Publications by authors named "Christopher C Parrish"

42 Publications

Shotgun Lipidomics for the Determination of Phospholipid and Eicosanoid Profiles in Atlantic Salmon ( L.) Muscle Tissue Using Electrospray Ionization (ESI)-MS/MS Spectrometric Analysis.

Int J Mol Sci 2021 Feb 25;22(5). Epub 2021 Feb 25.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.

Shotgun lipidomics was applied to identify and quantify phospholipids (PLs) in salmon muscle tissue by focusing on the distribution of ω-3 fatty acids (e.g., docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)) in the form of phospholipids, as well as to identify and quantify eicosanoids, which has not yet been attempted in Atlantic salmon muscle. Shotgun lipidomics enabled the identification of 43 PL species belonging to four different classes: phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), phosphatidylserines (PSs), and phosphatidylinositols (PIs). Among others, 16:0-22:6 PtdCho [M + Na] at 828.4 was the predominant PL species in salmon muscle tissue. The present study provided the quantification of individual phospholipid species, which has not been performed for salmon muscle tissue so far. In addition, two eicosanoids-prostaglandin E2 (PGE2) and prostaglandin F3α (PGF3α)-were identified for the first time in salmon muscle. Thus, the rapid and high-throughput shotgun lipidomics approach should shed new light on phospholipids and eicosanoids in salmon muscle tissue.
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http://dx.doi.org/10.3390/ijms22052272DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7956627PMC
February 2021

Effects of Varying Dietary Docosahexaenoic, Eicosapentaenoic, Linoleic, and α-Linolenic Acid Levels on Fatty Acid Composition of Phospholipids and Neutral Lipids in the Liver of Atlantic Salmon, .

J Agric Food Chem 2021 Mar 21;69(9):2697-2710. Epub 2021 Jan 21.

Cargill Animal Nutrition, Elk River 55330, Minnesota, United States.

Fish oil, the most abundant natural source of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), is a limited resource; however, terrestrial oils are used as an alternative in fish nutrition. The liver of Atlantic salmon is able to synthesize these two long-chain n-3 polyunsaturated fatty acids (n-3LC-PUFAs) from α-linolenic acid (ALA), but the dietary levels of EPA + DHA and the ratios of linoleic acid (LNA) to ALA may affect its abilities. Feeding Atlantic salmon four experimental diets containing EPA + DHA at 0.3 and 1.0% of dietary levels accompanied with high and low LNA/ALA ratios showed that low LNA/ALA ratios increased the proportions of EPA + DHA in phospholipids (PLs) and neutral lipids (NLs). The pattern of PL-to-NL ratios of n-3 LC-PUFA proportions matched the saw tooth pattern of LNA/ALA ratios in diets. Overall, when fish oil is removed from salmon diets, the dietary LNA/ALA ratio must be reduced to stimulate biosynthesis of n-3 LC-PUFAs in the liver.
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http://dx.doi.org/10.1021/acs.jafc.0c05182DOI Listing
March 2021

Influence of Dietary Long-Chain Polyunsaturated Fatty Acids and ω6 to ω3 Ratios on Head Kidney Lipid Composition and Expression of Fatty Acid and Eicosanoid Metabolism Genes in Atlantic Salmon ().

Front Mol Biosci 2020 14;7:602587. Epub 2020 Dec 14.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, Canada.

The interaction of dietary eicosapentaenoic acid and docosahexaenoic acid (EPA+DHA) levels with omega-6 to omega-3 ratios (ω6:ω3), and their impact on head kidney lipid metabolism in farmed fish, are not fully elucidated. We investigated the influence of five plant-based diets (12-week exposure) with varying EPA+DHA levels (0.3, 1.0, or 1.4%) and ω6:ω3 (high ω6, high ω3, or balanced) on tissue lipid composition, and transcript expression of genes involved in fatty acid and eicosanoid metabolism in Atlantic salmon head kidney. Tissue fatty acid composition was reflective of the diet with respect to C PUFA and MUFA levels (% of total FA), and ω6:ω3 (0.5-1.5). Fish fed 0.3% EPA+DHA with high ω6 (0.3% EPA+DHA↑ω6) had the highest increase in proportions (1.7-2.3-fold) and in concentrations (1.4-1.8-fold) of arachidonic acid (ARA). EPA showed the greatest decrease in proportion and in concentration (by ~½) in the 0.3% EPA+DHA↑ω6 fed fish compared to the other treatments. However, no differences were observed in EPA proportions among salmon fed the high ω3 (0.3 and 1.0% EPA+DHA) and balanced (1.4% EPA+DHA) diets, and DHA proportions were similar among all treatments. Further, the transcript expression of was lowest in the 0.3% EPA+DHA↑ω6 fed fish, and correlated positively with 20:3ω3, 20:4ω3 and EPA:ARA in the head kidney. This indicates that high dietary 18:3ω3 promoted the synthesis of ω3 LC-PUFA. Dietary EPA+DHA levels had a positive impact on and expression, and these transcripts positively correlated with tissue ΣMUFA. This supported the hypothesis that LC-PUFA synthesis is positively influenced by tissue MUFA levels in Atlantic salmon. The expression of was higher in the 0.3% EPA+DHA↑ω6 compared to the 0.3% EPA+DHA↑ω3 fed fish. Finally, significant correlations between head kidney fatty acid composition and the expression of eicosanoid synthesis-related transcripts (i.e., , and ) illustrated the constitutive relationships among fatty acids and eicosanoid metabolism in salmon.
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http://dx.doi.org/10.3389/fmolb.2020.602587DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7767880PMC
December 2020

Sterol Composition of Sponges, Cnidarians, Arthropods, Mollusks, and Echinoderms from the Deep Northwest Atlantic: A Comparison with Shallow Coastal Gulf of Mexico.

Mar Drugs 2020 Nov 27;18(12). Epub 2020 Nov 27.

Department of Ocean Sciences, Memorial University of Newfoundland, Marine Lab Rd., St. John's, NL A1C 5S7, Canada.

Triterpenoid biosynthesis is generally anaerobic in bacteria and aerobic in Eukarya. The major class of triterpenoids in bacteria, the hopanoids, is different to that in Eukarya, the lanostanoids, and their 4,4,14-demethylated derivatives, sterols. In the deep sea, the prokaryotic contribution to primary productivity has been suggested to be higher because local environmental conditions prevent classic photosynthetic processes from occurring. Sterols have been used as trophic biomarkers because primary producers have different compositions, and they are incorporated in primary consumer tissues. In the present study, we inferred food supply to deep sea, sponges, cnidarians, mollusks, crustaceans, and echinoderms from euphotic zone production which is driven by phytoplankton eukaryotic autotrophy. Sterol composition was obtained by gas chromatography and mass spectrometry. Moreover, we compared the sterol composition of three phyla (i.e., Porifera, Cnidaria, and Echinodermata) collected between a deep and cold-water region and a shallow tropical area. We hypothesized that the sterol composition of shallow tropical benthic organisms would better reflect their photoautotrophic sources independently of the taxonomy. Shallow tropical sponges and cnidarians from environments showed plant and zooxanthellae sterols in their tissues, while their deep-sea counterparts showed phytoplankton and zooplankton sterols. In contrast, echinoids, a class of echinoderms, the most complex phylum along with hemichordates and chordates (deuterostomes), did not show significant differences in their sterol profile, suggesting that cholesterol synthesis is present in deuterostomes other than chordates.
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http://dx.doi.org/10.3390/md18120598DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7761341PMC
November 2020

Minimizing marine ingredients in diets of farmed Atlantic salmon (Salmo salar): effects on liver and head kidney lipid class and fatty acid composition.

