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Sadauskas-Henrique H, Johannsson OE, Po BHK, Val AL, Wood CM. Emersion and recovery alter oxygen consumption, ammonia and urea excretion, and oxidative stress parameters, but not diffusive water exchange or transepithelial potential in the green crab (Carcinus maenas). J Exp Biol 2023:310408. [PMID: 37194789 DOI: 10.1242/jeb.245685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 05/08/2023] [Indexed: 05/18/2023]
Abstract
The green crab (C. maenas) is an "inshore" species affected by intertidal zonation patterns, facing periods of emersion during low tide, and submersion during high tide. During these periods of air and subsequent water exposure, these species can face physiological challenges. We examined changes in O2 consumption rate (MO2), ammonia (JAmmnet) and urea (JUreanet) excretion rates over sequential 14 h periods in seawater (32 ppt, control), in air, and during recovery in seawater after air exposure (13°C throughout). At the end of each exposure, the anterior (5th) and posterior (8th) gills, and the hepatopancreas were removed for measurements of oxidative stress parameters (TBARs and catalase in the gills and hepatopancreas, and protein carbonyls in the gills). MO2 remained unchanged during air exposure, but increased greatly (3.4-fold above control levels) during the recovery period. Ammonia and urea net fluxes (JAmmnet and JUreanet) were reduced by 98% during air exposure, but rebounded during recovery to >2-fold the control rates. Exchangeable water pools (VH2O), rate constants of diffusive water exchange (k), and unidirectional diffusive water flux rates (JH2O) (using tritiated water) and transepithelial potential (TEP) were also measured during control and recovery treatments, but exhibited no significant changes. Damage to proteins was not observed in either gill. However, lipid damage occurred in the anterior (respiratory) gill after the air exposure but not in the posterior (ionoregulatory) gill or hepatopancreas. Catalase activity also decreased significantly in recovery relative to levels during air exposure in both the anterior gill and hepatopancreas, but not in the posterior gill. The crabs did not modify water metabolism or permeability. We conclude that MO2 can be maintained during air exposure, it does not meet increased metabolic demand, and ammonia and urea-N excretion are impaired. As a result, all these parameters increase greatly during re-immersion recovery, and oxidative stress also occurs. Clearly, emersion is not without physiological costs.
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Affiliation(s)
- Helen Sadauskas-Henrique
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, Manaus, AM, Brazil
- Laboratory of Ecophysiology and Biochemistry of Aquatic Organisms, Santa Cecília University (Unisanta), Santos, SP, Brazil
- Bamfield Marine Sciences Centre, Bamfield, BC V0R 1B0, Canada
| | - Ora E Johannsson
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, Manaus, AM, Brazil
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
- Bamfield Marine Sciences Centre, Bamfield, BC V0R 1B0, Canada
| | - Beverly H K Po
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
- Bamfield Marine Sciences Centre, Bamfield, BC V0R 1B0, Canada
| | - Adalberto L Val
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, Manaus, AM, Brazil
| | - Chris M Wood
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, Manaus, AM, Brazil
- Department of Zoology, University of British Columbia, Vancouver, BC, Canada
- Bamfield Marine Sciences Centre, Bamfield, BC V0R 1B0, Canada
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Johannsson OE, Ferreira MS, Smith DS, Wood CM, Val AL. Interplay of oxygen and light in the photo-oxidation of dissolved organic carbon. Water Res 2021; 201:117332. [PMID: 34182350 DOI: 10.1016/j.watres.2021.117332] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Revised: 05/14/2021] [Accepted: 06/01/2021] [Indexed: 06/13/2023]
Abstract
Light energy and oxygen drive photo-oxidation of dissolved organic carbon (DOC). The longer the wavelength the greater its depth of penetration into water, changing the spectral environment with depth. We asked how oxygen concentration and light spectral composition might affect photo-oxidation processes in DOC. Outdoor experiments compared responses of fluorescence and absorbance indices to photo-oxidation of filtered (0.45 µm) Rio Negro water (Amazon Basin) under near-anoxia, normoxia and hyperoxia exposed to natural sunlight or reduced sunlight (≥340, reduced-UVR). Near-anoxia decreased all absorbance and fluorescence indices. Absorbance changed across the spectrum (≥250 nm) even under reduced-UVR provided that oxygen was present. This phenomenon maintains broader photo-oxidation and the release of CO2 at depth. Slope350-400 was responsive to changes in the irradiance field but not to oxygen concentration, while Slope275-295 responded to both. Thus, larger molecules are broken down near the water's surface and medium to smaller molecules continue to be processed at depth. The production of fulvic acid-like fluorescence required both UVB and oxygen, restricting its production to surface waters. The relatively small increase in R254/365 compared with the loss of SUVA254 under near-anoxia indicated a slower breakdown of larger DOC molecules as oxygen becomes limiting. Breakdown of larger molecules which absorb in the 350-400 nm range, appears to involve two steps - one by radiant energy and another involving oxygen. The study results reflect the dynamic gradients in photo-oxidation with depth.
