Impact of freshwater rearing history on Atlantic salmon gill response to viral stimulation post seawater transfer.

Land-based recirculating aquaculture systems (RAS) have risen in prevalence in recent years for Atlantic salmon production, enabling intensive production which allows increased growth and environmental control, but also having the potential for reducing water use and eutrophication. The Atlantic salmon has an anadromous life history with juvenile stages in freshwater (FW) and on-growing in seawater (SW), enabled by a transformational process known as smoltification. The timing of smoltification and transfer of smolts from FW to SW is critical under commercial production with high mortalities during this period. The impact of FW rearing system on immune function following seawater transfer (SWT) is not well understood. In this study parr were raised in either RAS or a traditional open-LOCH system until smolting and then transferred to a common marine environment. Two-weeks post-SWT fish were immune stimulated with a viral mimic (poly I:C) for 24 h to assess the ability to mount an antiviral immune response, assessed by whole transcriptome analysis of gill tissue, an important immune organ in fish. We show that unstimulated smolts reared in the LOCH had higher immune gene expression than those reared in RAS as determined by functional analysis. However, following stimulation, smolts reared in the RAS mounted a greater magnitude of response with a suite of immune genes displaying higher fold induction of transcription compared to LOCH reared smolts. We suggest RAS smolts have a lower steady state immune-associated transcriptome likely due to an unvarying environment, in terms of environmental factors and lack of exposure to pathogens, which shows a compensatory mechanism following stimulation allowing immune 'catch-up' with those reared in the LOCH. Alternatively, the RAS fish are experiencing an excessive response to the immune stimulation.

Micronutrient supplementation affects DNA methylation in male gonads with potential intergenerational epigenetic inheritance involving the embryonic development through glutamate receptor-associated genes.

BACKGROUND: DNA methylation has an important role in intergenerational inheritance. An increasing number of studies have reported evidence of germline inheritance of DNA methylation induced by nutritional signals in mammals. Vitamins and minerals as micronutrients contribute to growth performance in vertebrates, including Atlantic salmon (Salmo salar), and also have a role in epigenetics as environmental factors that alter DNA methylation status. It is important to understand whether micronutrients in the paternal diet can influence the offspring through alterations of DNA methylation signatures in male germ cells. RESULTS: Here, we show the effect of micronutrient supplementation on DNA methylation profiles in the male gonad through a whole life cycle feeding trial of Atlantic salmon fed three graded levels of micronutrient components. Our results strongly indicate that micronutrient supplementation affects the DNA methylation status of genes associated with cell signalling, synaptic signalling, and embryonic development. In particular, it substantially affects DNA methylation status in the promoter region of a glutamate receptor gene, glutamate receptor ionotropic, NMDA 3A-like (grin3a-like), when the fish are fed both medium and high doses of micronutrients. Furthermore, two transcription factors, histone deacetylase 2 (hdac2) and a zinc finger protein, bind to the hyper-methylated site in the grin3a-like promoter. An estimated function of hdac2 together with a zinc finger indicates that grin3a-like has a potential role in intergenerational epigenetic inheritance and the regulation of embryonic development affected by paternal diet. CONCLUSIONS: The present study demonstrates alterations of gene expression patterns and DNA methylation signatures in the male gonad when Atlantic salmon are fed different levels of micronutrients. Alterations of gene expression patterns are of great interest because the gonads are supposed to have limited metabolic activities compared to other organs, whereas alterations of DNA methylation signatures are of great importance in the field of nutritional epigenetics because the signatures affected by nutrition could be transferred to the next generation. We provide extensive data resources for future work in the context of potential intergenerational inheritance through the male germline.

Response of triploid Atlantic salmon (Salmo salar) to commercial vaccines.

