| 1. |
- Brijs, Jeroen, et al.
(författare)
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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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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 223:2
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Brijs, J., et al.
(författare)
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Prospects and pitfalls of using heart rate bio-loggers to assess the welfare of rainbow trout (Oncorhynchus mykiss) in aquaculture
- 2019
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Ingår i: Aquaculture. - : Elsevier BV. - 0044-8486 .- 1873-5622. ; 509, s. 188-197
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Tidskriftsartikel (refereegranskat)abstract
- - Investigating real-time stress responses during common aquaculture practices is necessary for improving the welfare of farmed fish. Recently, Star-Oddi DST milli-HRT bio-loggers capable of measuring heart rate (as an indicator for stress) in freely swimming fish have proved to be useful in this regard. However, despite the growing popularity of these devices, they have not yet been stringently evaluated and validated for use in fish. The present study is the first to do so by simultaneously recording heart rate of a commercially important salmonid species (rainbow trout, Oncorhynchus mykiss) using the abovementioned bio-loggers, as well as an established non-invasive wireless heart rate recording technique that has been demonstrated to provide more accurate recordings than those collected using traditional methods requiring a physical connection to recording equipment. The measurement error of the bio-loggers was <1 beat min −1 irrespective of the sampling period when only using measurements graded with the highest quality index (QI 0 ) and it is advised that only QI 0 measurements be used as inclusion of poorer quality measurements (QI 1–3 ) markedly reduce measurement accuracy. Furthermore, sufficiently long recovery periods should be employed prior to collecting data with these devices in salmonids, as anaesthesia and surgical implantation of bio-loggers resulted in transiently elevated resting heart rates for >72 h. Following the successful validation of these bio-loggers, the effects of common aquaculture practices such as netting, grouping and enforced activity on the cardiac performance of freely swimming rainbow trout were investigated. Prior to the subsequent exposure to the abovementioned stressors, mean heart rates of trout were ~42 beats min −1 . Following netting, trout increased heart rates by 57%, which recovered within 3 h. Grouping subsequently induced a more pronounced and prolonged stress response, as heart rates initially increased by 86% and then remained elevated throughout the 8 h recovery period. Consequently, trout were only able to further increase heart rates by 7% following enforced activity. This diminished cardiac response demonstrates a situation where the cumulative allostatic load induced by prior stressors is approaching a level where the animal struggles to perform normal physiological processes in the face of further challenges. These findings are important for the aquaculture industry as exposure to multiple stressors without sufficient recovery times has the potential to result in the collapse of cardiac scope, which combined with unfavourable environmental conditions could lead to increased mortality. © 2019 Elsevier B.V.
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| 3. |
- Carney Almroth, Bethanie, 1974, et al.
(författare)
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Warmer water temperature results in oxidative damage in an Antarctic fish, the bald notothen
- 2015
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Ingår i: Journal of Experimental Marine Biology and Ecology. - : Elsevier BV. - 0022-0981 .- 1879-1697. ; 468, s. 130-137
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Tidskriftsartikel (refereegranskat)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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| 4. |
- Gräns, Albin, 1979, et al.
(författare)
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Behavioural fever boosts the inflammatory response in rainbow trout Oncorhynchus mykiss
- 2012
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Ingår i: Journal of Fish Biology. - : Wiley. - 1095-8649 .- 0022-1112. ; 81:3, s. 1111-1117
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Tidskriftsartikel (refereegranskat)abstract
- Behavioural fever, manifested as an increased preferred temperature, was shown in rainbow trout Oncorhynchus mykiss following an injection of bacterial lipopolysaccharide. Simulated behavioural fever, through a 2·5° C water temperature rise following bacterial lipopolysaccharide injection, enhanced the expression of the cytokine interleukin-1β, in comparison with an untreated group held at the initial temperature. The present findings show that an important mediator in the immune response can be boosted through behavioural fever in fishes.
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| 5. |
- Näslund, Joacim, 1985, et al.
(författare)
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Fish density, but not environmental enrichment, affects the size of cerebellum in the brain of juvenile hatchery-reared Atlantic salmon
- 2019
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Ingår i: Environmental Biology of Fishes. - : Springer Science and Business Media LLC. - 0378-1909 .- 1573-5133. ; 102, s. 705-712
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a study on the environmentally dependent brain size plasticity in hatchery-reared Atlantic salmon Salmo salar L. Using a factorial experimental design, we tested whether tank fish density, local hatchery standard (150 fish ∙ m −2 ) vs. reduced (50 fish ∙ m −2 ) and structural enrichment, a bundle of submerged plastic stripes, had effects on the size of the cerebellar region of the brain. Fish reared at reduced density had smaller cerebella, while structural enrichment had no detectable effects. The density effect on cerebellum, which is involved in locomotion and cognition, confirms previous results from hatchery-reared Atlantic salmon. The lack of detectable positive effects of enrichment, which contrasts some previous studies, provide further evidence for a complex relationship between environmental complexity and brain growth.
