Fatty‐Acid Profile of Total and Polar Lipids in Cultured Rainbow Trout (Oncorhynchus mykiss) Raised in Freshwater and Seawater (Croatia) Determined by Transmethylation Method

Fatty acids from total lipids and polar lipids in cultured rainbow trout (Oncorhynchus mykiss) raised in seawater (SW) and freshwater (FW) were identified and quantified from the muscle samples in January, April, and July. The highest total lipid and polar lipid amounts were found in April. July contents of total lipids were low, but percent of the polyunsaturated fatty acids (PUFAs) was high in SW and FW environment (particularly n‐3 PUFAs). Variety of 17 fatty acids was identified by GC‐FID after transmethylation. The predominant fatty acids in rainbow trout from SW and FW were: docosahexaenoic acid among n‐3 PUFAs, palmitic acid among saturated fatty acids (SFAs), and oleic acid among monounsaturated fatty acids (MUFAs). Appreciably higher n‐3/n‐6 ratio was found in total lipids in April (6.40, FW fish) and in polar lipids in July (18.76; SW fish). High n‐3/n‐6 ratio in total lipids and polar lipids of rainbow trout from SW and FW, besides beneficial n‐3/n‐6 ratio in the commercial fish food, could be characteristic for the local environmental conditions (Croatia).     

Lipids and fatty acids of two pelagic cottoid fishes (Comephorus spp) endemic to Lake Baikal

Matured females of two Lake Baikal endemic fish species, Comephorus baicalensis and Comephorus dybowski, have been investigated for lipid of the whole body and specific tissues (liver, muscles, ovaries), phospholipid classes and fatty acids of neutral and polar lipids. Total lipid in the body (38.9% fresh weight), liver (23.5%) and muscles (14.5%) of C. baicalensis were greater than those of C. dybowski (4.7, 8.7 and 2.6%, respectively); only their ovaries were similar (5.3 and 5.6% lipid, respectively). In both species, phosphatidylcholine and phosphatidylethanolamine were the major phospholipids, ranging from 60.7 to 75.1% of total phospholipid and 14.5–25.7%, respectively. In most cases, monounsaturated fatty acids (MUFA) were the major fatty acid group in C. baicalensis, whereas polyunsaturated fatty acids (PUFA) were the major group in C. dybowski. The MUFA 18:1(n-9) prevailed over other fatty acids in C. baicalensis and varied from 19% in polar lipids of muscles to 56.1% in neutral lipids of muscles. In polar lipid of C. dybowski, the PUFA 22:6(n-3) prevailed over other fatty acids in muscles and ovaries, while 16:0 dominated polar liver lipids and neutral lipids of all tissues. Other major fatty acids included 16:1(n-7), 18:1(n-7), and 20:5(n-3). Values of the (n-3)/(n-6) fatty acid ratio for neutral lipids of C. baicalensis (0.5–0.9) are well below the range of values characteristic either for marine or freshwater fish, while these values for polar lipids (1.6–1.8) are in the range typical of freshwater fish. Neutral lipid fatty acid ratios in C. dybowski (2.5–3.1) allow it to be assigned to freshwater fish, but polar lipids (2.8–3.7) leave it intermediary between freshwater and marine fish.     

Seasonal variations of lipid fatty acids of boreal freshwater fish species

1. The fatty acid levels of muscle and liver lipids of perch, vendace and rainbow trout (Salmo gairdneri) cultivated in the same area (for comparison) were monitored. 2. The total lipid content in the muscle of perch (Perca fluviatilis) and vendace (Coregonus albula) was less than 50% of that in rainbow trout and a seasonal variation was clear only in vendace. 3. The relative amounts of polyunsaturated fatty acids as well as omega-3 acids were higher in vendace and perch than in cultivated rainbow trouts. Arachidonic acid content was much higher in vendace and perch than in rainbow trout. The content of monoenes was considerably higher in rainbow trout than in free freshwater fish. 4. The seasonal variations in the degree of unsaturation were small in fish muscle. 5. In the muscle of rainbow trout the relative amount of polyunsaturated fatty acids diminished with the increase of total lipids.     

