Identification of key nutrients for gonadal development by comparative analysis of proximate composition and fatty/amino acid profile in tissues and eggs of Chinese sturgeon (Acipenser sinensis Gray, 1835)

The present study was conducted to characterize the proximate composition and fatty/amino acid profile in muscle, liver and gonads obtained from farmed male and female Chinese sturgeon (Acipenser sinensis) with gonad development at stage II, and to discern the key nutrients for gonads by comparing the nutrients between tissues and between fish at different gonad stages. Chinese sturgeon were reared in an outdoor circular cement pool at temperatures ranging from 8°C to 26°C, and fed with 70% artificial diets and 30% frozen forage fish at a feeding rate of 0.2%–1.5% body weight according to the water temperature. Three male and three female A. sinensis were sampled for analyses. Results showed that the lipid content in gonads was significantly higher than in other tissues in both males and females (p < .05). The protein content in male and female gonads was significantly lower than that in the muscle (p < .05). Total content of mono‐unsaturated fatty acids (MUFA) in females was significantly higher than in males (p < .05), while the total content of n‐6 PUFA in females was significantly lower than in males (p < .05). Palmitic acid (C16:0) and oleic acid (C18:1n9) were the major saturated fatty acid (SFA) and MUFA, respectively, in both females and males. The contents of C18:2n6, C20:4n6 (ARA), C18:3n3 and C22:6n3 (DHA) in male gonads were significantly higher than in females (p < .05). The contents of ARA, EPA and DHA in gonads were lower, possibly playing a pivotal role in gonad development. Comparing the nutrients of ovaries in broodstocks at stages III and IV and the eggs at stage IV, the present study suggests that the lipid and fatty acid profile in fish is vital to the gonad development and that proper improvement of lipid nutrition in the broodstock diet to provide sufficient energy and essential fatty acids would be beneficial for the gonad development of Acipenser sinensis.     

Comparison of fatty acid profiles of spawning and non-spawning Pacific herring, Clupea harengus pallasi

Crude lipid and fatty acid composition from liver, intestine, roe, milt and flesh of spawning and non-spawning Pacific herring (Clupea harengus pallasi) were examined to determine the relative effects of spawning on the nutritional value of herring. Depletion of lipid due to spawning condition was significant (P < 0.01) in all organ tissues and flesh of spawning herring. The lipid content ranged from an average of 1.9 to 3.4% (wet weight basis) in different organ tissues of spawning herring, to 10.5 to 16% in non-spawning fish. The fatty acid profile exhibited many differences in the relative distribution of individual fatty acids among organ tissues and between the two fish groups. Oleic acid (C18:1n-9), a major monounsaturated fatty acid (MUFA) found in all tissue lipids, decreased significantly (P < 0.01) in spawning fish. The two monoenes, C20:1n-9 and C22:1n-11, occurred at high concentrations in the flesh but at only minor proportion in the digestive organs and gonads. Spawning herring also had significantly (P < 0.01) higher polyunsaturated fatty acids (PUFA) content in the organ tissues, particularly in the milt and ovary, with docosahexaenoic acid (C22:6n-3, DHA) having the greatest proportion. Among the n-6 fatty acids, only C18:2n-6 and C20:4n-6 occurred at notable amounts and were present in higher proportions in spawning fish. We concluded that although relatively higher n-3 fatty acid content was found in the organ lipids of spawning herring, they are not an energy-dense prey food source due to the fact that both flesh and gonads contain a very low amount of lipid.     

Comparison of body composition and sensory quality of wild and farmed whitefish (Coregonus macrophthalmus [Nüsslin, 1882])

