The Arctic charr Salvelinus alpinus L. is the most northerly distributed freshwater fish with a h... more The Arctic charr Salvelinus alpinus L. is the most northerly distributed freshwater fish with a holoArctic distribution. The species shows marked phenotypic diversity in morphology, life history and behaviour between populations (Johnson, 1980;
ence that one might use to check on an occasional item without having to trek over to the library... more ence that one might use to check on an occasional item without having to trek over to the library. Although the individual articles vary somewhat with the skill and competence of the more than 150 contributors, the articles show a regularity of editorial style that makes the encyclopedia pleasingly uniform. Anyone who wishes to have a convenient, readable, and brief reference work at hand should find this book quite satisfactory.
Paired box transcription factor 7 (Pax-7) cDNA was isolated from the skeletal muscle and brain of... more Paired box transcription factor 7 (Pax-7) cDNA was isolated from the skeletal muscle and brain of alevin and adult stages of Atlantic salmon, identifying 10 variants categorised as novel or established insertions (ins) or deletions (del). Two putative Pax-7 paralogs were identified (denoted Pax-7α and Pax-7β) on the basis of the length and sequences of intron 3 (218 and 248 bp) and versions of ins1 and ins2. Pax-7β contained a threonine variant of ins1 (GQY[T]GPEYVYCGT), and a shortened variant of ins2 (GEAS). Pattern identification revealed the threonine variant of ins1 includes a potential phosphorylation site (casein kinase II). Thus, the tetraploid Atlantic salmon genome appears to contain at least two putative copies and multiple splice variants of Pax-7. In situ hybridisation localised Pax-7 to mononuclear cells in the fast muscle of adult Atlantic salmon, while quantitative real-time PCR showed Pax-7α to be more highly expressed in brain than in skeletal muscle.
Growth in fish involves the recruitment and hypertrophy of muscle fibres. Muscle recruitment is p... more Growth in fish involves the recruitment and hypertrophy of muscle fibres. Muscle recruitment is particularly important in species that reach a large ultimate body size. The number of muscle fibres recruited to reach a particular girth varies between families and strains and is influenced by environmental factors including diet, exercise, light and temperature regimes. The resulting variation in muscle cellularity and associated changes in connective tissue matrix are thought to be important determinants of texture and other flesh quality characteristics. The state of knowledge about muscle development and growth is reviewed and potential practical applications of the research to flesh quality issues are discussed.
Early myogenesis was studied in the offspring of Atlantic salmon (Salmo salar L.) spawning in a l... more Early myogenesis was studied in the offspring of Atlantic salmon (Salmo salar L.) spawning in a lowland (Sheeoch) and an upland (Baddoch) tributary of the River Dee System, Aberdeenshire, Scotland. Eggs from each population were incubated at the simulated natural thermal regimes of each stream, which was on average 2.8 degrees C cooler for the Baddoch than for the Sheeoch. Relationships between muscle cellularity variables, the density of myonuclei and responses to temperature were investigated using multivariate statistical techniques. These revealed highly significant temperature effects (P<0.001) at hatch (H) and first feeding (FF) and significant interactions between population and temperature (P<0.001), indicating that Baddoch and Sheeoch salmon responded differently to the two temperature regimes. The total cross-sectional area of white muscle (WF.ta) at the adipose fin was relatively independent of temperature at hatch and first feeding in the Sheeoch population. In con...
The consequence of early thermal experience for subsequent growth patterns was investigated in At... more The consequence of early thermal experience for subsequent growth patterns was investigated in Atlantic salmon (Salmo salar L.). Spring- and autumn-running salmon were caught in upland (Baddoch) and lowland (Sheeoch) tributaries of the River Dee, Aberdeenshire, Scotland, respectively, on the final stages of their spawning migrations. The eggs were incubated at the simulated natural temperature regime of each stream, which was on average 2.8 degrees C lower for the Baddoch. The offspring, representing 11 families per population, were transferred at first feeding to constant environmental conditions (12–14 degrees C; 16h:8h light:dark photoperiod) and reared in replicate tanks. Salmon of both populations were longer and heavier at 6 and 12 weeks in fish initially reared under the cooler Baddoch regime. Length frequency distributions became bimodal after 18 weeks, and only the upper growth mode was studied. Modelling of length distributions at 40 weeks revealed significantly different ...
Muscle development and growth were investigated in diploid populations of normal-sex-ratio and al... more Muscle development and growth were investigated in diploid populations of normal-sex-ratio and all-female Atlantic salmon (Salmo salar L.) and their triploid counterparts produced by high-pressure treatment. Somites were formed at the rate of 6 h−1 in both diploids and triploids at 6 °C. The rostral-to-caudal development of myotubes, myofibrils and acetylcholinesterase staining at the myosepta was slightly more advanced in triploid than in diploid fish, although the differences were smaller than among individual families. The c-met receptor tyrosine kinase was used as a molecular marker for the satellite cells involved in postembryonic muscle growth. Satellite cell nuclei comprised 17.5 % of total myonuclei in smolts and they were 24 % more abundant in diploid than in triploid fish. Cells expressing the myogenic regulatory factor myf-6, a marker of satellite cells committed to differentiation, represented 14.8 % of total myonuclei in diploids and 12.5 % in triploids. At ambient temp...