While triploid Atlantic salmon represent a practical and affordable solution to the issues associated with sexual maturation in the salmonid aquaculture industry, empirical evidence suggests triploids are more susceptible to disease and vaccine side-effects than diploids. With vaccination now part of routine husbandry, it is essential their response be studied to confirm their suitability for commercial production. This study tested the response of triploid and diploid Atlantic salmon to vaccination with commercially available vaccines. Triploid and diploid Atlantic salmon siblings were injected with one of three commercial vaccines (or sham-vaccinated) and monitored for performance throughout a commercial production cycle. Sampling at smolt and harvest was undertaken along with individual weight and length assessments through the cycle. Antibody response to Aeromonas salmonicida vaccination was similar in both ploidy, with a positive response in vaccine-injected fish. For both adhesions and melanin, analysis found that higher scores were more likely to occur as the anticipated severity of the vaccine increased. In addition, for adhesion scores at smolt and melanin scores at smolt and harvest, triploids were statistically more likely to exhibit high scores than diploids. Triploids maintained a significantly higher body weight during freshwater and until 11 months post-seawater transfer, with diploids weighing significantly more at harvest. Growth, represented by thermal growth coefficient (TGC), decreased in both ploidy as the severity of adhesions increased, and regression patterns did not differ significantly between ploidy. Vertebral deformity prevalence was consistently higher in triploids (smolt 12.3 ± 4.5%; harvest 34.9 ± 5.9%) than diploids (smolt 0.8 ± 0.5%; harvest 15.9 ± 1.9%), with no significant difference between vaccine groups in each ploidy. This study demonstrates that triploids respond as well to vaccination as diploids and provides further supporting evidence of triploid robustness for commercial aquaculture.

GnRHa implants and size pairing effects on plasma and cephalic secretion sex steroids in Arapaima gigas.

Arapaima gigas, one of the world's largest freshwater fish, is considered an emerging species for aquaculture development in Brazil given its high growth rate and meat quality. However, the lack of reproductive control in captivity has limited the expansion of Arapaima farming. This study aimed to test the effects of hormonal induction using mGnRHa implants and size pairing on broodstock reproduction through the analyses of sex steroids. To do so, broodstock of different sizes (large, small or mixed) were paired and implanted. Plasma and cephalic secretion profiles of testosterone (T), 11-ketotestosterone (11-KT) and 17ß-oestradiol (E2) were analysed. Compared to control (non-implanted), implanted broodstock showed a significant increase in plasma 11-KT (large and small males) and T (large and mixed females) post GnRHa implantation. In females, a significant increase in plasma T levels was shown, however, E2 remained unchanged after implantation. Despite the lack of clear spawning induction, this study showed the potency of GnRHa on sex steroid production regardless of pairing groups. Interestingly, significant correlations between blood plasma and cephalic secretion levels of 11-KT in males and T in females were observed, indicating the possible release of pheromones through the cephalic canals of A. gigas.

Comparative ploidy response to experimental hydrogen peroxide exposure in Atlantic salmon (Salmo salar).

While research into the growth, survival, nutrition and, more recently, disease susceptibility of triploid Atlantic salmon has expanded, there remains an overall lack of studies assessing the response of triploids to chemical treatments. It is essential that the response of triploids to disease treatments be characterised to validate their suitability for commercial production. This study aimed to investigate and compare the stress and immune responses of triploid and diploid Atlantic salmon following an experimental treatment with hydrogen peroxide (H2O2). A dose response test was first undertaken to determine a suitable test dose for both diploid and triploid Atlantic salmon. Following this, diploids and triploids were exposed to H2O2 (1800 ppm) for 20 min, as per commercial practices, after which blood glucose and lactate, and plasma cortisol and lysozyme were measured, along with the expression of oxidative stress and immune-related genes. In the first 6 h post-exposure to H2O2, comparable mortalities occurred in both diploid and triploid Atlantic salmon. Cortisol, glucose and lactate were not significantly influenced by ploidy suggesting that, physiologically, triploid Atlantic salmon are able to cope with the stress associated with H2O2 exposure as well as their diploid counterparts. Exposure to H2O2 significantly elevated the expression of cat and sod2 in diploid livers and gr, il1ß and crp/sap1b in diploid gills, while it significantly decreased the expression of saa5 and crp/sap1a in diploid gills. In triploids, the expression levels of cat, hsp70, sod1, saa5, crp/sap1a and crp/sap1b in liver was significantly higher in fish exposed to H2O2 compared to control fish. The expression of gr, sod1 and il1ß in triploid gills was also elevated in response to H2O2 exposure. This study represents the first experimental evidence of the effects of H2O2 exposure on triploid Atlantic salmon and continues to support their application into commercial production.