This study compared the body composition (fillet yield, chemical composition and lipid quality of fillets) and sensory quality of captured wild (by gillnet in August 2011) with experimentally raised farmed (reared in concrete flow‐through raceways, average water temperature 10 ± 3°C) whitefish, Coregonus macrophthalmus, from Lake Constance. The study was conducted in 2011 using 28 wild and 24 farmed market‐sized fish of approximately equal total lengths (25.1 ± 1.21 and 25.6 ± 1.28 cm). Farmed female Coregonus macrophthalmus exhibited a 3.3% lower fillet yield resulting from larger gonads and a shallower body shape. The protein contents of farmed and wild fillets were equal (17.5% vs. 17.4%), but farmed fish fillets contained less moisture (76.1% vs.77.4%), less ash (1.2% vs. 1.6%), and more lipid (5.1% vs. 4.1%) than wild‐caught specimens. Levels of monounsaturated fatty acids (MUFA) were higher in farmed fish (42.0 vs. 31.0 g/100 g lipid), as well as the levels of polyunsaturated fatty acids (PUFA; 26.0 vs. 19.7 g/100 g lipid), in particular 22:6n?3 (docosahexaenoic acid, DHA; 7.3 vs. 2.1 g/100 g lipid). Conversely, wild fish fillets contained significantly more 20:4n?6 (arachidonic acid, AA; 1.6 vs. 0.4 g/100 g lipid) and 20:5n?3 (eicosapentaenoic acid, EPA; 4.1 vs. 3.2 g/100 g lipid). Sensory evaluation of odour, colour, texture and flavour by an experienced six‐person panel revealed a significant preference for the colour (79% vs. 21%) of farmed fish fillets. In conclusion, farmed whitefish can be strong competitors to wild whitefish in terms of product quality, with higher levels of healthy fatty acids and a more attractive fillet colour. Farmed Coregonus macrophthalmus thus represents a promising and pragmatic approach, compensating for the current capture decline in the whitefish fisheries of Lake Constance.     

Lipid composition of three geographical sources of brine shrimp nauplii (Artemia sp.)

• 1.1. Percentage of triacylglycerols (TG), free fatty acids (FFA) and phospholipids (PL) in the total lipids, the fatty acid composition of each of these lipid classes, and the percentage of cholesterol were determined by gas chromatography in three geographical sources (San Francisco Bay, SFB; Chinese, CH; Colombian, COL) of brine shrim (Artemia sp.) nauplii.
• 2.2. There were no significant differences among sources of brine shrimp in total lipids, TG or FFA with means for all sources of 17.8, 65.8 and 10.9%, respectively. Percentage of phospholipid was significantly higher in SFB and CH sources of brine shrimp, 25.1 and 26.5%, respectively, than in COL 18.3%.
• 3.3. Marked differences in percentages of 18:3 (n-3) (linolenic acid) and 20:5 (n-3) (eicosapentaenoic acid or EPA) were found among brine shrimp sources, and concentration of these two fatty acids were usually inversely related within sources. The CH source contained higher concentrations of EPA ( > 9.0%) than the COL and SFB sources (< 5.0%) in all three lipid classes analyzed. No 22:6 (n-3) (docosahexaenoic acid or DHA) was found in any brine shrimp source.
• 4.4. Fatty acid compositions of the TG and PL were similar and did not differ among sources of brine shrimp, while the FFA had a lower percentage of polyunsaturated fatty acids, but was similar among sources of brine shrimp.
• 5.5. Differences in n-3 fatty acid composition indicated a difference in nutritional quality among sources of brine shrimp for feeding larval fish.

     

Effect of diet on fatty acid compositions in Sciaenops ocellatus

The role of dietary polyunsaturated fatty acids (PUFAs) on the fatty acid composition of juvenile red drum Sciaenops ocellatus was investigated. Individuals (n = 435) were fed three natural diets (Gulf menhaden Brevoortia patronus, brown shrimp Farfantapenaeus aztecus and Atlantic brief squid Lolliguncula brevis) that had significantly different proximate composition, energy density and PUFA compositions for 40 days. Diets were characterized as containing: high lipid, high protein, high energy and low PUFA (fish‐based), low lipid, low protein, low energy, moderate PUFA (shrimp‐based), and low lipid, high protein, moderate energy and high PUFA levels (squid‐based), respectively. Specimens were collected at days 0, 5, 10, 20 and 40 to evaluate rate of dietary fatty acid composition in tissues. Two‐source mixing models were used to calculate dietary fatty acid accumulation in consumer tissues. Results indicated that juvenile red drum incorporated an average of 35% dietary PUFAs after 5 days. Although relative biomass and dietary proximate composition had an effect upon the dietary fatty acid contribution, red drum averaged 91% incorporation of the five most prevalent PUFAs [18 : 2 (n ? 6), 20 : 4 (n ? 6), 20 : 5 (n ? 3), 22 : 5 (n ? 3) and 22 : 6 (n ? 3)] across all diets after 40 days. Growth varied as a function of diet and rates were higher for individuals fed the squid diet than those fed shrimp or fish diets primarily due to increased levels of protein and PUFAs [including 22 : 6 (n ? 3); 25·8%] in the diet. Red drum fed squid exhibited the greatest increase in average dietary fatty acid contribution by day 5, a trend that continued for the duration of the experiment. Since PUFA composition in red drum was significantly influenced by diet in as few as 5 days and almost completely incorporated into body tissues after 40 days, results from this study support the premise that fatty acids (especially PUFAs) are promising dietary indicators and may be useful for future studies examining trophic relationships of estuarine and marine fishes.     

