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Disease resistance is related to inherent swimming performance in Atlantic salmon.

ABSTRACT: BACKGROUND: Like humans, fish can be classified according to their athletic performance. Sustained exercise training of fish can improve growth and physical capacity, and recent results have documented improved disease resistance in exercised Atlantic salmon. In this study we investigated the effects of inherent swimming performance and exercise training on disease resistance in Atlantic salmon.Atlantic salmon were first classified as either poor or good according to their swimming performance in a screening test and then exercise trained for 10 weeks using one of two constant-velocity or two interval-velocity training regimes for comparison against control trained fish (low speed continuously). Disease resistance was assessed by a viral disease challenge test (infectious pancreatic necrosis) and gene expression analyses of the host response in selected organs. RESULTS: An inherently good swimming performance was associated with improved disease resistance, as good swimmers showed significantly better survival compared to poor swimmers in the viral challenge test. Differences in mortalities between poor and good swimmers were correlated with cardiac mRNA expression of virus responsive genes reflecting the infection status. Although not significant, fish trained at constant-velocity showed a trend towards higher survival than fish trained at either short or long intervals. Finally, only constant training at high intensity had a significant positive effect on fish growth compared to control trained fish. CONCLUSIONS: This is the first evidence suggesting that inherent swimming performance is associated with disease resistance in fish.

SUBMITTER: Castro V

PROVIDER: S-EPMC3552842 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Disease resistance is related to inherent swimming performance in Atlantic salmon.

Castro Vicente V Grisdale-Helland Barbara B Jørgensen Sven M SM Helgerud Jan J Claireaux Guy G Farrell Anthony P AP Krasnov Aleksei A Helland Ståle J SJ Takle Harald H

BMC physiology 20130121

<h4>Background</h4>Like humans, fish can be classified according to their athletic performance. Sustained exercise training of fish can improve growth and physical capacity, and recent results have documented improved disease resistance in exercised Atlantic salmon. In this study we investigated the effects of inherent swimming performance and exercise training on disease resistance in Atlantic salmon.Atlantic salmon were first classified as either poor or good according to their swimming perfor ...[more]

PMID: 23336751

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Project description:Farmed and wild Atlantic salmon are exposed to many infectious and non-infectious challenges that can cause mortality when they enter the sea. Exercise before transfer promotes growth, health and survival in the sea. Swimming performance in juveniles at the freshwater parr stage is positively associated with resistance to some diseases. Genetic variation is likely to affect response to exercise. In this study we map genetic differences associated with aerobic exercise, swimming performance and genetic origin. Eggs from the selectively bred Bolaks salmon and wild Lærdal River salmon strains were reared until parr in a common environment. Swimming performance was assessed by subjecting the fish to either continuous hard exercise or control conditions for 18 days. Heart was sampled for examination of gene expression using RNA-seq (~60 fish/treatment).Lower expression of genes affecting immune function was found in domesticated than wild parr. Among wild parr under control exercise the expression of a large number of genes involved in general metabolism, stress and immune response was lower in superior swimmers suggesting that minimisation of energy expenditure during periods of low activity makes parr better able to sustain bursts of swimming for predator avoidance. A similar set of genes were down-regulated with training among wild parr with inferior swimming performance. These parr react to training in a way that their cardiac expression patterns become like the superior performing wild parr under control exercise conditions. Diversifying selection caused by breeding of domesticated stock, and adaptive pressures in wild stock, has affected the expression and frequency of single nucleotide polymorphisms (SNPs) for multiple functional groups of genes affecting diverse processes. SNPs associated with swimming performance in wild parr map to genes involved in energetic processes, coding for contractile filaments in the muscle and controlling cell proliferation.Domesticated parr have less phenotypic plasticity in response to training and lower expression of genes with functions affecting immune response. The genetic response to training is complex and depends on the background of parr and their swimming ability. Exercise should be tailored to the genetics and swimming performance of fish.