SUMMARYThe influence of freshwater environment on muscle growth in seawater was investigated in a... more SUMMARYThe influence of freshwater environment on muscle growth in seawater was investigated in an inbred population of farmed Atlantic salmon (Salmo salar L.). The offspring from a minimum of 64 families per group were incubated at either ambient temperature (ambient treatment) or in heated water(heated treatment). Growth was investigated using a mixed-effect statistical model with repeated measures, which included terms for treatment effect and random fish effects for individual growth rate (α) and the instantaneous growth rate per unit change in temperature (γ). Prior to seawater transfer, fish were heavier in the heated (61.6±1.0 g; N=298)than in the ambient (34.1±0.4 g; N=206) treatments, reflecting their greater growth opportunity: 4872 degree-days and 4281 degree-days,respectively. However, the subsequent growth rate of the heated group was lower, such that treatments had a similar body mass (3.7-3.9 kg) after approximately 450 days in seawater. The total cross-sectional area...
General and comparative endocrinology, Jun 19, 2017
Much attention has been given to insulin-like growth factor (Igf) pathways that regulate the bala... more Much attention has been given to insulin-like growth factor (Igf) pathways that regulate the balance of skeletal muscle protein synthesis and breakdown in response to a range of extrinsic and intrinsic signals. However, we have a less complete understanding of how the same signals modulate muscle mass upstream of such signalling, through a family of functionally-diverse Igf-binding proteins (Igfbps) that modify the availability of Igfs to the cell receptor Igf1r. We exposed cultured myotubes from Atlantic salmon (Salmo salar L.) to treatments recapturing three catabolic signals: inflammation (interleukin-1β), stress (dexamethasone) and fasting (amino acid deprivation), plus one anabolic signal: recovery of muscle mass post-fasting (supplementation of fasted myotubes with Igf-I and amino acids). The intended phenotype of treatments was confirmed by significant changes in myotube diameter and immunofluorescent staining of structural proteins. We quantified the mRNA-level regulation of...
Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (Gh) express Gh in multiple tiss... more Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (Gh) express Gh in multiple tissues which results in increased appetite and continuous high growth with satiation feeding. Restricting Gh-transgenics to the same lower ration (TR) as wild-type fish (WT) results in similar growth, but with the recruitment of fewer, larger diameter, muscle skeletal fibres to reach a given body size. In order to better understand the genetic mechanisms behind these different patterns of muscle growth and to investigate how the decoupling of Gh and nutritional signals affects gene regulation we used RNA-seq to compare the fast skeletal muscle transcriptome in TR and WT coho salmon. Illumina sequencing of individually barcoded libraries from 6 WT and 6 TR coho salmon yielded 704,550,985 paired end reads which were used to construct 323,115 contigs containing 19,093 unique genes of which >10,000 contained >90 % of the coding sequence. Transcripts coding for 31 genes required for myobla...
Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (GH) show substantially faster g... more Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (GH) show substantially faster growth than wild-type (WT) fish. We fed GH-transgenic salmon either to satiation (1 year; TF) or the same smaller ration of wild-type fish (2 years; TR), resulting in groups matched for body size to WT salmon. The myotomes of TF and WT fish had the same number and size distribution of muscle fibres, indicating a twofold higher rate of fibre recruitment in the GH transgenics. Unexpectedly, calorie restriction was found to decrease the rate of fibre production in transgenics, resulting in a 20% increase in average fibre size and reduced costs of ionic homeostasis. Genes for myotube formation were downregulated in TR relative to TF and WT fish. We suggest that muscle fibre size optimisation allows the reallocation of energy from maintenance to locomotion, explaining the observation that calorie-restricted transgenics grow at the same rate as WT fish whilst exhibiting markedly higher foraging...
A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline ... more A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline (PYD) cross-links in Atlantic salmon (Salmo salar L.) muscle. The method involved the extraction of tissue with NaOH prior to hydrolysis, which greatly reduced the amount of protein to be hydrolyzed and made downstream operations easier and more reproducible. The concentration of PYD was 426 pmol g-1 dry mass muscle in post-rigor muscle stored at 0°C and sampled 3 d after death. Hydroxproline (HYP) concentration was determined following NaOH extraction as a measure of collagen content. In post-rigor samples, the alkaline-insoluble HYP fraction comprised 18.3% of the total HYP. Scanning electron microscopy revealed shrinkage of muscle fibers and a retraction of the connective tissue matrix in smoked salmon. PYD concentration was relatively resistant to processing to the smoked product, decreasing by around 11.7%, as compared to a 22.2% decrease in HYP. There was a positive correlation between PYD concentration and the firmness of post-rigor muscle samples as measured by an instrumental texture analyzer, explaining 25% of the total variation. A weaker but still significant correlation was found between PYD concentration and firmness in the smoked product. There was no relationship between fillet firmness and total collagen concentration, although the correlation with HYP in the alkaline-insoluble fraction was significant at the 6% level (P) 0.057). Our results indicate that only 1-3% of collagen molecules are linked by nonreducible mature cross-links in harvest size farmed Atlantic salmon and that PYD concentration is an important raw material characteristic for flesh quality.