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Affiliation(s)
- Ora E Johannsson
- Zoology Department, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada.
| | - Marcio S Ferreira
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil.
| | - D Scott Smith
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, ON, N2L 3C5 Canada.
| | - Chris M Wood
- Zoology Department, University of British Columbia, Vancouver, BC, V6T 1Z4 Canada; Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil.
| | - Adalberto L Val
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
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Johannsson OE, Ferreira MS, Smith DS, Crémazy A, Wood CM, Val AL. Effects of natural light and depth on rates of photo-oxidation of dissolved organic carbon in a major black-water river, the Rio Negro, Brazil. Sci Total Environ 2020; 733:139193. [PMID: 32442875 DOI: 10.1016/j.scitotenv.2020.139193] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2020] [Revised: 04/09/2020] [Accepted: 05/01/2020] [Indexed: 06/11/2023]
Abstract
Systems rich in terrigenous dissolved organic carbon (DOC), like the Rio Negro, can contribute significant amounts of carbon dioxide back to the atmosphere and support important microbial communities. We investigated photo-oxidation in the Rio Negro: (1) the depth to which light causes complete photo-oxidation to CO2 and changes in DOC structure, (2) the daily rate of change of absorbance indices, (3) the relationship between sub-surface rates of photo-oxidation to CO2 and light exposure, (4) the areal rates of photo-oxidation, and (5) the stability of fluorophore signals. Experiments were run in an outdoor pool of Rio Negro water, under natural sunlight during the dry seasons of 2015 and 2018. In 2018, rates of complete photo-oxidation and changes in absorbance indices decayed exponentially, approaching their asymptotes between 9 and 15 cm depth. In 2015, direct absorbance indices ceased changing at 14 cm depth. Fluorescence of humic acid-like moieties continued to decrease, sometimes to 35-43 cm depth. This indicates that partial photo-oxidation of DOC, and thus interaction with the microbial community, occurs to greater depths than previously expected. Areal rates of CO2 production were 28.8 and 39.3 mg C m-2 d-1 (two experiments, October 2018). Sub-surface (1.1 cm) rates were strongly related to light levels, reaching a maximum of 0.68 mg C l-1 d-1 in September. Complete photo-oxidation ceased below 29.6 mW cm-2 d-1 UV radiation, providing a daily baseline for observable production of CO2. Absorbance indices changed by 9 to 14% d-1 at high light levels, except for R254/365 (4.4% d-1). Fluorophore emission ranges were stable between 2014 and 2018, indicating that emissions can be compared across time and space. This study contributes to better estimates and understanding of photo-oxidation in tropical, black-water rivers, which will be useful for carbon modelling.
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Affiliation(s)
- Ora E Johannsson
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| | - Marcio S Ferreira
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
| | - D Scott Smith
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada
| | - Anne Crémazy
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Biological Sciences, University of New Brunswick, Saint John, NB E2L 4L5, Canada
| | - Chris M Wood
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
| | - Adalberto L Val
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
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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. J Fish Biol 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] [What about the content of this article? (0)] [Affiliation(s)] [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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De Boeck G, Wood CM, Brix KV, Sinha AK, Matey V, Johannsson OE, Bianchini A, Bianchini LF, Maina JN, Kavembe GD, Papah MB, Kisipan ML, Ojoo RO. Fasting in the ureotelic Lake Magadi tilapia, Alcolapia grahami, does not reduce its high metabolic demand, increasing its vulnerability to siltation events. Conserv Physiol 2019; 7:coz060. [PMID: 31687141 PMCID: PMC6822538 DOI: 10.1093/conphys/coz060] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 07/16/2019] [Accepted: 07/25/2019] [Indexed: 06/10/2023]
Abstract
Lake Magadi, Kenya, is one of the most extreme aquatic environments on Earth (pH~10, anoxic to hyperoxic, high temperatures). Recently, increased water demand and siltation have threatened the viable hot springs near the margins of the lake where Alcolapia grahami, the only fish surviving in the lake, live. These Lake Magadi tilapia largely depend on nitrogen-rich cyanobacteria for food and are 100% ureotelic. Their exceptionally high aerobic metabolic rate, together with their emaciated appearance, suggests that they are energy-limited. Therefore, we hypothesized that during food deprivation, Magadi tilapia would economize their energy expenditure and reduce metabolic rate, aerobic performance and urea-N excretion. Surprisingly, during a 5-day fasting period, routine metabolic rates increased and swimming performance (critical swimming speed) was not affected. Urea-N excretion remained stable despite the lack of their N-rich food source. Their nitrogen use switched to endogenous sources as liver and muscle protein levels decreased after a 5-day fast, indicating proteolysis. Additionally, fish relied on carbohydrates with lowered muscle glycogen levels, but there were no signs indicating use of lipid stores. Gene expression of gill and gut urea transporters were transiently reduced as were gill rhesus glycoprotein Rhbg and Rhcg-2. The reduction in gill glutamine synthetase expression concomitant with the reduction in Rh glycoprotein gene expression indicates reduced nitrogen/ammonia metabolism, most likely decreased protein synthesis. Additionally, fish showed reduced plasma total CO2, osmolality and Na+ (but not Cl-) levels, possibly related to reduced drinking rates and metabolic acidosis. Our work shows that Lake Magadi tilapia have the capacity to survive short periods of starvation which could occur when siltation linked to flash floods covers their main food source, but their seemingly hardwired high metabolic rates would compromise long-term survival.
