Demonstration of the Deposition and Modification of Dietary Fatty Acids in Pinniped Blubber Using Radiolabelled Precursors

Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada
Physiological and Biochemical Zoology (Impact Factor: 2.4). 07/2004; 77(4):682-7. DOI: 10.1086/420945
Source: PubMed


Radioisotopes are commonly used to study the in vivo metabolism and deposition of dietary fatty acids in adipose tissue. The application of this approach to pinnipeds is problematic because of their large mass and blubber fat content. We have developed a method where labelled lipids can be fed to seals at financially feasible levels, with the radioactivity in individual fatty acids isolated from blubber detected with standard laboratory equipment. A combination of techniques including argentation thin layer chromatography, high performance liquid chromatography with ultraviolet detection, and independent liquid scintillation counting were employed. Juvenile gray seals (Halichoerus grypus) were fed either 0.5 mCi (3)H-labelled triolein (18:1n-9, n=2) or palmitic acid (16:0, n=2). Blubber samples were taken 12 h later, and the radioactivity in individual fatty acids was determined. Radioactivity was detected in only 18:1 from the animals fed (3)H-labelled triolein, indicating direct deposition without modification. Both animals fed (3)H-labelled palmitic acid showed clear peaks of radioactivity in 16:0; however, there was also significant activity (23%-29%) found in the desaturation product 16:1. Our results demonstrate that this method is sufficiently sensitive to track the deposition of labelled dietary lipids as well as modification products of ingested fatty acids and will be important in the application of fatty acid signatures to study predator diets.