Fish Physiol Biochem 2020 Dec 1;46(6):2331-2353. Epub 2020 Oct 1.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada.

Limited fish meal and fish oil supplies have necessitated research on alternatives for aquafeeds. Seven dietary treatments with different protein and lipid sources were formulated for farmed Atlantic salmon, and their effects on liver and head kidney lipid class, fatty acid, and elemental composition were studied. Fish meal, fish oil, and EPA + DHA content ranged from 5-35%, 0-12%, and 0.1-3%, respectively. Elemental analysis showed that the C to N ratio was higher in the head kidney than in the liver, which is consistent with higher content of total lipids in the head kidney compared with the liver. There was a greater susceptibility to dietary lipid alterations in the liver compared with the head kidney despite liver having a greater proportion of phospholipid and a much lower proportion of triacylglycerol. So long as fish oil levels were 5% or more of the diet, arachidonic acid (ARA) and docosahexaenoic acid (DHA) proportions were the same for each tissue as with feeding the marine diet with 12% fish oil; however, livers and head kidneys from fish fed the lowest amount of fish meal and fish oil had the lowest levels of eicosapentaenoic (EPA) and DHA and the highest ARA levels. Removal of fish oil and reduction of fish meal to 5% in diets of farmed Atlantic salmon affected elemental and lipid compositions of the liver and head kidney tissues potentially increasing susceptibility to inflammation. However, with 10% of the diet comprising fish meal and fish oil, lipid contents were comparable with fish fed marine-based diets.
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http://dx.doi.org/10.1007/s10695-020-00862-0DOI Listing
December 2020

Interaction between 6 and 3 fatty acids of different chain lengths regulates Atlantic salmon hepatic gene expression and muscle fatty acid profiles.

Philos Trans R Soc Lond B Biol Sci 2020 08 15;375(1804):20190648. Epub 2020 Jun 15.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, Canada A1C 5S7.

Atlantic salmon smolts (approx. 20-months old) were fed experimental diets with different combinations of omega-6:omega-3 fatty acids (FAs) (high-ω6, high-ω3, or balanced) and eicosapentaenoic acid plus docosahexaenoic acid (EPA + DHA) levels (0.3, 1.0 or 1.4%) for 12 weeks. Muscle FA (% total FA) reflected dietary C-polyunsaturated FA; however, muscle EPA per cent and content (mg g) were not different in salmon fed high-ω3 or balanced diets. Muscle DHA per cent was similar among treatments, while DHA content increased in fish fed 1.4% EPA + DHA, compared with those fed 0.3-1.0% EPA + DHA combined with high-ω6 FA. Muscle 20:36 (DGLA) content was highest in those fed high-ω6 with 0.3% EPA + DHA. Quantitative polymerase chain reaction analyses on liver RNA showed that the monounsaturated FA synthesis-related gene, was upregulated in fish fed 1.0% EPA + DHA with high-ω6 compared to those fed 0.3% EPA + DHA. In high-ω3-fed salmon, liver transcript levels were higher with 0.3% EPA + DHA than with 1.0% EPA + DHA. In high-ω6-fed fish, did not vary with EPA + DHA levels, but it was positively correlated with muscle ARA, 22:43 and DGLA. These results suggest dietary 18:33 elongation contributed to maintaining muscle EPA + DHA levels despite a two- to threefold change in dietary proportions, while 18:26 with 0.3% EPA + DHA increased muscle DGLA more than arachidonic acid (ARA). Positive correlations between hepatic and with muscle 6:3 and EPA + DHA + ARA, respectively, were confirmed by reanalysing data from a previous salmon trial with lower variations in dietary EPA + DHA and 6:3 ratios. This article is part of the theme issue 'The next horizons for lipids as 'trophic biomarkers': evidence and significance of consumer modification of dietary fatty acids'.
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http://dx.doi.org/10.1098/rstb.2019.0648DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7333962PMC
August 2020

Diet-Induced Physiological Responses in the Liver of Atlantic Salmon (Salmo salar) Inferred Using Multiplex PCR Platforms.

Mar Biotechnol (NY) 2020 Aug 4;22(4):511-525. Epub 2020 Jun 4.

Department of Ocean Sciences, Memorial University of Newfoundland, 0 Marine Lab Road, St. John's, NL, A1C 5S7, Canada.

The simultaneous quantification of several transcripts via multiplex PCR can accelerate research in fish physiological responses to diet and enable the development of superior aquafeeds for farmed fish. We designed two multiplex PCR panels that included assays for 40 biomarker genes representing key aspects of fish physiology (growth, metabolism, oxidative stress, and inflammation) and 3 normalizer genes. We used both panels to assess the physiological effects of replacing fish meal and fish oil by terrestrial alternatives on Atlantic salmon smolts. In a 14-week trial, we tested three diets based on marine ingredients (MAR), animal by-products and vegetable oil (ABP), and plant protein and vegetable oil (VEG). Dietary treatments affected the expression of genes involved in hepatic glucose and lipid metabolism (e.g., srebp1, elovl2), cell redox status (e.g., txna, prdx1b), and inflammation (e.g., pgds, 5loxa). At the multivariate level, gene expression profiles were more divergent between fish fed the marine and terrestrial diets (MAR vs. ABP/VEG) than between the two terrestrial diets (ABP vs. VEG). Liver ARA was inversely related to glucose metabolism (gck)- and growth (igfbp-5b1, htra1b)-related biomarkers and hepatosomatic index. Liver DHA and EPA levels correlated negatively with elovl2, whereas ARA levels correlated positively with fadsd5. Lower hepatic EPA/ARA in ABP-fed fish correlated with the increased expression of biomarkers related to mitochondrial function (fabp3a), oxidative stress (txna, prdx1b), and inflammation (pgds, 5loxa). The analysis of hepatic biomarker gene expression via multiplex PCR revealed potential physiological impacts and nutrient-gene interactions in Atlantic salmon fed lower levels of marine-sourced nutrients.
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http://dx.doi.org/10.1007/s10126-020-09972-5DOI Listing
August 2020

Evaluation of triacylglycerol (TAG) profiles and their contents in salmon muscle tissue using ESI-MS/MS spectrometry with multiple neutral loss scans.

Food Chem 2020 Sep 15;324:126816. Epub 2020 Apr 15.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL A1C 5S7, Canada.