Project description:Cardiac muscle is a principal target organ for exercise-induced acclimation mechanisms in fish and mammals, given that sustained aerobic exercise training improves cardiac output. Yet, the molecular mechanisms underlying such cardiac acclimation have been scarcely investigated in teleosts. Consequently, we studied mechanisms related to cardiac growth, contractility, vascularization, energy metabolism and myokine production in Atlantic salmon pre-smolts resulting from 10 weeks exercise-training at three different swimming intensities: 0.32 (control), 0.65 (medium intensity) and 1.31 (high intensity) body lengths s(-1). Cardiac responses were characterized using growth, immunofluorescence and qPCR analysis of a large number of target genes encoding proteins with significant and well-characterized function. The overall stimulatory effect of exercise on cardiac muscle was dependent on training intensity, with changes elicited by high intensity training being of greater magnitude than either medium intensity or control. Higher protein levels of PCNA were indicative of cardiac growth being driven by cardiomyocyte hyperplasia, while elevated cardiac mRNA levels of MEF2C, GATA4 and ACTA1 suggested cardiomyocyte hypertrophy. In addition, up-regulation of EC coupling-related genes suggested that exercised hearts may have improved contractile function, while higher mRNA levels of EPO and VEGF were suggestive of a more efficient oxygen supply network. Furthermore, higher mRNA levels of PPAR?, PGC1? and CPT1 all suggested a higher capacity for lipid oxidation, which along with a significant enlargement of mitochondrial size in cardiac myocytes of the compact layer of fish exercised at high intensity, suggested an enhanced energetic support system. Training also elevated transcription of a set of myokines and other gene products related to the inflammatory process, such as TNF?, NF?B, COX2, IL1RA and TNF decoy receptor. This study provides the first characterization of the underlying molecular acclimation mechanisms in the heart of exercise-trained fish, which resemble those reported for mammalian physiological cardiac growth.

Project description:Predicted future warming of aquatic environments could make fish vulnerable to naturally occurring fasting periods during migration between feeding and spawning sites, as these endeavours become energetically more expensive. In this study, Atlantic salmon (Salmo salar) acclimated to midrange (9°C) or elevated suboptimal (18°C) temperatures were subjected to critical (Ucrit) and sustained (4 hours at 80% Ucrit) swimming trials before and after 4 weeks of fasting. Fasting caused weight losses of 7.3% and 8.3% at 9°C and 18°C, respectively. The Ucrit was unaffected by fasting, but higher at 18°C. Fatigue was associated with higher plasma cortisol, osmolality, Na+ and Cl- at 18°C, and ionic disturbances were higher in fasted fish. All fish completed the sustained swim trials while maintaining constant oxygen uptake rates (ṀO2), indicating strictly aerobic swimming efforts. At low swimming speeds ṀO2 was downregulated in fasted fish by 23.8% and 15.6% at 9°C and 18°C, respectively, likely as an adaptation to preserve resources. However, at higher speeds ṀO2 became similar to fed fish showing that maximum metabolic rates were maintained. The changes in ṀO2 lowered costs of transport and optimal swimming speeds in fasted fish at both temperatures, but these energetic alterations were smaller at 18°C while routine ṀO2 was 57% higher than at 9°C. As such, this study shows that Atlantic salmon maintain both glycolytic and aerobic swimming capacities after extended fasting, even at elevated suboptimal temperatures, and adaptive metabolic downregulation provides increased swimming efficiency in fasted fish. Although, improved swimming energetics were smaller when fasting at the higher temperature while metabolism becomes elevated. This could affect migration success in warming climates, especially when considering interactions with other costly activities such as coping with parasites obtained when passing aquaculture sites during seaward travel or gonad development while being voluntarily anorexic during upriver travel to spawning grounds.

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Disease resistance is related to inherent swimming performance in Atlantic salmon.

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Disease resistance is related to inherent swimming performance in Atlantic salmon.

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