Seasonal dynamics of fatty acid composition in female northern pike (Esox lucius L.)

Seasonal changes in the fatty acid composition of neutral and polar lipids were measured in the ovary, liver, white muscle, and adipopancreatic tissue of northern pike. The role of environmental and physiological factors underlying these changes was evaluated. From late summer (August–September) to winter (January–March), the weight percentage of n-3 polyunsaturated fatty acids (especially 22:6n3) declined significantly in the neutral lipids of all somatic tissues examined. However, large quantities of n-3 polyunsaturated fatty acids accumulated in the recrude cing ovaries during fall and the weight percentage of n-3 polyunsaturated fatty acids in ovary polar lipids also increased significantly. Additionally, the n-3 polyunsaturated fatty acid content of somatic polar lipids increased significantly during fall due to increases in the total polar lipid content of the somatic tissues. This suggests that during fall n-3 polyunsaturated fatty acid are diverted away from somatic neutral lipids and thereby conserved for use in ovary construction and for incorporation into tissue polar lipids. The percentage of n-3 polyunsaturated fatty acid in ovary neutral lipids also declined during fall and early winter, perhaps as an adaptation to conserve these fatty acids for storage in oocyte polar lipids and later incorporation into cellular membranes of the developing embryo. Reductions in the n-3 polyunsaturated fatty acids content of somatic and ovarian neutral lipids during fall were compensated for specifically by increases in the percentage of monounsaturated fatty acids rather than saturated fatty acids. This suggests that the ratio of saturated to unsaturated fatty acids in pike neutral lipid, is regulated physiologically, and hence may influence the physiological functioning of these lipids. During fall and early winter the percentage of saturated fatty acids declined significantly in the polar lipids of all tissues examined. This change was consistent with the known effects of cold acclimation on the fatty acid composition of cellular membranes. As the ovaries were recrudescing from September to January, liver polar lipids exhibited significant decreases in the percentage of total polyunsaturated fatty acids and n-3 polyunsaturated fatty acids and increases in monounsaturated fatty acids, and acquired a fatty acid composition very similar to that of ovary polar lipids. Therefore, seasonal changes in the percentage of polyunsaturated and monounsaturated fatty acids in liver polar lipids probably reflect the liver's role in vitellogenesis rather than the effects of temperature on membrane fatty acid composition. At all times of year, the fatty acid compositions of white muscle and adipopancreatic tissue neutral lipids were very similar, which may indicate a close metabolic relationship between these lipid compartments.Abbreviations AP adipopancreatic - BHT butylated hydroxytoluene - CI confidence interval - EFA essential fatty acids - MUFA monounsaturated fatty acids - NL neutral lipids - PL polar lipids - PUFA polyunsaturated fatty acids - SFA saturated fatty acids     

Changes of the fatty acid composition in smolts of masu salmon (Oncorhynchus masou), associated with desmoltification and sea-water transfer

• 1.1. Tissue lipid compositions of desmoltified yearlings of masu salmon (Oncorhynchus masou) obtained by keeping smoltified fish in fresh water, were examined and compared to those of smoltified fish before and after transfer to sea-water (SW).
• 2.2. Lipid contents of muscle, liver, gut and gills of desmolts tended to increase compared to those of initial smolts.
• 3.3. The increased proportion of triacylglycerol (TG) and decreased proportion of phospholipids (PL) characterized the tissue lipids of desmolts.
• 4.4. Liver and muscle lipids showed no distinct differences both in content and proportion between initial and SW smolts, but gut and gill lipids of SW smolts decreased in content accompanied by a decrease of TG and an increase of PL in proportion.
• 5.5. Excepting muscle non-polar lipids, tissue lipids of desmolts contained more mono-unsaturated fatty acids and saturated fatty acids and less polyunsaturated fatty acids (PUFA), especially (n-3) PUFA such as 22:6(n-3), than those of initial and SW smolts.
• 6.6. No large differences in fatty acid composition were seen between initial and SW smolts except for the gut.
• 7.7. The proportion of (n-3) PUFA in the gut of SW smolts was higher than that of initial smolts.
• 8.8. The results indicated that masu salmon smolts can modify their lipid metabolism to adapt to ambient salinity changes. The proportion of (n-3) PUFA particularly in polar lipids, or in osmoregulatory organs such as gut and gills, was seen to be critical in lipid types of freshwater- or sea-water-adapted fish.

