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Harter TS, Smith EA, Salmerón C, Thies AB, Delgado B, Wilson RW, Tresguerres M. Soluble adenylyl cyclase is an acid-base sensor in rainbow trout red blood cells that regulates intracellular pH and haemoglobin-oxygen binding. Acta Physiol (Oxf) 2024:e14205. [PMID: 39031444 DOI: 10.1111/apha.14205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Revised: 06/12/2024] [Accepted: 07/04/2024] [Indexed: 07/22/2024]
Abstract
AIM To identify the physiological role of the acid-base sensing enzyme, soluble adenylyl cyclase (sAC), in red blood cells (RBC) of the model teleost fish, rainbow trout. METHODS We used: (i) super-resolution microscopy to determine the subcellular location of sAC protein; (ii) live-cell imaging of RBC intracellular pH (pHi) with specific sAC inhibition (KH7 or LRE1) to determine its role in cellular acid-base regulation; (iii) spectrophotometric measurements of haemoglobin-oxygen (Hb-O2) binding in steady-state conditions; and (iv) during simulated arterial-venous transit, to determine the role of sAC in systemic O2 transport. RESULTS Distinct pools of sAC protein were detected in the RBC cytoplasm, at the plasma membrane and within the nucleus. Inhibition of sAC decreased the setpoint for RBC pHi regulation by ~0.25 pH units compared to controls, and slowed the rates of RBC pHi recovery after an acid-base disturbance. RBC pHi recovery was entirely through the anion exchanger (AE) that was in part regulated by HCO3 --dependent sAC signaling. Inhibition of sAC decreased Hb-O2 affinity during a respiratory acidosis compared to controls and reduced the cooperativity of O2 binding. During in vitro simulations of arterial-venous transit, sAC inhibition decreased the amount of O2 that is unloaded by ~11%. CONCLUSION sAC represents a novel acid-base sensor in the RBCs of rainbow trout, where it participates in the modulation of RBC pHi and blood O2 transport though the regulation of AE activity. If substantiated in other species, these findings may have broad implications for our understanding of cardiovascular physiology in vertebrates.
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Affiliation(s)
- Till S Harter
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Emma A Smith
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Cristina Salmerón
- Department of Pharmacology, University of California San Diego, La Jolla, California, USA
| | - Angus B Thies
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Bryan Delgado
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
| | - Rod W Wilson
- Biosciences Department, College of Life and Environmental Sciences, University of Exeter, Exeter, UK
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, USA
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2
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Kämmer N, Reimann T, Braunbeck T. Neurotoxic pesticides change respiratory parameters in early gill-breathing, but not in skin-breathing life-stages of zebrafish (Danio rerio). AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2024; 267:106831. [PMID: 38244448 DOI: 10.1016/j.aquatox.2024.106831] [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: 10/27/2023] [Revised: 12/31/2023] [Accepted: 01/07/2024] [Indexed: 01/22/2024]
Abstract
Neurotoxic compounds can interfere with active gill ventilation in fish, which might lead to premature death in adult fish, but not in skin-breathing embryos of zebrafish, since these exclusively rely on passive diffusion across the skin. Regarding lethality, this respiratory failure syndrome (RFS) has been discussed as one of the main reasons for the higher sensitivity of adult fish in the acute fish toxicity test (AFT), if compared to embryos in the fish embryo toxicity test (FET). To further elucidate the relationship between the onset of gill respiration and death by a neurotoxic mode of action, a comparative study into oxygen consumption (MO2), breathing frequency (fv) and amplitude (fampl) was performed with 4 d old skin-breathing and 12 d old early gill-breathing zebrafish. Neurotoxic model substances with an LC50 FET/AFT ratio of > 10 were used: chlorpyrifos, permethrin, aldicarb, ziram, and fluoxetine. Exposure to hypoxia served as a positive control, whereas aniline was tested as an example of a narcotic substance interfering non-specifically with gill membranes. In 12 d old larvae, all substances caused an increase in MO2, fv and partly fampl, whereas effects were minor in 4 d old embryos. An increase of fv in 4 d old embryos following exposure to chlorpyrifos, aldicarb and hypoxia could not be correlated with an increased MO2 and might be attributed either to (1) to the successfully postponed decrease of arterial partial pressure of oxygen (PO2) through support of skin respiration by increased fv, (2) to an unspecific stimulation of the sphincter muscles at the base of the gill filaments, or (3) to the establishment of oxygen sensing for later stages. In gill-breathing 12 d old zebrafish, a concentration-dependent increase of fv was detected for aniline and chlorpyrifos, whereas for aldicarb, fluoxetine and permethrin, a decline of fv at higher substance concentrations was measured, most likely due to the onset of paralysis and/or fatigue of the gill filament sphincter muscles. Since alterations of fv serve to postpone the decrease in arterial PO2 and MO2 increased with decreasing fv, the respiratory failure syndrome could clearly be demonstrated in 12 d old zebrafish larvae. Passive respiration across the skin in zebrafish embryos could thus be confirmed as a probable reason for the lower sensitivity of early life-stages to neurotoxicants. Integration of respiratory markers into existing testing protocols with non-protected developmental stages such as embryos might help to not underestimate the toxicity of early life-stages of fish.
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Affiliation(s)
- Nadine Kämmer
- Aquatic Ecology and Toxicology Section, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, D-69210, Heidelberg, Germany.
| | - Tanja Reimann
- Aquatic Ecology and Toxicology Section, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, D-69210, Heidelberg, Germany
| | - Thomas Braunbeck
- Aquatic Ecology and Toxicology Section, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, D-69210, Heidelberg, Germany.
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Onukwufor JO, Somo DA, Richards JG, Wood CM. Osmo-respiratory compromise in the mosshead sculpin (Clinocottus globiceps): effects of temperature, hypoxia, and re-oxygenation on rates of diffusive water flux and oxygen uptake. FISH PHYSIOLOGY AND BIOCHEMISTRY 2023; 49:853-866. [PMID: 37526893 DOI: 10.1007/s10695-023-01226-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Accepted: 07/28/2023] [Indexed: 08/02/2023]
Abstract
In nature, mosshead sculpins (Clinocottus globiceps) are challenged by fluctuations in temperature and oxygen levels in their environment. However, it is unclear how mosshead sculpins modulate the permeability of their branchial epithelia to water and O2 in response to temperature or hypoxia stress. Acute decrease in temperature from 13 to 6 oC reduced diffusive water flux rate by 22% and ṀO2 by 51%, whereas acute increase in temperature from 13 to 25 oC increased diffusive water flux rate by 217% and ṀO2 by 140%, yielding overall Q10 values of 2.08 and 2.47 respectively. Acute reductions in oxygen tension from >95% to 20% or 10% air saturation did not impact diffusive water flux rates, however, ṀO2 was reduced significantly by 36% and 65% respectively. During 1-h or 3-h recovery periods diffusive water flux rates were depressed while ṀO2 exhibited overshoots beyond the normoxic control level. Many responses differed from those seen in our parallel earlier study on the tidepool sculpin, a cottid with similar hypoxia tolerance but much smaller gill area that occupies a similar environment. Overall, our data suggest that during temperature stress, diffusive water flux rates and ṀO2 follow the traditional osmo-respiratory compromise pattern, but during hypoxia and re-oxygenation stress, diffusive water flux rates are decoupled from ṀO2.
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Affiliation(s)
- John O Onukwufor
- Department of Zoology, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
- Department of Pharmacology and Physiology, University of Rochester Medical Center, Rochester, NY, 14642, USA.
| | - Derek A Somo
- 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
| | - Chris M Wood
- Department of Zoology, The University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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Kämmer N, Reimann T, Ovcharova V, Braunbeck T. A novel automated method for the simultaneous detection of breathing frequency and amplitude in zebrafish (Danio rerio) embryos and larvae. AQUATIC TOXICOLOGY (AMSTERDAM, NETHERLANDS) 2023; 258:106493. [PMID: 36963131 DOI: 10.1016/j.aquatox.2023.106493] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2023] [Revised: 03/09/2023] [Accepted: 03/10/2023] [Indexed: 06/18/2023]
Abstract
Stress responses of fish to disruption of oxygen homeostasis include adjusted oxygen consumption rate (MO2) as well as the hyperventilation consisting of changes in breathing frequency (fv) and amplitude (fampl). However, studying the HVR in very small organisms such as zebrafish (Danio rerio) embryos and larvae is challenging, and breathing movements (i.e., fv) are usually manually counted, which is time- and human resource-intense, error-prone and does not provide information on the amplitude of breathing movements of the response, the breathing amplitude (fampl). Hence, in the present study, a new automated method was developed to simultaneously measure fv and fampl in small zebrafish embryos and larvae with the computer software DanioScope™. To compare HVR strategies at different life-stages of zebrafish and the physiologically linked MO2, hatched 4 d old embryos and early gill-breathing 12 d old larvae were treated with the HVR-inducing neurotoxic compound lindane (γ-hexachlorocyclohexane; γ-HCH) as a model substance. Comparison of manually counted fv with fv data measured by DanioScope™ at both life-stages showed high to moderate agreement between the two methods with respect to fv in control fish and in fish treated with lower lindane concentrations (3 - 18% deviation at 25 µg/L γ-HCH). With increasing lindane concentrations (100 and 400 µg/L γ-HCH), however, manual counts showed an average underestimation of fv by up to 30%, mainly due to very fast, rapidly successive, and indistinct movements of the fish, which cannot be properly detected by manual counts. Automated measurement thus proved significantly more sensitive, although several pre- and post-processing steps are needed. The improved automated detection of fv and the first reliable estimation of fampl in small fish embryos and larvae, as well as the inclusion of MO2, may provide new insights into different respiratory strategies and may, thus, represent a tool to lower the detection limit for reactions of different life-stages of fish to environmental stressors. In the present study, this became evident, as early gill-breathing 12 d old zebrafish larvae showed symptoms of respiratory failure (i.e., increase in fv, fampl and MO2, followed by subsequent lethargy) after exposure to lindane, whereas skin-breathing in 4 d old embryos proved mainly insensitive to the paralytic effects of lindane.
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Affiliation(s)
- Nadine Kämmer
- Aquatic Ecology and Toxicology Section, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, Heidelberg D-69210, Germany.
| | - Tanja Reimann
- Aquatic Ecology and Toxicology Section, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, Heidelberg D-69210, Germany
| | - Viktoriia Ovcharova
- Aquatic Ecology and Toxicology Section, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, Heidelberg D-69210, Germany
| | - Thomas Braunbeck
- Aquatic Ecology and Toxicology Section, Centre for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, Heidelberg D-69210, Germany.
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Morrison PR, Bernal D, Sepulveda CA, Brauner CJ. The effect of temperature on haemoglobin-oxygen binding affinity in regionally endothermic and ectothermic sharks. J Exp Biol 2023; 226:286204. [PMID: 36576038 DOI: 10.1242/jeb.244979] [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: 09/07/2022] [Accepted: 12/20/2022] [Indexed: 12/29/2022]
Abstract
Haemoglobin (Hb)-O2 binding affinity typically decreases with increasing temperature, but several species of ectothermic and regionally endothermic fishes exhibit reduced Hb thermal sensitivity. Regionally endothermic sharks, including the common thresher shark (Alopias vulpinus) and lamnid sharks such as the shortfin mako shark (Isurus oxyrinchus), can maintain select tissues and organs warmer than ambient temperature by retaining metabolic heat with vascular heat exchangers. In the ectothermic bigeye thresher shark (Alopias superciliosus), diurnal movements above and below the thermocline subject the tissues, including the blood, to a wide range of operating temperatures. Therefore, blood-O2 transport must occur across internal temperature gradients in regionally endothermic species, and over the range of environmental temperatures encountered by the ectothermic bigeye thresher shark. While previous studies have shown temperature-independent Hb-O2 affinity in lamnid sharks, including shortfin mako, the Hb-O2 affinity of the common and bigeye thresher sharks is unknown. Therefore, we examined the effect of temperature on whole-blood Hb-O2 affinity in common thresher shark and bigeye thresher shark. For comparison, analyses were also conducted on the shortfin mako shark and two ectothermic species, blue shark (Prionace glauca) and spiny dogfish (Squalus acanthias). Blood-O2 binding affinity was temperature independent for common thresher shark and shortfin mako shark, which should prevent internal temperature gradients from negatively affecting blood-O2 transport. Blue shark and spiny dogfish blood-O2 affinity decreased with increasing temperature, as expected, but bigeye thresher shark blood exhibited both a reduced temperature dependence and a high Hb-O2 affinity, which likely prevents large changes in environment temperature and low environmental oxygen from affecting O2 uptake.