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Affiliation(s)
- Gudrun De Boeck
- SPHERE, Department of Biology, Groenenborgerlaan 171, University of Antwerp, Antwerp B-2020, Belgium
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Chris M Wood
- Department of Biology, McMaster University, 1280 Main St W, Hamilton, ON L8S 4K1, Canada
- Department of Zoology, University of British Columbia, 6270 Univ Blvd, Vancouver, BC V6T 1Z4, Canada
- Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Kevin V Brix
- Rosenstiel School of Marine and Atmospheric Sciences, University of Miami, 4600 Rickenbacker Causeway, Miami, FL 33149, USA
- EcoTox, 3211 19th Terrace, Miami, FL 33145, USA
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Amit K Sinha
- SPHERE, Department of Biology, Groenenborgerlaan 171, University of Antwerp, Antwerp B-2020, Belgium
- Department of Aquaculture and Fisheries, University of Arkansas, 1200 North Univ Dr, Pine Bluff, AR 71601, USA
| | - Victoria Matey
- Department of Biology, San Diego State University, 5500 Campanile Dr., San Diego, CA 92182, USA
| | - Ora E Johannsson
- Department of Zoology, University of British Columbia, 6270 Univ Blvd, Vancouver, BC V6T 1Z4, Canada
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Adalto Bianchini
- Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Ave Italia Km 8, Rio Grande, RS 96203-900, Brazil
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Lucas F Bianchini
- Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Ave Italia Km 8, Rio Grande, RS 96203-900, Brazil
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - John N Maina
- Department of Zoology, University of Johannesburg, PO Box 524 Auckland Park, Johannesburg 2006, South Africa
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Geraldine D Kavembe
- School of Dryland Agriculture Science and Technology, South Eastern Kenya University, PO Box 170, Kitui 90200, Kenya
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Michael B Papah
- Department of Animal and Food Sciences, University of Delaware, 531 S. College Ave., Newark, DE 19716, USA
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Mosiany L Kisipan
- Department of Veterinary Anatomy and Physiology, Egerton University, Njoro Campus PO Box 536, Egerton 20115, Kenya
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
| | - Rodi O Ojoo
- Department of Veterinary Anatomy and Physiology, University of Nairobi, Riverside Drive, Chiromo Campus, PO Box 30197-00100, Nairobi 30197, Kenya
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Johannsson OE, Giacomin M, Sadauskas-Henrique H, Campos DF, Braz-Mota S, Heinrichs-Caldas WD, Baptista R, Wood CM, Almeida-Val VMF, Val AL. Does hypoxia or different rates of re-oxygenation after hypoxia induce an oxidative stress response in Cyphocharax abramoides (Kner 1858), a Characid fish of the Rio Negro? Comp Biochem Physiol A Mol Integr Physiol 2018; 224:53-67. [PMID: 29864518 DOI: 10.1016/j.cbpa.2018.05.019] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 05/23/2018] [Accepted: 05/23/2018] [Indexed: 01/22/2023]
Abstract
We examined whether oxidative damage and antioxidant responses are more likely to occur during hypoxia or re-oxygenation in hypoxia-tolerant fish, and whether there is an influence of the rate of re-oxygenation. An hypoxia/re-oxygenation experiment using wild-caught Cyphocharax abramoides (Rio Negro, Brazil), was designed to answer these questions. Lipid peroxidation (MDA), a measure of oxidative damage, and antioxidant activities (superoxide dismutase (SOD), glutathione peroxidase (GPx), antioxidant capacity against peroxyl radicals (ACAP)), were measured in brain, gill and liver tissues after normoxia, 3-h hypoxia (2.7 kPa), and 3-h hypoxia followed by 1-h or 3-h re-oxygenation, implemented either immediately or slowly (3.0 kPa·h-1). Critical oxygen tension of routine oxygen consumption rate (Pcrit) (4.1 kPa) and the PO2 at loss of equilibrium (LOE) (1.7 kPa) were determined to set the experimental hypoxia exposure. The Regulation Index, a measure of oxyregulation with declining PO2, was 0.32. Oxidative damage occurred during hypoxia: no additional damage was observed during re-oxygenation. Tissues responded differentially. GPx and MDA rose in the brain and gills, and SOD (and likely GPx) in the liver during hypoxia. Antioxidants increased further at LOE. Rate of oxygen increase during re-oxygenation did not affect antioxidant responses. In brain and gills, GPx and MDA decreased or recovered after 1-h re-oxygenation. In liver, SOD remained high and GPx increased. In summary, C. abramoides incurred oxidative damage during hypoxic exposure with no additional damage inflicted during re-oxygenation: the rate of re-oxygenation was inconsequential. Literature data support conclusion of greater damage during hypoxia than during re-oxygenation in hypoxia-tolerant fish.
