| 1. |
- Andreassen, Anna H., et al.
(author)
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Brain dysfunction during warming is linked to oxygen limitation in larval zebrafish
- 2022
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In: Proceedings of the National Academy of Science of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:39
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Journal article (peer-reviewed)abstract
- Understanding the physiological mechanisms that limit animal thermal tolerance is crucial in predicting how animals will respond to increasingly severe heat waves. Despite their importance for understanding climate change impacts, these mechanisms underlying the upper thermal tolerance limits of animals are largely unknown. It has been hypothesized that the upper thermal tolerance in fish is limited by the thermal tolerance of the brain and is ultimately caused by a global brain depolarization. In this study, we developed methods for measuring the upper thermal limit (CTmax) in larval zebrafish (Danio rerio) with simultaneous recordings of brain activity using GCaMP6s calcium imaging in both free-swimming and agar-embedded fish. We discovered that during warming, CTmax precedes, and is therefore not caused by, a global brain depolarization. Instead, the CTmax coincides with a decline in spontaneous neural activity and a loss of neural response to visual stimuli. By manipulating water oxygen levels both up and down, we found that oxygen availability during heating affects locomotor-related neural activity, the neural response to visual stimuli, and CTmax. Our results suggest that the mechanism limiting the upper thermal tolerance in zebrafish larvae is insufficient oxygen availability causing impaired brain function.
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| 2. |
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| 3. |
- Bresolin de Souza, Karine, et al.
(author)
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Effects of increased CO2on fish gill and plasma proteome
- 2014
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In: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 9:7
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Journal article (peer-reviewed)abstract
- Ocean acidification and warming are both primarily caused by increased levels of atmospheric CO2, and marine organisms are exposed to these two stressors simultaneously. Although the effects of temperature on fish have been investigated over the last century, the long-term effects of moderate CO2 exposure and the combination of both stressors are almost entirely unknown. A proteomics approach was used to assess the adverse physiological and biochemical changes that may occur from the exposure to these two environmental stressors. We analysed gills and blood plasma of Atlantic halibut (Hippoglossus hippoglossus) exposed to temperatures of 12°C (control) and 18°C (impaired growth) in combination with control (400 μatm) or high-CO2 water (1000 μatm) for 14 weeks. The proteomic analysis was performed using two-dimensional gel electrophoresis (2DE) followed by Nanoflow LC-MS/MS using a LTQ-Orbitrap. The high-CO2 treatment induced the up-regulation of immune system-related proteins, as indicated by the up-regulation of the plasma proteins complement component C3 and fibrinogen β chain precursor in both temperature treatments. Changes in gill proteome in the high-CO2 (18°C) group were mostly related to increased energy metabolism proteins (ATP synthase, malate dehydrogenase, malate dehydrogenase thermostable, and fructose-1,6-bisphosphate aldolase), possibly coupled to a higher energy demand. Gills from fish exposed to high-CO 2 at both temperature treatments showed changes in proteins associated with increased cellular turnover and apoptosis signalling (annexin 5, eukaryotic translation elongation factor 1γ, receptor for protein kinase C, and putative ribosomal protein S27). This study indicates that moderate CO2-driven acidification, alone and combined with high temperature, can elicit biochemical changes that may affect fish health. © 2014 Bresolin de Souza et al.
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| 4. |
- Brijs, Jeroen, et al.
(author)
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Experimental manipulations of tissue oxygen supply do not affect warming tolerance of European perch
- 2015
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In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 218, s. 2448-2454
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Journal article (peer-reviewed)abstract
- A progressive inability of the cardiorespiratory system to maintain systemic oxygen supply at elevated temperatures has been suggested to reduce aerobic scope and the upper thermal limit of aquatic ectotherms. However, few studies have directly investigated the dependence of thermal limits on oxygen transport capacity. By manipulating oxygen availability (via environmental hyperoxia) and blood oxygen carrying capacity (via experimentally-induced anemia) in European perch (Perca fluviatilis, Linneaus), we investigated the effects of oxygen transport capacity on aerobic scope and the critical thermal maximum (CTmax). Hyperoxia resulted in a two-fold increase in aerobic scope at the control temperature of 23°C, but this did not translate to an elevated CTmax in comparison with control fish (34.6±0.1°C vs. 34.0±0.5°C, respectively). Anemia (∼43% reduction in haemoglobin concentration) did not cause a reduction in aerobic scope nor CTmax (33.8±0.3°C) compared with control fish. Additionally, oxygen consumption rates of anemic perch during thermal ramping increased in a similar exponential manner as in control fish, highlighting that perch have an impressive capacity to compensate for a substantial reduction in blood oxygen carrying capacity. Taken together, these results indicate that oxygen limitation is not a universal mechanism determining the CTmax of fishes.