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Affiliation(s)
- Phillip R Morrison
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
| | - Diego Bernal
- Department of Biology, University of Massachusetts, Dartmouth, MA 02747, USA
| | | | - Colin J Brauner
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada, V6T 1Z4
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Kwan GT, Tresguerres M. Elucidating the acid-base mechanisms underlying otolith overgrowth in fish exposed to ocean acidification. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 823:153690. [PMID: 35143791 DOI: 10.1016/j.scitotenv.2022.153690] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Revised: 01/11/2022] [Accepted: 02/01/2022] [Indexed: 06/14/2023]
Abstract
Over a decade ago, ocean acidification (OA) exposure was reported to induce otolith overgrowth in teleost fish. This phenomenon was subsequently confirmed in multiple species; however, the underlying physiological causes remain unknown. Here, we report that splitnose rockfish (Sebastes diploproa) exposed to ~1600 μatm pCO2(pH ~7.5) were able to fully regulated the pH of both blood and endolymph (the fluid that surrounds the otolith within the inner ear). However, while blood was regulated around pH 7.80, the endolymph was regulated around pH ~8.30. These different pH setpoints result in increased pCO2diffusion into the endolymph, which in turn leads to proportional increases in endolymph [HCO3-] and [CO32-]. Endolymph pH regulation despite the increased pCO2suggests enhanced H+removal. However, a lack of differences in inner ear bulk and cell-specific Na+/K+-ATPase and vacuolar type H+-ATPase protein abundance localization pointed out to activation of preexisting ATPases, non-bicarbonate pH buffering, or both, as the mechanism for endolymph pH-regulation. These results provide the first direct evidence showcasing the acid-base chemistry of the endolymph of OA-exposed fish favors otolith overgrowth, and suggests that this phenomenon will be more pronounced in species that count with more robust blood and endolymph pH regulatory mechanisms.
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Affiliation(s)
- Garfield T Kwan
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, USA; NOAA Fisheries Service, Southwest Fisheries Science Center, USA.
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, USA.
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7
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Acute Stress in Lesser-Spotted Catshark (Scyliorhinus canicula Linnaeus, 1758) Promotes Amino Acid Catabolism and Osmoregulatory Imbalances. Animals (Basel) 2022; 12:ani12091192. [PMID: 35565621 PMCID: PMC9105869 DOI: 10.3390/ani12091192] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Revised: 04/27/2022] [Accepted: 05/04/2022] [Indexed: 11/30/2022] Open
Abstract
Simple Summary In catsharks (Scyliorhinus canicula), air exposure induces amino acid catabolism altogether with osmoregulatory imbalances. This study describes a novel NHE isoform being expressed in gills that may be involved in ammonium excretion. Abstract Acute-stress situations in vertebrates induce a series of physiological responses to cope with the event. While common secondary stress responses include increased catabolism and osmoregulatory imbalances, specific processes depend on the taxa. In this sense, these processes are still largely unknown in ancient vertebrates such as marine elasmobranchs. Thus, we challenged the lesser spotted catshark (Scyliorhinus canicula) to 18 min of air exposure, and monitored their recovery after 0, 5, and 24 h. This study describes amino acid turnover in the liver, white muscle, gills, and rectal gland, and plasma parameters related to energy metabolism and osmoregulatory imbalances. Catsharks rely on white muscle amino acid catabolism to face the energy demand imposed by the stressor, producing NH4+. While some plasma ions (K+, Cl− and Ca2+) increased in concentration after 18 min of air exposure, returning to basal values after 5 h of recovery, Na+ increased after just 5 h of recovery, coinciding with a decrease in plasma NH4+. These changes were accompanied by increased activity of a branchial amiloride-sensitive ATPase. Therefore, we hypothesize that this enzyme may be a Na+/H+ exchanger (NHE) related to NH4+ excretion. The action of an omeprazole-sensitive ATPase, putatively associated to a H+/K+-ATPase (HKA), is also affected by these allostatic processes. Some complementary experiments were carried out to delve a little deeper into the possible branchial enzymes sensitive to amiloride, including in vivo and ex vivo approaches, and partial sequencing of a nhe1 in the gills. This study describes the possible presence of an HKA enzyme in the rectal gland, as well as a NHE in the gills, highlighting the importance of understanding the relationship between acute stress and osmoregulation in elasmobranchs.
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Harter TS, Clifford AM, Tresguerres M. Adrenergically induced translocation of red blood cell β-adrenergic sodium-proton exchangers has ecological relevance for hypoxic and hypercapnic white seabass. Am J Physiol Regul Integr Comp Physiol 2021; 321:R655-R671. [PMID: 34494485 DOI: 10.1152/ajpregu.00175.2021] [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: 01/02/2023]
Abstract
White seabass (Atractoscion nobilis) increasingly experience periods of low oxygen (O2; hypoxia) and high carbon dioxide (CO2, hypercapnia) due to climate change and eutrophication of the coastal waters of California. Hemoglobin (Hb) is the principal O2 carrier in the blood and in many teleost fishes Hb-O2 binding is compromised at low pH; however, the red blood cells (RBC) of some species regulate intracellular pH with adrenergically stimulated sodium-proton-exchangers (β-NHEs). We hypothesized that RBC β-NHEs in white seabass are an important mechanism that can protect the blood O2-carrying capacity during hypoxia and hypercapnia. We determined the O2-binding characteristics of white seabass blood, the cellular and subcellular response of RBCs to adrenergic stimulation, and quantified the protective effect of β-NHE activity on Hb-O2 saturation. White seabass had typical teleost Hb characteristics, with a moderate O2 affinity (Po2 at half-saturation; P50 2.9 kPa) that was highly pH-sensitive (Bohr coefficient -0.92; Root effect 52%). Novel findings from super-resolution microscopy revealed β-NHE protein in vesicle-like structures and its translocation into the membrane after adrenergic stimulation. Microscopy data were corroborated by molecular and phylogenetic results and a functional characterization of β-NHE activity. The activation of RBC β-NHEs increased Hb-O2 saturation by ∼8% in normoxic hypercapnia and by up to ∼20% in hypoxic normocapnia. Our results provide novel insight into the cellular mechanism of adrenergic RBC stimulation within an ecologically relevant context. β-NHE activity in white seabass has great potential to protect arterial O2 transport during hypoxia and hypercapnia but is less effective during combinations of these stressors.
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Affiliation(s)
- Till S Harter
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California
| | - Alexander M Clifford
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California
| | - Martin Tresguerres
- Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California
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Eom J, Wood CM. Understanding ventilation and oxygen uptake of Pacific hagfish (Eptatretus stoutii), with particular emphasis on responses to ammonia and interactions with other respiratory gases. J Comp Physiol B 2021; 191:255-271. [PMID: 33547930 DOI: 10.1007/s00360-020-01329-7] [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: 07/17/2020] [Revised: 10/18/2020] [Accepted: 11/15/2020] [Indexed: 11/24/2022]
Abstract
The hagfishes are an ancient and evolutionarily important group, with breathing mechanisms and gills very different from those of other fishes. Hagfish inhale through a single nostril via a velum pump, and exhale through multiple separate gill pouches. We assessed respiratory performance in E. stoutii (31 ppt, 12 ºC, 50-120 g) by measuring total ventilatory flow ([Formula: see text]) at the nostril, velar (respiratory) frequency (fr), and inspired (PIO2) and expired (PEO2) oxygen tensions at all 12 gill pouch exits plus the pharyngo-cutaneous duct (PCD) on the left side, and calculated ventilatory stroke volume (S[Formula: see text]), % O2 utilization, and oxygen consumption (ṀO2). At rest under normoxia, spontaneous changes in [Formula: see text] ranged from apnea to > 400 ml kg-1 min-1, due to variations in both fr and S[Formula: see text]; "normal" [Formula: see text] averaged 137 ml kg-1 min-1, ṀO2 was 718 µmol kg-1 h-1, so the ventilatory convection requirement for O2 was about 11 L mmol-1. Relative to anterior gill pouches, lower PEO2 values (i.e. higher utilization) occurred in the more posterior pouches and PCD. Overall, O2 utilization was 34% and did not change during hyperventilation but increased to > 90% during hypoventilation. Environmental hypoxia (PIO2 ~ 8% air saturation, 1.67 kPa, 13 Torr) caused hyperventilation, but neither acute hyperoxia (PIO2 ~ 275% air saturation, 57.6 kPa, 430 Torr) nor hypercapnia (PICO2 ~ 1% CO2, 1.0 kPa, 7.5 Torr) significantly altered [Formula: see text]. ṀO2 decreased in hypoxia and increased in hyperoxia but did not change in hypercapnia. Acute exposure to high environmental ammonia (HEA, 10 mM NH4HCO3) caused an acute decrease in [Formula: see text], in contrast to the hyperventilation of long-term HEA exposure described in a previous study. The hypoventilatory response to HEA still occurred during hypoxia and hyperoxia, but was blunted during hypercapnia. Under all treatments, ṀO2 increased with increases in [Formula: see text]. Overall, there were lower convection requirements for O2 during hyperoxia, higher requirements during hypoxia and hypercapnia, but unchanged requirements during HEA. We conclude that this "primitive" fish operates a flexible respiratory system with considerable reserve capacity.
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Affiliation(s)
- Junho Eom
- Department of Zoology, University of British Columbia, Vancouver, BC, V6T1Z4, Canada.
| | - Chris M Wood
- Department of Zoology, University of British Columbia, Vancouver, BC, V6T1Z4, Canada
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10
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Hannan KD, Munday PL, Rummer JL. The effects of constant and fluctuating elevated pCO 2 levels on oxygen uptake rates of coral reef fishes. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 741:140334. [PMID: 32603942 DOI: 10.1016/j.scitotenv.2020.140334] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2020] [Revised: 05/20/2020] [Accepted: 06/16/2020] [Indexed: 05/28/2023]
Abstract
Ocean acidification, resulting from increasing atmospheric carbon dioxide (CO2) emissions, can affect the physiological performance of some fishes. Most studies investigating ocean acidification have used stable pCO2 treatments based on open ocean predictions. However, nearshore systems can experience substantial spatial and temporal variations in pCO2. Notably, coral reefs are known to experience diel fluctuations in pCO2, which are expected to increase on average and in magnitude in the future. Though we know these variations exist, relatively few studies have included fluctuating treatments when examining the effects of ocean acidification conditions on coral reef species. To address this, we exposed two species of damselfishes, Amblyglyphidodon curacao and Acanthochromis polyacanthus, to ambient pCO2, a stable elevated pCO2 treatment, and two fluctuating pCO2 treatments (increasing and decreasing) over an 8 h period. Oxygen uptake rates were measured both while fish were swimming and resting at low-speed. These 8 h periods were followed by an exhaustive swimming test (Ucrit) and blood draw examining swimming metrics and haematological parameters contributing to oxygen transport. When A. polyacanthus were exposed to stable pCO2 conditions (ambient or elevated), they required more energy during the 8 h trial regardless of swimming type than fish exposed to either of the fluctuating pCO2 treatments (increasing or decreasing). These results were reflected in the oxygen uptake rates during the Ucrit tests, where fish exposed to fluctuating pCO2 treatments had a higher factorial aerobic scope than fish exposed to stable pCO2 treatments. By contrast, A. curacao showed no effect of pCO2 treatment on swimming or oxygen uptake metrics. Our results show that responses to stable versus fluctuating pCO2 differ between species - what is stressful for one species many not be stressful for another. Such asymmetries may have population- and community-level impacts under higher more variable pCO2 conditions in the future.
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Affiliation(s)
- Kelly D Hannan
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia.
| | - Philip L Munday
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia
| | - Jodie L Rummer
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811, Australia
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Wood CM, Pane EF, Heigenhauser GJF. Dichloroacetate reveals the presence of metabolic inertia at the start of exercise in rainbow trout (Oncorhynchus mykiss, Walbaum 1792). JOURNAL OF FISH BIOLOGY 2020; 97:1242-1246. [PMID: 32657450 DOI: 10.1111/jfb.14461] [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: 05/12/2020] [Revised: 07/05/2020] [Accepted: 07/10/2020] [Indexed: 06/11/2023]
Abstract
A lag in the increase in oxygen consumption (MO2 ) occurs at the start of sustainable exercise in trout. Waterborne dichloroacetate (0.58 and 3.49 mmol l-1 ), a compound which activates pyruvate dehydrogenase (PDH) by inhibiting PDH kinase in muscle, accelerates the increase in MO2 during the first 10 min of sustainable exercise when velocity is elevated to 75% critical swimming speed in a swim tunnel. There are no effects on MO2 thereafter or at rest. This indicates that a delay in PDH activation ("metabolic inertia") contributes to the lag phenomenon.