The cee (conserved edge expressed protein) gene was recently identified in a genome-wide screen t... more The cee (conserved edge expressed protein) gene was recently identified in a genome-wide screen to discover genes associated with myotube formation in fast muscle of pufferfish. Comparative genomic analyses indicate that cee arose some 1.6-1.8 billion years ago and is found as a singlecopy gene in most eukaryotic genomes examined. The complexity of its structure varies from an intronless gene in yeast and tunicates to nine exons and eight introns in vertebrates. cee is particularly conserved among vertebrates and is located in a syntenic region within tetrapods and between teleosts and invertebrates. Low dN/dS ratios in the cee coding region (0.02-0.09) indicate that the Cee protein is under strong purifying selection. In Atlantic salmon, cee is expressed in the superficial layers of developing organs and tissues. These data, together with functional screens in yeast and Caenorhabditis elegans, indicate that cee has a hitherto uncharacterized role in normal growth and development.
Follistatin (Fst) inhibits transforming growth factor-β (TGF-B) proteins and is a known regulator... more Follistatin (Fst) inhibits transforming growth factor-β (TGF-B) proteins and is a known regulator of amniote myogenesis. Here, we used phylogenetic, genomic and experimental approaches to study its evolution in teleosts. Phylogenetic analyses suggested that one fst gene (fst1) is common to euteleosts, but a second gene (fst2) is conserved specifically within the Ostariophysi. Zebrafish fst1/2 respectively appear on chromosomes 5 and 10 in two genomic regions, each with conserved synteny to a single region in tetrapods. Interestingly, other teleosts have two corresponding chromosomal regions with a similar repertoire of paralogues. Phylogenetic reconstruction clustered these gene duplicates into two sister clades branching from tetrapod sequences. We suggest that an ancestral fstcontaining chromosome was duplicated during the teleost whole genome duplication, but that fst2 was lost in lineages external to the Ostariophysi. We show that Fst1 of teleosts/ mammals has evolved under strong purifying selection, but the N-terminal of Fst2 may have evolved under positive selection. Furthermore, the tissue-specific expression of zebrafish fst2 was restricted to fewer tissues compared to its paralogue and the single fst1 orthologue of Atlantic salmon (Salmo salar). Zebrafish fst1/2 may have subfunctionalized relative to non-duplicated vertebrate lineages, as several regions in the fst promoter of tetrapods were conserved with one paralogue, but not both. Finally, we examined the embryonic expression of fst1 in a teleost outside the Ostariophysi (Atlantic salmon). During segmentation, fst1 was expressed in the anterior somite compartment but was excluded from muscle progenitors that strongly expressed myogenic regulatory factors (MRFs). Later, fst1 was expressed in myogenic progenitors of the pectoral fin buds and also within the pax7 + cell layer external to the myotome.
Growth of fast myotomal muscle in teleosts involves the continuous production of muscle fibres un... more Growth of fast myotomal muscle in teleosts involves the continuous production of muscle fibres until some genetically pre-determined length. The dwarf landlocked (Bleke) population of Atlantic salmon ( Salmo salar L.) from Byglands-fjord, Southern Norway mature at about 25 cm fork length and reach a maximum size of only 30 cm in the wild. The maximum diameter ( D max ) of fast muscle fibres in 4-year-old Bleke salmon (25–28 cm fork length) was 118 μm and not significantly different from that found in immature migratory salmon of a similar size. In contrast no evidence for active fibre recruitment was found in the Bleke salmon, such that the maximum fibre number, FN max , was only 21–30% of that reported in typical farmed and wild migratory populations, respectively. We hypothesise that, once established, the physiological consequences of the dwarf condition led to rapid selection for reduced fibre number, possibly to reduce the maintenance costs associated with ionic homeostasis.
This experiment on farmed Atlantic salmon (Salmo salar L.) was designed to investigate the effect... more This experiment on farmed Atlantic salmon (Salmo salar L.) was designed to investigate the effect of postsmolt photoperiodic regime on growth performance, muscle cellularity, and flesh quality in out-of-season produced smolts. The offspring from three pairs of half-sibling crosses were studied to provide information on the genetic variability of treatment effects. In both treatments, parr were initially held on 10-h light/14-h dark for 6 weeks from the 27 September until the 8 November 2000, and then transferred to continuous light. All fish were transferred from fresh to salt water on the 12 January. In treatment A (TA), smolts were transferred from continuous light to ambient short days (23 January 2001), whereas in treatment B, (TB) smolts were continued on 24-h light until natural day length approached the seasonal maximum (1 June 2001). Fish were reared in outdoor saltwater tanks and transferred to 5 Â 5 Â 5 m sea cages at the Feed Trial Unit, Loch Duich, Scotland on the 21 April 2001. In the 6-9 months following smoltification, the growth performance of 835 fish held on continuous light (TB) was superior to that of 715 fish returned to short days (TA). Thereafter, in five out of the six families, growth performance was higher in TA than TB groups, such that the average bodyweight of families was no different between treatments over the production cycle. Bodyweight,