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| 5. |
- Brijs, Jeroen, et al.
(author)
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Extreme blood-boosting capacity of an Antarctic fish represents an adaptation to life in a sub-zero environment
- 2020
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In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 223:2
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Journal article (peer-reviewed)abstract
- Blood doping, the practice of boosting the oxygen carrying capacity of blood, is an illegal strategy used by human athletes to enhance aerobic capacity and athletic performance. Interestingly, the practice of boosting blood oxygen carrying capacity is also naturally prevalent in the animal kingdom via the splenic release of stored erythrocytes. Here, we demonstrate that an Antarctic notothenioid fish, the bald notothen (Pagothenia borchgrevinki), is a master of this practice. Because of the sub-zero environment these fish inhabit, they sequester a large proportion of erythrocytes in the spleen during times of inactivity to reduce the energetic and physiological costs associated with continuously pumping highly viscous blood around the body. However, in response to metabolically demanding situations (i.e. exercise and feeding), these fish contract the spleen to eject stored erythrocytes into circulation, which boosts blood oxygen carrying capacity by up to 207% (cf. exercise-induced increases of ∼40-60% in a range of other vertebrates and ∼5-25% in blood-doping athletes). By evaluating cardiorespiratory differences between splenectomized (unable to release erythrocytes from the spleen) and sham-operated individuals, we demonstrate the metabolic benefits (i.e. aerobic scope increase of 103%) and the cardiovascular trade-offs (i.e. ventral aortic blood pressure and cardiac workload increase of 12% and 30%, respectively) associated with the splenic blood-boosting strategy. In conclusion, this strategy provides bald notothens with an extraordinary facultative aerobic scope that enables an active lifestyle in the extreme Antarctic marine environment, while minimizing the energetic and physiological costs of transporting highly viscous blood during times of reduced energetic demand.
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| 6. |
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| 7. |
- Carney Almroth, Bethanie, 1974, et al.
(author)
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Warmer water temperature results in oxidative damage in an Antarctic fish, the bald notothen
- 2015
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In: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 468, s. 130-137
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Journal article (peer-reviewed)abstract
- Global climate change is predicted to result in increases in water temperature in the polar regions, but the full consequences of this for marine fish species are not understood, especially with regard to cellular mechanisms underlying oxidative stress. Warmer temperatures could potentially result in increased oxidative stress, and it is not known whether stenothermal fish can cope with this on a cellular and physiological level. In order to address this, we exposed bald notothen (Pagothenta borchgrevinki), a fish species endemic to Antarctica, to an increase in temperature from -1.6 degrees C to 4 degrees C and measured the effects on oxidative stress including antioxidant defenses, oxidative damage in proteins and lipids, and transcriptional regulation of involved genes. We show that the fish responds to an acute (12 h) temperature increase with increased antioxidant defenses. However, these antioxidant defenses were similar to basal levels following long-term (3 weeks) exposure to the higher temperature and moreover, these individuals also had higher levels of oxidative damage. These results indicate that this species has the ability to alter levels of endogenous antioxidants, but that this response is transient and insufficient to protect against oxidative damage. These effects may have serious consequences for these fish in a warmer future since long-term consequences of this accumulation of damaged lipids and proteins are associated with aging and known to include decreased cellular function, disease and eventually cell death. (C) 2015 Elsevier B.V. All rights reserved.
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| 8. |
- Clark, T. D., et al.
(author)
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Aerobic scope measurements of fishes in an era of climate change: respirometry, relevance and recommendations
- 2013
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In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 216:15, s. 2771-2782
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Research review (peer-reviewed)abstract
- Measurements of aerobic scope [the difference between minimum and maximum oxygen consumption rate ((M) over dot(O2,min) and (M) over dot(O2,max), respectively)] are increasing in prevalence as a tool to address questions relating to fish ecology and the effects of climate change. However, there are underlying issues regarding the array of methods used to measure aerobic scope across studies and species. In an attempt to enhance quality control before the diversity of issues becomes too great to remedy, this paper outlines common techniques and pitfalls associated with measurements of (M) over dot(O2,min), (M) over dot(O2,max) and aerobic scope across species and under different experimental conditions. Additionally, we provide a brief critique of the oxygen-and capacity-limited thermal tolerance (OCLTT) hypothesis, a concept that is intricately dependent on aerobic scope measurements and is spreading wildly throughout the literature despite little evidence for its general applicability. It is the intention of this paper to encourage transparency and accuracy in future studies that measure the aerobic metabolism of fishes, and to highlight the fundamental issues with assuming broad relevance of the OCLTT hypothesis.
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| 9. |
- Clark, Timothy D., et al.
(author)
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Response to Farrell and to Portner and Giomi.
- 2013
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In: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 216:23, s. 4495-4497
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Journal article (peer-reviewed)
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| 10. |
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