美洲鳗鲡幼鱼饲料中鱼油的适宜添加水平研究

为研究饲料中鱼油添加水平对美洲鳗鲡(Anguilla rostrata)幼鱼生长性能、消化酶、体成分及肝脏脂肪代谢的影响, 以确定美洲鳗鲡幼鱼饲料中鱼油的适宜添加水平, 选用初始体重(8.34±0.12) g的美洲鳗鲡幼鱼800尾, 随机分成5组, 每组4个重复, 每个重复40尾; 分别投喂添加0(对照组)、3%(FO3组)、6%(FO6组)、9%(FO9组)和12%(FO12组)鱼油的试验饲料, 试验期56d。结果表明, 饲料中添加鱼油显著影响美洲鳗鲡幼鱼生长性能, FO6组美洲鳗鲡幼鱼的增重率、投饵率和饲料效率显著高于其他处理组(P<0.05)。与对照组相比, 鱼油添加组美洲鳗鲡幼鱼肠道脂肪酶活性显著提高(P<0.05), 蛋白酶和淀粉酶活性显著降低(P<0.05); FO6组、FO9组和FO12组全鱼粗脂肪含量显著提高(P<0.05), 全鱼粗蛋白质含量在FO12组显著降低(P<0.05), 全鱼水分和灰分含量无显著变化(P>0.05); FO9组和FO12组脂肪酸合成酶活性显著降低(P<0.05), FO12组脂蛋白酯酶和肝脂酶活性显著升高(P<0.05)。综上, 饲料中添加适宜鱼油水平可以提高美洲鳗鲡幼鱼的生长性能, 调节肠道脂肪酶活性、全鱼粗脂肪含量和肝脏脂肪代谢酶水平或活性; 美洲鳗鲡幼鱼获得最佳增重率和饲料效率时, 饲料中鱼油添加水平推荐为6.43%—6.78%。     

鲜活饵料和人工配合饲料对鳜肌肉营养成分和质构特性的影响

研究以饲喂鲜活饵料为对照组,比较分析人工饲料对鳜(Siniperca chuatsi)常规营养成分、氨基酸组成及营养价值评价、脂肪酸组成和肌肉质构特性的影响。实验结果显示,摄食人工饲料组鳜肌肉蛋白质水平与鲜活饵料组无显著性差异(P>0.05),粗脂肪含量显著较高(P<0.05)。在两种饲喂模式下鳜肌肉中氨基酸评分(AAS)、必需氨基酸指数(EAAI)、化学评分(CS)和F值均无显著差异(P>0.05),但第一限制性氨基酸均为蛋氨酸+半胱氨酸(Met+Cys),该结果可为鳜人工饲料配方优化提供指导。人工饲料组鳜肌肉中饱和脂肪酸(SFA)、单不饱和脂肪酸(MUFA)和多不饱和脂肪酸(PUFA)含量均极显著高(P<0.01),其中C20﹕5(EPA)和C22﹕6(DHA)含量极显著高于鲜活饵料组,表明人工饲料可通过营养素的均衡配比以提供更优质的脂肪酸营养。人工饲料组鳜肌肉硬度、咀嚼性、胶黏性及回复性均极显著高于鲜活饵料组(P<0.01),而黏性极显著低于鲜活饵料组(P<0.01),表明人工饲料饲喂提升了鳜的肌肉质构特性。综上所述,相比于鲜活饵料组,人工饲料...     