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Affiliation(s)
- Chris M Wood
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Eric F Pane
- Department of Biology, McMaster University, Hamilton, Ontario, Canada
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Parker JJ, Zimmer AM, Perry SF. Respirometry and cutaneous oxygen flux measurements reveal a negligible aerobic cost of ion regulation in larval zebrafish ( Danio rerio). J Exp Biol 2020; 223:jeb226753. [PMID: 32709624 DOI: 10.1242/jeb.226753] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 07/19/2020] [Indexed: 08/26/2023]
Abstract
Fishes living in fresh water counter the passive loss of salts by actively absorbing ions through specialized cells termed ionocytes. Ionocytes contain ATP-dependent transporters and are enriched with mitochondria; therefore ionic regulation is an energy-consuming process. The purpose of this study was to assess the aerobic costs of ion transport in larval zebrafish (Danio rerio). We hypothesized that changes in rates of Na+ uptake evoked by acidic or low Na+ rearing conditions would result in corresponding changes in whole-body oxygen consumption (ṀO2 ) and/or cutaneous oxygen flux (JO2 ), measured at the ionocyte-expressing yolk sac epithelium using the scanning micro-optrode technique (SMOT). Larvae at 4 days post-fertilization (dpf) that were reared under low pH (pH 4) conditions exhibited a higher rate of Na+ uptake compared with fish reared under control conditions (pH 7.6), yet they displayed a lower ṀO2 and no difference in cutaneous JO2 Despite a higher Na+ uptake capacity in larvae reared under low Na+ conditions, there were no differences in ṀO2 and JO2 at 4 dpf. Furthermore, although Na+ uptake was nearly abolished in 2 dpf larvae lacking ionocytes after morpholino knockdown of the ionocyte proliferation regulating transcription factor foxi3a, ṀO2 and JO2 were unaffected. Finally, laser ablation of ionocytes did not affect cutaneous JO2 Thus, we conclude that the aerobic costs of ion uptake by ionocytes in larval zebrafish, at least in the case of Na+, are below detection using whole-body respirometry or cutaneous SMOT scans, providing evidence that ion regulation in zebrafish larvae incurs a low aerobic cost.
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Affiliation(s)
- Julian J Parker
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5
| | - Alex M Zimmer
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5
| | - Steve F Perry
- Department of Biology, University of Ottawa, Ottawa, ON, Canada, K1N 6N5
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13
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Somo DA, Onukwufor JO, Wood CM, Richards JG. Interactive effects of temperature and hypoxia on diffusive water flux and oxygen uptake rate in the tidepool sculpin, Oligocottus maculosus. Comp Biochem Physiol A Mol Integr Physiol 2020; 250:110781. [PMID: 32763468 DOI: 10.1016/j.cbpa.2020.110781] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2020] [Revised: 07/31/2020] [Accepted: 07/31/2020] [Indexed: 01/07/2023]
Abstract
The osmorespiratory compromise hypothesis posits that respiratory epithelial characteristics and physiological regulatory mechanisms which promote gas permeability also increase permeability to ions and water. The hypothesis therefore predicts that physiological responses which increase effective gas permeability will result in increased effective ion and water permeabilities. Though analyses of water and gas effective permeabilities using high temperature have generally supported the hypothesis, water permeability responses to hypoxia remain equivocal and the combination of high temperature and hypoxia untested. We measured diffusive water flux (DWF) and oxygen uptake rate (Ṁo2) in response to acute temperature change, hypoxia, and the combination of high temperature and hypoxia in a hypoxia-tolerant intertidal fish, the tidepool sculpin (Oligocottus maculosus). In support of the osmorespiratory compromise hypothesis, Ṁo2 and DWF increased with temperature. In contrast, DWF decreased with hypoxia at a constant temperature, a result consistent with previously observed decoupling of water and gas effective permeabilities during hypoxia exposure in some hypoxia tolerant fishes. However, DWF levels during simultaneous high temperature and hypoxia exposure were not different from fish exposed to high temperature in normoxia, possibly suggesting a failure of the mechanism responsible for down-regulating DWF in hypoxia. These results, together with time-course analysis of hypoxia exposure and normoxic recovery, suggest that tidepool sculpins actively downregulate effective water permeability in hypoxia but the mechanism fails with multi-stressor exposure. Future investigations of the mechanistic basis of the regulation of gill permeability will be key to understanding the role of this regulatory ability in the persistence of this species in the dynamic intertidal environment.
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Affiliation(s)
- Derek A Somo
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| | - John O Onukwufor
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Chris M Wood
- 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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14
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Allen GJP, Kuan PL, Tseng YC, Hwang PP, Quijada-Rodriguez AR, Weihrauch D. Specialized adaptations allow vent-endemic crabs (Xenograpsus testudinatus) to thrive under extreme environmental hypercapnia. Sci Rep 2020; 10:11720. [PMID: 32678186 PMCID: PMC7367285 DOI: 10.1038/s41598-020-68656-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Accepted: 06/29/2020] [Indexed: 12/13/2022] Open
Abstract
Shallow hydrothermal vent environments are typically very warm and acidic due to the mixing of ambient seawater with volcanic gasses (> 92% CO2) released through the seafloor making them potential ‘natural laboratories’ to study long-term adaptations to extreme hypercapnic conditions. Xenograpsus testudinatus, the shallow hydrothermal vent crab, is the sole metazoan inhabitant endemic to vents surrounding Kueishantao Island, Taiwan, where it inhabits waters that are generally pH 6.50 with maximum acidities reported as pH 5.50. This study assessed the acid–base regulatory capacity and the compensatory response of X. testudinatus to investigate its remarkable physiological adaptations. Hemolymph parameters (pH, [HCO3−], \documentclass[12pt]{minimal}
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\begin{document}$${\text{P}}_{{{\text{CO}}_{2} }}$$\end{document}PCO2, [NH4+], and major ion compositions) and the whole animal’s rates of oxygen consumption and ammonia excretion were measured throughout a 14-day acclimation to pH 6.5 and 5.5. Data revealed that vent crabs are exceptionally strong acid–base regulators capable of maintaining homeostatic pH against extreme hypercapnia (pH 5.50, 24.6 kPa \documentclass[12pt]{minimal}
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\begin{document}$${\text{P}}_{{{\text{CO}}_{2} }}$$\end{document}PCO2) via HCO3−/Cl− exchange, retention and utilization of extracellular ammonia. Intact crabs as well as their isolated perfused gills maintained \documentclass[12pt]{minimal}
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\begin{document}$${\text{P}}_{{{\text{CO}}_{2} }}$$\end{document}PCO2tensions below environmental levels suggesting the gills can excrete CO2 against a hemolymph-directed \documentclass[12pt]{minimal}
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\begin{document}$${\text{P}}_{{{\text{CO}}_{2} }}$$\end{document}PCO2 gradient. These specialized physiological mechanisms may be amongst the adaptations required by vent-endemic animals surviving in extreme conditions.
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Affiliation(s)
- Garett J P Allen
- Biological Sciences, University of Manitoba, 190 Dysart Rd., Winnipeg, MB, R3T 2M8, Canada
| | - Pou-Long Kuan
- Institute of Cellular and Organismal Biology's Marine Research Station, Academia Sinica, No. 23-10 Dawen Rd., Jiaoxi, 262, Yilan County, Taiwan
| | - Yung-Che Tseng
- Institute of Cellular and Organismal Biology's Marine Research Station, Academia Sinica, No. 23-10 Dawen Rd., Jiaoxi, 262, Yilan County, Taiwan
| | - Pung-Pung Hwang
- Institute of Cellular and Organismal Biology, Academia Sinica, No. 128, Section 2, Academia Rd., Nangang District, Taipei City, 11529, Taiwan
| | | | - Dirk Weihrauch
- Biological Sciences, University of Manitoba, 190 Dysart Rd., Winnipeg, MB, R3T 2M8, Canada.
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15
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Ruiz-Jarabo I, Amanajás R, Baldisserotto B, Mancera J, Val A. Tambaqui (Colossoma macropomum) acclimated to different tropical waters from the Amazon basin shows specific acute-stress responses. Comp Biochem Physiol A Mol Integr Physiol 2020; 245:110706. [DOI: 10.1016/j.cbpa.2020.110706] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2020] [Revised: 04/14/2020] [Accepted: 04/14/2020] [Indexed: 10/24/2022]
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16
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The gaseous gastrointestinal tract of a seawater teleost, the English sole (Parophrys vetulus). Comp Biochem Physiol A Mol Integr Physiol 2020; 247:110743. [PMID: 32531535 DOI: 10.1016/j.cbpa.2020.110743] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2020] [Revised: 06/04/2020] [Accepted: 06/05/2020] [Indexed: 02/07/2023]
Abstract
There has been considerable recent progress in understanding the respiratory physiology of the gastrointestinal tract (GIT) in teleosts, but the respiratory conditions inside the GIT remain largely unknown, particularly the luminal PCO2 and PO2 levels. The GIT of seawater teleosts is of special interest due to its additional function of water absorption linked to HCO3- secretion, a process that may raise luminal PCO2 levels. Direct measurements of GIT PCO2 and PO2 using micro-optodes in the English sole (Parophrys vetulus; anaesthetized, artificially ventilated, 10-12 °C) revealed extreme luminal gas levels. Luminal PCO2 was 14-17 mmHg in the stomach and intestinal segments of fasted sole, considerably higher than arterial blood levels of 5 mmHg. Moreover, feeding, which raised intestinal HCO3- concentration, also raised luminal PCO2 to 34-50 mmHg. All these values were higher than comparable measurements in freshwater teleosts, and also greater than environmental CO2 levels of concern in aquaculture or global change scenarios. The PCO2 values in subintestinal vein blood draining the GIT of fed fish (28 mmHg) suggested some degree of equilibration with high luminal PCO2, whereas subintestinal vein PO2 levels were relatively low (9 mmHg). All luminal sections of the GIT were virtually anoxic (PO2 ≤ 0.3 mmHg), in both fasted and fed animals, a novel finding in teleosts.
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17
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Goodrich HR, Bayley M, Birgersson L, Davison WG, Johannsson OE, Kim AB, Le My P, Tinh TH, Thanh PN, Thanh HDT, Wood CM. Understanding the gastrointestinal physiology and responses to feeding in air-breathing Anabantiform fishes. JOURNAL OF FISH BIOLOGY 2020; 96:986-1003. [PMID: 32060920 DOI: 10.1111/jfb.14288] [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: 09/09/2019] [Revised: 12/16/2019] [Accepted: 02/13/2020] [Indexed: 06/10/2023]
Abstract
The Mekong Delta is host to a large number of freshwater species, including a unique group of facultative air-breathing Anabantiforms. Of these, the striped snakehead (Channa striata), the climbing perch (Anabas testudineus), the giant gourami (Osphronemus goramy) and the snakeskin gourami (Trichogaster pectoralis) are major contributors to aquaculture production in Vietnam. The gastrointestinal responses to feeding in these four species are detailed here. Relative intestinal length was lowest in the snakehead, indicating carnivory, and 5.5-fold greater in the snakeskin, indicating herbivory; climbing perch and giant gourami were intermediate, indicating omnivory. N-waste excretion (ammonia-N + urea-N) was greatest in the carnivorous snakehead and least in the herbivorous snakeskin, whereas the opposite trend was observed for net K+ excretion. Similarly, the more carnivorous species had a greater stomach acidity than the more herbivorous species. Measurements of acid-base flux to water indicated that the greatest postprandial alkaline tide occurred in the snakehead and a potential acidic tide in the snakeskin. Additional findings of interest were high levels of both PCO2 (up to 40 mmHg) and HCO3 - (up to 33 mM) in the intestinal chyme of all four of these air-breathing species. Using in vitro gut sac preparations of the climbing perch, it was shown that the intestinal net absorption of fluid, Na+ and HCO3 - was upregulated by feeding but not net Cl- uptake, glucose uptake or K+ secretion. Upregulated net absorption of HCO3 - suggests that the high chyme (HCO3 - ) does not result from secretion by the intestinal epithelium. The possibility of ventilatory control of PCO2 to regulate postprandial acid-base balance in these air-breathing fish is discussed.
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Affiliation(s)
- Harriet R Goodrich
- School of Biological Sciences, The University of Queensland, St Lucia, QLD, Australia
- College of Life and Environmental Sciences, The University of Exeter, Exeter, Devon, UK
| | - Mark Bayley
- Department of Bioscience, Zoophysiology Aarhus University, Aarhus, Denmark
| | - Lina Birgersson
- Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden
| | - William G Davison
- College of Life and Environmental Sciences, The University of Exeter, Exeter, Devon, UK
| | - Ora E Johannsson
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Anne B Kim
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
| | - Phuong Le My
- Department of Agriculture, Bac Lieu University, Bac Lieu, Vietnam
| | - Tran H Tinh
- Aquaculture and Fisheries, Department of Animal Sciences, Wageningen University and Research, Wageningen, The Netherlands
| | - Phuong N Thanh
- College of Aquaculture and Fisheries, Can Tho University, Cần Thơ, Vietnam
| | - Huong Do Thi Thanh
- College of Aquaculture and Fisheries, Can Tho University, Cần Thơ, Vietnam
| | - Chris M Wood
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
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18
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Gam LTH, Thanh Huong DT, Tuong DD, Phuong NT, Jensen FB, Wang T, Bayley M. Effects of temperature on acid-base regulation, gill ventilation and air breathing in the clown knifefish, Chitala ornata. J Exp Biol 2020; 223:jeb216481. [PMID: 32001546 DOI: 10.1242/jeb.216481] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 01/23/2020] [Indexed: 11/20/2022]
Abstract
Chitala ornata is a facultative air-breathing fish, which at low temperatures shows an arterial PCO2 (PaCO2 ) level only slightly elevated above that of water breathers. By holding fish with in-dwelling catheters at temperatures from 25 to 36°C and measuring blood gasses, we show that this animal follows the ubiquitous poikilotherm pattern of reducing arterial pH with increasing temperature. Surprisingly, the temperature increase caused an elevation of PaCO2 from 5 to 12 mmHg while the plasma bicarbonate concentration remained constant at around 8 mmol l-1 The temperature increase also gave rise to a larger fractional increase in air breathing than in gill ventilation frequency. These findings suggest that air breathing, and hence the partitioning of gas exchange, is to some extent regulated by acid-base status in air-breathing fish and that these bimodal breathers will be increasingly likely to adopt respiratory pH control as temperature rises, providing an interesting avenue for future research.