Early nutritional intervention can improve utilisation of vegetable-based diets in diploid and triploid Atlantic salmon (Salmo salar L.).

The present study investigated nutritional programming in Atlantic salmon to improve utilisation of a vegetable-based diet. At first exogenous feeding, fry were fed either a marine-based diet (Diet Mstimulus, 80% fishmeal (FM)/4% fish oil (FO)) or a vegetable-based diet (Diet Vstimulus, 10% FM/0% FO) for 3 weeks. Subsequently, all fish were then fed under the same conditions with a commercial, marine-based, diet for 15 weeks and thereafter challenged with a second V diet (Diet Vchallenge, 10% FM/0% FO) for 6 weeks. Diploid and triploid siblings were run in parallel to examine ploidy effects. Growth performance, feed intake, nutrient utilisation and intestinal morphology were monitored. Fish initially given Diet Vstimulus (V-fish) showed 24 % higher growth rate and 23 % better feed efficiency compared with M-fish when later challenged with Diet Vchallenge. There was no difference in feed intake between nutritional histories, but increased nutrient retentions highlighted the improved utilisation of a V diet in V-fish. There were generally few significant effects of nutritional history or ploidy on enteritis scores in the distal intestine after the challenge phase as only V-triploids showed a significant increase (P<0·05) in total score. The data highlighted that the positive effects were most likely a result of nutritional programming and the ability to respond better when challenged later in life may be attributed to physiological and/or metabolic changes induced by the stimulus. This novel study showed the potential of nutritional programming to improve the use of plant raw material ingredients in feeds for Atlantic salmon.

A comparison of disease susceptibility and innate immune response between diploid and triploid Atlantic salmon (Salmo salar) siblings following experimental infection with Neoparamoeba perurans, causative agent of amoebic gill disease.

Few studies have focussed on the health and immunity of triploid Atlantic salmon and therefore much is still unknown about their response to commercially significant pathogens. This is important if triploid stocks are to be considered for full-scale commercial production. This study aimed to investigate and compare the response of triploid and diploid Atlantic salmon to an experimental challenge with Neoparamoeba perurans, causative agent of amoebic gill disease (AGD). This disease is economically significant for the aquaculture industry. The results indicated that ploidy had no significant effect on gross gill score or gill filaments affected, while infection and time had significant effects. Ploidy, infection and time did not affect complement or anti-protease activities. Ploidy had a significant effect on lysozyme activity at 21 days post-infection (while infection and time did not), although activity was within the ranges previously recorded for salmonids. Stock did not significantly affect any of the parameters measured. Based on the study results, it can be suggested that ploidy does not affect the manifestation or severity of AGD pathology or the serum innate immune response. Additionally, the serum immune response of diploid and triploid Atlantic salmon may not be significantly affected by amoebic gill disease.

Effects of temperature on feed intake and plasma chemistry after exhaustive exercise in triploid brown trout (Salmo trutta L).