Effects of resveratrol and genistein on growth,nutrient utilization and fatty acid composition of rainbow trout

The replacement of the finite and costly resource fish oil is an important task for aquaculture nutrition. A promising approach could be the use of plant bioactives that may have the potential to influence the metabolism and the synthesis of n-3 long chain polyunsaturated fatty acids, especially EPA (20:5n-3) and DHA (22:6n-3). In this study, the two phytochemicals resveratrol (RV) and genistein (G) were investigated for their effects on fish growth, nutrient utilization and body nutrient composition alongside their effects on whole body fatty acid (FA) composition. In a feeding trial lasting 8 weeks, rainbow trout (initial BW: 81.4±0.5 g) were held in a recirculating aquaculture system and fed six experimental diets with varying fish oil levels as plain variants or supplemented with 0.3% of dry matter (DM) of either RV or G. The six diets were as follows: diet F4 had 4% DM fish oil, diet F0 had 0% DM fish oil, diets F4+RV, F4+G, F0+RV and F0+G were equal to the diets F4 and F0, respectively, and supplemented with the phytochemicals RV and G. The feeding of the F0+RV diet resulted in reduced feed intake, growth rate and slightly reduced whole body lipid levels. At the same time, the amount of polyunsaturated FA and the n-3/n-6 ratio were significantly increased in whole body homogenates of rainbow trout fed diet F0+RV in comparison to the F0 control. The feeding of the F0+G diet led to reduced feed intake, slightly increased protein utilization but did not significantly affect the whole body FA composition. Overall, feeding the fish oil-free diet supplemented with the phytochemicals resulted in more pronounced effects on fish performance and FA composition than the single factors per se (dietary fish oil level or phytochemical). Present data indicate that G might not be of profitable use for trout nutrition. In terms of FA composition, RV could be a potentially useful complement for fish oil. However, the impairment of growth and performance parameters as observed in the present study discourages its use in trout diets.     

Nutrient digestibility and intestinal enzyme activity of Clarias batrachus (Linn.) juveniles fed on dried fish and chicken viscera incorporated diets

A feeding trial was conducted for 56 days to study the effect of replacement of fish meal by dried fish and chicken viscera, and a combination of oil cakes, in the diet of Clarias batrachus juveniles. The nutritional values of these by-products were studied through a digestibility experiment. No significant difference in nutrient digestibility was observed in different diets. Even 19.59% lipid in the diet of catfish did not affect the nutrient digestibility. Both amylolytic and proteolytic enzymes in the intestine of juveniles were studied. A decreased protease activity due to replacement of animal protein by plant protein and a decreased (P < 0.01) aspartate aminotransferase (ASAT) activity could be observed after inclusion of 22% of dried fish viscera in the diet of the catfish. Though body lipid content increased in fish fed a high level of lipid, fat-free body composition did not vary among the fish fed on different diets.     

Mixture design as a potential tool in modeling the effect of light wavelength on Dunaliella salina cultivation: an alternative solution to increase microalgae lipid productivity for biodiesel production

Abstract

For a feasible microalgae biodiesel, increasing lipid productivity is a key parameter. An important cultivation parameter is light wavelength (λ). It can affect microalgal growth, lipid yield, and fatty acid composition. In the current study, the mixture design was used as an alternative to model the influence of the λ on the Dunaliella salina lipid productivity. The illumination was considered to be the mixture of different λ (the light colors blue, red, and green). All experiments were performed with and without sodium acetate (4?g/L), as carbon source, allowing the identification of the impact of the cultivation regimen (autotrophic or mixotrophic). Without sodium acetate, the highest lipid productivity was obtained using blue and red light. The use of mixotrophic cultivations significantly enhanced the results. The optimum obtained result was mixotrophic cultivation under 65% blue and 35% green light, resulting in biomass productivity of 105.06 mgL^?1day^?1, a lipid productivity of 53.47 mgL^?1day^?1, and lipid content of 50.89%. The main fatty acids of the oil obtained in this cultivation were oleic acid (36.52%) and palmitic acid (18.31%).     