     

不同养殖模式下三倍体虹鳟鱼肉品质差异的研究

以网箱(W)、工厂化循环水(G)和流水池塘(C)养殖4 kg左右的三倍体虹鳟为研究对象, 通过检测表观、肉质、气味及营养价值相关111个品质指标来评价不同养殖模式下三倍体虹鳟鱼肉品质的差异。结果表明, 在3种养殖模式下三倍体虹鳟鱼肉品质存在明显差异。其中, 网箱养殖三倍体虹鳟鱼肉色调角、硬度、内聚性、弹性、咀嚼性、汁液流失率和失水率均显著高于其他养殖模式(P<0.05), 而挥发性气味物质中1-庚醇、庚醛、辛醛、壬醛和气味活度总值显著低于其他养殖模式(P<0.05); 工厂化循环水养殖三倍体虹鳟肥满度和鱼肉的红色值、色度值、盐溶性蛋白含量、总脂肪酸含量和n-3脂肪酸含量显著高于其他养殖模式(P<0.05); 流水池塘养殖三倍体虹鳟肥满度、鱼肉的黄色值、色度值、水分、脂肪含量、n-3脂肪酸含量和多不饱和脂肪酸含量最低(P<0.05), 出肉率、黏附性、肌糖原含量及挥发性风味物质中1-辛烯-3-醇、2,3-辛二酮、戊醛、庚醛、辛醛、(E)-2-癸烯醛和气味活度总值最高(P<0.05)。总之, 三种养殖模式养殖的三倍体虹鳟品质各具特色: 网箱养殖三倍体虹鳟鱼肉质地坚实富有弹性, 挥发性风味物质含量较低; 工厂化循环水养殖三倍体虹鳟具有较红的肉色并富含不饱和脂肪酸; 流水池塘养殖三倍体虹鳟形体优美且出肉率相对较高, 挥发性风味物质含量丰富。     

Dietary n-3 polyunsaturated fatty acids modify fatty acid composition in hepatic and abdominal adipose tissue of sucrose-induced obese rats

The fatty acid profile of hepatocytes and adipocytes is determined by the composition of the dietary lipids. It remains unclear which fatty acid components contribute to the development or reduction of insulin resistance. The present work examined the fatty acid composition of both tissues in sucrose-induced obese rats receiving fish oil to determine whether the effect of dietary (n-3) polyunsaturated fatty acids (PUFAs) on the reversion of metabolic syndrome in these rats is associated to changes in the fatty acid composition of hepatocyte and adipocyte membrane lipids. Animals with metabolic syndrome were divided into a corn–canola oil diet group and a fish oil diet group, and tissues fatty acids composition were analyzed after 6 weeks of dietary treatment. Fatty acid profiles of the total membrane lipids were modified by the fatty acid composition of the diets fed to rats. N-3 PUFAs levels in animals receiving the fish oil diet plus sucrose in drinking water were significantly higher than in animals under corn–canola oil diets. It is concluded that in sucrose-induced obese rats, consumption of dietary fish oil had beneficial effects on the metabolic syndrome and that such effects would be conditioned by the changes in the n-3 PUFAs composition in hepatic and adipose tissues because they alter membrane properties and modify the type of substrates available for the production of active lipid metabolites acting on insulin resistance and obesity.     

Incorporation of [3H]Arachidonic and [14C]Eicosapentaenoic Acids into Glycerophospholipids and Their Metabolism via Lipoxygenases in Isolated Brain Cells from Rainbow Trout Oncorhaynchus mykaiss