Growth performance, muscle cellularity and flesh quality were investigated in Atlantic salmon (Sa... more Growth performance, muscle cellularity and flesh quality were investigated in Atlantic salmon (Salmo salar L.) fed either of two diet ranges [high protein (HP), or low protein (LP)], which differed in digestible protein/digestible energy ratios but were of equivalent digestible energy content (21.4 MJ kg À 1 wet weight). Smolts from an early maturing (Lochy) and a late maturing (Mowi) strain were PIT-tagged and reared together in duplicate 5 Â 5 Â 5-m sea cages for each diet. The Lochy and Mowi fish were harvested in May and August, respectively, after 417 and 515 days in seawater. The average body weight of fish in each cage at harvest was in the range 3.8-5.4 kg, with no significant difference between diets. The total cross-sectional area of white muscle and the number and diameter of muscle fibres was determined at the level of the first dorsal fin ray. The distribution of muscle fibre diameters was investigated using nonparametric smoothing and bootstrapping techniques. Diet had no effect on fibre size distribution or fibre number in the Mowi strain, and small but significant effects for the Lochy strain. At harvest, in Lochy salmon of average fork length 69 cm there were around 15% more fibres in fish fed the HP than LP ratio diets. However, the 50th percentile of fibre diameter was 20%
Two year classes of Atlantic salmon (Salmo salar L.) (Fanad-Mowi strain) were studied from the Ma... more Two year classes of Atlantic salmon (Salmo salar L.) (Fanad-Mowi strain) were studied from the Marine Harvest family selection program. Fish were harvested at ∼3 years of age in 2004 and 2005 and comprised 149 and 157 full-sib families. All the fish in each year class were reared under the same conditions. Following paternity analysis using DNA microsatellites a subset of 142 fish in 2004 and 70 fish in 2005 were selected from 28 families and the number and size of fast myotomal muscle fibres determined at 0.7 fork length (FL). Muscle fat content, flesh colour and pigment concentration were also measured. There was a tendency for fish sampled in 2005 to be heavier for a given fork length than in 2004, and for males to be longer than females reflecting sexual maturation. It was established that muscle fibre recruitment had ceased in all the fish sampled and the final fibre number had been reached. The average muscle fibre number per family ranged from 3.48 × 10 5 ± 1.7 × 10 4 to 4.65 × 10 5 ± 1.9 × 10 4 (Mean ± SE, n = 5 and 8 fish respectively). Fibre number showed no significant differences between male and female fish or with year class. In contrast, muscle fibre density (fibres per mm 2 muscle) was inversely related to FL, and higher in 2004 than 2005 reflecting a lower average fibre size. Myogenic progenitor cells were quantified using a specific marker, an antibody to paired box protein 7 (Pax-7). There were significant positive correlations between the density of Pax-7 positive cells and fibre number (R 2 = 0.20; F 1,59 = 15.0; P = 0.001) and muscle fibre density (R 2 = 0.30; F 1,59 = 25.8; P b 0.0001) standardized to a 4 kg fish. Flesh lipid content was positively correlated with FL, and was higher in 2005 than 2004. Multi-trait genetic models with sex nested within year were constructed with and without corrections for body length. Muscle fibre number and density showed medium heritabilities: 0.33 ± 0.05 (with body length as covariate) and 0.51 ± 0.09 and 0.26 ± 0.08 (without body length as covariate) (Mean ± SE). All phenotypic correlations between fibre number and density and quality traits were low or negative, but genetic correlation to visually assessed colour and pigment content were significantly positive (P b 0.05). There was also a strong and significant negative genetic correlation between fat content and both fibre number (−0.85) and fibre density (−0.76). The use of muscle fibre traits in breeding programs designed to improve flesh quality is discussed.
Muscle fibre cellularity was quantified during seawater growth in populations of predominantly Ž.... more Muscle fibre cellularity was quantified during seawater growth in populations of predominantly Ž. Ž. Ž. early strain X and late maturing strain Y Atlantic salmon Salmo salar L.. The fibre density Ž y2
Mixed families of Atlantic salmon (Salmo salar L.) were subject to two photoperiods to produce ac... more Mixed families of Atlantic salmon (Salmo salar L.) were subject to two photoperiods to produce accelerated and 1+ smolts in January and May 2001, respectively. The fish were reared in freshwater land-based tanks until October 2000 and then split into two groups: natural photoperiod (1+ smolts) and manipulated photoperiod (accelerated smolts). Fish were sorted into small and large grades and transferred to 12 sea cages at Gildesk3l Research Station, Northern Norway (13857V20UE, 67804V10UN) in May-June 2001. The four groups were reared in triplicate cages until October 2002. The number and size distributions of fast myotomal muscle fibres were determined at the level of the first dorsal fin for all groups in May 2002 (selected fish of 2.4 kg) and October 2002 (randomly sampled fish). The presence of muscle fibres less than 10 Am diameter indicated active fibre recruitment in all groups in May 2002. Muscle fibre number had reached its maximum value (FN max) in the October harvest. Analysis of variance revealed no significant difference in average values of FN max (6.6Â10 5 F1.4Â10 4), muscle fibre density (76.2F1.7 fibres mm À2 muscle) and fibre diameter (121.3F1.5 Am) between different photoperiod treatments (meanFS.E., n=66). Smoothed curves were fitted to the measurements of fibre diameter using a kernel function. Nonparametric Kolmogorov-Smirnov tests revealed no significant difference in the distribution of fibre size between accelerated and 1+ postsmolts. There were, however, significantly more muscle fibres in the large than small grade fish, probably reflecting genetic differences in FN max. Flesh quality was assessed as fillet firmness using an instrumental texture method. The total work (J) required to shear muscle samples of standardized thickness showed no significant difference between photoperiod treatments. It was concluded that the manipulation of photoperiod required to produce accelerated smolts did not affect muscle cellularity and flesh firmness in post-smolts of a commercial harvest weight.