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Affiliation(s)
- Le Thi Hong Gam
- College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam
| | - Do Thi Thanh Huong
- College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam
| | - Dang Diem Tuong
- College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam
| | - Nguyen Thanh Phuong
- College of Aquaculture and Fisheries, Can Tho University, Can Tho City, Vietnam
| | - Frank Bo Jensen
- Department of Biology, University of Southern Denmark, 5230 Odense, Denmark
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark
- Aarhus Institute of Advanced Studies, 8000 Aarhus C, Denmark
| | - Mark Bayley
- Zoophysiology, Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark
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19
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Dziergwa J, Singh S, Bridges CR, Kerwath SE, Enax J, Auerswald L. Acid-base adjustments and first evidence of denticle corrosion caused by ocean acidification conditions in a demersal shark species. Sci Rep 2019; 9:18668. [PMID: 31857600 PMCID: PMC6923475 DOI: 10.1038/s41598-019-54795-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 11/19/2019] [Indexed: 01/01/2023] Open
Abstract
Global ocean acidification is expected to chronically lower the pH to 7.3 (>2200 µatm seawater pCO2) by the year 2300. Acute hypercapnia already occurs along the South African west and south coasts due to upwelling- and low-oxygen events, with increasing frequency. In the present project we investigated the impact of hypercapnia on the endemic demersal shark species Haploblepharus edwardsii. Specifically, we experimentally analysed acid-base regulation during acute and chronic hypercapnia, the effects of chronic hypercapnia on growth rates and on denticle structure- and composition. While H. edwardsii are physiologically well adapted to acute and chronic hypercapnia, we observed, for the first time, denticle corrosion as a result of chronic exposure. We conclude that denticle corrosion could increase denticle turnover and compromise hydrodynamics and skin protection.
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Affiliation(s)
- Jacqueline Dziergwa
- Heinrich-Heine University, Düsseldorf, Institute of Metabolic Physiology/Ecophysiology, Düsseldorf, Germany
| | - Sarika Singh
- Ocean and Coastal Research, Department of Environmental Affairs (DEA), Cape Town, South Africa
| | - Christopher R Bridges
- Heinrich-Heine University, Düsseldorf, Institute of Metabolic Physiology/Ecophysiology, Düsseldorf, Germany
| | - Sven E Kerwath
- Branch: Fisheries Management, Department of Agriculture, Forestry and Fisheries (DAFF), Cape Town, South Africa
- Department of Animal Sciences, Stellenbosch University, Stellenbosch, South Africa
| | - Joachim Enax
- Institute of Inorganic Chemistry and Center for Nanointegration Duisburg-Essen (CeNIDE), University of Duisburg-Essen, Essen, Germany
| | - Lutz Auerswald
- Branch: Fisheries Management, Department of Agriculture, Forestry and Fisheries (DAFF), Cape Town, South Africa.
- Department of Animal Sciences, Stellenbosch University, Stellenbosch, South Africa.
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20
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G DP, Souza-Bastos LR, Giacomin M, Dolatto RG, Baika LM, Grassi MT, Ostrensky A, Wood CM. Acute exposure to the water-soluble fraction of gasoline (WSF G) affects oxygen consumption, nitrogenous-waste and Mg excretion, and activates anaerobic metabolism in the goldfish Carassius auratus. Comp Biochem Physiol C Toxicol Pharmacol 2019; 226:108590. [PMID: 31404698 DOI: 10.1016/j.cbpc.2019.108590] [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: 03/28/2019] [Revised: 07/26/2019] [Accepted: 08/08/2019] [Indexed: 10/26/2022]
Abstract
Contamination of aquatic environments by petroleum and its products (e.g. gasoline) is a hazard for aquatic organisms as a result of the potential toxicity of monocyclic aromatic hydrocarbons (BTEX) and polycyclic aromatic hydrocarbons (PAH). Our goal was to evaluate the acute effects of the water-soluble fraction of gasoline (WSFG) on nitrogen excretion, osmoregulation, and metabolism of goldfish Carassius auratus. We first chemically characterized the WSFG and then tested its effects on these physiological aspects of C. auratus, in several different exposure scenarios (0, 0.25, 5, 10 and 25% of WSFG). The WSFG contained high concentrations BTEX (toluene 70% and benzene 17%) relative to PAH (<1%), and low levels of several metals (Al, Fe, Zn, Sr). Routine O2 uptake rate (MO2) of goldfish was inhibited by exposure to 5% WSFG, and during post-exposure recovery, MO2 increased in a dose-dependent fashion. Ammonia excretion was not affected by exposure to WSFG, but urea-N excretion increased progressively with the WSFG concentration. The same pattern of dose/response was observed for net Mg2+ loss rates and steadily increasing plasma lactate concentrations. Loss rates of Na+, Ca2+, K+ and Cl-, and plasma concentrations of Mg2+ and urea-N were not significantly altered. We propose that acute exposure to WSFG inhibits aerobic metabolism and activates anaerobic metabolism, breaking down ATP such that bound Mg2+ is liberated and the purine ring component is metabolized to urea-N, both of which are subsequently excreted.
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Affiliation(s)
- Dal Pont G
- Integrated Group for Aquaculture and Environmental Studies, Dept. of Animal Science, Federal University of Paraná, Curitiba, P.R. 83035-050, Brazil; Programa de Pós-Graduação em Zootecnia, Universidade Federal do Paraná, Curitiba, PR ZIP 80035-050, Brazil; Department of Zoology, University of British Columbia, Vancouver, BC ZIP V6T 1Z4, Canada.
| | - Luciana Rodrigues Souza-Bastos
- Integrated Group for Aquaculture and Environmental Studies, Dept. of Animal Science, Federal University of Paraná, Curitiba, P.R. 83035-050, Brazil; Programa de Pós-Graduação em Zootecnia, Universidade Federal do Paraná, Curitiba, PR ZIP 80035-050, Brazil; Institute of Technology for Development - Lactec, Curitiba, PR ZIP 81531-980, Brazil.
| | - Marina Giacomin
- Department of Zoology, University of British Columbia, Vancouver, BC ZIP V6T 1Z4, Canada.
| | - Rafael Garrett Dolatto
- Grupo de Química Ambiental (GQA), Dept. of Chemistry, Federal University of Paraná, PO Box 19032, Curitiba, PR ZIP 81531-970, Brazil
| | - Loana Mara Baika
- Grupo de Química Ambiental (GQA), Dept. of Chemistry, Federal University of Paraná, PO Box 19032, Curitiba, PR ZIP 81531-970, Brazil
| | - Marco Tadeu Grassi
- Grupo de Química Ambiental (GQA), Dept. of Chemistry, Federal University of Paraná, PO Box 19032, Curitiba, PR ZIP 81531-970, Brazil.
| | - Antonio Ostrensky
- Integrated Group for Aquaculture and Environmental Studies, Dept. of Animal Science, Federal University of Paraná, Curitiba, P.R. 83035-050, Brazil.
| | - Chris M Wood
- Department of Zoology, University of British Columbia, Vancouver, BC ZIP V6T 1Z4, Canada.
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21
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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: 20] [Impact Index Per Article: 4.0] [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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22
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Du SNN, Choi JA, McCallum ES, McLean AR, Borowiec BG, Balshine S, Scott GR. Metabolic implications of exposure to wastewater effluent in bluegill sunfish. Comp Biochem Physiol C Toxicol Pharmacol 2019; 224:108562. [PMID: 31254663 DOI: 10.1016/j.cbpc.2019.108562] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/23/2019] [Revised: 06/18/2019] [Accepted: 06/25/2019] [Indexed: 02/01/2023]
Abstract
Effluent from wastewater treatment plants (WWTP) contains a complex mixture of contaminants and is a major worldwide source of aquatic pollution. We examined the effects of exposure to treated effluent from a municipal WWTP on the metabolic physiology of bluegill sunfish (Lepomis macrochirus). We studied fish that were wild-caught or experimentally caged (28 d) downstream of the WWTP, and compared them to fish that were caught or caged at clean reference sites. Survival was reduced in fish caged at the effluent-contaminated site compared to those caged at the reference site. Resting rates of O2 consumption (MO2) were higher in fish from the contaminated site, reflecting a metabolic cost of wastewater exposure. The increases in routine MO2 did not reduce aerobic scope (difference or quotient of maximal MO2 and resting MO2), suggesting that physiological compensations accompanied the metabolic costs of wastewater exposure. Fish exposed to wastewater also had larger hearts and livers. The activity of mitochondrial enzymes (cytochrome c oxidase, citrate synthase) per liver mass was unaltered across treatments, so the increased mass of this organ increased its cumulative oxidative capacity in the fish. Wastewater exposure also reduced glycogen content per liver mass. The effects of caging itself, based on comparisons between fish that were wild-caught or caged at clean sites, were generally subtle and not statistically significant. We conclude that exposure to wastewater effluent invokes a metabolic cost that leads to compensatory physiological adjustments that partially offset the detrimental metabolic impacts of exposure.
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Affiliation(s)
- Sherry N N Du
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada
| | - Jasmine A Choi
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada
| | - Erin S McCallum
- Department of Psychology, Neuroscience & Behaviour, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada
| | - Adrienne R McLean
- Department of Psychology, Neuroscience & Behaviour, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada
| | - Brittney G Borowiec
- Department of Biology, McMaster University, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada
| | - Sigal Balshine
- Department of Psychology, Neuroscience & 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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23
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Shartau RB, Damsgaard C, Brauner CJ. Limits and patterns of acid-base regulation during elevated environmental CO2 in fish. Comp Biochem Physiol A Mol Integr Physiol 2019; 236:110524. [DOI: 10.1016/j.cbpa.2019.110524] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 05/29/2019] [Accepted: 07/07/2019] [Indexed: 01/07/2023]
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24
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Eom J, Giacomin M, Clifford AM, Goss GG, Wood CM. Ventilatory sensitivity to ammonia in the Pacific hagfish ( Eptatretus stoutii), a representative of the oldest extant connection to the ancestral vertebrates. ACTA ACUST UNITED AC 2019; 222:jeb.199794. [PMID: 31221739 DOI: 10.1242/jeb.199794] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 06/16/2019] [Indexed: 12/30/2022]
Abstract
Ventilatory sensitivity to ammonia occurs in teleosts, elasmobranchs and mammals. Here, we investigated whether the response is also present in hagfish. Ventilatory parameters (nostril flow, pressure amplitude, velar frequency and ventilatory index, the last representing the product of pressure amplitude and frequency), together with blood and water chemistry, were measured in hagfish exposed to either high environmental ammonia (HEA) in the external sea water or internal ammonia loading by intra-vascular injection. HEA exposure (10 mmol l-1 NH4HCO3 or 10 mmol l-1 NH4Cl) caused a persistent hyperventilation by 3 h, but further detailed analysis of the NH4HCO3 response showed that initially (within 5 min) there was a marked decrease in ventilation (80% reduction in ventilatory index and nostril flow), followed by a later 3-fold increase, by which time plasma total ammonia concentration had increased 11-fold. Thus, hyperventilation in HEA appeared to be an indirect response to internal ammonia elevation, rather than a direct response to external ammonia. HEA-mediated increases in oxygen consumption also occurred. Responses to NH4HCO3 were greater than those to NH4Cl, reflecting greater increases over time in water pH and P NH3 in the former. Hagfish also exhibited hyperventilation in response to direct injection of isotonic NH4HCO3 or NH4Cl solutions into the caudal sinus. In all cases where hyperventilation occurred, plasma total ammonia and P NH3 levels increased significantly, while blood acid-base status remained unchanged, indicating specific responses to internal ammonia elevation. The sensitivity of breathing to ammonia arose very early in vertebrate evolution.