The incorporation of [3H]arachidonate [( 3H]AA) and [14C]eicosapentaenoate [( 14C]EPA) into glycerophospholipids was studied in isolated brain cells from rainbow trout, a teleost fish whose lipids are rich in (n-3) polyunsaturated fatty acids (PUFAs). EPA was incorporated into total lipid to a greater extent than AA, but the incorporation of both PUFAs into total glycerophospholipids was almost identical. The incorporation of both AA and EPA was greatest into phosphatidylethanolamine (PE). However, when expressed per milligram of individual phosphoglycerides, both AA and EPA were preferentially incorporated into phosphatidylinositol (PI), the preference being significantly greater with AA. On the same basis, significantly more EPA than AA was incorporated into phosphatidylcholine (PC). When double-labelled cells were challenged with calcium ionophore A23187, the 3H and 14C released from the cells closely paralleled each other, peaking at 10 min after addition of ionophore. The 12-monohydroxylated derivative was the pre-dominant lipoxygenase product from both AA and EPA with a rank order of 12-hydroxyeicosatetraenoic acid (12-HETE) greater than leukotriene B4 (LTB4) greater than 5-HETE greater than 15-HETE for the AA products and 12-hydroxyeicosapentaenoic acid (12-HEPE) greater than 5-HEPE greater than LTB5 greater than 15 HEPE for EPA products. The 3H/14C (dpm/dpm) ratios in the glycerophospholipids, total released radioactivity, and the lipoxygenase products suggested that PC rather than PI was the likely source of eicosanoid precursors in trout brain cells.     

The effects of dietary (n-3) fatty acid supplementation on lipid dynamics and composition in rat lymphocytes and liver microsomes

Rats were fed diets devoid of (n-3) fatty acids (olive oil supplementation) or high in (n-3) fatty acids (fish oil supplementation) for a period of 10 days. In spleen lymphocytes and liver microsomes derived from animals fed fish oil diets, relatively high levels of (n-3) eicosapentaenoic (20:5), docosapentaenoic (22:5) and docosahexaenoic acids (22:6) were obtained compared to minimal levels when fed the olive oil diet. When the average lipid motional properties were examined by measuring the fluorescence anisotropy of diphenylhexatriene, no significant different was found between intact liver microsomes from animals fed the two diets. However, when lipid motion was examined in vesicles of phosphatidylcholine, isolated from the microsomes from fish oil fed animals (21.4% (n-3) fatty acids), the fluorescence anisotropy was significantly less than the corresponding phosphatidylcholine from olive oil fed animals (5.6% (n-3) fatty acids), indicating a more disordered or fluid bilayer in the presence of higher levels of (n-3) fatty acids. Phosphatidylethanolamine (n-3) fatty acids were also elevated after fish oil supplementation (41.3% of total fatty acids), compared to the level after olive oil supplementation (21.4%). The major effect of the fish oil supplementation was a replacement of (n-6) arachidonic acid by the (n-3) fatty acids and when this was 'modeled', using liposomes of synthetic lipids, 1-palmitoyl-2-arachidonyl(n-6) or docosahexaenoyl(n-3)-phosphatidylcholine, significant differences in lipid motional properties were found, with the docosahexaenoate conferring a more disordered or fluid lipid environment. Thus it appears that although lipid order/fluidity can be significantly decreased by increases in the highly unsaturated (n-3) fatty acid levels, alterations in membrane domain organization and/or phospholipid molecular species composition effectively compensated for the changes, at least as far as average lipid motional properties in the intact membranes was concerned.     

Polyunsaturated fatty acid metabolism in fish cells: differential metabolism of (n-3) and (n-6) series acids by cultured cells originating from a freshwater teleost fish and from a marine teleost fish

1. The incorporation and metabolism of (n-3) and (n-6) polyunsaturated fatty acids (PUFA) supplemented to growing cultures were studied in rainbow trout (RTG-2) and turbot (TF) cell lines. 2. A fatty acid concentration of 20 microM considerably altered the fatty acid composition of the cells without affecting lipid class composition or the appearance of cytoplasmic lipid droplets. 3. Both cell lines exhibited considerable delta 6 desaturase activities. 4. Whereas delta 5 desaturase activity was expressed in RTG-2 cells, delta 4 desaturase activity was absent and, conversely, delta 4 desaturase activity was expressed in TF cells, but there was an apparent deficiency in the C18 to C20 elongase multi-enzyme complex. 5. The delta 6 desaturase activity in both cell lines showed little preference between 18:2(n-6) and 18:3(n-3) but the delta 5 desaturase activity of RTG-2 cells and the delta 4 desaturase activity of TF cells showed a preference for (n-3)PUFA. 6. Two fish oil concentrates were assessed for their ability to generate fatty acid compositions in the cell lines more closely resembling those of intact fish tissues.     