Dietary protein source affects lipid metabolism in the European seabass (Dicentrarchus labrax)

The study was undertaken to evaluate the effects of dietary protein sources on lipogenesis and fat deposition in a marine teleost, the European seabass (Dicentrarchus labrax). Four isonitrogenous (crude protein (CP, Nx6.25), 44% DM) and isoenergetic (22-23 kJ/g DM) diets were formulated to contain one of the following as the major protein source: fish meal (FM), one of two soy protein concentrates (SPC) and corn gluten meal (CGM). Apparent digestibility coefficients of the diets and raw ingredients, as well as soluble nitrogen (ammonia and urea) and phosphorus excretion were measured. Growth rates of seabass fed plant protein-based diets were significantly lower than those fed fish meal based diet. The protein utilisation was strongly correlated to the dietary essential amino acids index. Measurements of N excretion (ammonia and urea nitrogen) confirmed these data. Daily fat gain at the whole body level ranged between 1.1 to 1.7 g/kg BW, with the highest values being recorded in fish fed the fish meal based diet. Levels of plasma triglycerides and cholesterol were lower in fish fed soy protein diets than in those fed the diet solely based on fish meal. Soy protein rich diets decreased the activities of selected hepatic lipogenic enzymes (glucose 6-phosphate dehydrogenase, malic enzyme, ATP-citrate lysase, acetylcoenzyme A carboxylase and fatty acid synthetase). Highest lipogenic enzyme activities where found in fish fed the fish meal diet, except for fatty acid synthetase which was increased in seabass fed the corn-gluten meal based diets. Overall data suggest that dietary protein sources affects fat deposition and the lipogenic potential in European seabass.     

Effects of varying levels of dietary vitamin E (α‐tocopherol) on growth performance,proximate and fatty acid composition of juvenile silver pomfret (Pampus argenteus Euphrasen, 1788)

This study investigated the effects of elevated dietary levels of vitamin E (α‐tocopherol) on growth performance, proximate composition and fatty acid profiles of juvenile silver pomfret, Pampus argenteus. Three semi‐purified experimental diets were formulated to contain 49% protein and 16% lipid. High docosahexaenoic acid (DHA) tuna oil was added to the diets to supplement DHA. A graded level of vitamin E (0‐, 50‐, and 100 mg kg^?1) was added to experimental diets 1 to 3, respectively. Analyzed vit. E levels were 155.2, 195.3 and 236.4 mg kg^?1 in diets 1, 2 and 3, respectively. The experiment was conducted for 12 weeks with juvenile silver pomfret (29.6 ± 7.6 g) using a flow‐through system consisting of nine 1‐m³ tanks. Each treatment had three replicates and fish were stocked at the rate of 20 m^?3. Growth performance and feed utilization parameters of fish fed diets 2 and 3 were significantly (P < 0.05) higher than in fish fed diet 1, but the parameters in diets 2 and 3 did not differ significantly (P > 0.05). Although whole body protein levels were not influenced by the dietary vit. E levels, whole body lipid in fish fed diet 2 was significantly higher than in fish fed the other diets. The whole body vit. E levels in fish fed diet 2 (22.6 mg kg^?1) and diet 3 (24.1 mg kg^?1) were significantly (P < 0.05) higher than in those fed diet 1 (18.2 mg kg^?1). Whole body total saturated fatty acids were significantly lower, and DHA levels higher in fish fed diets 2 and 3 than those fed diet 1. The results of the present study suggest that increasing dietary supplementation of vit. E in high lipid diets enhances the growth performance of fish and that a dietary level of 196 mg kg^?1 vit. E is suitable for the growth of silver pomfret.     

Growth,biochemical, fatty acid composition,and mRNA levels of hepatic enzymes in genetically improved farmed tilapia (GIFT,Oreochromis niloticus) (Linnaeus, 1758) at different stocking densities