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Affiliation(s)
- Junho Eom
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, Canada V0R 1B0 .,Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Marina Giacomin
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, Canada V0R 1B0.,Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Alexander M Clifford
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, Canada V0R 1B0.,Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4.,Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9
| | - Greg G Goss
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, Canada V0R 1B0.,Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E9
| | - Chris M Wood
- Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC, Canada V0R 1B0.,Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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25
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Giacomin M, Dal Pont G, Eom J, Schulte PM, Wood CM. The effects of salinity and hypoxia exposure on oxygen consumption, ventilation, diffusive water exchange and ionoregulation in the Pacific hagfish (Eptatretus stoutii). Comp Biochem Physiol A Mol Integr Physiol 2019; 232:47-59. [PMID: 30878760 DOI: 10.1016/j.cbpa.2019.03.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 01/30/2019] [Accepted: 03/06/2019] [Indexed: 10/27/2022]
Abstract
Hagfishes (Class: Myxini) are marine jawless craniate fishes that are widely considered to be osmoconformers whose plasma [Na+], [Cl-] and osmolality closely resemble that of sea water, although they have the ability to regulate plasma [Ca2+] and [Mg2+] below seawater levels. We investigated the responses of Pacific hagfish to changes in respiratory and ionoregulatory demands imposed by a 48-h exposure to altered salinity (25 ppt, 30 ppt (control) and 35 ppt) and by an acute hypoxia exposure (30 Torr; 4 kPa). When hagfish were exposed to 25 ppt, oxygen consumption rate (MO2), ammonia excretion rate (Jamm) and unidirectional diffusive water flux rate (JH2O, measured with 3H2O) were all reduced, pointing to an interaction between ionoregulation and gas exchange. At 35 ppt, JH2O was reduced, though MO2 and Jamm did not change. As salinity increased, so did the difference between plasma and external water [Ca2+] and [Mg2+]. Notably, the same pattern was seen for plasma Cl-, which was kept below seawater [Cl-] at all salinities, while plasma [Na+] was regulated well above seawater [Na+], but plasma osmolality matched seawater values. MO2 was reduced by 49% and JH2O by 36% during hypoxia, despite a small elevation in overall ventilation. Our results depart from the "classical" osmorespiratory compromise but are in accord with responses in other hypoxia-tolerant fish; instead of an exacerbation of gill fluxes when gas transfer is upregulated, the opposite happens.
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Affiliation(s)
- Marina Giacomin
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Bamfield Marine Sciences Centre, Bamfield, British Columbia V0R 1B0, Canada.
| | - Giorgi Dal Pont
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Bamfield Marine Sciences Centre, Bamfield, British Columbia V0R 1B0, Canada; Integrated Group for Aquaculture and Environmental Studies, Department of Animal Science, Federal University of Paraná, Curitiba, Paraná 83035-050, Brazil
| | - Junho Eom
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Bamfield Marine Sciences Centre, Bamfield, British Columbia V0R 1B0, Canada.
| | - Patricia M Schulte
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| | - Chris M Wood
- Department of Zoology, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Bamfield Marine Sciences Centre, Bamfield, British Columbia V0R 1B0, Canada; Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
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26
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Hughes MC, Zimmer AM, Perry SF. Role of internal convection in respiratory gas transfer and aerobic metabolism in larval zebrafish ( Danio rerio). Am J Physiol Regul Integr Comp Physiol 2019; 316:R255-R264. [PMID: 30601704 DOI: 10.1152/ajpregu.00315.2018] [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] [Indexed: 11/22/2022]
Abstract
Purely diffusive O2 transport typically is insufficient to sustain aerobic metabolism in most multicellular organisms. In animals that are small enough, however, a high surface-to-volume ratio may allow passive diffusion alone to supply sufficient O2 transfer. The purpose of this study was to explore the impacts of internal convection on respiratory gas transfer in a small complex organism, the larval zebrafish ( Danio rerio). Specifically, we tested the hypothesis that internal convection is required for the normal transfer of the respiratory gases O2 and CO2 and maintenance of resting aerobic metabolic rate in larvae at 4 days postfertilization (dpf). Morpholino knockdown of the vascular endothelial growth factor (VEGF) or cardiac troponin T (TNNT2) proteins allowed an examination of gas transfer in two independent models lacking internal convection. With the use of a scanning micro-optrode technique to measure regional epithelial O2 fluxes ( Jo2), it was demonstrated that larvae lacking convection exhibited reduced Jo2 in regions spanning the head to the trunk. Moreover, the acute loss of internal convection caused by heart stoppage resulted in reduced rates of cutaneous Jo2, an effect that was reversed upon the restoration of internal convection. With the use of whole body respirometry, it was shown that loss of internal convection was associated with reduced resting rates of O2 consumption and CO2 excretion in larvae at 4 dpf. The results of these experiments clearly demonstrate that internal convection is required to maintain resting rates of respiratory gas transfer in larval zebrafish.
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Affiliation(s)
- Malcolm C Hughes
- Department of Biology, University of Ottawa , Ottawa, Ontario , Canada
| | - Alex M Zimmer
- Department of Biology, University of Ottawa , Ottawa, Ontario , Canada
| | - Steve F Perry
- Department of Biology, University of Ottawa , Ottawa, Ontario , Canada
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27
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Lee DJ, Matthews PGD. Quantifying the acid-base status of dragonflies across their transition from breathing water to breathing air. J Exp Biol 2019; 222:jeb.210294. [DOI: 10.1242/jeb.210294] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Accepted: 10/23/2019] [Indexed: 11/20/2022]
Abstract
Amphibiotic dragonflies show a significant increase in hemolymph total CO2 (TCO2) as they transition from water-breathing to air-breathing. This study examines the hemolymph acid-base status of dragonflies from two families (Aeshnidae and Libellulidae) as they transition from water to air. CO2 solubility (αCO2) and the apparent carbonic acid dissociation constant (pKapp) were determined in vitro, and pH/bicarbonate [HCO3−] plots were produced by equilibrating hemolymph samples with PCO2 between 0.5-5 kPa in custom-built rotating microtonometers. Hemolymph αCO2 varied little between families and across development (mean 0.355±0.005 mmol l−1 kPa−1) while the pKapp was between 6.23 to 6.27, similar to values determined for grasshopper hemolymph. However, the non-HCO3− buffer capacity for dragonfly hemolymph was uniformly low relative to other insects (3.6 to 5.4 mmol l−1 pH−1). While aeshnid dragonflies maintained this level as bimodally-breathing late-final instars and air-breathing adults, the buffer capacity of bimodally-breathing late-final instar Libellula nymphs increased substantially to 9.9 mmol l−1 pH−1. Using the pH/[HCO3−] plots and in vivo measurements of TCO2 and PCO2 from early-final instar nymphs, it was calculated that the in vivo hemolymph pH was 7.8 for an aeshnid nymph and 7.9 for a libellulid nymph, respectively. The pH/[HCO3−] plots show that the changes in acid-base status experienced by dragonflies across their development are more moderate than those seen in vertebrate amphibians. Whether these differences are due to dragonflies being secondarily aquatic, or arise from intrinsic differences between insect and vertebrate gas exchange and acid-base regulatory mechanisms, remains an open question.
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Affiliation(s)
- Daniel J. Lee
- Department of Zoology, University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada
| | - Philip G. D. Matthews
- Department of Zoology, University of British Columbia, Vancouver, B.C., V6T 1Z4, Canada
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28
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Brauner CJ, Shartau RB, Damsgaard C, Esbaugh AJ, Wilson RW, Grosell M. Acid-base physiology and CO2 homeostasis: Regulation and compensation in response to elevated environmental CO2. FISH PHYSIOLOGY 2019. [DOI: 10.1016/bs.fp.2019.08.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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29
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Wang Y, Hu M, Wu F, Storch D, Pörtner HO. Elevated pCO 2 Affects Feeding Behavior and Acute Physiological Response of the Brown Crab Cancer pagurus. Front Physiol 2018; 9:1164. [PMID: 30246790 PMCID: PMC6110915 DOI: 10.3389/fphys.2018.01164] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Accepted: 08/03/2018] [Indexed: 11/25/2022] Open
Abstract
Anthropogenic climate change exposes marine organisms to CO2 induced ocean acidification (OA). Marine animals may make physiological and behavioral adaptations to cope with OA. Elevated pCO2 may affect metabolism, feeding, and energy partition of marine crabs, and thereby affect their predator-prey dynamics with mussels. Therefore, we examined the effects of simulated future elevated pCO2 on feeding behavior and energy metabolism of the brown crab Cancer pagurus. Following 54 days of pre-acclimation to control CO2 levels (360 μatm) at 11°C, crabs were exposed to consecutively increased oceanic CO2 levels (2 weeks for 1200 and 2300 μatm, respectively) and subsequently returned to control CO2 level (390 μatm) for 2 weeks in order to study their potential to acclimate elevated pCO2 and recovery performance. Standard metabolic rate (SMR), specific dynamic action (SDA) and feeding behavior of the crabs were investigated during each experimental period. Compared to the initial control CO2 conditions, the SMRs of CO2 exposed crabs were not significantly increased, but increased significantly when the crabs were returned to normal CO2 levels. Conversely, SDA was significantly reduced under high CO2 and did not return to control levels during recovery. Under high CO2, crabs fed on smaller sized mussels than under control CO2; food consumption rates were reduced; foraging parameters such as searching time, time to break the prey, eating time, and handling time were all significantly longer than under control CO2, and prey profitability was significantly lower than that under control conditions. Again, a two-week recovery period was not sufficient for feeding behavior to return to control values. PCA results revealed a positive relationship between feeding/SDA and pH, but negative relationships between the length of foraging periods and pH. In conclusion, elevated pCO2 caused crab metabolic rate to increase at the expense of SDA. Elevated pCO2 affected feeding performance negatively and prolonged foraging periods. These results are discussed in the context of how elevated pCO2 may impair the competitiveness of brown crabs in benthic communities.
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Affiliation(s)
- Youji Wang
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Shanghai Ocean University, Ministry of Education, Shanghai, China
- National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
- Department of Integrative Ecophysiology, Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
- International Research Center for Marine Biosciences at Shanghai Ocean University, Ministry of Science and Technology, Shanghai, China
| | - Menghong Hu
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Shanghai Ocean University, Ministry of Education, Shanghai, China
- National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
- Department of Integrative Ecophysiology, Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Fangli Wu
- Key Laboratory of Exploration and Utilization of Aquatic Genetic Resources, Shanghai Ocean University, Ministry of Education, Shanghai, China
- National Demonstration Center for Experimental Fisheries Science Education, Shanghai Ocean University, Shanghai, China
| | - Daniela Storch
- Department of Integrative Ecophysiology, Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Hans-Otto Pörtner
- Department of Integrative Ecophysiology, Alfred-Wegener-Institute, Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
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30
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Bernal D, Reid JP, Roessig JM, Matsumoto S, Sepulveda CA, Cech JJ, Graham JB. Temperature effects on the blood oxygen affinity in sharks. FISH PHYSIOLOGY AND BIOCHEMISTRY 2018; 44:949-967. [PMID: 29508119 DOI: 10.1007/s10695-018-0484-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2017] [Accepted: 02/19/2018] [Indexed: 06/08/2023]
Abstract
In fish, regional endothermy (i.e., the capacity to significantly elevate tissue temperatures above ambient via vascular heat exchangers) in the red swimming muscles (RM) has evolved only in a few marine groups (e.g., sharks: Lamnidae, Alopiidae, and teleosts Scombridae). Within these taxa, several species have also been shown to share similar physiological adaptations to enhance oxygen delivery to the working tissues. Although the hemoglobin (Hb) of most fish has a decreased affinity for oxygen with an increase in temperature, some regionally endothermic teleosts (e.g., tunas) have evolved Hbs that have a very low or even an increased affinity for oxygen with an increase in temperature. For sharks, however, blood oxygen affinities remain largely unknown. We examined the effects of temperature on the blood oxygen affinity in two pelagic species (the regionally endothermic shortfin mako shark and the ectothermic blue shark) at 15, 20, and 25 °C, and two coastal ectothermic species (the leopard shark and brown smooth-hound shark) at 10, 15, and 20 °C. Relative to the effects of temperature on the blood oxygen affinity of ectothermic sharks (e.g., blue shark), shortfin mako shark blood was less affected by an increase in temperature, a scenario similar to that documented in some of the tunas. In the shortfin mako shark, this may act to prevent premature oxygen dissociation from Hb as the blood is warmed during its passage through vascular heat exchangers. Even though the shortfin mako shark and blue shark occupy a similar niche, the effects of temperature on blood oxygen affinity in the latter more closely resembled that of the blood in the two coastal shark species examined in this study. The only exception was a small, reverse temperature effect (an increase in blood oxygen affinity with temperature) observed during the warming of the leopard shark blood under simulated arterial conditions, a finding that is likely related to the estuarine ecology of this species. Taken together, we found species-specific differences in how temperature affects blood oxygen affinity in sharks, with some similarities between the regionally endothermic sharks and several regionally endothermic teleost fishes.
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Affiliation(s)
- Diego Bernal
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, La Jolla, CA, 92093, USA.