Seasonal changes of fatty acid composition and thermotropic behavior of polar lipids from marine macrophytes

Major glyco- and phospholipids as well as betaine lipid 1,2-diacylglycero-O-4'-(N,N,N-tri-methyl)-homoserine (DGTS) were isolated from five species of marine macrophytes harvested in the Sea of Japan in summer and winter at seawater temperatures of 20-23 and 3 degrees C, respectively. GC and DSC analysis of lipids revealed a common increase of ratio between n-3 and n-6 polyunsaturated fatty acids (PUFAs) of polar lipids from summer to winter despite their chemotaxonomically different fatty acid (FA) composition. Especially, high level of different n-3 PUFAs was observed in galactolipids in winter. However, the rise in FA unsaturation did not result in the lowering of peak maximum temperature of phase transition of photosynthetic lipids (glycolipids and phosphatidylglycerol (PG)) in contrast to non-photosynthetic ones [phosphatidylcholine (PC) and phosphatidylethanolamine (PE)]. Different thermotropic behavior of these lipid groups was accompanied by higher content of n-6 PUFAs from the sum of n-6 and n-3 PUFAs in PC and PE compared with glycolipids and PG in both seasons. Seasonal changes of DSC transitions and FA composition of DGTS studied for the first time were similar to PC and PE. Thermograms of all polar lipids were characterized by complex profiles and located in a wide temperature range between -130 and 80 degrees C, while the most evident phase separation occurred in PGs in both seasons. Polarizing microscopy combined with DSC has shown that the liquid crystal - isotropic melt transitions of polar lipids from marine macrophytes began from 10 to 30 degrees C mostly, which can cause the thermal sensitivity of plants to superoptimal temperatures in their environment.     

The fatty acid composition of oophagous tadpoles (Chirixalus eiffingeri) fed conspecific or chicken egg yolk

We compared the lipid content and fatty acid composition of (1) the egg yolk of three anuran species (Chirixalus eiffingeri, Rhacophorus moltrechti and Buergeria robustus) and chicken eggs; and (2) C. eiffingeri tadpoles fed conspecific eggs or chicken egg yolk. Anuran and chicken egg yolk contained more non-polar than polar lipids but the proportions varied among species. Chicken egg yolk contained low amounts of 22:5n-3 in the polar lipid fraction, and B. robustus eggs did not contain any n-3 or n-6 non-polar lipids. The specific variation of lipid contents and fatty acid composition may relate to the maternal diet and/or breeding biology. In C. eiffingeri tadpoles that fed chicken yolk or frog egg yolk, the dominant components of polar and non-polar lipids were 16:0, 18:0, 18:1, and 18:2n-6, or 20:4n-6 fatty acids. C. eiffingeri eggs contained more n-3 fatty acids (e.g. 18:3n-3 and 20:5n-3) than chicken egg yolk, and tadpoles fed conspecific eggs contained more of these fatty acids than tadpoles fed chicken egg yolk. The compositional differences in the fatty acids between C. eiffingeri tadpoles that fed frog egg or chicken egg yolk are the reflection of the variation in the dietary sources. Our results suggest a direct incorporation of fatty acids into the body without or minimal modification, which provide an important insight into the physiological aspects of cannibalism.     

Effects of selenium deficiency on fatty acid metabolism in rats fed fish oil-enriched diets.