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| 6. |
- Näslund, Joacim, 1985, et al.
(författare)
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Hatchery tank enrichment affects cortisol levels and shelter-seeking in Atlantic salmon (Salmo salar)
- 2013
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - : Canadian Science Publishing. - 0706-652X .- 1205-7533. ; 70:4, s. 585-590
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Tidskriftsartikel (refereegranskat)abstract
- Stocking programs using hatchery-reared salmon are often implemented for augmenting natural populations. However, survival of these fish is often low compared with wild conspecifics, possibly because of genetic, physiological, and behavioural deficiencies. Here, we compared presmolt Atlantic salmon (Salmo salar) from three different environmental treatments (barren environment, plastic tube enrichment, and plastic shredding enrichment) with regard to plasma cortisol levels, shelter-seeking behaviour, and fin deterioration. Basal plasma cortisol levels were higher in barren-reared fish, indicating higher stress levels, while no differences were found in acute cortisol response after a 30 min confinement test. Shelter-seeking was higher in salmon reared in enriched tanks when tested alone, but not when tested in small groups. Barren-reared fish had higher levels of fin deterioration over winter, potentially owing to higher aggression levels. These results suggest that enrichment can reduce the impact of stressors experienced in the hatchery and thus increase fish welfare. Tank enrichment may also be used to produce salmon better adapted for the more complex environment encountered after release.
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| 7. |
- Rosengren, Malin, 1982, et al.
(författare)
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Born to be wild: effects of rearing density and environmental enrichment on stress, welfare, and smolt migration in hatchery-reared Atlantic salmon
- 2017
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - : Canadian Science Publishing. - 0706-652X .- 1205-7533. ; 74:3, s. 396-405
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Tidskriftsartikel (refereegranskat)abstract
- Hatchery-reared salmonids released into the wild generally have poor survivability compared with wild conspecifics. To assess potential hatchery rearing improvements, behavioral and physiological effects of reducing animal density and adding in-tank shelter were investigated. Atlantic salmon (Salmo salar) parr were placed in barren or shelter-enriched tanks at high or low density up until release as smolts. Lowered density rendered positive effects on growth and intestinal barrier function, and both lowered density and shelter decreased conspecific aggression, as inferred by fin damage. Furthermore, while the presence of shelter decreased stress hormone levels following human disturbance, it also decreased growth and smolt migration success, an effect particularly pronounced at high densities. Therefore, we suggest that this type of structural enrichment should be avoided for Atlantic salmon smolts held at high densities and conclude that a lowered animal density with or without shelter has the highest potential in producing a more resilient smolt for stocking.
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| 8. |
- Rosengren, Malin, 1982
(författare)
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Fish coping with stress-Physiology and behaviour in salmonids with focus on stress coping styles, rearing conditions and smolt migration
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- When animals are reared for conservational releases it is paramount to avoid reducing genetic and phenotypic variation over time. Therefore, an understanding of how behavioural and physiological traits affect the performance of an individual both within the captive and the wild environment is required. To preserve threatened populations of salmonids, large numbers of hatchery-raised juveniles are released each year. The captive environment do, however, differ in many aspects from the wild, and the standard hatchery practice, using high animal densities and barren tanks, raise questions concerning stress levels, misdirected selection pressures and a naivety of the released fish when coping with the wild environment. The overall aim of this thesis is therefore to extend the knowledge-base on stress physiology and behaviour of salmonids with special focus on individual variation, stress coping styles and conservational releases. The objectives are to increase the understanding of how behavioural and physiological traits are related to each other, how they are maintained during juvenile development and how they are modulated by environmental factors like the rearing environment. The results from the present thesis shows that lowering the animal density and adding structural enrichment to the rearing tanks reduces aggression and stress levels while in captivity, as well as have a positive influence on physiological and phenotypic traits important for survival after release. However, fish reared with in-tank shelter at high densities showed a lower post-release survival during smolt migration. These results highlight the importance of thoroughly examining interaction effects of hatchery alterations before implementation. Furthermore, salmon showing early emergence from the spawning nest as well as a bold behavioural profile had a lower maximum metabolic rate and aerobic capacity prior to release, compared to those with late emergence and a more cautious behavioural profile. While this may have no clear negative implications for the individual in the hatchery, after release it could result in greater risk of predation caused by higher risk-taking and possible impaired swimming capacity and recovery from exhaustion. These results highlight how the selection pressure might differ between different behavioural profiles and environments. In rainbow trout, individual variation in systemic cortisol output during stress (HPI-axis reactivity) also had an impact on metabolic rate and on the stress sensitive barrier function of the intestine. HPI-axis reactivity was further linked to other stress related neuronal systems in the forebrain and to behavioural traits. The findings of this thesis broadens the knowledge-base on stress physiology and behaviour of salmonids and how they are interlinked with and modulated by environmental factors. In conclusion, the rearing environment, behavioural profile and stress reactivity of an individual will affect its ability to cope with challenges both in captivity and in the wild. There is much to gain in continuing the work on finding hatchery alterations, where a reduced rearing density together with structural enrichment is a promising candidate to implement both increased welfare and post-release performance.