- Department of Biology, University of Massachusetts, Dartmouth, MA, 02747, USA.
| | - Joseph P Reid
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA, 95616, USA
| | - Julie M Roessig
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA, 95616, USA
| | - Shinsyu Matsumoto
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA, 95616, USA
| | - Chugey A Sepulveda
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, La Jolla, CA, 92093, USA
- Pfleger Institute of Environmental Research, Oceanside, CA, 92054, USA
| | - Joseph J Cech
- Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA, 95616, USA
| | - Jeffrey B Graham
- Center for Marine Biotechnology and Biomedicine, Scripps Institution of Oceanography, La Jolla, CA, 92093, USA
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31
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Clifford AM, Weinrauch AM, Goss GG. Dropping the base: recovery from extreme hypercarbia in the CO2 tolerant Pacific hagfish (Eptatretus stoutii). J Comp Physiol B 2017; 188:421-435. [PMID: 29290001 DOI: 10.1007/s00360-017-1141-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 11/24/2017] [Accepted: 12/12/2017] [Indexed: 01/13/2023]
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32
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Weinrauch AM, Clifford AM, Goss GG. Post-prandial physiology and intestinal morphology of the Pacific hagfish (Eptatretus stoutii). J Comp Physiol B 2017; 188:101-112. [DOI: 10.1007/s00360-017-1118-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 07/04/2017] [Accepted: 07/11/2017] [Indexed: 12/26/2022]
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33
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Clifford AM, Weinrauch AM, Edwards SL, Wilkie MP, Goss GG. Flexible ammonia handling strategies using both cutaneous and branchial epithelia in the highly ammonia-tolerant Pacific hagfish. Am J Physiol Regul Integr Comp Physiol 2017; 313:R78-R90. [PMID: 28515081 DOI: 10.1152/ajpregu.00351.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 05/08/2017] [Accepted: 05/08/2017] [Indexed: 12/20/2022]
Abstract
Hagfish consume carrion, potentially exposing them to hypoxia, hypercapnia, and high environmental ammonia (HEA). We investigated branchial and cutaneous ammonia handling strategies by which Pacific hagfish (Eptatretus stoutii) tolerate and recover from high ammonia loading. Hagfish were exposed to HEA (20 mmol/l) for 48 h to elevate plasma total ammonia (TAmm) levels before placement into divided chambers for a 4-h recovery period in ammonia-free seawater where ammonia excretion (JAmm) was measured independently in the anterior and posterior compartments. Localized HEA exposures were also conducted by subjecting hagfish to HEA in either the anterior or posterior compartments. During recovery, HEA-exposed animals increased JAmm in both compartments, with the posterior compartment comprising ~20% of the total JAmm compared with ~11% in non-HEA-exposed fish. Plasma TAmm increased substantially when whole hagfish and the posterior regions were exposed to HEA. Alternatively, plasma TAmm did not elevate after anterior localized HEA exposure. JAmm was concentration dependent (0.05-5 mmol/l) across excised skin patches at up to eightfold greater rates than in skin sections that were excised from HEA-exposed hagfish. Skin excised from more posterior regions displayed greater JAmm than those from more anterior regions. Immunohistochemistry with hagfish-specific anti-rhesus glycoprotein type c (α-hRhcg; ammonia transporter) antibody was characterized by staining on the basal aspect of hagfish epidermis while Western blotting demonstrated greater expression of Rhcg in more posterior skin sections. We conclude that cutaneous Rhcg proteins are involved in cutaneous ammonia excretion by Pacific hagfish and that this mechanism could be particularly important during feeding.
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Affiliation(s)
- Alexander M Clifford
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada; .,Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada
| | - Alyssa M Weinrauch
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.,Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada
| | - Susan L Edwards
- Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada.,Department of Biology, Appalachian State University, Boone, North Carolina; and
| | - Michael P Wilkie
- Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada.,Department of Biology and Laurier Institute for Water Science, Wilfrid Laurier University, Waterloo, Ontario, Canada
| | - Greg G Goss
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada.,Bamfield Marine Sciences Centre, Bamfield, British Columbia, Canada
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Regan MD, Richards JG. Rates of hypoxia induction alter mechanisms of O 2 uptake and the critical O 2 tension of goldfish. ACTA ACUST UNITED AC 2017; 220:2536-2544. [PMID: 28476894 DOI: 10.1242/jeb.154948] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2016] [Accepted: 05/02/2017] [Indexed: 12/23/2022]
Abstract
The rate of hypoxia induction (RHI) is an important but overlooked dimension of environmental hypoxia that may affect an organism's survival. We hypothesized that, compared with rapid RHI, gradual RHI will afford an organism more time to alter plastic phenotypes associated with O2 uptake and subsequently reduce the critical O2 tension (Pcrit) of the rate of O2 uptake (ṀO2 ). We investigated this by determining Pcrit values for goldfish exposed to short (∼24 min), typical (∼84 min) and long (∼480 min) duration Pcrit trials to represent different RHIs. Consistent with our predictions, long duration Pcrit trials yielded significantly lower Pcrit values (1.0-1.4 kPa) than short and typical duration trials, which did not differ (2.6±0.3 and 2.5±0.2 kPa, respectively). Parallel experiments revealed these time-related shifts in Pcrit were associated with changes to aspects of the O2 transport cascade that took place over the hypoxia exposures: gill surface areas and haemoglobin-O2 binding affinities were significantly higher in fish exposed to gradual RHIs over 480 min than fish exposed to rapid RHIs over 60 min. Our results also revealed that the choice of respirometric technique (i.e. closed versus intermittent) does not affect Pcrit or routine ṀO2 , despite the significantly reduced water pH and elevated CO2 and ammonia levels measured following closed-circuit Pcrit trials of ∼90 min. Together, our results demonstrate that gradual RHIs result in alterations to physiological parameters that enhance O2 uptake in hypoxic environments. An organism's innate Pcrit is therefore most accurately determined using rapid RHIs (<90 min) so as to avoid the confounding effects of hypoxic acclimation.
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Affiliation(s)
- Matthew D Regan
- Department of Zoology, University of British Columbia, 6270 University Blvd, Vancouver, British Columbia, Canada V6T 1Z4
| | - Jeffrey G Richards
- Department of Zoology, University of British Columbia, 6270 University Blvd, Vancouver, British Columbia, Canada V6T 1Z4
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35
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Blewett TA, Ransberry VE, McClelland GB, Wood CM. Investigating the mechanisms of Ni uptake and sub-lethal toxicity in the Atlantic killifish Fundulus heteroclitus in relation to salinity. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2016; 211:370-381. [PMID: 26796747 DOI: 10.1016/j.envpol.2016.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2015] [Revised: 12/24/2015] [Accepted: 01/01/2016] [Indexed: 06/05/2023]
Abstract
The Atlantic killifish (Fundulus heteroclitus) is a resilient estuarine species that may be subjected to anthropogenic contamination of its natural habitat, by toxicants such as nickel (Ni). We investigated Ni accumulation and potential modes of Ni toxicity, in killifish, as a function of environmental salinity. Killifish were acclimated to 4 different salinities [0 freshwater (FW), 10, 30 and 100% seawater (SW)] and exposed to 5 mg/L of Ni for 96 h. Tissue Ni accumulation, whole body ions, critical swim speed and oxidative stress parameters were examined. SW was protective against Ni accumulation in the gills and kidney. Addition of Mg and Ca to FW protected against gill Ni accumulation, suggesting competition with Ni for uptake. Concentration-dependent Ni accumulation in the gill exhibited saturable relationships in both FW- and SW-acclimated fish. However SW fish displayed a lower Bmax (i.e. lower number of Ni binding sites) and a lower Km (i.e. higher affinity for Ni binding). No effect of Ni exposure was observed on critical swim speed (Ucrit) or maximum rate of oxygen consumption (MO2max). Markers of oxidative stress showed either no effect (e.g. protein carbonyl formation), or variable effects that appeared to depend more on salinity than on Ni exposure. These data indicate that the killifish is very tolerant to Ni toxicity, a characteristic that may facilitate the use of this species as a site-specific biomonitor of contaminated estuaries.
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Affiliation(s)
- Tamzin A Blewett
- Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada.
| | | | - Grant B McClelland
- Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Chris M Wood
- Department of Biology, McMaster University, Hamilton, ON, L8S 4K1, Canada; Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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36
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Regan MD, Gill I, Richards JG. Calorespirometry reveals that goldfish prioritize aerobic metabolism over metabolic rate depression in all but near-anoxic environments. J Exp Biol 2016; 220:564-572. [DOI: 10.1242/jeb.145169] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Accepted: 11/21/2016] [Indexed: 10/20/2022]
Abstract
Metabolic rate depression (MRD) has long been proposed as the key metabolic strategy of hypoxic survival, but surprisingly the effects of changes in hypoxic O2 tensions (PwO2) on MRD are largely unexplored. We simultaneously measured the O2 consumption rate (ṀO2) and metabolic heat of goldfish using calorespirometry to test the hypothesis that MRD is employed at hypoxic PwO2s and initiated just below Pcrit, the PwO2 below which ṀO2 is forced to progressively decline as the fish oxyconforms to decreasing PwO2. Specifically, we used closed-chamber and flow-through calorespirometry together with terminal sampling experiments to examine the effects of PwO2 and time on ṀO2, metabolic heat and anaerobic metabolism (lactate and ethanol production). The closed-chamber and flow-through experiments yielded slightly different results. Under closed-chamber conditions with a continually decreasing PwO2, goldfish showed a Pcrit of 3.0±0.3 kPa and metabolic heat production was only depressed at PwO2 between 0 and 0.67 kPa. Under flow-through conditions with PwO2 held at a variety of oxygen tensions for 1 and 4 h, goldfish also initiated MRD between 0 and 0.67 kPa but maintained ṀO2 to 0.67 kPa, indicating that Pcrit is at or below this PwO2. Anaerobic metabolism was strongly activated at PwO2 ≤1.3 kPa, but only used within the first hour at 1.3 and 0.67 kPa as anaerobic end-products did not accumulate between 1 and 4 h exposure. Taken together, it appears that goldfish reserve MRD for near-anoxia, supporting routine metabolic rate at sub-Pcrit PwO2s with the help of anaerobic glycolysis in the closed-chamber experiments, and aerobically after an initial (<1 h) activation of anaerobic metabolism in the flow-through experiments, even at 0.67 kPa PwO2.
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Affiliation(s)
- Matthew D. Regan
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada
| | - Ivan Gill
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada
| | - Jeffrey G. Richards
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC V6T 1Z4, Canada
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37
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Clifford AM, Zimmer AM, Wood CM, Goss GG. It's all in the gills: Evaluation of O2 uptake in Pacific hagfish refutes a major respiratory role for the skin. J Exp Biol 2016; 219:2814-2818. [DOI: 10.1242/jeb.141598] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 07/01/2016] [Indexed: 01/02/2023]
Abstract
Hagfish skin has been reported as an important site for ammonia excretion and as the major site of systemic oxygen acquisition. However, debate remains whether cutaneous O2 uptake is the dominant route of uptake; all evidence supporting this hypothesis has been derived using indirect measurements. Here we use separating chambers and direct measurements of oxygen consumption and ammonia excretion to quantify cutaneous and branchial exchanges in Pacific hagfish (Eptatretus stoutii) at rest and following exhaustive exercise. Hagfish primarily relied on the gills for both O2 uptake (81.0%) and ammonia excretion (70.7%). Following exercise, both O2 uptake and ammonia excretion increased, but only across the gill; cutaneous exchange was not increased. When branchial O2 availability was reduced by exposure to anteriorly-localized hypoxia (∼4.6 kPa O2), cutaneous O2 consumption was only slightly elevated on an absolute basis. These results refute a major role for cutaneous O2 acquisition in the Pacific hagfish.
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Affiliation(s)
- Alexander M. Clifford
- Department of Biological Sciences, University of Alberta, 116 St. and 85 Ave., Edmonton, Alberta, T6G 2R3, Canada
- Bamfield Marine Sciences Centre, 100 Pachena Rd., Bamfield, British Columbia, V0R 1B0, Canada
| | - Alex M. Zimmer
- Bamfield Marine Sciences Centre, 100 Pachena Rd., Bamfield, British Columbia, V0R 1B0, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Chris M. Wood
- Bamfield Marine Sciences Centre, 100 Pachena Rd., Bamfield, British Columbia, V0R 1B0, Canada
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Greg G. Goss
- Department of Biological Sciences, University of Alberta, 116 St. and 85 Ave., Edmonton, Alberta, T6G 2R3, Canada
- Bamfield Marine Sciences Centre, 100 Pachena Rd., Bamfield, British Columbia, V0R 1B0, Canada
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38
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Gillis TE, Regan MD, Cox GK, Harter TS, Brauner CJ, Richards JG, Farrell AP. Characterizing the metabolic capacity of the anoxic hagfish heart. ACTA ACUST UNITED AC 2015; 218:3754-61. [PMID: 26486366 DOI: 10.1242/jeb.125070] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 09/28/2015] [Indexed: 01/31/2023]
Abstract
Pacific hagfish, Eptatretus stoutii, can recover from 36 h of anoxia at 10°C. Such anoxia tolerance demands the mobilization of anaerobic fuels and the removal of metabolic wastes--processes that require a functional heart. The purpose of this study was to measure the metabolic response of the excised, cannulated hagfish heart to anoxia using direct calorimetry. These experiments were coupled with measurements of cardiac pH and metabolite concentrations, at multiple time points, to monitor acid-base balance and anaerobic ATP production. We also exposed hagfish to anoxia to compare the in vitro responses of the excised hearts with the in vivo responses. The calorimetry results revealed a significant reduction in the rate of metabolic heat production over the first hour of anoxia exposure, and a recovery over the subsequent 6 h. This response is likely attributable to a rapid anoxia-induced depression of aerobic ATP-production pathways followed by an upregulation of anaerobic ATP-production pathways such that the ATP production rate was restored to that measured in normoxia. Glycogen-depletion measurements suggest that metabolic processes were initially supported by glycolysis but that an alternative fuel source was used to support the sustained rates of ATP production. The maintenance of intracellular pH during anoxia indicates a remarkable ability of the myocytes to buffer/regulate protons and thus protect cardiac function. Altogether, these results illustrate that the low metabolic demand of the hagfish heart allows for near-routine levels of cardiac metabolism to be supported anaerobically. This is probably a significant contributor to the hagfish's exceptional anoxia tolerance.