The hepatic fatty acid metabolism was investigated in rats stressed by selenium deficiency and enhanced fish oil intake. Changes in the composition of lipids, peroxides, and fatty acids were studied in the liver of rats fed either a Sedeficient (8 microg Se/kg) or a Se-adequate (300 microg Se/kg) diet, both rich in n-3 fatty acid-containing fish oil (100 g/kg diet) and vitamin E (146 mg alpha-tocopherol/kg diet). The two diets were identical except for their Se content. Se deficiency led to a decrease in hair coat density and quality as well as to changes in liver lipids, individual lipid fractions and phospholipid fatty acid composition of the liver. The low Se status did reduce total and reduced glutathione in the liver but did not affect the hepatic malondialdehyde level. In liver phospholipids (PL), Se deficiency significantly reduced levels of palmitic acid [16:0], fatty acids of the n-3 series such as DHA [22:6 n-3], and other long-chain polyunsaturates C-20-C-22, but increased n-6 fatty acids such as linoleic acid (LA) [18:2 n-6]. Thus, the conversion of LA to arachidonic acid was reduced and the ratio of n-6/n-3 fatty acids was increased. As in liver PL, an increase in the n-6/n-3 ratio was also observed in the mucosal total fatty acids of the small intestine. These results suggest that in rats with adequate vitamin E and enhanced fish oil intake, Se deficiency affects the lipid concentration and fatty acid composition in the liver. The changes may be related to the decreased levels of selenoenzymes with antioxidative functions. Possible effects of Se on absorption, storage and desaturation of fatty acids were also discussed.     

Nonspecific immune response of rainbow trout (Oncorhynchus mykiss Walbaum) in relation to different status of vitamin E and highly unsaturated fatty acids

This study was designed to examine the effects of dietary vitamin E (VE) on modulation of immune responses when supplied with two levels of n-3 highly unsaturated fatty acids (n-3 HUFA) in rainbow trout, Oncorhynchus mykiss. Six semipurified diets were prepared containing three levels of dietary VE (0, 100 or 1000 mg alpha-tocopheryl acetate kg(-1) diet) and n-3 HUFA either at 20 or 48% of dietary lipid provided from fish oil or docosahexaenoic acid (DHA) concentrated fish oil respectively. The diets were fed to rainbow trout (100 g initial mean weight) for 15 weeks. The VE, vitamin C (VC) content in plasma and tissues and the nonspecific immune responses, both humoral (alternative complement activity, total immunoglobulin) and cellular (phagocytosis, nonspecific cytotoxicity) were examined. VE contents in the kidney reflected the dietary input but were lower in fish fed 48% n-3 HUFA diets, and could have impaired some of immune responses compared to fish fed 20% n-3 HUFA. VC contents in kidney followed the same pattern as VE. Both humoral and cellular immune functions deteriorated in fish fed VE deficient diets whereas improvement in most of the parameters corresponded to its supplementation. However, the higher dose of dietary VE did not substantially enhance the responses assayed compared to the 100 mg dose. Besides clearly indicating the role of VE in maintaining the immune functions in fish in relation to dietary n-3 HUFA, this study has revealed that optimum health benefits could be achieved when VE is maintained slightly above the levels generally recommended for normal growth.     

Effects of n-3 polyunsaturated dietary supplementation on the reproductive capacity of male turkeys

To measure the effects of dietary n-3 polyunsaturated fatty acid (PUFA) supplementation on the reproductive capacity of adult male turkeys in industrial flocks, the males of 22 commercial farms were fed either a standard diet or a fish oil diet enriched in n-3 PUFAs. The fatty acid composition of the spermatozoa and reproductive performance were measured throughout the reproductive period. The fish oil diet very effectively increased the percentage of n-3 fatty acids (FA) (22:5n-3 and 22:6n-3) in spermatozoa and correspondingly decreased the percentage of n-6 PUFAs (20:4-6 and 22:4n-6): the n-3/n-6 ratio in spermatozoa fatty acids were 0.04-0.07 with the standard diet and 0.32-0.4 with the fish oil diet. These changes did not affect the spermatozoa content of n-9 PUFAs, particularly of 22:3n-9 which is abundant in turkey spermatozoa (9-12% of the total fatty acids). The supplementation was effective in the middle as at the end of the reproductive period. The reproductive capacity of males was modified by the diet and the positive effect of the n-3 supplemented diet increased with age (increase in hatching rates of nearly 2 points at 48-58 weeks for males fed fish oil diet). These results indicate that an increase in the dietary ratio of n-3/n-6 PUFAs is valuable to sustain the reproductive capacity of male turkeys especially when they are getting older.     