The Arctic charr Salvelinus alpinus L. is the most northerly distributed freshwater fish with a h... more The Arctic charr Salvelinus alpinus L. is the most northerly distributed freshwater fish with a holoArctic distribution. The species shows marked phenotypic diversity in morphology, life history and behaviour between populations (Johnson, 1980;
ence that one might use to check on an occasional item without having to trek over to the library... more ence that one might use to check on an occasional item without having to trek over to the library. Although the individual articles vary somewhat with the skill and competence of the more than 150 contributors, the articles show a regularity of editorial style that makes the encyclopedia pleasingly uniform. Anyone who wishes to have a convenient, readable, and brief reference work at hand should find this book quite satisfactory.
Paired box transcription factor 7 (Pax-7) cDNA was isolated from the skeletal muscle and brain of... more Paired box transcription factor 7 (Pax-7) cDNA was isolated from the skeletal muscle and brain of alevin and adult stages of Atlantic salmon, identifying 10 variants categorised as novel or established insertions (ins) or deletions (del). Two putative Pax-7 paralogs were identified (denoted Pax-7α and Pax-7β) on the basis of the length and sequences of intron 3 (218 and 248 bp) and versions of ins1 and ins2. Pax-7β contained a threonine variant of ins1 (GQY[T]GPEYVYCGT), and a shortened variant of ins2 (GEAS). Pattern identification revealed the threonine variant of ins1 includes a potential phosphorylation site (casein kinase II). Thus, the tetraploid Atlantic salmon genome appears to contain at least two putative copies and multiple splice variants of Pax-7. In situ hybridisation localised Pax-7 to mononuclear cells in the fast muscle of adult Atlantic salmon, while quantitative real-time PCR showed Pax-7α to be more highly expressed in brain than in skeletal muscle.
Growth in fish involves the recruitment and hypertrophy of muscle fibres. Muscle recruitment is p... more Growth in fish involves the recruitment and hypertrophy of muscle fibres. Muscle recruitment is particularly important in species that reach a large ultimate body size. The number of muscle fibres recruited to reach a particular girth varies between families and strains and is influenced by environmental factors including diet, exercise, light and temperature regimes. The resulting variation in muscle cellularity and associated changes in connective tissue matrix are thought to be important determinants of texture and other flesh quality characteristics. The state of knowledge about muscle development and growth is reviewed and potential practical applications of the research to flesh quality issues are discussed.
Early myogenesis was studied in the offspring of Atlantic salmon (Salmo salar L.) spawning in a l... more Early myogenesis was studied in the offspring of Atlantic salmon (Salmo salar L.) spawning in a lowland (Sheeoch) and an upland (Baddoch) tributary of the River Dee System, Aberdeenshire, Scotland. Eggs from each population were incubated at the simulated natural thermal regimes of each stream, which was on average 2.8 degrees C cooler for the Baddoch than for the Sheeoch. Relationships between muscle cellularity variables, the density of myonuclei and responses to temperature were investigated using multivariate statistical techniques. These revealed highly significant temperature effects (P<0.001) at hatch (H) and first feeding (FF) and significant interactions between population and temperature (P<0.001), indicating that Baddoch and Sheeoch salmon responded differently to the two temperature regimes. The total cross-sectional area of white muscle (WF.ta) at the adipose fin was relatively independent of temperature at hatch and first feeding in the Sheeoch population. In con...
The consequence of early thermal experience for subsequent growth patterns was investigated in At... more The consequence of early thermal experience for subsequent growth patterns was investigated in Atlantic salmon (Salmo salar L.). Spring- and autumn-running salmon were caught in upland (Baddoch) and lowland (Sheeoch) tributaries of the River Dee, Aberdeenshire, Scotland, respectively, on the final stages of their spawning migrations. The eggs were incubated at the simulated natural temperature regime of each stream, which was on average 2.8 degrees C lower for the Baddoch. The offspring, representing 11 families per population, were transferred at first feeding to constant environmental conditions (12–14 degrees C; 16h:8h light:dark photoperiod) and reared in replicate tanks. Salmon of both populations were longer and heavier at 6 and 12 weeks in fish initially reared under the cooler Baddoch regime. Length frequency distributions became bimodal after 18 weeks, and only the upper growth mode was studied. Modelling of length distributions at 40 weeks revealed significantly different ...
Muscle development and growth were investigated in diploid populations of normal-sex-ratio and al... more Muscle development and growth were investigated in diploid populations of normal-sex-ratio and all-female Atlantic salmon (Salmo salar L.) and their triploid counterparts produced by high-pressure treatment. Somites were formed at the rate of 6 h−1 in both diploids and triploids at 6 °C. The rostral-to-caudal development of myotubes, myofibrils and acetylcholinesterase staining at the myosepta was slightly more advanced in triploid than in diploid fish, although the differences were smaller than among individual families. The c-met receptor tyrosine kinase was used as a molecular marker for the satellite cells involved in postembryonic muscle growth. Satellite cell nuclei comprised 17.5 % of total myonuclei in smolts and they were 24 % more abundant in diploid than in triploid fish. Cells expressing the myogenic regulatory factor myf-6, a marker of satellite cells committed to differentiation, represented 14.8 % of total myonuclei in diploids and 12.5 % in triploids. At ambient temp...