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Affiliation(s)
- Ora E Johannsson
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil; Zoology Department, University of British Columbia, Vancouver, B.C. V6T 1Z4, Canada.
| | - Marina Giacomin
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil; Zoology Department, University of British Columbia, Vancouver, B.C. V6T 1Z4, Canada
| | - Helen Sadauskas-Henrique
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil; UNISANTA (Universidade Santa Cecília), Sustainability of Coastal and Marine Ecosystems, 277 Oswaldo Cruz, Boqueirão, 11045-907 Santos, São Paulo, Brazil
| | - Derek F Campos
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
| | - Susana Braz-Mota
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
| | - Waldir D Heinrichs-Caldas
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
| | - Ramon Baptista
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
| | - Chris M Wood
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil; Zoology Department, University of British Columbia, Vancouver, B.C. V6T 1Z4, Canada.
| | - Vera Maria F Almeida-Val
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil
| | - Adalberto L Val
- Laboratory of Ecophysiology and Molecular Evolution, Brazilian National Institute for Research of the Amazon, INPA, Manaus, AM, Brazil.
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Bianchini LF, Wood CM, Bergman HL, Johannsson OE, Laurent P, Chevalier C, Kisipan ML, Kavembe GD, Papah MB, Brix KV, De Boeck G, Maina JN, Ojoo RO, Bianchini A. Metabolism and antioxidant defense in the larval chironomid Tanytarsus minutipalpus: adjustments to diel variations in the extreme conditions of Lake Magadi. Biol Open 2017; 6:83-91. [PMID: 27895051 PMCID: PMC5278425 DOI: 10.1242/bio.021139] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Insect larvae are reported to be a major component of the simple but highly productive trophic web found in Lake Magadi (Kenya, Africa), which is considered to be one of the most extreme aquatic environments on Earth. Previous studies show that fish must display biochemical and physiological adjustments to thrive under the extreme conditions of the lake. However, information for invertebrates is lacking. In the present study, the occurrence of the larval chironomid Tanytarsus minutipalpus is reported in Lake Magadi for the first time. Additionally, changes in larval metabolism and antioxidant defense correlated with diel variations in the extremely hostile environmental conditions of the lake are described. Wide variations in water temperature (20.2-29.3°C) and dissolved oxygen content (3.2-18.6 mg O2 l−1) were observed at different times of day, without significant change in water pH (10.0±0.03). Temperature and dissolved oxygen were higher at 13:00 h (29.3±0.4°C and 18.6±1.0 mg O2 l−1) and 19:00 h (29.3±0.8°C and 16.2±1.6 mg O2 l−1) and lower at 01:00 h (21.1±0.1°C and 10.7±0.03 mg O2 l−1) and 07:00 h (20.2±0.4°C and 3.2±0.7 mg O2 l−1). Significant and parallel increases in parameters related to metabolism (cholinesterase, glucose, cholesterol, urea, creatinine and hemoglobin) and the antioxidant system (SOD, GPx, GR, GSH and GSSG) were observed in larvae collected at 13:00 h. In contrast, no significant changes were observed in pro-oxidants (ROS and NO), TOSC and oxidative damage parameters (LPO and DNA damage). Therefore, the observed increases in temperature and dissolved O2 content in Lake Magadi were associated with changes in the antioxidant system of T. minutipalpus larvae. Adjustments performed by the chironomid larvae were efficient in maintaining body homeostasis, as well as protecting biomolecules against oxidative damage, so that oxidative stress did not occur. GSH-GSSG and GPx-GR systems appeared to play an essential role in the adjustments displayed by the chironomid larvae during the diel changes in the extreme conditions of Lake Magadi. Summary: Insect larvae display adjustments in metabolism and oxidative status to overcome the diel variations in the extreme and harsh physicochemical conditions of Lake Magadi, a saline and alkaline lake in Kenya.
