Effect of varying dietary levels of ω6 polyunsaturated fatty acids during the early ontogeny of the sea scallop, Placopecten magellanicus

This study investigated the effects of selected microalgal diets on growth, survival and fatty acid composition of sea scallops, Placopecten magellanicus, from egg hatching to postlarvae. Scallops were offered Pavlova lutheri (MONO) and Pavlova sp. (strain CCMP 459, P459) in combination with Chaetoceros muelleri (CHGRA) and P459 alone. These diets exhibited varying proportions of ω6 docosapentaenoic acid (22:5ω6, DPA) which represented 8.9% of total fatty acids in P459 compared to 5.4% in P459-CHGRA and only 0.5% in MONO-CHGRA. For experiment I, larvae were fed three diets (MONO-CHGRA, P459-CHGRA or P459 alone) for 35 days after fertilization. For experiment II, larvae were fed P459-CHGRA for 21 days and split among the three diets until 39 days post-fertilization. For experiment III, 4-day-old larvae were exposed to P459-CHGRA until they become postlarvae. MONO-CHGRA failed to produce pediveligers when fed to early veligers but yielded competent larvae when fed to late veligers. This may be related to the low ω6 DPA content of this diet. High accumulation of DPA by early veligers suggests a nutritional requirement for this fatty acid. Unialgal P459 supported lower pediveliger production and lower growth rate than other diets containing CHGRA. This may be the effect of higher levels of energetic substrates in CHGRA-containing diets. Finally, P459-CHGRA yielded the best survival and growth rate during the whole larval period. All three experiments showed marked arachidonic acid (20:4ω6, AA) accumulation in early veligers (4 to 21 days) and in pediveligers (32 to 43 days). Accumulation of AA during metamorphosis might reflect stimulation of immune functions due to pathogen infection and degradation of larval organs or the role of AA in cell signalling processes associated with tissue reorganization. Early veligers markedly accumulate DPA likely in response to low docosahexaenoic acid (22:6ω3, DHA) concentrations in the three tested diets. The potential role and effect of DPA as a substitute for DHA is discussed.     

Ammonia toxicity as a criterion for the evaluation of larval quality in the prawn Macrobrachium rosenbergii

The feasibility of a short-term ammonia toxicity test as an evaluation criterion for larval quality was assessed in three trials. In each one, Macrobrachium rosenbergii larvae originating from the same spawn were nutritionally differentiated in two groups by feeding them either a nutrient-rich (Artemia nauplii enriched for 24 h with n-3 highly unsaturated fatty acids (HUFA) and ascorbic acid (AA)) or a nutrient-poor diet (Artemia nauplii starved for 24 h). Throughout their development, larvae from both treatments were exposed during 24 h to six concentrations of total ammonia (NH₄⁺+NH₃) and a control (no ammonia added). Based on mortality rates, the median lethal concentration for 50% of the population (LC₅₀) was estimated. As expected from earlier work, larvae fed the optimal diet presented higher n-3 HUFA and AA contents as well as higher growth and metamorphosis rates. From the moment the effect of diet quality was analytically detectable in the tissues of the larvae, the ammonia test was able to distinguish both groups of larvae. Differences in ammonia tolerance were observed as early as larval stage 4 and remained evident throughout larval development. The short-term ammonia toxicity test proved to be a valuable, sensitive and reproducible criterion for the establishment of larval quality.     