Identification and quantification of triacylglycerols (TAGs) in salmon muscle tissue were conducted using electrospray ionization (ESI)-MS/MS in a triple quadrupole mass spectrometer. The confirmation of three fatty acid moieties of individual TAGs was determined using the multiple neutral loss (NL) scanning mode. A total of 98 TAGs were identified, and the predominant TAG species were 16:0-18:0-20:5 (10.4%), 18:1-18:2-22:6 (9.0%), and 18:0-18:1-22:6 (16.4%) in salmon muscle tissue. NL scanning was an effective means to confirm the three fatty acid moieties of the TAGs, leading to the rapid and accurate identification of individual TAGs. To the best of our knowledge, this is the first application of multiple neutral loss scanning to identify TAGs in salmonoid tissue, and many TAG species have been newly identified (i.e., 18:1-18:2-22:6, 16:0-18:2-20:5, 18:1-18:2-20:5, etc.). This study showed that the shotgun lipidomic approach along with NL scans is a useful means for studying TAG metabolism in fish.
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http://dx.doi.org/10.1016/j.foodchem.2020.126816DOI Listing
September 2020

Liver Transcriptome Profiling Reveals That Dietary DHA and EPA Levels Influence Suites of Genes Involved in Metabolism, Redox Homeostasis, and Immune Function in Atlantic Salmon (Salmo salar).

Mar Biotechnol (NY) 2020 Apr 10;22(2):263-284. Epub 2020 Feb 10.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, A1C 5S7, Canada.

The optimal dietary requirement of omega-3 long-chain polyunsaturated fatty acids (ω3 LC-PUFA), namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), for Atlantic salmon that promotes growth and health warrants careful investigation. We used 44K microarrays to study the influence of increasing levels of dietary DHA + EPA (0, 1.0, and 1.4% of the diet, as formulated) in the presence of high linoleic acid (LA) on Atlantic salmon growth and liver transcriptome. After a 14-week feeding trial, Atlantic salmon fed diet ω3LC0 (i.e. 0% of DHA + EPA) showed significantly lower final weight and weight gain, and higher feed conversion ratio compared with ω3LC1.0 and ω3LC1.4 diet groups. The microarray experiment identified 55 and 77 differentially expressed probes (Rank Products analyses; PFP < 10%) in salmon fed diets ω3LC1.4 and ω3LC1.0 compared with those fed diet ω3LC0, respectively. The comparison between ω3LC1.4 and ω3LC1.0 revealed 134 differentially expressed probes. The microarray results were confirmed by qPCR analyses of 22 microarray-identified transcripts. Several key genes involved in fatty acid metabolism including LC-PUFA synthesis were upregulated in fish fed ω3LC0 compared with both other groups. Hierarchical clustering and linear regression analyses of liver qPCR and fatty acid composition data demonstrated significant correlations. In the current study, 1.0% ω3 LC-PUFA seemed to be the minimum requirement for Atlantic salmon based on growth performance; however, multivariate statistical analyses (PERMANOVA and SIMPER) showed that fish fed ω3LC1.0 and ω3LC1.4 diets had similar hepatic fatty acid profiles but marked differences in the transcript expression of biomarker genes involved in redox homeostasis (mgst1), immune responses (mxb, igmb, irf3, lect2a, srk2, and lyz2), and LC-PUFA synthesis (srebp1, fadsd5, and elovl2). This research has provided new insights into dietary requirement of DHA and EPA and their impact on physiologically important pathways in addition to lipid metabolism in Atlantic salmon.
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http://dx.doi.org/10.1007/s10126-020-09950-xDOI Listing
April 2020

Cardiac mitochondrial function, nitric oxide sensitivity and lipid composition following hypoxia acclimation in sablefish.

J Exp Biol 2019 11 27;222(Pt 22). Epub 2019 Nov 27.

Department of Ocean Sciences, Memorial University, St. John's, NL A1C 5S7, Canada.

In fishes, the effect of O limitation on cardiac mitochondrial function remains largely unexplored. The sablefish () encounters considerable variations in environmental oxygen availability, and is an interesting model for studying the effects of hypoxia on fish cardiorespiratory function. We investigated how hypoxia acclimation (6 months at 40% then 3 weeks at 20% air saturation) and anoxia-reoxygenation affected sablefish cardiac mitochondrial respiration and reactive oxygen species (ROS) release rates using high-resolution fluorespirometry. Further, we investigated how hypoxia acclimation affected the sensitivity of mitochondrial respiration to nitric oxide (NO), and compared mitochondrial lipid and fatty acid (FA) composition between groups. Hypoxia acclimation did not alter mitochondrial coupled or uncoupled respiration, or respiratory control ratio, ROS release rates, or superoxide dismutase activity. However, it increased citrate synthase activity (by ∼20%), increased the sensitivity of mitochondrial respiration to NO inhibition (i.e., the NO IC was 25% lower), and enhanced the recovery of respiration (by 21%) and reduced ROS release rates (by 25-30%) post-anoxia. In addition, hypoxia acclimation altered mitochondrial FA composition [increasing arachidonic acid (20:4ω6) and eicosapentaenoic acid (20:5ω3) proportions by 11 and 14%, respectively], and SIMPER analysis revealed that the phospholipid:sterol ratio was the largest contributor (24%) to the dissimilarity between treatments. Overall, these results suggest that hypoxia acclimation may protect sablefish cardiac bioenergetic function during or after periods of O limitation, and that this may be related to alterations in mitochondrial sensitivity to NO and to adaptive changes in membrane composition (fluidity).
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http://dx.doi.org/10.1242/jeb.208074DOI Listing
November 2019

Effect of plant-based diets with varying ratios of ω6 to ω3 fatty acids on growth performance, tissue composition, fatty acid biosynthesis and lipid-related gene expression in Atlantic salmon (Salmo salar).

Comp Biochem Physiol Part D Genomics Proteomics 2019 06 16;30:290-304. Epub 2019 Mar 16.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's A1C 5S7, NL. Canada. Electronic address:

Little is known about how variation in omega-6 to omega-3 (ω6:ω3) fatty acid (FA) ratios affects lipid metabolism and eicosanoid synthesis in salmon, and the potential underlying molecular mechanisms. The current study examined the impact of five plant-based diets (12-week exposure) with varying ω6:ω3 (0.3-2.7) on the growth, tissue lipid composition (muscle and liver), and hepatic transcript expression of lipid metabolism and eicosanoid synthesis-related genes in Atlantic salmon. Growth performance and organ indices were not affected by dietary ω6:ω3. The liver and muscle FA composition was highly reflective of the diet (ω6:ω3 of 0.2-0.8 and 0.3-1.9, respectively) and suggested elongation and desaturation of the ω3 and ω6 precursors 18:3ω3 and 18:2ω6. Furthermore, proportions of ω6 and ω3 PUFA in both tissues showed significant positive correlations with dietary inclusion (% of diet) of soy and linseed oils, respectively. Compound-specific stable isotope analysis (CSIA) further demonstrated that liver long-chain polyunsaturated fatty acid (LC-PUFA) synthesis (specifically 20:5ω3 and 20:4ω6) was largely driven by dietary 18:3ω3 and 18:2ω6, even when 20:5ω3 and 22:6ω3 were supplied at levels above minimum requirements. In addition, significant positive and negative correlations were identified between the transcript expression of LC-PUFA synthesis-related genes and liver ω6 and ω3 LC-PUFA, respectively, further supporting FA biosynthesis. Liver ω3 LC-PUFA also correlated negatively with the eicosanoid synthesis-related transcripts pgds and cox1. This is the first study to use CSIA, hepatic transcriptome, and tissue lipid composition analyses concurrently to demonstrate the impact of plant-based diets with varying ω6:ω3 on farmed Atlantic salmon.
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http://dx.doi.org/10.1016/j.cbd.2019.03.004DOI Listing
June 2019

The Potential Impact of Hydrocarbons on Mussels in Port au Port Bay, Newfoundland.