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Affiliation(s)
- Lucas F Bianchini
- Programa de Pós-Graduação em Ciências Fisiológicas: Fisiologia Animal Comparada, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Avenida Itália km 8, Rio Grande, RS 96203-900, Brazil
| | - Chris M Wood
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1.,Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Harold L Bergman
- Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071, USA
| | - Ora E Johannsson
- Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4
| | - Pierre Laurent
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Claudine Chevalier
- Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
| | - Mosiany L Kisipan
- Department of Veterinary Anatomy and Physiology, Faculty of Veterinary Medicine and Surgery, Egerton University, P.O. Box 536 - 20115, Egerton, Kenya
| | - Geraldine D Kavembe
- Department of Biology, South Eastern Kenya University, Kitui 170-90200, Kenya
| | - Michael B Papah
- Department of Veterinary Anatomy and Physiology, University of Nairobi, P.O. Box 30197, Nairobi 00100, Kenya
| | | | - Gudrun De Boeck
- SPHERE, Department of Biology, University of Antwerp, Antwerp 2020, Belgium
| | - John N Maina
- Department of Zoology, University of Johannesburg, Johannesburg 2006, South Africa
| | - Rodi O Ojoo
- Department of Veterinary Anatomy and Physiology, University of Nairobi, P.O. Box 30197, Nairobi 00100, Kenya
| | - Adalto Bianchini
- Programa de Pós-Graduação em Ciências Fisiológicas: Fisiologia Animal Comparada, Instituto de Ciências Biológicas, Universidade Federal do Rio Grande, Avenida Itália km 8, Rio Grande, RS 96203-900, Brazil
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Crémazy A, Wood CM, Smith DS, Ferreira MS, Johannsson OE, Giacomin M, Val AL. Investigating copper toxicity in the tropical fish cardinal tetra (Paracheirodon axelrodi) in natural Amazonian waters: Measurements, modeling, and reality. Aquat Toxicol 2016; 180:353-363. [PMID: 27969548 DOI: 10.1016/j.aquatox.2016.10.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 09/29/2016] [Accepted: 10/13/2016] [Indexed: 06/06/2023]
Abstract
Copper at high concentrations is an ionoregulatory toxicant in fish and its toxicity is known to be strongly modulated by the water chemistry. The toxicity of Cu to the tropical fish cardinal tetra (Paracheirodon axelrodi) was investigated in waters from two major rivers of the Amazon watershed: the Rio Negro (filtered <0.45μm, pH 5.6, DOC=8.4 mgL-1, Na=33μM, Ca=8μM) and the Rio Solimões (filtered <0.45μm, pH 6.7, DOC=2.8 mgL-1, Na=185μM, Ca=340μM), as well as in a natural "reference water" (groundwater) which was almost DOC-free (pH 6.0, DOC=0.34 mgL-1, Na=53μM, Ca=5μM). Acute 96-h mortality, Cu bioaccumulation and net flux rates of Na+, Cl-, K+ and total ammonia were determined in P. axelrodi exposed in each water. Copper speciation in each water was determined by two thermodynamic models and by potentiometry, and its toxicity was predicted based on the biotic ligand model (BLM) framework. Our results indicate that high Na+ loss is the main mode of toxic action of Cu in P. axelrodi, in accordance with general theory. Cardinal tetra showed a particularly high ability to tolerate Cu and to maintain Na+ balance, similar to the ability of this and other endemic Rio Negro species to tolerate low pH and ion-poor conditions. Cu toxicity was lower in Rio Negro than in the other two waters tested, and the free [Cu2+] at the LC50, as determined by any of the three speciation methods tested, was approximately 10-fold higher. This variation could not be captured by a realistic set of BLM parameters. At least in part, this observation may be due to gill physiological alterations induced by the abundant dissolved organic matter of the Rio Negro. The implication of this observation is that, for metals risk assessment in tropical waters, similar to the Rio Negro, care must be used in applying BLM models developed using temperate DOC and temperate species.