Fatty acid compositions of gonadal material and diets of the sea urchin, Psammechinus miliaris: trophic and nutritional implications

The fatty acid compositions of gonadal material was examined for the sea urchin Psammechinus miliaris (Gmelin) held in aquaria and fed either salmon feed pellets or the macroalga, Laminaria saccharina for 18 months. Gonadal material was also examined from P. miliaris collected from four field sites, including commercial scallop lines encrusted with the mussel, Mytilus edulis, sea cages stocked with Atlantic salmon Salmo salar and two intertidal sea-loch sites, characterised by either a fine mud or a macroalgal substratum. The fatty acid compositions of known and potential dietary material was examined. The proportions of certain fatty acids in the gonads of P. miliaris were significantly affected by diet type and location. Docosahexaenoic acid (DHA) 22:6 n-3 was significantly higher in the gonads of the sea urchins fed salmon feed in aquaria and collected from the salmon cages and scallop lines than in the gonads of the sea urchins fed L. saccharina in aquaria and collected from the intertidal sea loch sites. The salmon feed and the mussel tissue also contained a high proportion of this fatty acid. Stearidonic acid 18:4 n-3 and arachidonic acid 20:4 n-6, however, were found in significantly higher proportions than DHA in the gonads of the sea urchins fed L. saccharina and collected from the two intertidal sea-loch sites. L. saccharina was also found to contain high proportions of stearidonic and arachidonic acid. The gonads of the sea urchins collected from the intertidal site, characterised by a mud substratum, and from the scallop lines were found to contain a lower 18:1 n-9/18:1 n-7 ratio and a higher proportion of branched and odd-chained fatty acids, signifying a high dietary bacterial input, than the sea urchins held in the aquaria and collected from the salmon cage. 20:2 and 22:2 non-methylene-interrupted dienoic fatty acids (NMIDs) were found in P. miliaris fed diets lacking these fatty acids suggesting de novo biosynthesis. These results, therefore, suggest that the proportions/ratios of certain fatty acids in the gonads of P. miliaris could be used to give an indication of the predominant diet type of this species in the wild.     

Effect of dietary polyunsaturated fatty acids on reproductive output and larval growth of bivalves

The pre-spawning condition of adult bivalves is influenced by quantity and quality of available food. For bivalves, the essential polyunsaturated fatty acids (PUFAs) eicosapentaenoic acid (EPA) 20:5(n-3) and docosahexaenoic acid (DHA) 22:6(n-3) are presumed to determine the nutritional value of algae. Macoma balthica kept on a broodstock diet supplemented with PUFAs spawned a larger number of eggs (average 22220) per female and larger sized eggs (106.7 μm) compared to adults kept on a diet without PUFA supplementation (962.5 eggs with average size 99.8 μm).Larvae of M. balthica from the same parental pool however did not profit from a diet where a part was replaced with PUFA spheres. Instead, larvae reared on Isochrysis sp. showed lower mortality and higher growth rates than larvae fed on the same algae supplemented with lipid spheres. Crassostrea gigas larvae showed no clear response to a PUFA supplemented diet.     

Effects of the levels of fatty acids and carbohydrates in a diet on the biosynthesis of fatty acids in larvae of the silkworm, Bombyx mori

The effects of varying levels of fatty acids and carbohydrates in the diet on fatty acid synthesis from glucose in the larvae of the silkworm, Bombyx mori, were investigated. Elevation of the level of dietary fatty acids resulted in the decrease of the rate of fatty acid synthesis in the larvae. The addition of palmitate, stearate, or oleate to a diet had an inhibitory effect on fatty acid synthesis. The prolonged feeding of larvae on a diet containing a high level of fatty acid intensified the depression of the synthesis. The inhibitory effect of dietary fatty acid was found in the presence of both high and low levels of dietary carbohydrates. On the other hand, the rate of fatty acid synthesis was greatly accelerated by increasing the level of sucrose in a diet but not by the addition of starch. Furthermore, the fatty acid composition of the larval tissue shows a marked difference between the two groups of larvae fed on a diet containing sucrose and on a diet containing potato starch. Palmitic and oleic acid contents of larval tissue were increased significantly on the sucrose diet.     

Energy vs. essential fatty acids: what do scallop larvae (Argopecten purpuratus) need most?