Adv Mar Biol 2018;81:1-22. Epub 2018 Oct 15.

Department of Earth Sciences, Memorial University of Newfoundland, St. John's, NL, Canada. Electronic address:

Since 2012, the scallop fishery in Port au Port Bay, Newfoundland, Canada has experienced a drastic decline, while no decline was observed in adjacent St. George's Bay. Local fishermen have raised concerns about an abandoned oil exploration well in the Port au Port Bay. This study investigated the potential impact of petroleum hydrocarbons on sediments and blue mussels [Mytilus edulis] (a proxy organism for scallops) in the area. Sediments from both bays were characterized for their hydrocarbons and compared to potential petroleum hydrocarbon sources. Mussels were analysed for health indices and their C content. The results showed that the concentration of hydrocarbons found in the sediments of the fishing ground was within the range of unpolluted marine sediments and that the hydrocarbons present were likely from a mixture of sources. The health indices of the mussels in Port au Port Bay were similar to the health indices of mussels in St. George's Bay and the C content of the mussels from both bays was modern. These data suggest that the Port au Port fishing ground was not solely contaminated from crude oil leaking from an oil exploration well, that the mussels were not contaminated with petroleum hydrocarbons, and that Port au Port mussels were just as healthy as the mussels of St. George's Bay. Therefore, whatever caused the scallop decline was most likely scallop- and bay-specific. During this study a fast and efficient method for extracting petroleum hydrocarbons from sediment using accelerated solvent extraction with integrated silica gel was developed.
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http://dx.doi.org/10.1016/bs.amb.2018.09.003DOI Listing
March 2019

Functional diversity and nutritional content in a deep-sea faunal assemblage through total lipid, lipid class, and fatty acid analyses.

PLoS One 2018 12;13(11):e0207395. Epub 2018 Nov 12.

Department of Ocean Sciences, Memorial University, St. John's, NL, Canada.

Lipids are key compounds in marine ecosystems being involved in organism growth, reproduction, and survival. Despite their biological significance and ease of measurement, the use of lipids in deep-sea studies is limited, as is our understanding of energy and nutrient flows in the deep ocean. Here, a comprehensive analysis of total lipid content, and lipid class and fatty acid composition, was used to explore functional diversity and nutritional content within a deep-sea faunal assemblage comprising 139 species from 8 phyla, including the Chordata, Arthropoda, and Cnidaria. A wide range of total lipid content and lipid class composition suggested a diversified set of energy allocation strategies across taxa. Overall, phospholipid was the dominant lipid class. While triacylglycerol was present in most taxa as the main form of energy storage, a few crustaceans, fish, jellyfishes, and corals had higher levels of wax esters/steryl esters instead. Type and amount of energy reserves may reflect dietary sources and environmental conditions for certain deep-sea taxa. Conversely, the composition of fatty acids was less diverse than that of lipid class composition, and large proportions of unsaturated fatty acids were detected, consistent with the growing literature on cold-water species. In addition, levels of unsaturation increased with depth, likely suggesting an adaptive strategy to maintain normal membrane structure and function in species found in deeper waters. Although proportions of n-3 fatty acids were high across all phyla, representatives of the Chordata and Arthropoda were the main reservoirs of these essential nutrients, thus suggesting health benefits to their consumers.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0207395PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6231680PMC
April 2019

Changes in the liver transcriptome of farmed Atlantic salmon (Salmo salar) fed experimental diets based on terrestrial alternatives to fish meal and fish oil.

BMC Genomics 2018 Nov 3;19(1):796. Epub 2018 Nov 3.

Department of Ocean Sciences, Memorial University of Newfoundland, 1 Marine Lab Road, St. John's, NL, A1C 5S7, Canada.

Background: Dependence on marine natural resources threatens the sustainability of Atlantic salmon aquaculture. In the present study, Atlantic salmon fed for 14 weeks with an experimental diet based on animal by-products and vegetable oil (ABP) exhibited reduced growth performance compared with others fed a fish meal/fish oil based experimental diet (MAR) and a plant protein/vegetable oil-based experimental diet (VEG). To characterize the molecular changes underlying the differences in growth performance, we conducted a 44 K microarray study of the liver transcriptome of the three dietary groups.

Results: The microarray experiment identified 122 differentially expressed features (Rank Products, PFP < 10%). Based on their associated Gene Ontology terms, 46 probes were classified as metabolic and growth-relevant genes, 25 as immune-related, and 12 as related to oxidation-reduction processes. The microarray results were validated by qPCR analysis of 29 microarray-identified transcripts. Diets significantly modulated the transcription of genes involved in carbohydrate metabolism (gck and pfkfb4), cell growth and proliferation (sgk2 and htra1), apoptosis (gadd45b), lipid metabolism (fabp3, idi1, sqs), and immunity (igd, mx, ifit5, and mhcI). Hierarchical clustering and linear correlation analyses were performed to find gene expression patterns among the qPCR-analyzed transcripts, and connections between them and muscle and liver lipid composition. Overall, our results indicate that changes in the liver transcriptome and tissue lipid composition were driven by cholesterol synthesis up-regulation by ABP and VEG diets, and the lower carbohydrate intake in the ABP group. Two of the microarray-identified genes (sgk2 and htra1) might be key to explaining glucose metabolism regulation and the dietary-modulation of the immune system in fish. To evaluate the potential of these genes as predictive biomarkers, we subjected the qPCR data to a stepwise discriminant analysis. Three sets of no more than four genes were found to be able to predict, with high accuracy (67-94%), salmon growth and fatty acid composition.

Conclusions: This study provides new findings on the impact of terrestrial animal and plant products on the nutrition and health of farmed Atlantic salmon, and a new method based on gene biomarkers for potentially predicting desired phenotypes, which could help formulate superior feeds for the Atlantic salmon aquaculture industry.
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http://dx.doi.org/10.1186/s12864-018-5188-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6215684PMC
November 2018

Optimizing long chain-polyunsaturated fatty acid synthesis in salmonids by balancing dietary inputs.

PLoS One 2018 10;13(10):e0205347. Epub 2018 Oct 10.

Canadian Food Inspection Agency- Meat Hygiene Program, Guelph Ontario, Canada.