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| 9. |
- Rosengren, Malin, 1982, et al.
(författare)
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High risk no gain-metabolic performance of hatchery reared Atlantic salmon smolts, effects of nest emergence time, hypoxia avoidance behaviour and size
- 2017
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Ingår i: Physiology & Behavior. - : Elsevier BV. - 0031-9384 .- 1873-507X. ; 175, s. 104-112
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Tidskriftsartikel (refereegranskat)abstract
- When animals are reared for conservational releases it is paramount to avoid reducing genetic and phenotypic variation over time. This requires an understanding of how diverging behavioural and physiological traits affect performance both in captivity and after release. In Atlantic salmon, emergence time from the spawning gravel has been linked to certain behavioural and physiological characteristics and to the concept of stress coping styles. Early emerging fry has for example been shown to be bolder and more aggressive and to have higher standard metabolic rates compared to late emerging fry. The first aim was therefore to examine if emergence latency affect the behavioural stress coping response also beyond the fry and parr stage. This was done using a hypoxia avoidance test, where an active behavioural avoidance response can be related to higher risk taking. No behavioural differences were found between the two emergence fractions either at the parr or pre-smolt stage, instead smaller individuals were more prone to express an "active" hypoxia avoidance response. Further, an individual expressing a "passive" response as parr were also more prone to express this behaviour at the pre-smolt stage. While there are some previous studies showing that early emerging individuals with a bolder personality may be favored within a hatchery setting it is not known to what extent these early differences persist to affect performance after release. The second aim was therefore to compare the physiological performance at the time of release as smolts using the two subgroups; 1) early emerging fish showing active hypoxia avoidance (Early + Bold) and 2) late emerging fish showing a passive hypoxia response (Late + Shy). The Early + Bold group showed a higher red blood cell swelling, suggesting a higher adrenergic output during stress, whereas there was no difference in post-stress plasma cortisol or physiological smolt status. While there was no difference in standard metabolic rate between the groups, the Early + Bold group exhibited a lower maximum metabolic rate and aerobic scope following strenuous swimming. In captivity this may have no clear negative effects, but in the wild, a more risk prone behavioural profile linked to a lower aerobic capacity to escape from e.g. a predator attack, could clearly be disadvantageous.
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| 10. |
- Rosengren, Malin, 1982, et al.
(författare)
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The brain-gut axis of fish: Rainbow trout with low and high cortisol response show innate differences in intestinal integrity and brain gene expression
- 2018
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Ingår i: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480 .- 1095-6840. ; 257, s. 235-245
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Tidskriftsartikel (refereegranskat)abstract
- © 2017 Elsevier Inc. In fish, the stress hormone cortisol is released through the action of the hypothalamic pituitary interrenal axis (HPI-axis). The reactivity of this axis differs between individuals and previous studies have linked this to different behavioural characteristics and stress coping styles. In the current study, low and high responding (LR and HR) rainbow trout in terms of cortisol release during stress were identified, using a repeated confinements stress test. The expression of stress related genes in the forebrain and the integrity of the stress sensitive primary barrier of the intestine was examined. The HR trout displayed higher expression levels of mineralocorticoid and serotonergic receptors and serotonergic re-uptake pumps in the telencephalon during both basal and stressed conditions. This confirms that HPI-axis reactivity is linked also to other neuronal behavioural modulators, as both the serotonergic and the corticoid system in the telencephalon are involved in behavioural reactivity and cognitive processes. Involvement of the HPI-axis in the brain-gut-axis was also found. LR trout displayed a lower integrity in the primary barrier of the intestine during basal conditions compared to the HR trout. However, following stress exposure, LR trout showed an unexpected increase in intestinal integrity whereas the HR trout instead suffered a reduction. This could make the LR individuals more susceptible to pathogens during basal conditions where instead HR individuals would be more vulnerable during stressed conditions. We hypothesize that these barrier differences are caused by regulation/effects on tight junction proteins possibly controlled by secondary effects of cortisol on the intestinal immune barrier or differences in parasympathetic reactivity.
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