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Affiliation(s)
- Todd E Gillis
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada N1G 2W1
| | - Matthew D Regan
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Georgina K Cox
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Till S Harter
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Colin J Brauner
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Jeff G Richards
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
| | - Anthony P Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada V6T 1Z4
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Rummer JL, Brauner CJ. Root Effect Haemoglobins in Fish May Greatly Enhance General Oxygen Delivery Relative to Other Vertebrates. PLoS One 2015; 10:e0139477. [PMID: 26436414 PMCID: PMC4593521 DOI: 10.1371/journal.pone.0139477] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Accepted: 09/14/2015] [Indexed: 11/19/2022] Open
Abstract
The teleost fishes represent over half of all extant vertebrates; they occupy nearly every body of water and in doing so, occupy a diverse array of environmental conditions. We propose that their success is related to a unique oxygen (O2) transport system involving their extremely pH-sensitive haemoglobin (Hb). A reduction in pH reduces both Hb-O2 affinity (Bohr effect) and carrying capacity (Root effect). This, combined with a large arterial-venous pH change (ΔpHa-v) relative to other vertebrates, may greatly enhance tissue oxygen delivery in teleosts (e.g., rainbow trout) during stress, beyond that in mammals (e.g., human). We generated oxygen equilibrium curves (OECs) at five different CO2 tensions for rainbow trout and determined that, when Hb-O2 saturation is 50% or greater, the change in oxygen partial pressure (ΔPO2) associated with ΔpHa-v can exceed that of the mammalian Bohr effect by at least 3-fold, but as much as 21-fold. Using known ΔpHa-v and assuming a constant arterial-venous PO2 difference (Pa-vO2), Root effect Hbs can enhance O2 release to the tissues by 73.5% in trout; whereas, the Bohr effect alone is responsible for enhancing O2 release by only 1.3% in humans. Disequilibrium states are likely operational in teleosts in vivo, and therefore the ΔpHa-v, and thus enhancement of O2 delivery, could be even larger. Modeling with known Pa-vO2 in fish during exercise and hypoxia indicates that O2 release from the Hb and therefore potentially tissue O2 delivery may double during exercise and triple during some levels of hypoxia. These characteristics may be central to performance of athletic fish species such as salmonids, but may indicate that general tissue oxygen delivery may have been the incipient function of Root effect Hbs in fish, a trait strongly associated with the adaptive radiation of teleosts.
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Affiliation(s)
- Jodie L. Rummer
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4 Canada
- ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, QLD 4811 Australia
- * E-mail:
| | - Colin J. Brauner
- Department of Zoology, University of British Columbia, 6270 University Blvd., Vancouver, BC, V6T 1Z4 Canada
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40
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Hagfish: Champions of CO2 tolerance question the origins of vertebrate gill function. Sci Rep 2015; 5:11182. [PMID: 26057989 PMCID: PMC4460890 DOI: 10.1038/srep11182] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Accepted: 04/07/2015] [Indexed: 11/30/2022] Open
Abstract
The gill is widely accepted to have played a key role in the adaptive radiation of early vertebrates by supplanting the skin as the dominant site of gas exchange. However, in the most basal extant craniates, the hagfishes, gills play only a minor role in gas exchange. In contrast, we found hagfish gills to be associated with a tremendous capacity for acid-base regulation. Indeed, Pacific hagfish exposed acutely to severe sustained hypercarbia tolerated among the most severe blood acidoses ever reported (1.2 pH unit reduction) and subsequently exhibited the greatest degree of acid-base compensation ever observed in an aquatic chordate. This was accomplished through an unprecedented increase in plasma [HCO3−] (>75 mM) in exchange for [Cl−]. We thus propose that the first physiological function of the ancestral gill was acid-base regulation, and that the gill was later co-opted for its central role in gas exchange in more derived aquatic vertebrates.
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41
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Nielsen PM, Fago A. Inhibitory effects of nitrite on the reactions of bovine carbonic anhydrase II with CO2 and bicarbonate consistent with zinc-bound nitrite. J Inorg Biochem 2015; 149:6-11. [PMID: 25951615 DOI: 10.1016/j.jinorgbio.2015.04.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2014] [Revised: 04/21/2015] [Accepted: 04/21/2015] [Indexed: 11/28/2022]
Abstract
Carbonic anhydrase (CA) is a zinc enzyme that catalyzes hydration of carbon dioxide (CO2) and dehydration of bicarbonate in red blood cells, thus facilitating CO2 transport and excretion. Bovine CA II may also react with nitrite to generate nitric oxide, although nitrite is a known inhibitor of the CO2 hydration reaction. To address the potential in vivo interference of these reactions and the nature of nitrite binding to the enzyme, we here investigate the inhibitory effect of 10-30 mM nitrite on Michaelis-Menten kinetics of CO2 hydration and bicarbonate dehydration by stopped-flow spectroscopy. Our data show that nitrite significantly affects the apparent dissociation constant KM for CO2 (11 mM) and bicarbonate (221 mM), and the turnover number kcat for the CO2 hydration (1.467 × 10(6) s(-1)) but not for the bicarbonate dehydration (7.927 × 10(5) s(-1)). These effects demonstrate mixed and competitive inhibition for the reaction with CO2 and bicarbonate, respectively, and are consistent with nitrite binding to the active site zinc. The high apparent dissociation constant found here for CO2, bicarbonate and nitrite (16-120 mM) are all overall consistent with published data and reveal a large capacity of free enzyme available for binding each of the three substrates at their in vivo levels, with little or no significant interference among reactions. The low affinity of the enzyme for nitrite suggests that the in vivo interaction between red blood cell CA II and nitrite requires compartmentalization at the anion exchanger protein of the red cell membrane to be physiologically relevant.
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Affiliation(s)
- Per M Nielsen
- Department of Bioscience, Aarhus University, C.F. Møllers Alle 3, DK-8000 Aarhus C, Denmark.
| | - Angela Fago
- Department of Bioscience, Aarhus University, C.F. Møllers Alle 3, DK-8000 Aarhus C, Denmark.
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42
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Oellermann M, Lieb B, Pörtner HO, Semmens JM, Mark FC. Blue blood on ice: modulated blood oxygen transport facilitates cold compensation and eurythermy in an Antarctic octopod. Front Zool 2015; 12:6. [PMID: 25897316 PMCID: PMC4403823 DOI: 10.1186/s12983-015-0097-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Accepted: 02/16/2015] [Indexed: 11/30/2022] Open
Abstract
INTRODUCTION The Antarctic Ocean hosts a rich and diverse fauna despite inhospitable temperatures close to freezing, which require specialist adaptations to sustain animal activity and various underlying body functions. While oxygen transport has been suggested to be key in setting thermal tolerance in warmer climates, this constraint is relaxed in Antarctic fishes and crustaceans, due to high levels of dissolved oxygen. Less is known about how other Antarctic ectotherms cope with temperatures near zero, particularly the more active invertebrates like the abundant octopods. A continued reliance on the highly specialised blood oxygen transport system of cephalopods may concur with functional constraints at cold temperatures. We therefore analysed the octopod's central oxygen transport component, the blue blood pigment haemocyanin, to unravel strategies that sustain oxygen supply at cold temperatures. RESULTS To identify adaptive compensation of blood oxygen transport in octopods from different climatic regions, we compared haemocyanin oxygen binding properties, oxygen carrying capacities as well as haemolymph protein and ion composition between the Antarctic octopod Pareledone charcoti, the South-east Australian Octopus pallidus and the Mediterranean Eledone moschata. In the Antarctic Pareledone charcoti at 0°C, oxygen unloading by haemocyanin was poor but supported by high levels of dissolved oxygen. However, lower oxygen affinity and higher oxygen carrying capacity compared to warm water octopods, still enabled significant contribution of haemocyanin to oxygen transport at 0°C. At warmer temperatures, haemocyanin of Pareledone charcoti releases most of the bound oxygen, supporting oxygen supply at 10°C. In warm water octopods, increasing oxygen affinities reduce the ability to release oxygen from haemocyanin at colder temperatures. Though, unlike Eledone moschata, Octopus pallidus attenuated this increase below 15°C. CONCLUSIONS Adjustments of haemocyanin physiological function and haemocyanin concentrations but also high dissolved oxygen concentrations support oxygen supply in the Antarctic octopus Pareledone charcoti at near freezing temperatures. Increased oxygen supply by haemocyanin at warmer temperatures supports extended warm tolerance and thus eurythermy of Pareledone charcoti. Limited haemocyanin function towards colder temperatures in Antarctic and warm water octopods highlights the general role of haemocyanin oxygen transport in constraining cold tolerance in octopods.
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Affiliation(s)
- Michael Oellermann
- />Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | - Bernhard Lieb
- />Institute of Zoology, Johannes Gutenberg-Universität, Müllerweg 6, 55099 Mainz, Germany
| | - Hans-O Pörtner
- />Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
| | - Jayson M Semmens
- />Fisheries, Aquaculture and Coasts Centre, Institute for Marine and Antarctic Studies (IMAS), University of Tasmania, Hobart, Tasmania 7001 Australia
| | - Felix C Mark
- />Alfred-Wegener-Institute Helmholtz Centre for Polar and Marine Research, Am Handelshafen 12, 27570 Bremerhaven, Germany
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43
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Tilleman L, Germani F, De Henau S, Helbo S, Desmet F, Berghmans H, Van Doorslaer S, Hoogewijs D, Schoofs L, Braeckman BP, Moens L, Fago A, Dewilde S. A globin domain in a neuronal transmembrane receptor of Caenorhabditis elegans and Ascaris suum: molecular modeling and functional properties. J Biol Chem 2015; 290:10336-52. [PMID: 25666609 DOI: 10.1074/jbc.m114.576520] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2014] [Indexed: 01/12/2023] Open
Abstract
We report the structural and biochemical characterization of GLB-33, a putative neuropeptide receptor that is exclusively expressed in the nervous system of the nematode Caenorhabditis elegans. This unique chimeric protein is composed of a 7-transmembrane domain (7TM), GLB-33 7TM, typical of a G-protein-coupled receptor, and of a globin domain (GD), GLB-33 GD. Comprehensive sequence similarity searches in the genome of the parasitic nematode, Ascaris suum, revealed a chimeric protein that is similar to a Phe-Met-Arg-Phe-amide neuropeptide receptor. The three-dimensional structures of the separate domains of both species and of the full-length proteins were modeled. The 7TM domains of both proteins appeared very similar, but the globin domain of the A. suum receptor surprisingly seemed to lack several helices, suggesting a novel truncated globin fold. The globin domain of C. elegans GLB-33, however, was very similar to a genuine myoglobin-type molecule. Spectroscopic analysis of the recombinant GLB-33 GD showed that the heme is pentacoordinate when ferrous and in the hydroxide-ligated form when ferric, even at neutral pH. Flash-photolysis experiments showed overall fast biphasic CO rebinding kinetics. In its ferrous deoxy form, GLB-33 GD is capable of reversibly binding O2 with a very high affinity and of reducing nitrite to nitric oxide faster than other globins. Collectively, these properties suggest that the globin domain of GLB-33 may serve as a highly sensitive oxygen sensor and/or as a nitrite reductase. Both properties are potentially able to modulate the neuropeptide sensitivity of the neuronal transmembrane receptor.
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Affiliation(s)
| | | | - Sasha De Henau
- the Department of Biology, Ghent University, 9000 Ghent, Belgium
| | - Signe Helbo
- the Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark
| | - Filip Desmet
- Physics, University of Antwerp, 2610 Antwerp, Belgium
| | | | | | - David Hoogewijs
- the Institute of Physiology and Zürich Center for Integrative Human Physiology, University of Zürich, 8006 Zürich, Switzerland, Institute of Physiology, University of Duisburg-Essen, D-45147 Essen, Germany, and
| | - Liliane Schoofs
- the Functional Genomics and Proteomics Group, KU Leuven, 3000 Leuven, Belgium
| | - Bart P Braeckman
- the Department of Biology, Ghent University, 9000 Ghent, Belgium
| | - Luc Moens
- From the Departments of Biomedical Sciences and
| | - Angela Fago
- the Department of Bioscience, Aarhus University, 8000 Aarhus, Denmark
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44
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Gillis T, Regan M, Cox G, Harter T, Brauner C, Richards J, Farrell A. Characterizing the metabolic capacity of the anoxic hagfish heart. J Exp Biol 2015. [DOI: 10.https://doi.org/10.1242/jeb.125070] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Pacific hagfish, Eptatretus stoutii, can recover from 36 h of anoxia at 10°C. Such anoxia tolerance demands the mobilization of anaerobic fuels and the removal of metabolic wastes, processes that require a functional heart. The purpose of this study was to measure the metabolic response of the excised, cannulated hagfish heart to anoxia using direct calorimetry. These experiments were coupled with measurements of cardiac pH and metabolite concentrations, at multiple time points, to monitor acid-base balance and anaerobic ATP-production. We also exposed hagfish to anoxia to compare the in vitro responses of the excised hearts with the in vivo responses. The calorimetry results revealed a significant reduction in the rate of metabolic heat production over the first hour of anoxia exposure, and a recovery over the subsequent 6 h. This response was likely attributable to a rapid anoxia-induced depression of aerobic ATP-production pathways followed by an up-regulation of anaerobic ATP-production pathways such that the ATP production rate was restored to that measured in normoxia. Glycogen-depletion measurements suggest that metabolic processes were initially supported by glycolysis but that an alternate fuel source was used to support the sustained rates of ATP production. The maintenance of intracellular pH during anoxia indicates a remarkable ability of the myocytes to buffer/regulate protons and thus protect cardiac function. Altogether, these results illustrate that the low metabolic demand of the hagfish heart allows for near-routine levels of cardiac metabolism to be supported anaerobically. This is likely a significant contributor to the hagfish's exceptional anoxia tolerance.