Investigated were the effects of stocking density on juvenile growth performance, serum biochemistry, fatty acid composition, and mRNA levels of enzymes involved in lipid metabolism in genetically improved farmed tilapia (GIFT), Oreochromis niloticus. Juvenile fish (n = 900) were distributed into 15 tanks at five initial stocking densities (75, 150, 225, 300, and 375 g/m³ per 800‐L tank, represented as D1–D5, respectively). Temperature was maintained at 28 ± 0.3°C, and water flow rate into the tanks was about 8 L/min. The fish accepted floating pelleted feed (crude protein 28%, crude lipid 6%, and gross energy 149.2 KJ/g diet). The feed amount offered was 4%–8% of body weight. At the end of the 60‐day experiment, the final stocking densities were 1,454.18, 2,010.60, 2,913.13, 3,819.73, and 4,380.80 g/m³, respectively. Growth and body mass coefficient of variation were significantly affected (p < .05). No differences in feed conversion rate or survival were found (p > .05). Muscle lipid contents decreased with stocking density from D1 to D5. Serum total protein and cholesterol levels were not affected by the stocking density but the D5 group produced the highest serum cortisol and lactate levels and the lowest glucose levels compared to those of the other groups. Lower muscle saturated fatty acid and n?3 polyunsaturated fatty acid contents were observed in the D4 group than in the other groups, whereas the reverse was found in the n?6 polyunsaturated fatty acid content. Hepatic glucose 6‐phosphate dehydrogenase, fatty acid synthetase, hormone‐sensitive triglyceride lipase, and lipoprotein lipase mRNA levels were significantly upregulated in response to a high density. These data suggest that the GIFT adapted to high‐density conditions by altering the composition of muscle fatty acid and stimulating lipid metabolic enzymes. These mechanisms may help fish respond to high stocking density stress in intensive aquaculture systems.     

Lipids in the daubed shanny (Teleostei: Leptoclinus maculatus) in Svalbard waters

The daubed shanny, Leptoclinus maculatus, is a common fish species in Arctic and North Atlantic waters and has an important role in high-latitude ecosystems as a link between lower trophic levels and many fish, marine mammal and seabird species. Its biology and ecology have, however, remained largely unstudied. The primary aim of this study was to increase the knowledge about the daubed shanny by analysing total lipids, lipid-classes and the fatty acid composition of liver, muscle and female gonads in adults from the high Arctic archipelago of Svalbard. In female gonads, the triacylglycerols and wax esters in addition to cholesterol esters were dominant among the stored lipids. Triacylglycerols dominated in the liver, whereas structural lipids, such as phospholipids and cholesterols, were the most important lipids in muscles. Phosphatidylcholine and phosphatidylethanolamine were major phospholipids in all organs studied. The fatty acid spectrum of the investigated organs was characterized by a high amount of monounsaturated fatty acids, particularly in the liver. Polyunsaturated fatty acids, particularly 22:6(n-3) and 20:4(n-6), were prevalent in muscle tissues. The lipid and fatty acid spectra in the organs during this period of life are tightly connected with the activation of the liver metabolism and the storage of lipids in the developed female gonads. Lipid accumulation and distribution in gonads are transferred to optimal development of embryos and larvae in Arctic waters.     

The reproduction strategy of oyster ostrea edulis L. from the biochemical point of view

• 1.1. Influence of the biochemical composition of food (four species of micro-algae and one mixture) on the biochemical composition of gonads and larvae of O. edulis (total protein, lipid, carbohydrate, ash content, neutral and polar lipid class composition, amino acid composition and fatty acid composition of total, neutral and polar lipids) and the size of newly released larvae have been investigated.
• 2.2. Precentage of total lipids and triacylglycerols in gonads depends on that in algae (r = 0.52 and 0.69 accordingly).
• 3.3. Gonads rich in lipids had a higher level of triacylglycerols, phospholipids, polar lipids and a lower value of the ratio phosphatidylethanolamine/phosphatidylcholine (PE/PC) than gonads with a low lipid content.
• 4.4. Amino acid composition of gonads depends on that of food, in this case, essential acids are preferentially accumulated (Asp acid, Ser, Ala, Cys, Tyr and Pro) and two non-essential (Thr and Lys).
• 5.5. Fatty acid composition of total lipids of gonads was rather stable; except for the two essential acids 20:523 and 22:6w3, their percentage depends on that of food r = 0.65 and 0.65 accordingly). Fatty acid composition of neutral lipids was more diverse (in number and degree of variety) as compared to polar lipids.
• 6.6. Larvae released from oysters with gonads rich in lipids had a higher percentage of lipids, triacylglycerols, size and a lower ash percentage and value of ratio PE/PC, as compared to larvae from gonads with low lipid content. Total lipid and triacylglycerol contents in gonads correlate rather well with those in larvae (r = 0.77 and 0.47 accordingly).
• 7.7. Phospholipid class composition of larvae strongly depends on that of gonads. All the correlations are high and positive in character (except for phosphatidylinositol).
• 8.8. Amino acid composition of larvae depends on that of gonads and, as in the case with gonads, the same essential acids are accumulated in the first place.
• 9.9. Fatty acid composition of total lipids of newly released larvae was rather stable and independent on that of gonads except for total polyunsaturated acids (r = 0.70) and 20:5w3 (r = 0.65). Fatty acid composition of neutral lipids was lesser diverse (in number and degree of variation) as compared to polar lipids.

