crit, as did nonlinear regression using a hyperbolic (Michaelis-Menten) function. Using nonlinear regression fit to an exponential (modified Weibull) function, or linear regression of Ṁ O2 versus P O2 at low P O2 , and determining P crit as the P O2 when Ṁ O2 equals standard metabolic rate (SMR) yielded values that were consistent across fish and among experimental trials. The magnitude of the difference in P crit determined by alternative calculation methods exceeded the differences determined in closed and intermittent-flow respirometry, highlighting the need to standardize analytical as well as experimental approaches in determining P crit.
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Affiliation(s)
- Jessica E Reemeyer
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
| | - Bernard B Rees
- Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA
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32
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Schwieterman GD, Crear DP, Anderson BN, Lavoie DR, Sulikowski JA, Bushnell PG, Brill RW. Combined Effects of Acute Temperature Change and Elevated pCO 2 on the Metabolic Rates and Hypoxia Tolerances of Clearnose Skate ( Rostaraja eglanteria), Summer Flounder ( Paralichthys dentatus), and Thorny Skate ( Amblyraja radiata). BIOLOGY 2019; 8:biology8030056. [PMID: 31357558 PMCID: PMC6783964 DOI: 10.3390/biology8030056] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 07/14/2019] [Accepted: 07/18/2019] [Indexed: 01/02/2023]
Abstract
Understanding how rising temperatures, ocean acidification, and hypoxia affect the performance of coastal fishes is essential to predicting species-specific responses to climate change. Although a population's habitat influences physiological performance, little work has explicitly examined the multi-stressor responses of species from habitats differing in natural variability. Here, clearnose skate (Rostaraja eglanteria) and summer flounder (Paralichthys dentatus) from mid-Atlantic estuaries, and thorny skate (Amblyraja radiata) from the Gulf of Maine, were acutely exposed to current and projected temperatures (20, 24, or 28 °C; 22 or 30 °C; and 9, 13, or 15 °C, respectively) and acidification conditions (pH 7.8 or 7.4). We tested metabolic rates and hypoxia tolerance using intermittent-flow respirometry. All three species exhibited increases in standard metabolic rate under an 8 °C temperature increase (Q10 of 1.71, 1.07, and 2.56, respectively), although this was most pronounced in the thorny skate. At the lowest test temperature and under the low pH treatment, all three species exhibited significant increases in standard metabolic rate (44-105%; p < 0.05) and decreases in hypoxia tolerance (60-84% increases in critical oxygen pressure; p < 0.05). This study demonstrates the interactive effects of increasing temperature and changing ocean carbonate chemistry are species-specific, the implications of which should be considered within the context of habitat.
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Affiliation(s)
- Gail D Schwieterman
- Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062, USA.
| | - Daniel P Crear
- Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062, USA
| | - Brooke N Anderson
- Marine Sciences Department, University of New England, Biddeford, ME 04005, USA
| | - Danielle R Lavoie
- Department of Biology, Marine Biology, and Environmental Science, Roger Williams University, Bristol, RI 02809, USA
| | - James A Sulikowski
- School of Mathematical & Natural Sciences, Arizona State University, Glendale, AZ 85306, USA
| | - Peter G Bushnell
- Department of Biological Sciences, Indiana University South Bend, South Bend, IN, 46615, USA
| | - Richard W Brill
- Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, VA 23062, USA
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