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Affiliation(s)
- T.E. Gillis
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G-2W1
| | - M.D. Regan
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - G.K. Cox
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - T.S. Harter
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - C.J. Brauner
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - J.G. Richards
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - A.P. Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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45
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Gillis T, Regan M, Cox G, Harter T, Brauner C, Richards J, Farrell A. Characterizing the metabolic capacity of the anoxic hagfish heart. J Exp Biol 2015. [DOI: 10.https:/doi.org/10.1242/jeb.125070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/27/2023]
Abstract
Pacific hagfish, Eptatretus stoutii, can recover from 36 h of anoxia at 10°C. Such anoxia tolerance demands the mobilization of anaerobic fuels and the removal of metabolic wastes, processes that require a functional heart. The purpose of this study was to measure the metabolic response of the excised, cannulated hagfish heart to anoxia using direct calorimetry. These experiments were coupled with measurements of cardiac pH and metabolite concentrations, at multiple time points, to monitor acid-base balance and anaerobic ATP-production. We also exposed hagfish to anoxia to compare the in vitro responses of the excised hearts with the in vivo responses. The calorimetry results revealed a significant reduction in the rate of metabolic heat production over the first hour of anoxia exposure, and a recovery over the subsequent 6 h. This response was likely attributable to a rapid anoxia-induced depression of aerobic ATP-production pathways followed by an up-regulation of anaerobic ATP-production pathways such that the ATP production rate was restored to that measured in normoxia. Glycogen-depletion measurements suggest that metabolic processes were initially supported by glycolysis but that an alternate fuel source was used to support the sustained rates of ATP production. The maintenance of intracellular pH during anoxia indicates a remarkable ability of the myocytes to buffer/regulate protons and thus protect cardiac function. Altogether, these results illustrate that the low metabolic demand of the hagfish heart allows for near-routine levels of cardiac metabolism to be supported anaerobically. This is likely a significant contributor to the hagfish's exceptional anoxia tolerance.
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Affiliation(s)
- T.E. Gillis
- Department of Integrative Biology, University of Guelph, Guelph, ON, Canada, N1G-2W1
| | - M.D. Regan
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - G.K. Cox
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - T.S. Harter
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - C.J. Brauner
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - J.G. Richards
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - A.P. Farrell
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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46
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Malte CL, Jakobsen SL, Wang T. A critical evaluation of automated blood gas measurements in comparative respiratory physiology. Comp Biochem Physiol A Mol Integr Physiol 2014; 178:7-17. [DOI: 10.1016/j.cbpa.2014.07.022] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/23/2014] [Accepted: 07/23/2014] [Indexed: 10/25/2022]
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47
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Heuer RM, Grosell M. Physiological impacts of elevated carbon dioxide and ocean acidification on fish. Am J Physiol Regul Integr Comp Physiol 2014; 307:R1061-84. [DOI: 10.1152/ajpregu.00064.2014] [Citation(s) in RCA: 258] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Most fish studied to date efficiently compensate for a hypercapnic acid-base disturbance; however, many recent studies examining the effects of ocean acidification on fish have documented impacts at CO2 levels predicted to occur before the end of this century. Notable impacts on neurosensory and behavioral endpoints, otolith growth, mitochondrial function, and metabolic rate demonstrate an unexpected sensitivity to current-day and near-future CO2 levels. Most explanations for these effects seem to center on increases in Pco2 and HCO3− that occur in the body during pH compensation for acid-base balance; however, few studies have measured these parameters at environmentally relevant CO2 levels or directly related them to reported negative endpoints. This compensatory response is well documented, but noted variation in dynamic regulation of acid-base transport pathways across species, exposure levels, and exposure duration suggests that multiple strategies may be utilized to cope with hypercapnia. Understanding this regulation and changes in ion gradients in extracellular and intracellular compartments during CO2 exposure could provide a basis for predicting sensitivity and explaining interspecies variation. Based on analysis of the existing literature, the present review presents a clear message that ocean acidification may cause significant effects on fish across multiple physiological systems, suggesting that pH compensation does not necessarily confer tolerance as downstream consequences and tradeoffs occur. It remains difficult to assess if acclimation responses during abrupt CO2 exposures will translate to fitness impacts over longer timescales. Nonetheless, identifying mechanisms and processes that may be subject to selective pressure could be one of many important components of assessing adaptive capacity.
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Affiliation(s)
- Rachael M. Heuer
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Marine Biology and Fisheries, Miami, Florida
| | - Martin Grosell
- Rosenstiel School of Marine and Atmospheric Science, University of Miami, Marine Biology and Fisheries, Miami, Florida
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48
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Cooper CA, Regan MD, Brauner CJ, De Bastos ESR, Wilson RW. Osmoregulatory bicarbonate secretion exploits H(+)-sensitive haemoglobins to autoregulate intestinal O2 delivery in euryhaline teleosts. J Comp Physiol B 2014; 184:865-76. [PMID: 25160040 PMCID: PMC4171588 DOI: 10.1007/s00360-014-0844-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Revised: 04/01/2014] [Accepted: 04/11/2014] [Indexed: 11/30/2022]
Abstract
Marine teleost fish secrete bicarbonate (HCO3 (-)) into the intestine to aid osmoregulation and limit Ca(2+) uptake by carbonate precipitation. Intestinal HCO3 (-) secretion is associated with an equimolar transport of protons (H(+)) into the blood, both being proportional to environmental salinity. We hypothesized that the H(+)-sensitive haemoglobin (Hb) system of seawater teleosts could be exploited via the Bohr and/or Root effects (reduced Hb-O2 affinity and/or capacity with decreasing pH) to improve O2 delivery to intestinal cells during high metabolic demand associated with osmoregulation. To test this, we characterized H(+) equilibria and gas exchange properties of European flounder (Platichthys flesus) haemoglobin and constructed a model incorporating these values, intestinal blood flow rates and arterial-venous acidification at three different environmental salinities (33, 60 and 90). The model suggested red blood cell pH (pHi) during passage through intestinal capillaries could be reduced by 0.14-0.33 units (depending on external salinity) which is sufficient to activate the Bohr effect (Bohr coefficient of -0.63), and perhaps even the Root effect, and enhance tissue O2 delivery by up to 42 % without changing blood flow. In vivo measurements of intestinal venous blood pH were not possible in flounder but were in seawater-acclimated rainbow trout which confirmed a blood acidification of no less than 0.2 units (equivalent to -0.12 for pHi). When using trout-specific values for the model variables, predicted values were consistent with measured in vivo values, further supporting the model. Thus this system is an elegant example of autoregulation: as the need for costly osmoregulatory processes (including HCO3 (-) secretion) increases at higher environmental salinity, so does the enhancement of O2 delivery to the intestine via a localized acidosis and the Bohr (and possibly Root) effect.
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Affiliation(s)
- C. A. Cooper
- Department of Chemistry, Wilfrid Laurier University, 75 University Ave. West, Waterloo, ON N2L 3C5 Canada
| | - M. D. Regan
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC Canada
| | - C. J. Brauner
- Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, BC Canada
| | - E. S. R. De Bastos
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Exeter, Devon EX4 4QD UK
| | - R. W. Wilson
- Biosciences, College of Life and Environmental Sciences, University of Exeter, Geoffrey Pope Building, Exeter, Devon EX4 4QD UK
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Helbo S, Gow AJ, Jamil A, Howes BD, Smulevich G, Fago A. Oxygen-linked S-nitrosation in fish myoglobins: a cysteine-specific tertiary allosteric effect. PLoS One 2014; 9:e97012. [PMID: 24879536 PMCID: PMC4039430 DOI: 10.1371/journal.pone.0097012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 04/15/2014] [Indexed: 11/18/2022] Open
Abstract
The discovery that cysteine (Cys) S-nitrosation of trout myoglobin (Mb) increases heme O2 affinity has revealed a novel allosteric effect that may promote hypoxia-induced nitric oxide (NO) delivery in the trout heart and improve myocardial efficiency. To better understand this allosteric effect, we investigated the functional effects and structural origin of S-nitrosation in selected fish Mbs differing by content and position of reactive cysteine (Cys) residues. The Mbs from the Atlantic salmon and the yellowfin tuna, containing two and one reactive Cys, respectively, were S-nitrosated in vitro by reaction with Cys-NO to generate Mb-SNO to a similar yield (∼0.50 SH/heme), suggesting reaction at a specific Cys residue. As found for trout, salmon Mb showed a low O2 affinity (P50 = 2.7 torr) that was increased by S-nitrosation (P50 = 1.7 torr), whereas in tuna Mb, O2 affinity (P50 = 0.9 torr) was independent of S-nitrosation. O2 dissociation rates (koff) of trout and salmon Mbs were not altered when Cys were in the SNO or N-ethylmaleimide (NEM) forms, suggesting that S-nitrosation should affect O2 affinity by raising the O2 association rate (kon). Taken together, these results indicate that O2-linked S-nitrosation may occur specifically at Cys107, present in salmon and trout Mb but not in tuna Mb, and that it may relieve protein constraints that limit O2 entry to the heme pocket of the unmodified Mb by a yet unknown mechanism. UV-Vis and resonance Raman spectra of the NEM-derivative of trout Mb (functionally equivalent to Mb-SNO and not photolabile) were identical to those of the unmodified Mb, indicating that S-nitrosation does not affect the extent or nature of heme-ligand stabilization of the fully ligated protein. The importance of S-nitrosation of Mb in vivo is confirmed by the observation that Mb-SNO is present in trout hearts and that its level can be significantly reduced by anoxic conditions.
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Affiliation(s)
- Signe Helbo
- Department of Bioscience, Aarhus University, Aarhus, Denmark
| | - Andrew J. Gow
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, New Jersey, United States of America
| | - Amna Jamil
- Department of Pharmacology and Toxicology, Ernest Mario School of Pharmacy, Rutgers University, Piscataway, New Jersey, United States of America
| | - Barry D. Howes
- Department of Chemistry “Ugo Schiff”, University of Firenze, Sesto Fiorentino (FI), Italy
| | - Giulietta Smulevich
- Department of Chemistry “Ugo Schiff”, University of Firenze, Sesto Fiorentino (FI), Italy
| | - Angela Fago
- Department of Bioscience, Aarhus University, Aarhus, Denmark
- * E-mail:
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Guffey SC, Goss GG. Time course of the acute response of the North Pacific spiny dogfish shark (Squalus suckleyi) to low salinity. Comp Biochem Physiol A Mol Integr Physiol 2014; 171:9-15. [PMID: 24518388 DOI: 10.1016/j.cbpa.2014.02.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 01/23/2014] [Accepted: 02/04/2014] [Indexed: 10/25/2022]
Abstract
Dogfish are considered stenohaline sharks but are known to briefly enter estuaries. The acute response of North Pacific spiny dogfish (Squalus suckleyi) to lowered salinity was tested by exposing sharks to 21‰ salinity for 48 h. Temporal trends in blood pH, plasma osmolality, CO2, HCO3(-), Na(+), Cl(-), K(+), and urea concentrations, and in the rates of urea efflux and O2 consumption, were quantified. The rate of O2 consumption exhibited cyclic variation and was significantly depressed by lowered salinity. After 9 h, plasma [Cl(-)] stabilized at 9% below initial levels, while plasma [Na(+)] decreased by more than 20% within the first 12 h. Plasma [urea] dropped by 15% between 4 and 6 h, and continued to decrease. The rate of urea efflux increased over time, peaking after 36 h at 72% above the initial rate. Free-swimming sharks subjected to the same salinity challenge survived over 96 h and differed from cannulated sharks with respect to patterns of Na(+) and urea homeostasis. This high-resolution study reveals that dogfish exposed to 21‰ salinity can maintain homeostasis of Cl(-) and pH, but Na(+) and urea continue to be lost, likely accounting for the inability of the dogfish to fully acclimate to reduced salinity.
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Affiliation(s)
- Samuel C Guffey
- Department of Biological Sciences, CW405 Biological Sciences Bldg, University of Alberta, Edmonton, AB T6G 2E9, Canada; Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC V0R 1B0, Canada.
| | - Greg G Goss
- Department of Biological Sciences, CW405 Biological Sciences Bldg, University of Alberta, Edmonton, AB T6G 2E9, Canada; Bamfield Marine Sciences Centre, 100 Pachena Road, Bamfield, BC V0R 1B0, Canada.
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