Larvae of the Chilean–Peruvian scallop Argopecten purpuratus were fed a Dunaliella tertiolecta diet (Dun-diet) supplemented with lipid emulsions, rich in 20:5n-3 (EmEPA), 22:6n-3 (EmDHA) or in saturated fatty acids (EmCOCO). A mixed algal diet of Isochrysis galbana (T-iso) and Chaetoceros neogracile served as a positive control (St-diet). Lipid supplementation to the Dun-diet improved the larval growth and increased the percentage of eyed larvae significantly, compared to the non-supplemented Dun-diet because of the extra energy supplied and not because of its fatty acid composition. No significant differences were observed between supplementation with EmEPA, EmDHA or EmCOCO. A mixture of 20% EmEPA+20% EmDHA (40% EmHUFA) was more efficient in raising the total lipid content in larvae than 40% EmCOCO. Both emulsions increased the triacylglycerol content in larvae compared to the non-supplemented Dun-diet. The best result, however, was obtained with the St-diet, probably because of a more suitable 18:2n-6/18:3n-3 ratio and a higher level of arachidonic acid. A positive relationship between the 18:2n-6/18:3n-3 ratio and the larval performance was found. No significant difference was observed in post-settlement larval size or percentage of metamorphosed larvae between the St-diet and the St-diet supplemented with 20% EmHUFA or 20% EmCOCO. The metamorphosed larvae had a constant DHA/EPA ratio of 3.7, independent from the diet, which suggested a metabolic control of the two fatty acids and a species-dependency of the ratio.     

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.     

Dietary lipid quality and mitochondrial membrane composition in trout: responses of membrane enzymes and oxidative capacities

To examine whether membrane fatty acid (FA) composition has a greater impact upon specific components of oxidative phosphorylation or on overall properties of muscle mitochondria, rainbow trout (Oncorhynchus mykiss) were fed two diets differing only in FA composition. Diet 1 was enriched in 18:1n-9 and 18:2n-6 while Diet 2 was enriched in 22:6n-3. The FA composition of mitochondrial phospholipids was strongly affected by diet. 22:6n-3 levels were twice as high (49 %) in mitochondrial phospholipids of fish fed Diet 2 than in those fed Diet 1. 18:2n-6 content of the phospholipids also followed the diets, whereas 18:1n-9 changed little. All n-6 FA, most notably 22:5n-6, were significantly higher in fish fed Diet 1. Nonetheless, total saturated FA, total monounsaturated FA and total polyunsaturated FA in mitochondrial phospholipids varied little. Despite a marked impact of diet on specific FA levels in mitochondrial phospholipids, only non-phosphorylating (state 4) rates were higher in fish fed Diet 2. Phosphorylating rates (state 3), oxygen consumption due to flux through the electron transport chain complexes as well as the corresponding spectrophotometric activities did not differ with diet. Body mass affected state 4 rates and cytochrome c oxidase and F ₀ F ₁ ATPase activities while complex I showed a diet-specific effect of body mass. Only the minor FA that were affected by body mass were correlated with functional properties. The regulated incorporation of dietary FA into phospholipids seems to allow fish to maintain critical membrane functions even when the lipid quality of their diets varies considerably, as is likely in their natural environment.     

Deficit of didocosahexaenoyl phospholipid in the eyes of larval sea bass fed an essential fatty acid deficient diet

Larval sea bass Dicentrarchus labrax of 27 days old were reared on Artemia enriched with Super Selco©, Tuna Orbital Oil or Yeast. The first diet is commonly used in mariculture for larval rearing, the second diet was designed to deliver an optimal docosahexaenoic acid (22: 6n-3) to eicosapentaenoic acid (20: 5n-3) ratio, and the third diet was deficient in docosahexaenoic acid (22: 6n-3). The eyes of these larvae were analysed after 28 days and the molecular species of the three main phospholipid classes, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) determined. Eyes from larvae fed Artemia enriched with yeast showed large decreases in molecular species containing 22: 6n-3 compared to those supplemented with tuna orbital oil, most notably in 16: 0/22: 6n-3 PC which fell from 10.6 to 0.4%, in 22: 6n-3/22: 6n-3 and 18: 1/22: 6n-3 PE which fell from 29.6 to 0.3% and from 10.8 to 1.1% respectively, and in 22: 6n-3/22: 6n-3 PS which fell from 34.3 to 1.7%. Molecular species containing all other fatty acids, and especially 20: 5n-3, were elevated in eyes from the yeast-supplemented fish. In larvae fed Artemia enriched with Super Selco, amounts of eye 22: 6n-3/22: 6n-3 phospholipid were slightly lower in all three phospholipid classes compared to eyes from the tuna orbital oil-supplemented larvae. There was also a trend of decreased saturated fatty acid/22: 6n-3 and monounsaturated fatty acid/22: 6n-3 molecular species in all classes from the Super Selco-supplemented fish, the deficits being made up with molecular species containing 20: 5n-3 and 22: 5n-3. These results are discussed in relation to larval viability with particular respect to visual function.     