SUMMARYThe influence of freshwater environment on muscle growth in seawater was investigated in a... more SUMMARYThe influence of freshwater environment on muscle growth in seawater was investigated in an inbred population of farmed Atlantic salmon (Salmo salar L.). The offspring from a minimum of 64 families per group were incubated at either ambient temperature (ambient treatment) or in heated water(heated treatment). Growth was investigated using a mixed-effect statistical model with repeated measures, which included terms for treatment effect and random fish effects for individual growth rate (α) and the instantaneous growth rate per unit change in temperature (γ). Prior to seawater transfer, fish were heavier in the heated (61.6±1.0 g; N=298)than in the ambient (34.1±0.4 g; N=206) treatments, reflecting their greater growth opportunity: 4872 degree-days and 4281 degree-days,respectively. However, the subsequent growth rate of the heated group was lower, such that treatments had a similar body mass (3.7-3.9 kg) after approximately 450 days in seawater. The total cross-sectional area...
General and comparative endocrinology, Jun 19, 2017
Much attention has been given to insulin-like growth factor (Igf) pathways that regulate the bala... more Much attention has been given to insulin-like growth factor (Igf) pathways that regulate the balance of skeletal muscle protein synthesis and breakdown in response to a range of extrinsic and intrinsic signals. However, we have a less complete understanding of how the same signals modulate muscle mass upstream of such signalling, through a family of functionally-diverse Igf-binding proteins (Igfbps) that modify the availability of Igfs to the cell receptor Igf1r. We exposed cultured myotubes from Atlantic salmon (Salmo salar L.) to treatments recapturing three catabolic signals: inflammation (interleukin-1β), stress (dexamethasone) and fasting (amino acid deprivation), plus one anabolic signal: recovery of muscle mass post-fasting (supplementation of fasted myotubes with Igf-I and amino acids). The intended phenotype of treatments was confirmed by significant changes in myotube diameter and immunofluorescent staining of structural proteins. We quantified the mRNA-level regulation of...
Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (Gh) express Gh in multiple tiss... more Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (Gh) express Gh in multiple tissues which results in increased appetite and continuous high growth with satiation feeding. Restricting Gh-transgenics to the same lower ration (TR) as wild-type fish (WT) results in similar growth, but with the recruitment of fewer, larger diameter, muscle skeletal fibres to reach a given body size. In order to better understand the genetic mechanisms behind these different patterns of muscle growth and to investigate how the decoupling of Gh and nutritional signals affects gene regulation we used RNA-seq to compare the fast skeletal muscle transcriptome in TR and WT coho salmon. Illumina sequencing of individually barcoded libraries from 6 WT and 6 TR coho salmon yielded 704,550,985 paired end reads which were used to construct 323,115 contigs containing 19,093 unique genes of which >10,000 contained >90 % of the coding sequence. Transcripts coding for 31 genes required for myobla...
Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (GH) show substantially faster g... more Coho salmon (Oncorhynchus kisutch) transgenic for growth hormone (GH) show substantially faster growth than wild-type (WT) fish. We fed GH-transgenic salmon either to satiation (1 year; TF) or the same smaller ration of wild-type fish (2 years; TR), resulting in groups matched for body size to WT salmon. The myotomes of TF and WT fish had the same number and size distribution of muscle fibres, indicating a twofold higher rate of fibre recruitment in the GH transgenics. Unexpectedly, calorie restriction was found to decrease the rate of fibre production in transgenics, resulting in a 20% increase in average fibre size and reduced costs of ionic homeostasis. Genes for myotube formation were downregulated in TR relative to TF and WT fish. We suggest that muscle fibre size optimisation allows the reallocation of energy from maintenance to locomotion, explaining the observation that calorie-restricted transgenics grow at the same rate as WT fish whilst exhibiting markedly higher foraging...
A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline ... more A simple HPLC method is presented to quantify the low concentration of hydroxylysyl pyridinoline (PYD) cross-links in Atlantic salmon (Salmo salar L.) muscle. The method involved the extraction of tissue with NaOH prior to hydrolysis, which greatly reduced the amount of protein to be hydrolyzed and made downstream operations easier and more reproducible. The concentration of PYD was 426 pmol g-1 dry mass muscle in post-rigor muscle stored at 0°C and sampled 3 d after death. Hydroxproline (HYP) concentration was determined following NaOH extraction as a measure of collagen content. In post-rigor samples, the alkaline-insoluble HYP fraction comprised 18.3% of the total HYP. Scanning electron microscopy revealed shrinkage of muscle fibers and a retraction of the connective tissue matrix in smoked salmon. PYD concentration was relatively resistant to processing to the smoked product, decreasing by around 11.7%, as compared to a 22.2% decrease in HYP. There was a positive correlation between PYD concentration and the firmness of post-rigor muscle samples as measured by an instrumental texture analyzer, explaining 25% of the total variation. A weaker but still significant correlation was found between PYD concentration and firmness in the smoked product. There was no relationship between fillet firmness and total collagen concentration, although the correlation with HYP in the alkaline-insoluble fraction was significant at the 6% level (P) 0.057). Our results indicate that only 1-3% of collagen molecules are linked by nonreducible mature cross-links in harvest size farmed Atlantic salmon and that PYD concentration is an important raw material characteristic for flesh quality.