The physiological effect of temperature on feed intake and haematological parameters after exhaustive swimming in diploid and triploid brown trout (Salmo trutta) was investigated. Trout were exposed to an incremental temperature challenge (2 °C/day) from ambient (6 °C) to either 10 or 19 °C. Feed intake profiles did not differ between ploidy at 10 °C; however, triploids had a significantly higher total feed intake at 19 °C. After 24 days, each temperature-ploidy group was exposed to exhaustive swimming for 10 min. The haematological response differed between ploidy, with the magnitude of the response affected by temperature and ploidy. Post-exercise, acid-base and ionic differences were observed. Plasma lactate increased significantly from rest for both temperature and ploidy groups, but glucose increased significantly at higher temperature. Post-exercise, triploids at 19 °C had significantly higher osmolality and cholesterol than diploids, but differences were resumed within 4 h. Elevated alkaline phosphatase (ALP) and aspartate aminotransferase (AST) in fish at higher temperature suggested greater tissue damage; however, both ploidy responded similarly. Despite no significant differences in deformity prevalence, the type and location of deformities observed differed between ploidy (decreased intervertebral space with higher prevalence in tail area and fin regions for diploids, while vertebral compression, fusion in cranial and caudal trunks for triploids). These results suggest triploids have greater appetite than diploids at elevated temperature and that triploids suffer similar blood disturbances after exercise as diploids. These findings have implications for the management of freshwater ecosystems and suggest that stocking triploid brown trout may offer an alternative to diploid brown trout.

A comparison of the response of diploid and triploid Atlantic salmon (Salmo salar) siblings to a commercial furunculosis vaccine and subsequent experimental infection with Aeromonas salmonicida.

Sterile triploid fish represent a solution to the problems associated with sexual maturation and escapees in aquaculture. However, as disease outbreaks continue to cause significant economic losses to the industry, it is essential that the response of triploids to disease and disease treatments be characterised. The aim of this study was to compare the response of triploid Atlantic salmon to a commercial furunculosis vaccine with that of diploid fish, and to assess the vaccine efficacy in the two ploidies through an experimental infection with Aeromonas salmonicida. Diploid and triploid Atlantic salmon were injected intraperitoneally with either phosphate buffered saline, liquid paraffin adjuvant or a commercial furunculosis vaccine. Following vaccination, growth, adhesion scores and a variety of assays to assess immune function, such as respiratory burst and antibody response, were measured. Vaccination did not have a significant effect on the weight of either ploidy prior to challenge at 750° days. Adhesion scores were significantly higher in vaccinated fish compared to unvaccinated fish, although no effect of ploidy was observed. Ploidy significantly affected respiratory burst activity following vaccination, however, with triploids exhibiting higher activity than diploids. Combined with lower white blood cell numbers observed in the triploids, it may be that this low cell number is compensated for by increased cellular activity. Ploidy however, did not have a significant effect on complement activity or antibody response, with significantly higher antibody levels detected in all vaccinated fish compared to unvaccinated controls. In addition, both ploidy groups were well protected following challenge with no difference in the relative percentage survival. Based on these results, it appears that ploidy does not affect the severity of adhesions that result post-vaccinate or in the fish's immune response following vaccination, and the furunculosis vaccine performs equally well in both diploid and triploid Atlantic salmon.

Taxonomy and stratigraphic distribution of Lotagnostus (Agnostida: Agnostidae) and associated trilobites and conodonts in the Upper Cambrian (Furongian) of Laurentia.