The increasing use of terrestrial plant lipids to replace of fish oil in commercial aquafeeds requires understanding synthesis and storage of long chain-polyunsaturated fatty acids (LC-PUFA) in farmed fish. Manipulation of dietary fatty acids may maximize tissue storage of LC-PUFA, through increased production and selective utilization. A data synthesis study was conducted to estimate optimal levels of fatty acids that may maximize the production and storage of LC-PUFA in the edible portion of salmonids. Data were compiled from four studies with Atlantic salmon, rainbow trout, and steelhead trout (total n = 180) which were fed diets containing different terrestrial-based oils to replace fish oil. LC-PUFA (%) were linearly correlated between diet and muscle tissue (p < 0.001; r2 > 44%), indicating proportional storage after consumption. The slope, or retention rate, was highest for docosahexaenoic acid (DHA) at 1.23, indicating that an additional 23% of DHA was stored in the muscle. Dietary saturated fatty acids were positively related to DHA stored in the muscle (p < 0.001; r2 = 22%), which may involve membrane structural requirements, as well as selective catabolism. DHA was found to be optimally stored with a dietary n-3: n-6 ratio of 1.03: 1. These new results provide a baseline of optimal dietary ratios that can be tested experimentally to determine the efficacy of balancing dietary fatty acids for maximum LC-PUFA storage.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0205347PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6179257PMC
March 2019

Minimizing marine ingredients in diets of farmed Atlantic salmon (Salmo salar): Effects on growth performance and muscle lipid and fatty acid composition.

PLoS One 2018 21;13(9):e0198538. Epub 2018 Sep 21.

Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL, Canada.

Due to limited fish meal and fish oil resources and their high costs for the aquaculture industry, it is necessary to find alternative sustainable sources of protein and lipids. Therefore, seven different diets were formulated with different levels of animal by-products, vegetable proteins, fish oil and rapeseed oil, to feed farmed Atlantic salmon, and their effects on growth performance, muscle lipid class, and fatty acid composition were examined. Protein sources included anchovy, poultry, feather, blood, corn, soy and wheat. Growth performance indicated that the diet with the lowest fish meal and fish oil content resulted in the lowest weight gain and final weight, followed by the diet containing the highest level of animal by-products. The lipid class analysis showed no statistical difference in the muscle total lipid content using different diets. However, significant statistical differences were observed among the main lipid classes; triacylglycerols, phospholipids, and sterols. The diet containing 1.4% omega-3 long-chain fatty acids resulted in the highest content of triacylglycerols and phospholipids. Diets containing medium and low levels of fish oil and fish meal, respectively, led to as high a level of ω3 fatty acids in muscle as when fish were fed diets with high levels of fish meal and fish oil. The results of this study suggest that feeding a diet containing low levels of fish meal and moderate levels of fish oil does not significantly affect ω3 fatty acid composition in muscle. Fish meal could be reduced to 5% without affecting growth as long as there was a minimum of 5% fish oil, and animal by-products did not exceed 26% of the diet.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0198538PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6150467PMC
February 2019

Corrigendum to "Urban sewage lipids in the suspended particulate matter of a coral reef under river influence in the South West Gulf of Mexico" [Water Res. 123 (2017) 192-205].

Water Res 2017 12;126:530

Instituto de Ciencias Marinas y Pesquerías, Universidad Veracruzana, Calle Hidalgo 617, Colonia Río Jamapa, Boca del Río, Veracruz, Mexico.

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http://dx.doi.org/10.1016/j.watres.2017.10.026DOI Listing
December 2017

Transcriptome profiling of antiviral immune and dietary fatty acid dependent responses of Atlantic salmon macrophage-like cells.

BMC Genomics 2017 Sep 8;18(1):706. Epub 2017 Sep 8.

Department of Ocean Sciences, Memorial University of Newfoundland, 1 Marine Lab Road, St. John's, NL, A1C 5S7, Canada.

Background: Due to the limited availability and high cost of fish oil in the face of increasing aquaculture production, there is a need to reduce usage of fish oil in aquafeeds without compromising farm fish health. Therefore, the present study was conducted to determine if different levels of vegetable and fish oils can alter antiviral responses of salmon macrophage-like cells (MLCs). Atlantic salmon (Salmo salar) were fed diets containing 7.4% (FO7) or 5.1% (FO5) fish oil. These diets were designed to be relatively low in EPA + DHA (i.e. FO7: 1.41% and FO5: 1%), but near the requirement level, and resulting in comparable growth. Vegetable oil (i.e. rapeseed oil) was used to balance fish oil in experimental diets. After a 16-week feeding trial, MLCs isolated from fish in these dietary groups were stimulated by a viral mimic (dsRNA: pIC) for 6 h (qPCR assay) and 24 h (microarray and qPCR assays).

Results: The fatty acid composition of head kidney leukocytes varied between the two dietary groups (e.g. higher 20:5n-3 in the FO7 group). Following microarray assays using a 44K salmonid platform, Rank Products (RP) analysis showed 14 and 54 differentially expressed probes (DEP) (PFP < 0.05) between the two diets in control and pIC groups (FO5 vs. FO7), respectively. Nonetheless, Significance Analysis of Microarrays (SAM, FDR < 0.05) identified only one DEP between pIC groups of the two diets. Moreover, we identified a large number (i.e. 890 DEP in FO7 and 1128 DEP in FO5 overlapping between SAM and RP) of pIC-responsive transcripts, and several of them were involved in TLR-/RLR-dependent and cytokine-mediated pathways. The microarray results were validated as significantly differentially expressed by qPCR assays for 2 out of 9 diet-responsive transcripts and for all of the 35 selected pIC-responsive transcripts.

Conclusion: Fatty acid-binding protein adipocyte (fabp4) and proteasome subunit beta type-8 (psmb8) were significantly up- and down-regulated, respectively, in the MLCs of fish fed the diet with a lower level of fish oil, suggesting that they are important diet-responsive, immune-related biomarkers for future studies. Although the different levels of dietary fish and vegetable oils involved in this study affected the expression of some transcripts, the immune-related pathways and functions activated by the antiviral response of salmon MLCs in both groups were comparable overall. Moreover, the qPCR revealed transcripts responding early to pIC (e.g. lgp2, map3k8, socs1, dusp5 and cflar) and time-responsive transcripts (e.g. scarb1-a, csf1r, traf5a, cd80 and ctsf) in salmon MLCs. The present study provides a comprehensive picture of the putative molecular pathways (e.g. RLR-, TLR-, MAPK- and IFN-associated pathways) activated by the antiviral response of salmon MLCs.
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http://dx.doi.org/10.1186/s12864-017-4099-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5591513PMC
September 2017

Urban sewage lipids in the suspended particulate matter of a coral reef under river influence in the South West Gulf of Mexico.

Water Res 2017 10 22;123:192-205. Epub 2017 Jun 22.

Instituto de Ciencias Marinas y Pesquerías, Universidad Veracruzana, Calle Hidalgo 617, Colonia Río Jamapa, Boca del Río, Veracruz, Mexico.