Fatty acid composition of individual polar lipid classes from marine macrophytes

Major glycolipids [monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol (SQDG)) and phospholipids (phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylglycerol (PG)] as well as betaine lipid 1,2-diacylglycero-O-4'-(N,N,N-tri-methyl)-homoserine (DGTS) were isolated from Anfeltia tobuchiensis (Rhodophyta), Laminaria japonica, Sargassum pallidum (Phaeophyta), Ulva fenestrata (Chlorophyta) and Zostera marina (Embriophyta), harvested in the Sea of Japan. GC analysis of their fatty acid (FA) composition revealed that the n-6 polyunsaturated FAs (PUFAs) shared the most part of the sum of n-6 and n-3 PUFAs in PC and PE compared with glycolipids and PG. In algae, it was related to the prevalence of 20:4n-6 over 20:5n-3 in non-photosynthetic lipids. Percentage of n-6 PUFAs as well as the sum of n-3 and n-6 PUFAs decreased in the following sequence: PC-->PE-->PG. The saturation increased in the lines of MGDG-->DGDG-->SQDG and PC-->PE-->PG. PG was close to SQDG by the level of saturation. Distribution of C(18) and C(20) PUFAs in polar lipids depended on taxonomic position of macrophytes. Balance between C(18) and C(20) PUFAs was preferably shifted to the side of C(20) PUFAs in PC and PE that was observed in contrast to glycolipids and PG from L. japonica containing both series of FAs. The set of major FAs of polar lipid classes can essentially differ from each other and from total lipids of macrophytes. For example, MGDG was found to accumulate characteristic fatty acids 16:4n-3, 16:3n-3, 18:3n-6 and 18:4n-3, 20:3n-6 in U. fenestrata, Z. marina, L. japonica and S. pallidum, respectively.     

Lipid classes and fatty acid composition of rotifers (Brachionus plicatilis) fed two algal diets

Rotifers (Brachionus plicatilis), maintained on baker's yeast, were fed for 24h upon two algal diets, Isochrysis galbana (diet A) and Isochrysis galbana + Nannochloropsis gaditana (diet B). (These algal diets were selected for their potential use as essential fatty acid (EFA) boosters, taking into account the requirements of fish larvae). The effect of these algal diets on total lipid content, lipid classes and fatty acid composition was studied. The total lipid content increased after feeding upon both diets but no significant differences were found between the two types. Neutral lipid and polar lipid contents increased and a positive correlation was observed between the neutral lipids content of rotifers and that of the food supplied. However, the content of polar lipids in rotifers did not depend upon that of the diet. The increase in neutral lipid content was found to be higher in rotifers fed upon diet B, compared to diet A which increased the phospholipid content. Non-enriched rotifers contained only small amounts of polyenoic fatty acids, i.e. 18:3n-6, 18:3n-3, 20:4n-6, 20:5n-3 and 22:6n-3, the contents of which increased significantly by feeding both diets. The EFA composition (20:4n-6, 20:5n-3 and 22:6n-3) of neutral lipids and phopholipids in rotifers reflected the EFA composition of each diet. Diet B-fed rotifers had the highest content in 20:4n-6 and 20:5n-3, whereas rotifers fed diet A and the highest 22:6n-3 content. The mixed diet I. galbana + N. gaditana enhanced substantially the composition of lipid classes i.e. neutral lipids and of n-3 PUFA of rotifers in comparison with Isochrysis or yeast diets.     

Incorporation and modification of dietary fatty acids in gill polar lipids by two bivalve species Crassostrea gigas and Ruditapes philippinarum