Two Lotagnostus-dominated faunas from the Windfall Formation at Ninemile Canyon in the Antelope Range of Nevada, USA, are described: an older Lotagnostus nolani Fauna and younger L. rushtoni Fauna. The former is dominated by two morphs of Lotagnostus, one strongly scrobiculate and the other smooth to weakly scrobiculate. Both morphs fall within the broad concept advocated for L. americanus by Peng et al. (2015). The numerous (>1400 sclerites) specimens of Lotaganostus in collections of the L. nolani Fauna confirm that the two morphs do not intergrade and remain distinct throughout ontogeny. Both display multiple traits that distinguish them from the type material of L. americanus, justifying treatment as separate species. Similarly unique, diagnostic features were identified to restore the Asian species L. punctatus and L. asiaticus to full species status, whereas deficiencies in the type material for L. americanus warrant restriction of the name to the holotype. New species described from the Windfall include five agnostoids (Lotagnostus nolani, L. clarki, L. morrisoni, L. rushtoni, and Neoagnostus parki) and one trilobite (Bienvillia eurekensis). Plicatolina nyensis Taylor is reassigned to Mendoparabolina on the form of its pygidium. Conodonts from the Catlin Member of the Windfall Formation and overlying informal Caryocaris shale member of the Goodwin Formation at Ninemile Canyon provide a late Sunwaptan (Eoconodontus Zone) age for the Lotagnostus rushtoni Fauna and assign the entire Caryocaris shale to the early Ordovician Rossodus manitouensis Zone. Combined with published data on trilobite faunas, the conodont faunas confirm strong diachroneity for the top of the Catlin, and a lack of overlap in age between the Caryocaris shale and Bullwhacker Member of the Windfall in ranges to the north and east. Co-occurrence of Lotagnostus nolani and Mendoparabolina nyensis establishes age equivalence of the L. nolani Fauna with the Hedinaspis-Charchaqia (HC) Fauna at the base of the Hales Limestone in the Hot Creek Range, and earlier correlations of the latter with the L. punctatus Zone in Asia are supported. However, isolation of the HC Fauna in starved-basin deposits above a major sequence boundary at the base of the Hales, and ecologic restriction of Lotagnostus to lower slope and basinal environments that prevented association with endemic shallow marine taxa, renders correlation into the biostratigraphy of Laurentian upper slope and platform imprecise on the order of 10s, if not 100s of meters.

In vivo efficacy of ferrihydrite as an enterosorbent for arsenic: short-term evaluation in rodents.

The use of dietary adsorbents to reduce arsenic (As) exposure is innovative. Ferrihydrite successfully sorbs arsenite and asenate over a wide range of pH conditions and the As-ferrihydrite complexes are stable in gastrointestinal (GIT) models. Our objectives were to (1) compare structural characteristics (using x-ray diffraction and Fourier-transform infrared [FTIR] spectroscopy) and As binding affinities of industrially produced ferrihydrite (IDF) and lab-synthesized ferrihydrite and (2) evaluate the efficacy of the material displaying the best sorption capability as an As enterosorbent in a short-term mammalian model. Lab-synthesized ferrihydrite displayed superior binding affinity for both arsenate and arsenite in vitro, which led to its use in the in vivo portion of the study. Young Sprague-Dawley male rats were fed either a control diet or a 0.5% w/w ferrihydrite feed. After 1 wk of acclimation, rats were given 0.5 ml of 500 mg/L arsenate or arsenite via gavage with or without ferrihydrite. Rats were then transferred to metabolism cages, and urine collected after 24 and 48 h was analyzed for total As. Rats were evaluated daily for signs of morbidity and mortality for up to 1 wk. Ferrihydrite reduced mean urinary As levels by 74.9% and 43.6% after 24 h and 49.1% and 39.5% after 48 h for arsenite- and arsenate-treated groups, respectively. Importantly, treatment groups receiving ferrihydrite displayed no signs of As-related toxicity. All As reductions were statistically significant except for arsenate treatments at 24 h. Data suggest that, as an enterosorbent, ferrihydrite reduces bioavailability after As exposures.

Comparison of Diploid and Triploid Atlantic Salmon (Salmo salar) Physiological Embryonic Development.

Diploid and triploid Atlantic salmon show distinct physiological differences including heart, brain, and digestive system morphology, propensity for certain deformities, temperature tolerance as eggs and once hatched, and different nutritional requirements. Whilst several studies have looked in detail at the rate of embryogenesis in diploid salmon, no study has compared the rate of embryogenesis between ploidies from fertilisation to hatch. This study based its assessment on a seminal paper by Gorodilov (1996) and used the same techniques to compare the rate at which triploid and diploid embryos developed morphological characteristics. Whilst no significant difference was found, this study provides well-needed justification for the assumption that both ploidies develop at the same rate and gives scientific weight to studies which involve manipulation at these stages of development. Two factors that did differ, however, were the timing of hatch, and mortality. Triploids hatched more quickly than diploids and reached 50% hatch at a significantly earlier point. Triploids also suffered from a significantly higher rate of mortality.