Dietary low linolenic acid compared with docosahexaenoic acid alter synaptic plasma membrane phospholipid fatty acid composition and sodium-potassium ATPase kinetics in developing rats

The objective of this study was to investigate if maternal dietary 20:4n-6 arachidonic acid (AA) and 22:6n-3 compared with adequate or low levels of 18:3n-3 linolenic acid (LNA) increases synaptic plasma membrane (SPM) cholesterol and phospholipid content, phospholipid 20:4n-6 and 22:6n-3 content, and Na,K-ATPase kinetics in rat pups at two and five weeks of age. At parturition, Sprague-Dawley rats were fed semi-purified diets containing either AA + docosahexaenoic acid (DHA), adequate LNA (control; 18:2n-6 : 18:3n-3 ratio of 7.1 : 1) or low LNA (18:2n-6 : 18:3n-39 ratio of 835 : 1). During the first two weeks of life, the rat pups received only their dams' milk. After weaning, pups received the same diet as their respective dams to five weeks of age. No significant difference was observed among rat pups fed the diet treatments for SPM cholesterol or total and individual phospholipid content at two and five weeks of age. Fatty acid analysis revealed that maternal dietary AA + DHA, compared with feeding the dams the control diet or the low LNA diet, increased 20:4n-6 in phosphatidylserine and 22:6n-3 content of SPM phospholipids. Rats fed dietary AA + DHA or the control diet exhibited a significantly increased Vmax for SPM Na,K-ATPase. Diet treatment did not alter the Km (affinity) of SPM Na,K-ATPase in rat pups at two and five weeks of age. It is concluded that dietary AA + DHA does not alter SPM cholesterol and phospholipid content but increases the 22:6n-3 content of SPM phospholipids modulating activity of Na,K-ATPase.     

Does a large-scale continuous algal production system provide a stable supply of fatty acids to bivalve hatcheries?

The variation of fatty acid (FA) content and composition of the microalgal production (Isochrysis sp., Pavlova lutheri and Chaetoceros muelleri) in a continuous large-scale production system (500-L bags) used in hatcheries were analysed. The variation of the FAs was analysed in replicate bags over time for the different species. Total FA content (pg cell⁻¹) increased significantly (p < 0.05) in the P. lutheri and C. muelleri bags over time. The content of the essential FAs (arachidonic acid (ARA), eicosapentaenoic acid (EPA), n-6 docosapentaenoic acid (n-6 DPA) and docosahexaenoic acid (DHA)) increased over time in all of the species, except for DHA in Isochrysis sp. The content of EPA and ARA were highest in C. muelleri, whilst n-6 DPA and DHA were highest in Isochrysis sp. The FA composition in the C. muelleri bags showed large variability between bags at the beginning of the experiment, but decreased over time. In contrast, the FA composition of Isochrysis sp. and P. lutheri did not vary much over time, but larger variability was observed between the replicate bags. The results indicate that, even though the essential polyunsaturated FAs (PUFAs) varied between the different species, the total microalgal production secured a stable and increased supply of all the essential PUFAs to the scallop larvae and spat.     