     

Jellyfish as Prey: Frequency of Predation and Selective Foraging of Boops boops (Vertebrata,Actinopterygii) on the Mauve Stinger Pelagia noctiluca (Cnidaria,Scyphozoa)

In recent years, jellyfish blooms have attracted considerable scientific interest for their potential impacts on human activities and ecosystem functioning, with much attention paid to jellyfish as predators and to gelatinous biomass as a carbon sink. Other than qualitative data and observations, few studies have quantified direct predation of fish on jellyfish to clarify whether they may represent a seasonally abundant food source. Here we estimate predation frequency by the commercially valuable Mediterranean bogue, Boops boops on the mauve stinger jellyfish, Pelagia noctiluca, in the Strait of Messina (NE Sicily). A total of 1054 jellyfish were sampled throughout one year to quantify predation by B. boops from bite marks on partially eaten jellyfish and energy density of the jellyfish. Predation by B. boops in summer was almost twice that in winter, and they selectively fed according to medusa gender and body part. Calorimetric analysis and biochemical composition showed that female jellyfish gonads had significantly higher energy content than male gonads due to more lipids and that gonads had six-fold higher energy content than the somatic tissues due to higher lipid and protein concentrations. Energetically, jellyfish gonads represent a highly rewarding food source, largely available to B. boops throughout spring and summer. During the remainder of the year, when gonads were not very evident, fish predation switched towards less-selective foraging on the somatic gelatinous biomass. P. noctiluca, the most abundant jellyfish species in the Mediterranean Sea and a key planktonic predator, may represent not only a nuisance for human leisure activities and a source of mortality for fish eggs and larvae, but also an important resource for fish species of commercial value, such as B. boops.     

Effect of dietary conjugated linoleic acid (CLA) on lipid composition, metabolism and gene expression in Atlantic salmon (Salmo salar) tissues

Dietary conjugated linoleic acid (CLA) affects fat deposition and lipid metabolism in mammals, including livestock. To determine CLA effects in Atlantic salmon (Salmo salar), a major farmed fish species, fish were fed for 12 weeks on diets containing fish oil or fish oil with 2% and 4% CLA supplementation. Fatty acid composition of the tissues showed deposition of CLA with accumulation being 2 to 3 fold higher in muscle than in liver. CLA had no effect on feed conversion efficiency or growth of the fish but there was a decreased lipid content and increased protein content after 4% CLA feeding. Thus, the protein:lipid ratio in whole fish was increased in fish fed 4% CLA and triacylglycerol in liver was decreased. Liver beta-oxidation was increased whilst both red muscle beta-oxidation capacity and CPT1 activity was decreased by dietary CLA. Liver highly unsaturated fatty acid (HUFA) biosynthetic capacity was increased and the relative proportion of liver HUFA was marginally increased in salmon fed CLA. CLA had no effect on fatty acid Delta6 desaturase mRNA expression, but fatty acid elongase mRNA was increased in liver and intestine. In addition, the relative compositions of unsaturated and monounsaturated fatty acids changed after CLA feeding. CLA had no effect on PPARalpha or PPARgamma expression in liver or intestine, although PPARbeta2A expression was reduced in liver at 4% CLA feeding. CLA did not affect hepatic malic enzyme activity. Thus, overall, the effect of dietary CLA was to increase beta-oxidation in liver, to reduce levels of total body lipid and liver triacylglycerol, and to affect liver fatty acid composition, with increased elongase expression and HUFA biosynthetic capacity.     