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Available from: Suzanne Budge, Nov 03, 2014
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    • "In the assessment of food-web structures in fresh water and marine ecosystems, fatty acid composition and their ∂ 13 C are used to trace food resources through multiple food chains (e.g. Budge et al., 2004; Mayzaud et al., 2007). In aquaculture, lipids are studied because some of them are essential and have to be taken up by the organisms and key information on their distribution is required to optimize larval feeding and large mass culturing for commercial use (e.g. "
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    ABSTRACT: Growth rate, C:N ratio, phospholipid-derived fatty acids (PLFA) distribution and organic carbon isotope composition (∂13C) of both life stages of the Prymnesiophyceae Emiliania huxleyi (Lohmann), Calcidiscus leptoporus (Murray and Blackman) and Syracosphaera pulchra (Lohman) were analyzed. Cultures were grown at two different CO2 partial pressures (pCO2, 400 and 760 μatm) under nutrient-replete conditions. Growth rates (μ) increased at 760 μatm in all species. C:N ratios were unaffected by pCO2 in C. leptoporus and in the diploid stage of E. huxleyi; they significantly decreased in the haploid stage of E. huxleyi and in both life stages of S. pulchra. At 400 μatm, high similarity was found between the lipid composition of C. leptoporus and S. pulchra differing from that of E. huxleyi. The haploid and diploid life stages showed significant differences in mono- and polyunsaturated C18 fatty acids (MUFA and PUFA), which were more abundant in either stage depending on the species. Except for palmitoleic, vaccenic acids and docosahexaeonic acid (DHA), C. leptoporus and S. pulchra fatty acids were lower compared to those of E. huxleyi. Differences in ∂13C between particulate organic carbon (POC) and PLFA (∆∂13Clipid-POC) showed common trends at both pCO2: palmitoleic, oleic acids and DHA were systematically depleted compared to total cell biomass, C18 PUFA were enriched while saturated fatty acids (SAFA) were enriched in C. leptoporus and S. pulchra and depleted in E. huxleyi. Elevated pCO2 influenced PLFA abundance, ∂13C of lipids and POC in a highly species-specific way. Fatty acids were generally more depleted at 760 μatm than at 400 μatm but the effect was variable among PLFA classes. The relationship between coccolithophore isotopic and PLFA composition and CO2 concentration are analyzed and consequent variations in the future web-chain related to changes in carbonate chemistry are discussed.
    Full-text · Article · Oct 2010 · Journal of Experimental Marine Biology and Ecology
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    • "In these species, preformed dietary FA are less likely to enter typical lipid synthetic pathways and such processes are, in any case, inhibited by diets containing adequate or excess fat, as well as those high in long-chain PUFA (Nelson 1992) . Additionally, desaturation of exogenously consumed FA may be confined primarily to the D 9 desaturase enzyme acting on some saturated 16:0 (e.g., Budge et al. 2004) . Thus, FA that have been elongated and desaturated within marine birds and mammals are unlikely to make a significant contribution to their adipose FA stores. "
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    ABSTRACT: Food web structure, predator–prey dynamics, foraging behavior, and consequences of these factors for individual growth, reproduction and survival are central to our understanding of ecosystem structure and functioning. Moreover, in the current context of understanding (and managing) ecosystems in the face of ongoing environmental change, important questions include: What are the critical prey of key consumers in relation to prey abundance, availability, and nutritional quality? What are the ecosystem processes responsible for food web production? And, how do these processes respond to changes in physical forcing? A fundamental require-ment to understand any of these areas is an accurate assessment of trophic relationships and consumer diets. However, in aquatic, and especially marine ecosystems, such information is generally not easily or reliably obtained. In these systems, the relative inaccessibility of free-ranging organisms and the inability to directly observe species interactions make it difficult to accurately characterize diet. Traditional approaches, such as examining gut contents, have well-recognized biases in addition to representing only snapshots of recent meals and may therefore not be reliable indicators of long-term diet (Iverson et al. 2004). Thus, alternative approaches have been developed, which use various types of trophic markers. One of the most promising of these approaches is the use of lipids and fatty acids (FA) to study food web dynamics.
    Full-text · Chapter · Jun 2009
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    • "Normally the polar lipids dominate and sometimes the plasma is poor in the neutral lipids that are expected to reflect the diet more than the polar ones. Given that there is also extensive metabolism of fatty acids by animals, which alters their FAS from that of their food (Budge, Cooper & Iverson 2004; Cooper, Iverson & Heras 2005; Käkelä et al . 2005; Cooper, Iverson & Rouvinen-Watt 2006; Stowasser et al . "
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    ABSTRACT: Summary • Tissue fatty acid signatures (FAS) can complement traditional methods of studying seabird diets. Although plasma lipid FAS are known to indicate dietary changes qualitatively, here we test whether they can be used to determine the proportions of different dietary items in a quantitative manner. • Captive herring gulls (Larus argentatus) were fed North Atlantic plaice Pleuronectes platessa (demersal species made available to wild seabirds by fisheries) and herring Clupea harengus (pelagic fish often found naturally in their diet) with different mixing ratios (0%, 10%, 20% and 50% herring). • Major fatty acids did not indicate diet, but several minor components in plasma, for example, 14 : 0, 18 : 3n-3, 18 : 4n-3 and C20–22 monounsaturated fatty acids (MUFA), showed good correlations with diet composition. Different fatty acids were incorporated from diet into plasma lipids with different calibration coefficients. • Together with dose-dependent but inefficient (low calibration coefficient) transfer of 22 : 1n-11 (a major fatty acid of herring) to the plasma FAS of the gulls, the percentages of potential chain shortening products of 22 : 1n-11, that is, 20 : 1n-11, 18 : 1n-11 and 16 : 1n-11 increased with increasing proportion of herring in the diet. Notably, the dietary supply of these fatty acids itself did not change. Thus the metabolic products of certain dietary fatty acids can reflect the amount of their dietary precursors in a quantitative way. • Despite the fact that many major fatty acids in FAS of seabird plasma are greatly modified by endogenous metabolism, several minor components of FAS (in this experiment 14 : 0, branched chain 17 : 0, 18 : 1n-7, 18 : 3n-3, 18 : 4n-3, C20–22 MUFA with their chain shortening products, and 22 : 4n-6) that can be accurately and reliably quantified by gas chromatography, vary proportionally to diet composition, allowing their use for monitoring temporal and spatial differences in seabird diet.
    Full-text · Article · Sep 2008 · Functional Ecology
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