Nutritional quality of suspended particulate matter (SPM) and the degree of human fecal pollution in the largest coral reef system in the southwest Gulf of Mexico were evaluated using lipid classes, fatty acids (FA) and sterols in the dry and rainy seasons. High proportions of triacylglycerols and saturated and monounsaturated FA were detected in the SPM however it was considered poor quality because it had low proportions of highly unsaturated FA which can be used to determine production of marine biogenic material of dietary value to pelagic and benthic organisms. Urban sewage organic carbon was traced with coprostanol. The reference value of coprostanol from the point source of pollution was set using two samples from a sewage treatment plant processing waste from >140,000 people near the coral reef system, and it was contrasted with one river station and nine marine stations including six coral reefs. The concentration of coprostanol in the SPM was 3621 ± 98 ng L comprising 26% of total sterols. During the dry season, the river was contaminated upstream with human feces as evidenced by coprostanol at 1823 ng L, the 5β-coprostanol: cholesterol ratio at 0.5, and 5β-coprostanol: [5α-cholestanol+5β-coprostanol] at 0.7. In contrast, marine stations had concentrations of coprostanol lower than a suggested regulation limit for tropical marine coastal waters (30 ng L), ranging between 6 and 28 ng L. During the rainy season a dilution effect was detected in the river, however significantly higher concentrations of coprostanol in the marine stations were detected ranging between 15 and 215 ng L, higher than the tentative tropical regulation range (30-100 ng L). Among the reefs, the nearshore one, 14.3 km from the treatment plant, was more exposed to human-fecal pollution, and offshore reefs, >17.3 km from the plant, had a lower degree of contamination. Finally, only three stations were clearly uncontaminated during both seasons including two reefs in the south located 21.8 and 35.6 km from the plant, with no presence of coprostanol. Contamination in the rainy season likely comes from a village with untreated sewage located 9.3-32 km from the reefs, and from the second largest Mexican river flowing into the Gulf of Mexico which has a watershed covering three states with lower than average sewage treatment. Inclusion of coprostanol monitoring could be a key factor in the management of this coral reef system.
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http://dx.doi.org/10.1016/j.watres.2017.06.061DOI Listing
October 2017

The dietary replacement of marine ingredients by terrestrial animal and plant alternatives modulates the antiviral immune response of Atlantic salmon (Salmo salar).

Fish Shellfish Immunol 2017 May 24;64:24-38. Epub 2017 Feb 24.

Department of Ocean Sciences, Memorial University of Newfoundland, 1 Marine Lab Road, St. John's, NL A1C 5S7, Canada. Electronic address:

The effects of replacing marine ingredients by terrestrial ingredients on the health of Atlantic salmon (Salmo salar) are poorly understood. During a 14-week trial, Atlantic salmon fed a fish meal-fish oil based diet (MAR) showed similar growth performance to others fed a plant protein/vegetable oil based diet (VEG), whereas poorer performance was observed in those fed an animal by-product meal/vegetable oil based diet (ABP). At the end of the trial, salmon were injected with either phosphate-buffered saline (PBS) or the viral mimic polyriboinosinic polyribocytidylic acid (pIC) and sampled for head kidney RNA after 24 h. The levels of 27 immune-related transcripts, and of 5 others involved in eicosanoid synthesis (including paralogues in both cases) were measured in the head kidney of the salmon using qPCR. All of the assayed immune-related genes and cox2 were pIC-induced, while the other eicosanoid synthesis-related genes were pIC-repressed. Linear regression was used to establish correlations between different immune transcripts, elucidating the cascade of responses to pIC and specialization among paralogues. Regarding the effect of diet on the antiviral immune response, pIC-treated fish fed diets ABP and VEG showed higher transcript levels of tlr3, irf1b, stat1a, isg15b, and gig1 compared to those fed diet MAR. We infer that the observed dietary immunomodulation could be due to the lower proportion of arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) in diets ABP and VEG. Furthermore, our results suggest a major role of dietary ARA in Atlantic salmon immunity, as low ARA proportion in diet VEG coincided with the highest pIC-induction of some immune transcripts (tlr7, stat1c, mxb, and gig1) and the lowest levels of transcripts encoding eicosanoid-synthesizing enzymes (5loxa, 5loxb, and pgds). In contrast, the high ARA/EPA ratio of diet ABP appeared to favor increased expression of transcripts involved in the synthesis of pro-inflammatory eicosanoids (5loxa and 5loxb) and chemotaxis (ccl19b). In conclusion, our findings show that nutritionally balanced plant-based diets may enhance the immune response of Atlantic salmon. Future studies should explore the possible advantages of plant-based diets in Atlantic salmon exposed to a viral infection.
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http://dx.doi.org/10.1016/j.fsi.2017.02.040DOI Listing
May 2017

Copper affects biochemical and physiological responses of Selenastrum gracile (Reinsch).

Ecotoxicology 2016 Oct 20;25(8):1468-1477. Epub 2016 Jul 20.

Departamento de Hidrobiologia, Centro de Ciências Biológicas e da Saúde (CCBS), Universidade Federal de São Carlos (UFSCar), Rodovia Washington Luís, Km 235, São Carlos, SP, 13565-905, Brazil.

Copper is an essential metal for several physiological and metabolic processes, but a narrow range regulate its effect in phytoplankton cells. It can affect the production of biomolecules and be toxic at concentrations slightly above those required, e.g. decreasing photosynthesis and increasing respiration. The aims of this study were to analyse the changes in growth and chlorophyll a synthesis, and in biochemistry (total carbohydrates, proteins, lipids and fatty acids) of the freshwater microalga Selenastrum gracile after exposure to copper. Exponentially growing cells were exposed to 5 concentrations of free copper ions (Cu) ranging from 0.7 (control) to 13 × 10 M for up to 120 h. Free Cu ion concentrations were calculated through the chemical equilibrium model MINEQL. We observed that copper was responsible for a decrease in cell density and an increase in total protein and lipid production, but no effect on total carbohydrates was detected. The increase in phospholipids and sterols and a decrease in saturated fatty acids under copper exposure suggest a change in conformation of the cell membrane, by decreasing its fluidity. We suggest this serves the cell as a system to avoid the internalization of metal, thereby acting as a detoxifying mechanism.
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http://dx.doi.org/10.1007/s10646-016-1698-7DOI Listing
October 2016

Remarkable Shifts in Offspring Provisioning during Gestation in a Live-Bearing Cnidarian.

PLoS One 2016 22;11(4):e0154051. Epub 2016 Apr 22.

Society for the Exploration and Valuing of the Environment (SEVE), Portugal Cove-St. Philips, Newfoundland and Labrador, Canada.

Animals display diverse means of producing and provisioning offspring, from eggs to embryos and juveniles. While external development predominates, many forms of embryonic incubation have evolved, including placentation in mammals and a number of understudied variants in basal metazoans that could help understand evolutionary diversification. Here we studied the brooding sea anemone Aulactinia stella, using behavioural, morphological and biochemical indicators of offspring phenotype to characterize gestation and elucidate parental and sibling relationships. The pronounced variance in juvenile weight within broods was not strongly related to any of the typical external predictors (adult weight, clutch size, sampling date, environmental conditions). Lipid concentration was significantly higher in the tissues of the small juveniles than in those of large juveniles or adult, and fatty acid profiles tended to set small juveniles apart. Finally, intra-brood feeding on external resources was documented in larger juveniles. These results are consistent with ontogenetic shifts in nutrition, from vitellogenic provisioning to post-zygotic nourishment to a prenatal form of nursing upon acquisition of feeding organs, highlighting matrotrophic and conflict-driven mechanisms acting on offspring phenotype during gestation.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0154051PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4841577PMC
March 2017

Lipid Classes and Fatty Acids in Ophryotrocha cyclops, a Dorvilleid from Newfoundland Aquaculture Sites.

PLoS One 2015 26;10(8):e0136772. Epub 2015 Aug 26.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, NL, Canada.