Formation and degradation of lipid bodies found in the riboflavin-producing fungus Ashbya gossypii

Microdroplets in the hyphae of Ashbya gossypii were found to become stained by Nile red. Purification of the stainable substance showed that the yellow fluorescent bodies consisted of triacylglycerol. During growth on glucose as the carbon source 8%–12% of the mycelial dry weight was found to be neutral lipid. When glucose declined in the medium, the content decreased to 3%–4% and the respiration quotient shifted to 0.6 indicating a reserve function of the fat. The fatty acid composition of the storage lipid was found to be strongly influenced by the carbon source. Mycelia cultivated on glucose contained 5% linoleic acid and 20% palmitoleic acid in their neutral fat while linoleic acid made up 54% and palmitoleic acid was not detectable (< 0.1%) in soybean-oil-grown mycelia. When plant oil was given as the sole carbon source, the fatty acid composition of the storage lipid showed a high similarity to the fed fat. ¹⁴C-labelled free oleic acid added to a culture growing on soybean oil was immediately incorporated into the fungal lipid. A pulse of 0.9 g/l free palmitoleic acid, fed during growth on olive oil, increased the content of this particular fatty acid in the fungal triacylglycerol from 0.8% to 9.6%. In addition, a liberation of free fatty acid and diacylglyceride was found in the culture supernatant when pure triolein was given as the sole carbon source. Obviously, the fungus cleaved the lipid serving as the carbon source extracellularly and used the liberated fatty acids for its storage lipid formation.This paper is dedicated to Prof. Dr. F. Wagner on the occasion of his 65th birthday     

饲料中不同蛋白、脂肪水平对春鲤生长、饲料利用和体成分的影响

研究旨在探讨洱海土著鱼类春鲤(Cyprinus longipectoralis)(初始体重0.55 g)对蛋白质和脂肪的需求量。实验采用3×3双因子设计,蛋白水平为33%、39%和45%,脂肪水平为5%、8%和11%,共9组等能饲料。实验在水温为(28±2)℃的室内微流水系统中进行,为期56d。实验结果表明:随着蛋白水平的提高,摄食率显著降低(P<0.05),饲料效率、能量沉积率、鱼体水分和脂肪含量显著升高(P<0.05),但特定生长率、蛋白质效率、蛋白沉积率、鱼体灰分含量和能值均无显著变化(P>0.05)。随着脂肪水平的提高,特定生长率、蛋白沉积率和鱼体蛋白含量显著下降,鱼体脂肪含量显著上升(P<0.05),而摄食率、饲料效率、能量沉积率、鱼体水分和灰分含量以及能值则无明显变化(P>0.05)。通过折线回归分析得出,当饲料中蛋脂比为7.30时,春鲤有最大的特定生长率。研究结果表明,春鲤饲料中适宜的蛋白和脂肪水平分别为33%—34%和4%—5%。     

Cold storage effects on flesh quality of rainbow trout Oncorhynchus mykiss (Walbaum, 1792) fed diets containing different vegetable oils

The intention of this experiment was to assess the effects of different sources of dietary lipid on the fatty acid composition of the fillet and liver and the flesh quality traits of rainbow trout (Oncorhynchus mykiss) after a 70‐day feeding period. Four iso‐nitrogenous (approx. 51% crude protein) and iso‐lipidic (approx. 14% crude lipid) experimental diets were formulated. The control diet contained only fish oil (FO) as the primary lipid source. In the other three dietary treatments, fish oil was replaced by 100% (LO30/SO35/SFO35) and 70% (FO30/LO35/SO35 or FO30/SO35/SFO35) sesame oil (SO), linseed oil (LO), or sunflower oil (SFO). Triplicate groups of 40 rainbow trout (~46 g) held under similar culture conditions were hand‐fed daily to apparent satiation for 70 days. At the end of the feeding trials, no difference in growth performance among experimental groups was noted (P > 0.05). There were some differences in the proximate composition of fish fillets (P < 0.05): the eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels were highest in fish fed the control diet (P < 0.05); and EPA and DHA levels in fish fed the FO30/LO35/SO35 diet were closest to the control diet (P < 0.05). In contrast, fish fed the diet containing 100% plant oils (LO30/SO35/SFO35) had the highest level of total n‐6 fatty acids in the fillet and liver. In a 12‐day refrigerated storage at 1°C the thiobarbituric acid (TBA), trimethylamin nitrogen (TMA‐N) and pH values gradually increased in all dietary groups (P < 0.05). The chemical indicators of spoilage, TBA, TMA‐N, and pH values were within the limit of acceptability for human consumption.