DNA extraction from recently fertilised Atlantic salmon embryos for use in microsatellite validation of triploidy.

The current methods used for producing triploid Atlantic salmon are generally reliable but not infallible, and each batch of triploids must be validated to ensure consumer trust and licensing compliance. Microsatellites have recently been shown to offer a cheaper and more convenient alternative to traditional flow cytometry for triploidy validation in a commercial setting. However, incubating eggs to at least the eyed stage for microsatellite validation poses challenges, such as reduced quality and performance of triploids produced from later eggs in the stripping season. To address these issues, we propose another option: extracting DNA from recently fertilised eggs for use in conjunction with microsatellite validation. To achieve this, we have developed an optimized protocol for HotSHOT extraction that can rapidly and cheaply extract DNA from Atlantic salmon eggs, which can then be used for triploidy validation through microsatellites. Our approach offers a simpler and more cost-effective way to validate triploidy, without the need for skilled dissection or expensive kits.

Micronutrient supplementation affects transcriptional and epigenetic regulation of lipid metabolism in a dose-dependent manner.

Micronutrients (vitamins and minerals) have been less well studied compared to macronutrients (fats, proteins, and carbohydrates) although they play important roles in growth, metabolism, and maintenance of tissues. Hence, there is growing interest to understand the influence of micronutrients across various aspects in nutritional research. In the last two decades, aquaculture feeds have been shifted to containing more plant-based materials to meet the increasing demand and maintain the sustainability in the industry. A recent whole life cycle feeding trial of Atlantic salmon (Salmo salar) with graded levels of micronutrient packages has concluded that the levels of several B-vitamins and microminerals need to be increased from the current recommendation levels for optimal growth and fish welfare when plant-based diets are used. Here, we show the effect of micronutrient supplementation on hepatic transcriptional and epigenetic regulation in a dose dependent manner. . Specifically, our aim is to reveal the mechanisms of altered cell metabolism, which results in improved growth performance by micronutrient surpluses, at gene expression and DNA methylation levels. Our results strongly indicate that micronutrient supplementation suppresses gene expression in lipid metabolism in a dose-dependent manner and broadly affects DNA methylation in cell-adhesion and cell-signalling. In particular, it increases DNA methylation levels on the acetyl-CoA carboxylase alpha promoter in a concentration-dependent manner, which further suggests that acetyl-CoA carboxylase alpha is an upstream epigenetic regulator controlling its downstream lipid biosynthesis activities. This study demonstrates a comprehensive analysis to reveal an important role of micronutrients in lipid metabolism through epigenetic control of gene expression.

Enhanced micronutrient supplementation in low marine diets reduced vertebral malformation in diploid and triploid Atlantic salmon (Salmo salar) parr, and increased vertebral expression of bone biomarker genes in diploids.

Previously we showed that, for optimum growth, micronutrient levels should be supplemented above current National Research Council (2011) recommendations for Atlantic salmon when they are fed diets formulated with low levels of marine ingredients. In the present study, the impact of graded levels (100, 200, 400%) of a micronutrient package (NP) on vertebral deformities and bone gene expression were determined in diploid and triploid salmon parr fed low marine diets. The prevalence of radiologically detectable spinal deformities decreased with increasing micronutrient supplementation in both ploidy. On average, triploids had a higher incidence of spinal deformity than diploids within a given diet. Micronutrient supplementation particularly reduced prevalence of fusion deformities in diploids and compression and reduced spacing deformities in triploids. Prevalence of affected vertebrae within each spinal region (cranial, caudal, tail and tail fin) varied significantly between diet and ploidy, and there was interaction. Prevalence of deformities was greatest in the caudal region of triploids and the impact of graded micronutrient supplementation in reducing deformities also greatest in triploids. Diet affected vertebral morphology with length:height (L:H) ratio generally increasing with level of micronutrient supplementation in both ploidy with no difference between ploidy. Increased dietary micronutrients level in diploid salmon increased the vertebral expression of several bone biomarker genes including bone morphogenetic protein 2 (bmp2), osteocalcin (ostcn), alkaline phosphatase (alp), matrix metallopeptidase 13 (mmp13), osteopontin (opn) and insulin-like growth factor 1 receptor (igf1r). In contrast, although some genes showed similar trends in triploids, vertebral gene expression was not significantly affected by dietary micronutrients level. The study confirmed earlier indications that dietary micronutrient levels should be increased in salmon fed diets with low marine ingredients and that there are differences in nutritional requirements between ploidies.