The cee (conserved edge expressed protein) gene was recently identified in a genome-wide screen t... more The cee (conserved edge expressed protein) gene was recently identified in a genome-wide screen to discover genes associated with myotube formation in fast muscle of pufferfish. Comparative genomic analyses indicate that cee arose some 1.6-1.8 billion years ago and is found as a singlecopy gene in most eukaryotic genomes examined. The complexity of its structure varies from an intronless gene in yeast and tunicates to nine exons and eight introns in vertebrates. cee is particularly conserved among vertebrates and is located in a syntenic region within tetrapods and between teleosts and invertebrates. Low dN/dS ratios in the cee coding region (0.02-0.09) indicate that the Cee protein is under strong purifying selection. In Atlantic salmon, cee is expressed in the superficial layers of developing organs and tissues. These data, together with functional screens in yeast and Caenorhabditis elegans, indicate that cee has a hitherto uncharacterized role in normal growth and development.
Follistatin (Fst) inhibits transforming growth factor-β (TGF-B) proteins and is a known regulator... more Follistatin (Fst) inhibits transforming growth factor-β (TGF-B) proteins and is a known regulator of amniote myogenesis. Here, we used phylogenetic, genomic and experimental approaches to study its evolution in teleosts. Phylogenetic analyses suggested that one fst gene (fst1) is common to euteleosts, but a second gene (fst2) is conserved specifically within the Ostariophysi. Zebrafish fst1/2 respectively appear on chromosomes 5 and 10 in two genomic regions, each with conserved synteny to a single region in tetrapods. Interestingly, other teleosts have two corresponding chromosomal regions with a similar repertoire of paralogues. Phylogenetic reconstruction clustered these gene duplicates into two sister clades branching from tetrapod sequences. We suggest that an ancestral fstcontaining chromosome was duplicated during the teleost whole genome duplication, but that fst2 was lost in lineages external to the Ostariophysi. We show that Fst1 of teleosts/ mammals has evolved under strong purifying selection, but the N-terminal of Fst2 may have evolved under positive selection. Furthermore, the tissue-specific expression of zebrafish fst2 was restricted to fewer tissues compared to its paralogue and the single fst1 orthologue of Atlantic salmon (Salmo salar). Zebrafish fst1/2 may have subfunctionalized relative to non-duplicated vertebrate lineages, as several regions in the fst promoter of tetrapods were conserved with one paralogue, but not both. Finally, we examined the embryonic expression of fst1 in a teleost outside the Ostariophysi (Atlantic salmon). During segmentation, fst1 was expressed in the anterior somite compartment but was excluded from muscle progenitors that strongly expressed myogenic regulatory factors (MRFs). Later, fst1 was expressed in myogenic progenitors of the pectoral fin buds and also within the pax7 + cell layer external to the myotome.
Growth of fast myotomal muscle in teleosts involves the continuous production of muscle fibres un... more Growth of fast myotomal muscle in teleosts involves the continuous production of muscle fibres until some genetically pre-determined length. The dwarf landlocked (Bleke) population of Atlantic salmon ( Salmo salar L.) from Byglands-fjord, Southern Norway mature at about 25 cm fork length and reach a maximum size of only 30 cm in the wild. The maximum diameter ( D max ) of fast muscle fibres in 4-year-old Bleke salmon (25–28 cm fork length) was 118 μm and not significantly different from that found in immature migratory salmon of a similar size. In contrast no evidence for active fibre recruitment was found in the Bleke salmon, such that the maximum fibre number, FN max , was only 21–30% of that reported in typical farmed and wild migratory populations, respectively. We hypothesise that, once established, the physiological consequences of the dwarf condition led to rapid selection for reduced fibre number, possibly to reduce the maintenance costs associated with ionic homeostasis.
This experiment on farmed Atlantic salmon (Salmo salar L.) was designed to investigate the effect... more This experiment on farmed Atlantic salmon (Salmo salar L.) was designed to investigate the effect of postsmolt photoperiodic regime on growth performance, muscle cellularity, and flesh quality in out-of-season produced smolts. The offspring from three pairs of half-sibling crosses were studied to provide information on the genetic variability of treatment effects. In both treatments, parr were initially held on 10-h light/14-h dark for 6 weeks from the 27 September until the 8 November 2000, and then transferred to continuous light. All fish were transferred from fresh to salt water on the 12 January. In treatment A (TA), smolts were transferred from continuous light to ambient short days (23 January 2001), whereas in treatment B, (TB) smolts were continued on 24-h light until natural day length approached the seasonal maximum (1 June 2001). Fish were reared in outdoor saltwater tanks and transferred to 5 Â 5 Â 5 m sea cages at the Feed Trial Unit, Loch Duich, Scotland on the 21 April 2001. In the 6-9 months following smoltification, the growth performance of 835 fish held on continuous light (TB) was superior to that of 715 fish returned to short days (TA). Thereafter, in five out of the six families, growth performance was higher in TA than TB groups, such that the average bodyweight of families was no different between treatments over the production cycle. Bodyweight,