Ingestion rates and dietary lipids affect growth and fatty acid composition of Dendraster excentricus larvae

This study investigated the effect of single and mixed algal diets on growth, fatty acid composition and ingestion rates for Dendraster excentricus larvae. Larvae were assigned to three single algal diet treatments Isochrysis galbana, Dunaliella tertiolecta or Rhodomonas sp. and four mixed algal diet treatments D. tertiolecta and Rhodomonas, I. galbana and D. tertiolecta, I. galbana and Rhodomonas, D. tertiolecta, Isochrysis galbana and Rhodomonas sp. Small amounts (0.36-0.6%) of stearic acid (18:0) were seen in the three algae used but a relatively large percentage (7-25%) of this SAFA was found in Dendraster larvae. The alga D. tertiolecta had the highest percentage (51.7%) of the short chain polyunsaturated fatty acid (PUFA) linolenic acid 18:3(n-3) and trace amounts (0.02-0.14%) of the long chain PUFAs eicosapentanoic (EPA, 20:5(n-3) and docosahexanoic acids (DHA, 22:6(n-3)). However, sand dollar larvae demonstrated the ability to elongate and desaturate shorter chain (18 carbon) polyunsaturated fatty acids (PUFA) to longer chain (20 carbon) n-3 PUFA. Thus high levels of 18:3(n-3) in D. tertiolecta led to high levels of EPA and low levels of 18:3(n-3) in Dendraster larvae fed this diet. Rhodomonas sp. had the highest percentage of stearidonic acid (18:4(n-3), 38.14%) and EPA (10.6%). Despite high levels of 18:4(n-3) in Rhodomonas sp. this acid was absent or found at very low levels in larvae fed this alga, or any combination of this alga. I. galbana had the highest percentage of DHA(14.3%) but was almost devoid of EPA (0.43%). Although Rhodomonas sp. and I. galbana had high levels of EPA and DHA sand dollar larvae did not incorporate higher levels of these long chain PUFAs into their lipids compared to those fed the alga D. tertiolecta. Dendraster larvae synthesized a number of 20 and 22 carbon non-methylene interrupted dienes (NMID), with levels increasing with larval stage. Higher ingestion rates were observed for Dendraster larvae fed single algal diets (Rhodomonas sp. or D. tertiolecta) and lower ingestion rates for those fed mixed algal diets. The highest ingestion rates were for 8-arm Dendraster larvae fed the large alga Rhodomonas sp. presented as a single algal diet. When fed a combination of three algae, selection of particles varied slightly depending on stage with 8-arm larvae ingesting slightly more of the larger algal cell in the mixture than 6-arm larvae. The present study suggests that regardless of the ratios given larvae might have an optimum ratio of different sized particles at which they can feed. The mixed algal diet of I. galbana and D. tertiolecta was the best algal diet leading to significantly larger larvae with high survival and development to metamorphosis. The single algal diets of Rhodomonas sp. or Dunaliella tertiolecta were the second and third best algal diets based on growth and survival to metamorphosis.     

Strong influences of larval diet history on subsequent post-settlement growth in the freshwater mollusc Dreissena polymorpha

A significant seasonal variation in size at settlement has been observed in newly settled larvae of Dreissena polymorpha in Lake Constance. Diet quality, which varies temporally and spatially in freshwater habitats, has been suggested as a significant factor influencing the life history and development of freshwater invertebrates. Accordingly, experiments were conducted with field-collected larvae to test the proposal that diet quality can determine planktonic larval growth rates, size at settlement and subsequent post-metamorphic growth rates. Larvae were fed one of two diets or starved. One diet was composed of cyanobacterial cells, which are deficient in polyunsaturated fatty acids (PUFAs) and the other was a mixed diet rich in PUFAs. Freshly metamorphosed animals from the starvation treatment had a carbon content per individual 70% lower than that of larvae fed the mixed diet. This apparent exhaustion of larval internal reserves resulted in a 50% reduction of the post-metamorphic growth rates. Growth was also reduced in animals previously fed the cyanobacterial diet. Hence, low food quantity or low food quality during the larval stage of D. polymorpha, lead to irreversible effects for post-metamorphic animals and are related to inferior competitive abilities.     