A new opportunistic annelid (Ophryotrocha cyclops) discovered on benthic substrates underneath finfish aquaculture sites in Newfoundland (NL) may be involved in the remediation of organic wastes. At those aquaculture sites, bacterial mats and O. cyclops often coexist and are used as indicators of organic enrichment. Little is known on the trophic strategies used by these annelids, including whether they might consume bacteria or other aquaculture-derived wastes. We studied the lipid and fatty acid composition of the annelids and their potential food sources (degraded flocculent organic matter, fresh fish pellets and bacterial mats) to investigate feeding relationships in these habitats and compared the lipid and fatty acid composition of annelids before and after starvation. Fish pellets were rich in lipids, mainly terrestrially derived C18 fatty acids (18:1ω9, 18:2ω6, 18:3ω3), while bacterial samples were mainly composed of ω7 fatty acids, and flocculent matter appeared to be a mixture of fresh and degrading fish pellets, feces and bacteria. Ophryotrocha cyclops did not appear to store excessive amounts of lipids (13%) but showed a high concentration of ω3 and ω6 fatty acids, as well as a high proportion of the main fatty acids contained in fresh fish pellets and bacterial mats. The dorvilleids and all potential food sources differed significantly in their lipid and fatty acid composition. Interestingly, while all food sources contained low proportions of 20:5ω3 and 20:2ω6, the annelids showed high concentrations of these two fatty acids, along with 20:4ω6. A starvation period of 13 days did not result in a major decrease in total lipid content; however, microscopic observations revealed that very few visible lipid droplets remained in the gut epithelium after three months of starvation. Ophryotrocha cyclops appears well adapted to extreme environments and may rely on lipid-rich organic matter for survival and dispersal in cold environments.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0136772PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4550312PMC
May 2016

Spatial Patterns and Temperature Predictions of Tuna Fatty Acids: Tracing Essential Nutrients and Changes in Primary Producers.

PLoS One 2015 2;10(7):e0131598. Epub 2015 Jul 2.

CSIRO Oceans and Atmosphere Flagship, Hobart, Tasmania, Australia; CSIRO Food, Nutrition and Bioproducts Flagship, Hobart, Tasmania, Australia.

Fatty acids are among the least understood nutrients in marine environments, despite their profile as key energy components of food webs and that they are essential to all life forms. Presented here is a novel approach to predict the spatial-temporal distributions of fatty acids in marine resources using generalized additive mixed models. Fatty acid tracers (FAT) of key primary producers, nutritional condition indices and concentrations of two essential long-chain (≥C20) omega-3 fatty acids (EFA) measured in muscle of albacore tuna, Thunnus alalunga, sampled in the south-west Pacific Ocean were response variables. Predictive variables were: location, time, sea surface temperature (SST) and chlorophyll-a (Chla), and phytoplankton biomass at time of catch and curved fork length. The best model fit for all fatty acid parameters included fish length and SST. The first oceanographic contour maps of EFA and FAT (FATscapes) were produced and demonstrated clear geographical gradients in the study region. Predicted changes in all fatty acid parameters reflected shifts in the size-structure of dominant primary producers. Model projections show that the supply and availability of EFA are likely to be negatively affected by increases in SST especially in temperate waters where a 12% reduction in both total fatty acid content and EFA proportions are predicted. Such changes will have large implications for the availability of energy and associated health benefits to high-order consumers. Results convey new concerns on impacts of projected climate change on fish-derived EFA in marine systems.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0131598PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4489677PMC
April 2016

Complex offspring size effects: variations across life stages and between species.

Ecol Evol 2015 Mar 14;5(5):1117-29. Epub 2015 Feb 14.

Department of Ocean Sciences, Memorial University St. John's, Newfoundland and Labrador, A1C 5S7, Canada.

Classical optimality models of offspring size and number assume a monotonically increasing relationship between offspring size and performance. In aquatic organisms with complex life cycles, the size-performance function is particularly hard to grasp because measures of performance are varied and their relationships with size may not be consistent throughout early ontogeny. Here, we examine size effects in premetamorphic (larval) and postmetamorphic (juvenile) stages of brooding marine animals and show that they vary contextually in strength and direction during ontogeny and among species. Larger offspring of the sea anemone Urticina felina generally outperformed small siblings at the larval stage (i.e., greater settlement and survival rates under suboptimal conditions). However, results differed when analyses were conducted at the intrabrood versus across-brood levels, suggesting that the relationship between larval size and performance is mediated by parentage. At the juvenile stage (15 months), small offspring were less susceptible than large ones to predation by subadult nudibranchs and both sizes performed similarly when facing adult nudibranchs. In a sympatric species with a different life history (Aulactinia stella), all juveniles suffered similar predation rates by subadult nudibranchs, but smaller juveniles performed better (lower mortalities) when facing adult nudibranchs. Size differences in premetamorphic performance of U. felina were linked to total lipid contents of larvae, whereas size-specific predation of juvenile stages followed the general predictions of the optimal foraging strategy. These findings emphasize the challenge in gathering empirical support for a positive monotonic size-performance function in taxa that exhibit complex life cycles, which are dominant in the sea.
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http://dx.doi.org/10.1002/ece3.1320DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4364825PMC
March 2015

Atlantic salmon (Salmo salar) liver transcriptome response to diets containing Camelina sativa products.

Comp Biochem Physiol Part D Genomics Proteomics 2015 Jun 2;14:1-15. Epub 2015 Feb 2.

Department of Ocean Sciences, Memorial University of Newfoundland, 1 Marine Lab Road, St. John's, NL A1C 5S7, Canada. Electronic address:

Due to increasing demand for fish oil (FO) and fish meal (FM) in aquafeeds, more sustainable alternatives such as plant-derived oils and proteins are needed. Camelina sativa products are viable feed ingredients given the high oil and crude protein content in the seed. Atlantic salmon were fed diets with complete or partial replacement of FO and/or FM with camelina oil (CO) and/or camelina meal (CM) in a 16-week trial [Control diet: FO; Test diets: 100% CO replacement of FO (100CO), or 100CO with solvent-extracted FM (100COSEFM), 10% CM (100CO10CM), or SEFM+10% CM (100COSEFM10CM)]. Diet composition, growth, and fatty acid analyses for this feeding trial were published previously. A 44K microarray experiment identified liver transcripts that responded to 100COSEFM10CM (associated with reduced growth) compared to controls, yielding 67 differentially expressed features (FDR<5%). Ten microarray-identified genes [cpt1, pcb, bar, igfbp-5b (2 paralogues), btg1, dnph1, lect-2, clra, klf9, and fadsd6a], and three additional genes involved in lipid metabolism [elovl2, elovl5 (2 paralogues), and fadsd5], were subjected to QPCR with liver templates from all 5 dietary treatments. Of the microarray-identified genes, only bar was not QPCR validated. Both igfbp-5b paralogues were significantly down-regulated, and fadsd6a was significantly up-regulated, in all 4 camelina-containing diet groups compared with controls. Multivariate statistics were used to correlate hepatic desaturase and elongase gene expression data with tissue fatty acid profiles, indicating the involvement of these genes in LC-PUFA biosynthesis. This nutrigenomic study provides molecular biomarkers for use in developing novel aquafeeds using camelina products.
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http://dx.doi.org/10.1016/j.cbd.2015.01.005DOI Listing
June 2015

Combined nitrogen limitation and cadmium stress stimulate total carbohydrates, lipids, protein and amino acid accumulation in Chlorella vulgaris (Trebouxiophyceae).