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Affiliation(s)
- Anne Crémazy
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| | - Chris M Wood
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - D Scott Smith
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, ON N2L 3C5, Canada
| | - Márcio S Ferreira
- Laboratory of Ecophysiology and Molecular Evolution, National Institute for Amazonian Research, Manaus, AM, Brazil
| | - Ora E Johannsson
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Marina Giacomin
- Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Adalberto L Val
- Laboratory of Ecophysiology and Molecular Evolution, National Institute for Amazonian Research, Manaus, AM, Brazil
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Wood CM, Robertson LM, Johannsson OE, Val AL. Mechanisms of Na+ uptake, ammonia excretion, and their potential linkage in native Rio Negro tetras (Paracheirodon axelrodi, Hemigrammus rhodostomus, and Moenkhausia diktyota). J Comp Physiol B 2014; 184:877-90. [PMID: 25106686 DOI: 10.1007/s00360-014-0847-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2014] [Revised: 07/10/2014] [Accepted: 07/19/2014] [Indexed: 12/13/2022]
Abstract
Mechanisms of Na(+) uptake, ammonia excretion, and their potential linkage were investigated in three characids (cardinal, hemigrammus, moenkhausia tetras), using radiotracer flux techniques to study the unidirectional influx (J in), efflux (J out), and net flux rates (J net) of Na(+) and Cl(-), and the net excretion rate of ammonia (J Amm). The fish were collected directly from the Rio Negro, and studied in their native "blackwater" which is acidic (pH 4.5), ion-poor (Na(+), Cl(-) ~20 µM), and rich in dissolved organic matter (DOM 11.5 mg C l(-1)). J in (Na) , J in (Cl) , and J Amm were higher than in previous reports on tetras obtained from the North America aquarium trade and/or studied in low DOM water. In all three species, J in (Na) was unaffected by amiloride (10(-4) M, NHE and Na(+) channel blocker), but both J in (Na) and J in (Cl) were virtually eliminated (85-99 % blockade) by AgNO3 (10(-7) M). A time course study on cardinal tetras demonstrated that J in (Na) blockade by AgNO3 was very rapid (<5 min), suggesting inhibition of branchial carbonic anhydrase (CA), and exposure to the CA-blocker acetazolamide (10(-4) M) caused a 50 % reduction in J in (Na) .. Additionally, J in (Na) was unaffected by phenamil (10(-5) M, Na(+) channel blocker), bumetanide (10(-4) M, NKCC blocker), hydrochlorothiazide (5 × 10(-3) M, NCC blocker), and exposure to an acute 3 unit increase in water pH. None of these treatments, including partial or complete elimination of J in (Na) (by acetazolamide and AgNO3 respectively), had any inhibitory effect on J Amm. Therefore, Na(+) uptake in Rio Negro tetras depends on an internal supply of H(+) from CA, but does not fit any of the currently accepted H(+)-dependent models (NHE, Na(+) channel/V-type H(+)-ATPase), or co-transport schemes (NCC, NKCC), and ammonia excretion does not fit the current "Na(+)/NH4 (+) exchange metabolon" paradigm. Na(+), K(+)-ATPase and V-type H(+)-ATPase activities were present at similar levels in gill homogenates, Acute exposure to high environmental ammonia (NH4Cl, 10(-3) M) significantly increased J in (Na) , and NH4 (+) was equally or more effective than K(+) in activating branchial Na(+),(K(+)) ATPase activity in vitro. We propose that ammonia excretion does not depend on Na(+) uptake, but that Na(+) uptake (by an as yet unknown H(+)-dependent apical mechanism) depends on ammonia excretion, driven by active NH4 (+) entry via basolateral Na(+),(K(+))-ATPase.
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Affiliation(s)
- Chris M Wood
- Department of Biology, McMaster University, 1280 Main St. West, Hamilton, ON, L8S 4K1, Canada,
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Johannsson OE, Bergman HL, Wood CM, Laurent P, Kavembe DG, Bianchini A, Maina JN, Chevalier C, Bianchini LF, Papah MB, Ojoo RO. Air breathing in Magadi tilapia Alcolapia grahami, under normoxic and hyperoxic conditions, and the association with sunlight and reactive oxygen species. J Fish Biol 2014; 84:844-863. [PMID: 24673646 DOI: 10.1111/jfb.12289] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Accepted: 10/26/2013] [Indexed: 06/03/2023]
Abstract
Observations of the Magadi tilapia Alcolapia grahami in hot, highly alkaline Lake Magadi revealed that they air breathe not only during hypoxia, as described previously, but also during normoxia and hyperoxia. Air breathing under these latter conditions occurred within distinct groupings of fish (pods) and involved only a small proportion of the population. Air breathing properties (duration and frequency) were quantified from video footage. Air breathing within the population followed a diel pattern with the maximum extent of pod formation occurring in early afternoon. High levels of reactive oxygen species (ROS) in the water may be an irritant that encourages the air-breathing behaviour. The diel pattern of air breathing in the field and in experiments followed the diel pattern of ROS concentrations in the water which are amongst the highest reported in the literature (maximum daytime values of 2.53 – 8.10 μM H₂O₂). Interlamellar cell masses (ILCM) occurred between the gill lamellae of fish from the lagoon with highest ROS and highest oxygen levels, while fish from a normoxic lagoon with one third the ROS had little or no ILCM. This is the first record of air breathing in a facultative air-breathing fish in hyperoxic conditions and the first record of an ILCM in a cichlid species.