The effect of micronutrient supplementation on growth and hepatic metabolism in diploid and triploid Atlantic salmon (Salmo salar) parr fed a low marine ingredient diet.

The effects of low marine ingredient diets supplemented with graded levels (L1, L2, L3) of a micronutrient package (NP) on growth and metabolic responses were studied in diploid and triploid salmon parr. Diploids fed L2 showed significantly improved growth and reduced liver, hepatic steatosis, and viscerosomatic indices, while fish fed L3 showed suppressed growth rate 14 weeks post feeding. In contrast, dietary NP level had no effect on triploid performance. Whole body mineral composition, with exception of copper, did not differ between diet or ploidy. Whole fish total AAs and N-metabolites showed no variation by diet or ploidy. Free circulating AAs and white muscle N-metabolites were higher in triploids than diploids, while branch-chained amino acids were higher in diploids than triploids. Diploids had higher whole body α-tocopherol and hepatic vitamins K1 and K2 than triploids. Increased tissue B-vitamins for niacin and whole-body folate with dietary NP supplementation were observed in diploids but not triploids, while whole body riboflavin was higher in diploids than triploids. Hepatic transcriptome profiles showed that diploids fed diet L2 was more similar to that observed in triploids fed diet L3. In particular, sterol biosynthesis pathways were down-regulated, whereas cytochrome P450 metabolism was up-regulated. One­carbon metabolism was also affected by increasing levels of supplementation in both ploidies. Collectively, results suggested that, for optimised growth and liver function, micronutrient levels be supplemented above current National Research Council (2011) recommendations for Atlantic salmon when fed low marine ingredient diets. The study also suggested differences in nutritional requirements between ploidy.

Impact of Salmonid alphavirus infection in diploid and triploid Atlantic salmon (Salmo salar L.) fry.

With increasing interest in the use of triploid salmon in commercial aquaculture, gaining an understanding of how economically important pathogens affect triploid stocks is important. To compare the susceptibility of diploid and triploid Atlantic salmon (Salmo salar L.) to viral pathogens, fry were experimentally infected with Salmonid alphavirus sub-type 1 (SAV1), the aetiological agent of pancreas disease (PD) affecting Atlantic salmon aquaculture in Europe. Three groups of fry were exposed to the virus via different routes of infection: intraperitoneal injection (IP), bath immersion, or cohabitation (co-hab) and untreated fry were used as a control group. Mortalities commenced in the co-hab challenged diploid and triploid fish from 11 days post infection (dpi), and the experiment was terminated at 17 dpi. Both diploid and triploid IP challenged groups had similar levels of cumulative mortality at the end of the experimental period (41.1% and 38.9% respectively), and these were significantly higher (p < 0.01) than for the other challenge routes. A TaqMan-based quantitative PCR was used to assess SAV load in the heart, a main target organ of the virus, and also liver, which does not normally display any pathological changes during clinical infections, but exhibited severe degenerative lesions in the present study. The median viral RNA copy number was higher in diploid fish compared to triploid fish in both the heart and the liver of all three challenged groups. However, a significant statistical difference (p < 0.05) was only apparent in the liver of the co-hab groups. Diploid fry also displayed significantly higher levels of pancreatic and myocardial degeneration than triploids. This study showed that both diploid and triploid fry are susceptible to experimental SAV1 infection. The lower virus load seen in the triploids compared to the diploids may possibly be related to differences in cell metabolism between the two groups, however, further investigation is necessary to confirm this and also to assess the outcome of PD outbreaks in other developmental stages of the fish when maintained in commercial production systems.