微颗粒饲料与冰冻桡足类对大黄鱼稚鱼生长、存活和体成分的影响(英文)

评估三种新开发的微颗粒饲料(Diet 1,Diet 2和Diet 3)、一种混合饲料(Diet 4:Diet 3和冰冻桡足类混合投喂)和冰冻桡足类(Diet 5)对25–60日龄大黄鱼稚鱼的饲喂效果。Diet 1组大黄鱼稚鱼的特定生长率(SGR,7.97%/d)和成活率(40.0%)最高,而Diet 5组稚鱼的SGR(4.15%/d)和成活率(20.4%)最低。Diet 4组稚鱼的成活率与Diet 1组差异不显著,但其SGR低于后者。从稚鱼的SGR和成活率看,三种微颗粒饲料中,Diet 1要优于Diet 2和Diet 3。各处理组中每桶稚鱼的生物量与SGR有相似的变化趋势。各微颗粒饲料组稚鱼的体蛋白含量差异不显著,低于Diet 4组,但高于Diet 5组。而微颗粒饲料组稚鱼的脂肪含量(10.6%–13.3%)均显著高于Diet 4组(7.6%)和Diet 5组(7.2%)。尽管冷冻桡足类中C20:4n–6(AA)的含量稍低于微颗粒饲料,但Diet 4和Diet 5组稚鱼的AA含量均显著高于微颗粒饲料组。Diet 4和Diet 5组稚鱼的C22:6n–3(DHA)分别高于其相应饲料中的含量。相反地,微颗粒饲料组稚鱼的C20:5n–3(EPA)低于微颗粒饲料中的含量。这些结果表明,Diet 4和Diet 5组稚鱼体内AA、DHA和EPA的沉积效率高于微颗粒饲料组。研究表明,大黄鱼稚鱼可用微颗粒饲料"断奶"。基于Diet 1优于Diet 2和Diet 3,可将其作为进一步研究的基础配方。此外,有必要对各处理组大黄鱼稚鱼消化酶和消化道的变化进行研究以综合评估微颗粒饲料的效果。     

Maternal dietary n-3 fatty acids alter immune cell fatty acid composition and leukotriene production in growing chicks

The effect of feeding different amounts of n-6 and n-3 fatty acids (FA) to hens on immune tissue FA composition and leukotriene production of hatched chicks was investigated. Hens were fed diets supplemented with either 3.0% sunflower oil (Diet I), 1.5% sunflower+1.5% fish oil (Diet II), or 3.0% fish oil (Diet III) for 46 days. The hatched chicks were fed a diet containing C18:3n-3, but devoid of longer chain n-6 and n-3 FA, for 21 days. Spleen docosahexaenoic acid (DHA) content was higher in chicks from hens fed Diet III (P<0.05). The bursa content of arachidonic acid was lower in chicks hatched from hens fed Diet III (P<0.05), and the ratio of n-6 to n-3 FA was significantly higher in bursa of chicks hatched to hens fed Diet I (P<0.05). Eicosapentaenoic acid (EPA) and DHA contents were higher in bursa of chicks hatched from hens fed Diet III (P<0.05). Thrombocytes from chicks hatched to hens fed Diet III produced the most leukotriene B(5) (LTB(5)). The ratio of LTB(5) to LTB(4) concentrations was also highest (P<0.05) in chicks hatched to hens fed Diet III. These results indicate that modulating maternal dietary n-6 and n-3 FA may alter leukotriene production in chicks, which could lead to less inflammatory-related disorders in poultry.     