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Wood CM, Nawata CM, Wilson JM, Laurent P, Chevalier C, Bergman HL, Bianchini A, Maina JN, Johannsson OE, Bianchini LF, Kavembe GD, Papah MB, Ojoo RO. Rh proteins and NH4(+)-activated Na+-ATPase in the Magadi tilapia (Alcolapia grahami), a 100% ureotelic teleost fish. ACTA ACUST UNITED AC 2014; 216:2998-3007. [PMID: 23885087 DOI: 10.1242/jeb.078634] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The small cichlid fish Alcolapia grahami lives in Lake Magadi, Kenya, one of the most extreme aquatic environments on Earth (pH ~10, carbonate alkalinity ~300 mequiv l(-1)). The Magadi tilapia is the only 100% ureotelic teleost; it normally excretes no ammonia. This is interpreted as an evolutionary adaptation to overcome the near impossibility of sustaining an NH3 diffusion gradient across the gills against the high external pH. In standard ammoniotelic teleosts, branchial ammonia excretion is facilitated by Rh glycoproteins, and cortisol plays a role in upregulating these carriers, together with other components of a transport metabolon, so as to actively excrete ammonia during high environmental ammonia (HEA) exposure. In Magadi tilapia, we show that at least three Rh proteins (Rhag, Rhbg and Rhcg2) are expressed at the mRNA level in various tissues, and are recognized in the gills by specific antibodies. During HEA exposure, plasma ammonia levels and urea excretion rates increase markedly, and mRNA expression for the branchial urea transporter mtUT is elevated. Plasma cortisol increases and branchial mRNAs for Rhbg, Rhcg2 and Na(+),K(+)-ATPase are all upregulated. Enzymatic activity of the latter is activated preferentially by NH4(+) (versus K(+)), suggesting it can function as an NH4(+)-transporter. Model calculations suggest that active ammonia excretion against the gradient may become possible through a combination of Rh protein and NH4(+)-activated Na(+)-ATPase function.
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Affiliation(s)
- Chris M Wood
- Department of Biology, McMaster University, Hamilton, ON, Canada.
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Papah MB, Kisia SM, Ojoo RO, Makanya AN, Wood CM, Kavembe GD, Maina JN, Johannsson OE, Bergman HL, Laurent P, Chevalier C, Bianchini A, Bianchini LF, Onyango DW. Morphological evaluation of spermatogenesis in Lake Magadi tilapia (Alcolapia grahami): a fish living on the edge. Tissue Cell 2013; 45:371-82. [PMID: 23916093 DOI: 10.1016/j.tice.2013.06.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2013] [Revised: 06/06/2013] [Accepted: 06/29/2013] [Indexed: 11/19/2022]
Abstract
Spermatogenesis in Lake Magadi tilapia (Alcolapia grahami), a cichlid fish endemic to the highly alkaline and saline Lake Magadi in Kenya, was evaluated using light and transmission electron microscopy. Spermatogenesis, typified by its three major phases (spermatocytogenesis, meiosis and spermiogenesis), was demonstrated by the presence of maturational spermatogenic cells namely spermatogonia, spermatocytes, spermatids and spermatozoa. Primary spermatogonia, the largest of all the germ cells, underwent a series of mitotic divisions producing primary spermatocytes, which then entered two consecutive meiotic divisions to produce secondary spermatocytes and spermatids. Spermatids, in turn, passed through three structurally distinct developmental stages typical of type-I spermiogenesis to yield typical primitive anacrosomal spermatozoa of the externally fertilizing type (aquasperm). The spermatozoon of this fish exhibited a spheroidal head with the nucleus containing highly electron-dense chromatin globules, a midpiece containing ten ovoid mitochondria arranged in two rows and a flagellum formed by the typical 9 + 2 microtubule axoneme. In addition, the midpiece, with no cytoplasmic sheath, appeared to end blindly distally in a lobe-like pattern around the flagellum; a feature that was unique and considered adaptive for the spermatozoon of this species to the harsh external environment. These observations show that the testis of A. grahami often undergoes active spermatogenesis despite the harsh environmental conditions to which it is exposed on a daily basis within the lake. Further, the spermiogenic features and spermatozoal ultrastructure appear to be characteristic of Cichlidae and, therefore, may be of phylogenetic significance.