Two bivalve species Crassostrea gigas and Ruditapes philippinarum were fed eight weeks with three mono-specific algae diets: T-Isochrysis galbana, Tetraselmis suecica, Chaetoceros calcitrans, selected on the basis of their polyunsaturated fatty acid (PUFA) composition. The incorporation and the modification of dietary fatty acids in C. gigas and R. philippinarum gill lipids were analysed and compared. Essential PUFA (20:4n-6, 20:5n-3 and 22:6n-3) and non-methylene interrupted PUFAs (known to be synthesised from monounsaturated precursors) contents of gill polar lipid of both species were greatly influenced by the dietary conditioning. Interestingly, oysters and clams responded differentially to the mono-specific diets. Oysters maintained higher 20:5n-3 level and higher 22:2j/22:i and n-7/n-9 ratio in gill polar lipids than clams. To better discriminate dietary and species influences on the fatty acid composition, a Principal Component Analysis followed by a MANOVA on the two most explicative components was performed. These statistical analyses showed that difference in fatty acid compositions attributable to species were just as significant as the diet inputs. The differences of gill fatty acid compositions between oysters and clams are speculated to result of an intrinsic species characteristic and perhaps of a group characteristic: Fillibranch vs. Eulamellibranch.     

Three-Year Breeding Cycle of Rainbow Trout (Oncorhynchus mykiss) Fed a Plant-Based Diet,Totally Free of Marine Resources: Consequences for Reproduction,Fatty Acid Composition and Progeny Survival

Terrestrial plant resources are increasingly used as substitutes for fish meal and fish oil in fish feed in order to reduce the reliance of aquaculture on marine fishery resources. Although many studies have been conducted to assess the effects of such nutritional transition, no whole breeding cycles of fish fed diets free from marine resources has been reported to date. We therefore studied the reproductive performance of trout after a complete cycle of breeding while consuming a diet totally devoid of marine ingredients and thus of n-3 long chain polyunsaturated fatty acids (n-3 LC-PUFAs) that play a major role in the formation of ova. Two groups of female rainbow trout were fed from first feeding either a commercial diet (C, marine and plant ingredients), or a 100% plant-based diet (V, blend of plant proteins and vegetable oils). Livers, viscera, carcasses and ova were sampled at spawning and analyzed for lipids and fatty acids. Although the V-diet was devoid of n-3 LC-PUFAs, significant amounts of EPA and DHA were found in livers and ova, demonstrating efficient bioconversion of linolenic acid and selective orientation towards the ova. Some ova were fertilized to assess the reproductive performance and offspring survival. We observed for the first time that trout fed a 100% plant-based diet over a 3-year breeding cycle were able to produce ova and viable alevins, although the ova were smaller. The survival of offspring from V-fed females was lower (-22%) at first spawning, but not at the second. Our study showed that, in addition to being able to grow on a plant-based diet, rainbow trout reared entirely on such a diet can successfully produce ova in which neo-synthesized n-3 LC-PUFAs are accumulated, leading to viable offspring. However, further adjustment of the feed formula is still needed to optimize reproductive performance.     

Fatty acid composition and lipid peroxidation of soft-shelled turtle, Pelodiscus sinensis, fed different dietary lipid sources

Juvenile soft-shelled turtles (Pelodiscus sinensis) were fed 7 diets containing 8% of lard, soybean oil, olive oil, menhaden fish oil, or mixtures of 1 to 1 ratio of fish oil and lard, soybean oil, olive oil for 10 weeks. Growth and muscle proximate compositions of the turtles were not affected by different dietary treatments (p>0.05). Fatty acid profiles in muscle polar lipids, muscle non-polar lipids, and liver polar lipids reflected the fatty acid composition of dietary lipid source. Turtles fed diets containing fish oil generally contained significantly higher (p<0.05) proportion of highly unsaturated fatty acids (HUFA) in both polar and non-polar lipids of muscle and polar fraction of liver lipids than those fed other oils. Non-polar fraction of liver lipids from all groups of turtles contained less than 1% of HUFA. All turtles contained relatively high proportions of oleic acid in their lipids regardless of the dietary lipid source. Further, lipid peroxidation in both muscle tissue and liver microsomes of turtles fed fish oil as the sole lipid source was greater (p<0.05) than those fed fish oil-free diets. Turtles fed olive oil as the sole lipid source had the lowest lipid peroxidation rate among all dietary groups. The results indicate that dietary n-3 HUFA may not be crucial for optimal growth of soft-shelled turtles although they may be used for metabolic purpose. Further, high level of dietary HUFA not only increases the HUFA content in turtle tissues, but also enhances the susceptibility of these tissues to lipid peroxidation.