EVALUATION OF MICRODIETS VERSUS FROZEN COPEPODSON GROWTH, SURVIVAL AND SELECTED CHEMICALCOMPOSITION OF LARGE YELLOW CROAKERPSEUDOSCIAENA CROCEA LARVAE

Three newly developed microdiets (MDs: Diet 1, Diet 2 and Diet 3), one co–feeding diet (Diet 4, combinedDiet 3 with frozen copepods) and frozen copepods (Diet 5) were tested for weaning large yellow croaker (Pseudosciaenacrocea) larvae from 25 to 60 days after hatching (DAH). The highest final specific growth rate (SGR, 7.97%/d) and sur-vival (40.0%) were observed in fish fed Diet 1, while those were the lowest in fish fed Diet 5 (4.15%/d and 20.4%, re-spectively). The survival of larvae fed Diet 4 showed no significant difference (P>0.05) from that of larvae fed Diet 1.However, SGR of larvae fed Diet 4 was significantly lower (P<0.05) than that of larvae fed Diet 1. Among the MDs,Diet 1 was proved to be superior to Diet 2 and Diet 3 for both SGR and survival. For all treatments, biomass in each tankwas observed a similar trend as SGR. Whole-body protein was not significantly different (P>0.05) among fish fed theMDs, which was lower than that of fish fed Diet 4, but higher than that of fish fed Diet 5. Fish fed the MDs had signifi-cantly higher (P<0.05) lipid deposition (10.6%—13.3%) than fish fed either Diet 4 (7.6%) or Diet 5 (7.2%). DietaryC20:4n-6 (AA) level was significantly lower (P<0.05) in Diet 5 than that in the MDs. However, the AA level was sig-nificantly higher (P<0.05) in fish fed either Diet 4 or Diet 5 than that in fish fed the MDs. The exceeded C22:6n-3 (DHA)levels in fish compared to their corresponding diets were found in those fed either Diet 4 or Diet 5. Inversely, C20:5n-3(EPA) and DHA levels decreased in fish fed the MDs relative to their proportions in MDs. These results showed that fishfed either Diet 4 or Diet 5 had higher efficiency of AA, DHA and EPA deposition than fish fed the MDs. This study sug-gested that large yellow croaker larvae could be successfully weaned by MD. Future research should be based on for-mula of Diet 1, since it was superior to Diet 2 and Diet 3. In addition, changes of digestive enzymes and digestive tractof large yellow croaker larvae fed different diets need to be investigated for an overall evaluation.     

Omega-3 fatty acid deficiency increases constitutive pro-inflammatory cytokine production in rats: Relationship with central serotonin turnover

Omega-3 (n-3) fatty acid deficiency, elevated inflammatory signaling, and central serotonin (5-HT) turnover have separately been implicated in the pathophysiology of major depressive disorder (MDD). In the present study we investigated the interrelationship between n-3 fatty acid status, pro-inflammatory signaling activity, and central 5-HT turnover in vivo. Rats were fed diets with or without the n-3 fatty acid precursor α-linolenic acid (ALA) during perinatal development (E0-P100), and a subset of rats fed the ALA− diet were switched to the ALA+ diet post-weaning (P21-P100, repletion). In adulthood (P100), plasma interleukin-6 (IL-6), tumor necrosis factor-alpha (TNFα), and C-reactive protein (CRP) levels were measured. Additionally, indices of liver n-6 fatty acid biosynthesis, erythrocyte fatty acid composition, and regional brain monoamine turnover were determined. Indices of liver delta-6 desaturase activity were up-regulated in n-3-deficient rats, and were associated with greater erythrocyte membrane arachidonic acid (AA, 20:4 n-6) composition. Plasma IL-6 (p=0.001), TNFα (p=0.02), and CRP (p=0.001) concentrations were significantly greater in n-3-deficient rats relative to controls. The 5-HIAA/5-HT ratio was significantly greater in frontal cortex, hypothalamus, and ventral striatum of n-3-deficient rats relative to controls. Changes in membrane n-3 and n-6 fatty acid composition, elevations in plasma IL-6 and TNFα, and increased central 5-HT turnover were all prevented by normalization of n-3 fatty acid status. Erythrocyte docosahexaenoic acid (DHA, 22:6 n-3) was inversely correlated, and AA and the AA/DHA and AA/eicosapentaenoic acid ratios were positively correlated, with plasma IL-6, TNFα, and CRP levels. Plasma IL-6 levels were positively correlated with 5-HIAA/5-HT ratios in all brain regions. These preclinical data provide evidence for a functional link between n-3 fatty acid deficiency, elevated peripheral inflammatory signaling, and increased central 5-HT turnover.     