Growth performance, muscle cellularity and flesh quality were investigated in Atlantic salmon (Sa... more Growth performance, muscle cellularity and flesh quality were investigated in Atlantic salmon (Salmo salar L.) fed either of two diet ranges [high protein (HP), or low protein (LP)], which differed in digestible protein/digestible energy ratios but were of equivalent digestible energy content (21.4 MJ kg À 1 wet weight). Smolts from an early maturing (Lochy) and a late maturing (Mowi) strain were PIT-tagged and reared together in duplicate 5 Â 5 Â 5-m sea cages for each diet. The Lochy and Mowi fish were harvested in May and August, respectively, after 417 and 515 days in seawater. The average body weight of fish in each cage at harvest was in the range 3.8-5.4 kg, with no significant difference between diets. The total cross-sectional area of white muscle and the number and diameter of muscle fibres was determined at the level of the first dorsal fin ray. The distribution of muscle fibre diameters was investigated using nonparametric smoothing and bootstrapping techniques. Diet had no effect on fibre size distribution or fibre number in the Mowi strain, and small but significant effects for the Lochy strain. At harvest, in Lochy salmon of average fork length 69 cm there were around 15% more fibres in fish fed the HP than LP ratio diets. However, the 50th percentile of fibre diameter was 20%
Two year classes of Atlantic salmon (Salmo salar L.) (Fanad-Mowi strain) were studied from the Ma... more Two year classes of Atlantic salmon (Salmo salar L.) (Fanad-Mowi strain) were studied from the Marine Harvest family selection program. Fish were harvested at ∼3 years of age in 2004 and 2005 and comprised 149 and 157 full-sib families. All the fish in each year class were reared under the same conditions. Following paternity analysis using DNA microsatellites a subset of 142 fish in 2004 and 70 fish in 2005 were selected from 28 families and the number and size of fast myotomal muscle fibres determined at 0.7 fork length (FL). Muscle fat content, flesh colour and pigment concentration were also measured. There was a tendency for fish sampled in 2005 to be heavier for a given fork length than in 2004, and for males to be longer than females reflecting sexual maturation. It was established that muscle fibre recruitment had ceased in all the fish sampled and the final fibre number had been reached. The average muscle fibre number per family ranged from 3.48 × 10 5 ± 1.7 × 10 4 to 4.65 × 10 5 ± 1.9 × 10 4 (Mean ± SE, n = 5 and 8 fish respectively). Fibre number showed no significant differences between male and female fish or with year class. In contrast, muscle fibre density (fibres per mm 2 muscle) was inversely related to FL, and higher in 2004 than 2005 reflecting a lower average fibre size. Myogenic progenitor cells were quantified using a specific marker, an antibody to paired box protein 7 (Pax-7). There were significant positive correlations between the density of Pax-7 positive cells and fibre number (R 2 = 0.20; F 1,59 = 15.0; P = 0.001) and muscle fibre density (R 2 = 0.30; F 1,59 = 25.8; P b 0.0001) standardized to a 4 kg fish. Flesh lipid content was positively correlated with FL, and was higher in 2005 than 2004. Multi-trait genetic models with sex nested within year were constructed with and without corrections for body length. Muscle fibre number and density showed medium heritabilities: 0.33 ± 0.05 (with body length as covariate) and 0.51 ± 0.09 and 0.26 ± 0.08 (without body length as covariate) (Mean ± SE). All phenotypic correlations between fibre number and density and quality traits were low or negative, but genetic correlation to visually assessed colour and pigment content were significantly positive (P b 0.05). There was also a strong and significant negative genetic correlation between fat content and both fibre number (−0.85) and fibre density (−0.76). The use of muscle fibre traits in breeding programs designed to improve flesh quality is discussed.
Muscle fibre cellularity was quantified during seawater growth in populations of predominantly Ž.... more Muscle fibre cellularity was quantified during seawater growth in populations of predominantly Ž. Ž. Ž. early strain X and late maturing strain Y Atlantic salmon Salmo salar L.. The fibre density Ž y2
Mixed families of Atlantic salmon (Salmo salar L.) were subject to two photoperiods to produce ac... more Mixed families of Atlantic salmon (Salmo salar L.) were subject to two photoperiods to produce accelerated and 1+ smolts in January and May 2001, respectively. The fish were reared in freshwater land-based tanks until October 2000 and then split into two groups: natural photoperiod (1+ smolts) and manipulated photoperiod (accelerated smolts). Fish were sorted into small and large grades and transferred to 12 sea cages at Gildesk3l Research Station, Northern Norway (13857V20UE, 67804V10UN) in May-June 2001. The four groups were reared in triplicate cages until October 2002. The number and size distributions of fast myotomal muscle fibres were determined at the level of the first dorsal fin for all groups in May 2002 (selected fish of 2.4 kg) and October 2002 (randomly sampled fish). The presence of muscle fibres less than 10 Am diameter indicated active fibre recruitment in all groups in May 2002. Muscle fibre number had reached its maximum value (FN max) in the October harvest. Analysis of variance revealed no significant difference in average values of FN max (6.6Â10 5 F1.4Â10 4), muscle fibre density (76.2F1.7 fibres mm À2 muscle) and fibre diameter (121.3F1.5 Am) between different photoperiod treatments (meanFS.E., n=66). Smoothed curves were fitted to the measurements of fibre diameter using a kernel function. Nonparametric Kolmogorov-Smirnov tests revealed no significant difference in the distribution of fibre size between accelerated and 1+ postsmolts. There were, however, significantly more muscle fibres in the large than small grade fish, probably reflecting genetic differences in FN max. Flesh quality was assessed as fillet firmness using an instrumental texture method. The total work (J) required to shear muscle samples of standardized thickness showed no significant difference between photoperiod treatments. It was concluded that the manipulation of photoperiod required to produce accelerated smolts did not affect muscle cellularity and flesh firmness in post-smolts of a commercial harvest weight.
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