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Affiliation(s)
- M B Papah
- Dept. of Veterinary Anatomy and Physiology, University of Nairobi, 30197-00100 Nairobi, Kenya.
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Abstract
We conducted a study to determine the contribution of lethal and nonlethal effects to a predator's net effect on a prey's population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus, on zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both systems indicated that the prey species Daphnia mendotae, Daphnia retrocurva, and Bosmina longirostris inhabited deeper portions of the water column as Bythotrephes biomass increased, possibly as an avoidance response to predation. This induced migration reduces predation risk but also can reduce birth rate due to exposure to cooler temperatures. We estimated the nonlethal (i.e., resulting from reduced birth rate) and lethal (i.e., consumptive) effects of Bythotrephes on D. mendotae and Bosmina longirostris. These estimates used diel field survey data of the vertical gradient of zooplankton prey density, Bythotrephes density, light intensity, and temperature with growth and predation rate models derived from laboratory studies. Results indicate that nonlethal effects played a substantial role in the net effect of Bythotrephes on several prey population growth rates in the field, with nonlethal effects on the same order of magnitude as or greater (up to 10-fold) than lethal effects. Our results further indicate that invasive species can have strong nonlethal, behaviorally based effects, despite short evolutionary coexistence with prey species.
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Affiliation(s)
- Kevin L Pangle
- Michigan State University, Department of Fisheries and Wildlife, 13 Natural Resources Building, East Lansing, Michigan 48824-1222, USA.
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Malkin SY, Johannsson OE, Taylor WD. Small-bodied zooplankton communities yet strong top-down effects on phytoplankton in the absence of fish. ACTA ACUST UNITED AC 2006. [DOI: 10.1127/0003-9136/2006/0165-0313] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Sloman KA, Wood CM, Scott GR, Wood S, Kajimura M, Johannsson OE, Almeida-Val VMF, Val AL. Tribute to R. G. Boutilier: The effect of size on the physiological and behavioural responses of oscar,Astronotus ocellatus, to hypoxia. J Exp Biol 2006; 209:1197-205. [PMID: 16547292 DOI: 10.1242/jeb.02090] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
SUMMARYThe physiological and behavioural responses of two size groups of oscar(Astronotus ocellatus) to hypoxia were studied. The physiological responses were tested by measuring ṀO2 during decreasing environmental oxygen tensions. Larger oscars were better able to maintain oxygen consumption during a decrease in PO2, regulating routine ṀO2 to a significantly lower PO2 threshold (50 mmHg)than smaller oscars (70 mmHg). Previous studies have also demonstrated a longer survival time of large oscars exposed to extreme hypoxia, coupled with a greater anaerobic enzymatic capability. Large oscars began aquatic surface respiration (ASR) at the oxygen tension at which the first significant decrease in ṀO2was seen (50 mmHg). Interestingly, smaller oscars postponed ASR to around 22 mmHg, well beyond the PO2 at which they switched from oxyregulation to oxyconformation. Additionally, when given the choice between an hypoxic environment containing aquatic macrophyte shelter and an open normoxic environment, small fish showed a greater preference for the hypoxic environment. Thus shelter from predators appears particularly important for juveniles, who may accept a greater physiological compromise in exchange for safety. In response to hypoxia without available shelter, larger fish reduced their level of activity (with the exception of aggressive encounters) to aid metabolic suppression whereas smaller oscars increased their activity, with the potential benefit of finding oxygen-rich areas.
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Affiliation(s)
- Katherine A Sloman
- School of Biological Sciences, University of Plymouth, Devon, PL4 8AA, UK.
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Neilson MA, Painter DS, Warren G, Hites RA, Basu I, Weseloh DVC, Whittle DM, Christie G, Barbiero R, Tuchman M, Johannsson OE, Nalepa TF, Edsall TA, Fleischer G, Bronte C, Smith SB, Baumann PC. Ecological monitoring for assessing the state of the nearshore and open waters of the Great Lakes. Environ Monit Assess 2003; 88:103-117. [PMID: 14570412 DOI: 10.1023/a:1025500619900] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The Great Lakes Water Quality Agreement stipulates that the Governments of Canada and the United States are responsible for restoring and maintaining the chemical, physical and biological integrity of the waters of the Great Lakes Basin Ecosystem. Due to varying mandates and areas of expertise, monitoring to assess progress towards this objective is conducted by a multitude of Canadian and U.S. federal and provincial/state agencies, in cooperation with academia and regional authorities. This paper highlights selected long-term monitoring programs and discusses a number of documented ecological changes that indicate the present state of the open and nearshore waters of the Great Lakes.
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Affiliation(s)
- Melanie A Neilson
- Environment Canada, Environmental Conservation Branch-Ontario Region, Burlington, ON, Canada.
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