Aquat Toxicol 2015 Mar 8;160:87-95. Epub 2015 Jan 8.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, Newfoundland A1C 5S7, Canada.

Metals have interactive effects on the uptake and metabolism of nutrients in microalgae. However, the effect of trace metal toxicity on amino acid composition of Chlorella vulgaris as a function of varying nitrogen concentrations is not known. In this research, C. vulgaris was used to investigate the influence of cadmium (10(-7) and 2.0×10(-8)molL(-1) Cd) under varying nitrogen (2.9×10(-6), 1.1×10(-5) and 1.1×10(-3)molL(-1)N) concentrations on its growth rate, biomass and biochemical composition. Total carbohydrates, total proteins, total lipids, as well as individual amino acid proportions were determined. The combination of Cd stress and N limitation significantly inhibited growth rate and cell density of C. vulgaris. However, increasing N limitation and Cd stress stimulated higher dry weight and chlorophyll a production per cell. Furthermore, biomolecules like total proteins, carbohydrates and lipids increased with increasing N limitation and Cd stress. Ketogenic and glucogenic amino acids were accumulated under the stress conditions investigated in the present study. Amino acids involved in metal chelation like proline, histidine and glutamine were significantly increased after exposure to combined Cd stress and N limitation. We conclude that N limitation and Cd stress affects the physiology of C. vulgaris by not only decreasing its growth but also stimulating biomolecule production.
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http://dx.doi.org/10.1016/j.aquatox.2015.01.002DOI Listing
March 2015

Direct determination of fatty acids in fish tissues: quantifying top predator trophic connections.

Oecologia 2015 Jan 7;177(1):85-95. Epub 2014 Nov 7.

Department of Ocean Sciences, Memorial University of Newfoundland, St. John's, Newfoundland, A1C 5S7, Canada,

Fatty acids are a valuable tool in ecological studies because of the large number of unique structures synthesized. They provide versatile signatures that are being increasingly employed to delineate the transfer of dietary material through marine and terrestrial food webs. The standard procedure for determining fatty acids generally involves lipid extraction followed by methanolysis to produce methyl esters for analysis by gas chromatography. By directly transmethylating ~50 mg wet samples and adding an internal standard it was possible to greatly simplify the analytical methodology to enable rapid throughput of 20-40 fish tissue fatty acid analyses a day including instrumental analysis. This method was verified against the more traditional lipid methods using albacore tuna and great white shark muscle and liver samples, and it was shown to provide an estimate of sample dry mass, total lipid content, and a condition index. When large fatty acid data sets are generated in this way, multidimensional scaling, analysis of similarities, and similarity of percentages analysis can be used to define trophic connections among samples and to quantify them. These routines were used on albacore and skipjack tuna fatty acid data obtained by direct methylation coupled with literature values for krill. There were clear differences in fatty acid profiles among the species as well as spatial differences among albacore tuna sampled from different locations.
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http://dx.doi.org/10.1007/s00442-014-3131-3DOI Listing
January 2015

Characterization of the fatty acyl elongase (elovl) gene family, and hepatic elovl and delta-6 fatty acyl desaturase transcript expression and fatty acid responses to diets containing camelina oil in Atlantic cod (Gadus morhua).

Comp Biochem Physiol B Biochem Mol Biol 2014 Sep 24;175:9-22. Epub 2014 Jun 24.

Department of Ocean Sciences, Memorial University of Newfoundland, 1 Marine Lab Road, St. John's, NL A1C 5S7, Canada. Electronic address:

For aquaculture to become sustainable, there is a need to substitute fish oil [FO, rich in ω3 long chain polyunsaturated fatty acids (LC-PUFA) such as 20:5ω3 (EPA) and 22:6ω3 (DHA)] in aquafeed with plant oils such as camelina oil [CO, rich in C18 PUFA such as 18:3ω3 (ALA) and 18:2ω6 (LNA)]. The LC-PUFA are essential components in fish diets for maintaining optimal health, physiology and growth. However, most marine fish including Atlantic cod are inefficient at producing LC-PUFA from shorter chain precursors. Since elovl genes encode enzymes that play key roles in fatty acid biosynthesis, we hypothesized that they may be involved in Atlantic cod responses to diets rich in 18:3ω3 and 18:2ω6. Ten members of the cod elovl gene family were characterized at the mRNA level. RT-PCR was used to study constitutive expression of elovl transcripts in fifteen tissues. Some transcripts (e.g. elovl5) were ubiquitously expressed, while others had tissue-specific expression (e.g. elovl4a in brain and eye). Cod fed a CO-containing diet (100% CO replacement of FO and including solvent-extracted fish meal) had significantly lower weight gain, with significant up-regulation of elovl5 and fadsd6 transcripts in the liver as shown by QPCR analysis, compared with cod on a FO control diet after a 13-week trial. Multivariate statistical analyses (SIMPER and PCA) indicated that high 18:3ω3 and/or low ω3 LC-PUFA levels in the liver were associated with the up-regulation of elovl5 and fadsd6, which are involved in LC-PUFA biosynthesis in cod.
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http://dx.doi.org/10.1016/j.cbpb.2014.06.005DOI Listing
September 2014

Lipid, fatty acid and energy density profiles of white sharks: insights into the feeding ecology and ecophysiology of a complex top predator.

PLoS One 2014 28;9(5):e97877. Epub 2014 May 28.

CSIRO Wealth from Ocean Flagship, Division of Marine and Atmospheric Research, Hobart, Australia.

Lipids are major sources of metabolic energy in sharks and are closely linked to environmental conditions and biological cycles, such as those related to diet, reproduction and migration. In this study, we report for the first time, the total lipid content, lipid class composition and fatty acid profiles of muscle and liver tissue of white sharks, Carcharodon carcharias, of various lengths (1.5-3.9 m), sampled at two geographically separate areas off southern and eastern Australia. Muscle tissue was low in total lipid content (<0.9% wet mass, wm) and was dominated by phospholipids (>90% of total lipid) and polyunsaturated fatty acids (34±12% of total fatty acids). In contrast, liver was high in total lipid which varied between 51-81% wm and was dominated by triacylglycerols (>93%) and monounsaturated fatty acids (36±12%). With knowledge of total lipid and dry tissue mass, we estimated the energy density of muscle (18.4±0.1 kJ g-1 dm) and liver (34.1±3.2 kJ g-1 dm), demonstrating that white sharks have very high energetic requirements. High among-individual variation in these biochemical parameters and related trophic markers were observed, but were not related to any one biological or environmental factor. Signature fatty acid profiles suggest that white sharks over the size range examined are generalist predators with fish, elasmobranchs and mammalian blubber all contributing to the diet. The ecological applications and physiological influences of lipids in white sharks are discussed along with recommendations for future research, including the use of non-lethal sampling to examine the nutritional condition, energetics and dietary relationships among and between individuals. Such knowledge is fundamental to better understand the implications of environmental perturbations on this iconic and threatened species.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0097877PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4037211PMC
June 2015