Influence of Development and Dietary Phospholipid Content and Composition on Intestinal Transcriptome of Atlantic Salmon (Salmo salar).

The inclusion of intact phospholipids in the diet is essential during larval development and can improve culture performance of many fish species. The effects of supplementation of dietary phospholipid from marine (krill) or plant (soy lecithin) sources were investigated in Atlantic salmon, Salmo salar. First feeding fry were fed diets containing either krill oil or soybean lecithin supplying phospholipid at 2.6%, 3.2%, 3.6% and 4.2% of diet. Fish were sampled at ~ 2.5 g (~1,990°day post fertilization, dpf) and ~10 g (2,850°dpf). By comparison of the intestinal transcriptome in specifically chosen contrasts, it was determined that by 2,850°dpf fish possessed a profile that resembled that of mature and differentiated intestinal cell types with a number of changes specific to glycerophospholipid metabolism. It was previously shown that intact phospholipids and particularly phosphatidylcholine are essential during larval development and that this requirement is associated with the inability of enterocytes in young fry to endogenously synthesize sufficient phospholipid for the efficient export of dietary lipid. In the immature phase (~1,990°dpf), the dietary phospholipid content as well as its class composition impacted on several biochemical and morphological parameters including growth, but these differences were not associated with differences in intestinal transcriptomes. The results of this study have made an important contribution to our understanding of the mechanisms associated with lipid transport and phospholipid biosynthesis in early life stages of fish.

Radiological remodelling of the acetabulum in Perthes' disease.

Thirty-four patients were studied throughout the evolution of Perthes' disease. The acetabular changes included osteopoenia of the roof, irregularity of its contour, and decrease in its depth. These changes were proportional to the femoral head involvement. The purpose of the study was to assess the effect of the morphological changes of the femoral head on the acetabulum and the outcome, and to determine the extent to which coxa magna and acetabular enlargement induced by Perthes disease in childhood persist into adolescence. Radioisotope scans of the hip were examined in fourteen children with unilateral Perthes' disease and comparison was made with the contralateral hip. These scans showed increased uptake on the lateral part of the acetabulum and no uptake over the avascular part of the femoral head. Average follow-up was ten years and children were followed up on average from six years to fifteen years of age. Six readings of the measurements of various dimensions of the acetabulum and the femoral head were done. CT scan also showed irregularity in the acetabulum. Statistical tests lead to the conclusion that the decrease in the depth of the acetabulum was secondary to the femoral head involvement and the extent of its dimensional changes affected the final congruity between the femoral head and the acetabulum. Also the remodelling potential of the acetabulum decreases as the child grows older. Therefore containment procedures could be done by femoral osteotomy in younger children, whereas acetabular osteotomy may benefit older children.

Triploid and diploid Atlantic salmon show similar susceptibility to infection with salmon lice Lepeophtheirus salmonis.

BACKGROUND: Sea lice infection is the most expensive disease factor for Atlantic salmon sea-cage farming. For triploid salmon to be accepted as a commercial possibility, investigation of susceptibility of triploid salmon to sea lice infection is a fundamental milestone. The susceptibility of diploid and triploid salmon to infection with Lepeophtheirus salmonis was examined in a tank trial in Scotland, a tank trial in Norway and a cage trial in Scotland. RESULTS: Following a single infection challenge, results indicated a significant correlation between fish size and the number of attached sea lice. Triploid fish were larger than diploids at the smolt stage. In the tank trials, no difference was found between infection levels on diploids and triploids after a single infection challenge. The tank trial in Scotland continued with a second infection challenge of the same fish, which also showed no infection differences between ploidies. A borderline correlation between first infection and re-infection intensity was found for PIT-tagged diploid salmon examined after each challenge. No significant difference in louse infection between diploid and triploid salmon (∼2 kg) was found in the cage trial undertaken under commercial conditions. CONCLUSION: This study concludes that triploid Atlantic salmon are not more susceptible to sea louse infection than diploid fish.