Dietary omega-6 fatty acid lowering increases bioavailability of omega-3 polyunsaturated fatty acids in human plasma lipid pools

BackgroundDietary linoleic acid (LA, 18:2n-6) lowering in rats reduces n-6 polyunsaturated fatty acid (PUFA) plasma concentrations and increases n-3 PUFA (eicosapentaenoic (EPA) and docosahexaenoic acid (DHA)) concentrations.ObjectiveTo evaluate the extent to which 12 weeks of dietary n-6 PUFA lowering, with or without increased dietary n-3 PUFAs, alters unesterified and esterified plasma n-6 and n-3 PUFA concentrations in subjects with chronic headache.DesignSecondary analysis of a randomized trial. Subjects with chronic headache were randomized for 12 weeks to (1) average n-3, low n-6 (L6) diet; or (2) high n-3, low n-6 LA (H3–L6) diet. Esterified and unesterified plasma fatty acids were quantified at baseline (0 weeks) and after 12 weeks on a diet.ResultsCompared to baseline, the L6 diet reduced esterified plasma LA and increased esterified n-3 PUFA concentrations (nmol/ml), but did not significantly change plasma arachidonic acid (AA, 20:4n-6) concentration. In addition, unesterified EPA concentration was increased significantly among unesterified fatty acids. The H3–L6 diet decreased esterified LA and AA concentrations, and produced more marked increases in esterified and unesterified n-3 PUFA concentrations.ConclusionDietary n-6 PUFA lowering for 12 weeks significantly reduces LA and increases n-3 PUFA concentrations in plasma, without altering plasma AA concentration. A concurrent increase in dietary n-3 PUFAs for 12 weeks further increases n-3 PUFA plasma concentrations and reduces AA.     

The essential dietary fatty acid requirement of the tufted apple budmoth, Platynota idaeusalis

The tufted apple budmoth, Platynota idaeusalis (Walker), was reared non-axenically for two successive generations on a casein-based semisynthetic diet. The qualitative essential fatty acid requirement for growth, development and normal pupal-adult ecdysis was studied using the non-axenic casein-based semisynthetic diets with and without various 99% pure fatty acids. Linoleic or linolenic acids caused accelerated larval development; linoleic, linolenic and arachidonic acids showed similar activity in body weight gain and survival to pupal-adult ecdysis. Linoleic or linolenic acids were active in alleviating wing deformities; arachidonic acid was partially active in alleviating wing deformities at the one dietary concentration evaluated. Activity of arachidonic acid as an essential fatty acid for P. idaeusalis is unique among insects, except for mosquitoes. The essential fatty acid deficiency syndrome of the adult, resulting from the larvae feeding on fat-deficient diets, was greatly reduced when larvae were fed on a diet adequate in essential fatty acid during either their early or late development.     

Biological and biochemical characteristics for quality control of Harmonia axyridis (Pallas) (Coleoptera, Coccinellidae) reared on a liver-based diet

Biological and biochemical parameters of a flightless strain of Harmonia axyridis, fed on a pork liver-based artificial diet and on Ephestia kuehniella eggs as controls, were compared. The diet-grown larvae showed a significantly longer developmental time and a lower adult emergence rate compared to control larvae. The weights of the newly emerged adults were significantly higher for adults fed E. kuehniella eggs during their larval stages than fed the artificial diet. In contrast, larval food source had no effect on the duration of the pre-oviposition period or adult longevity. For adults fed on E. kuehniella eggs as larvae, a significantly longer pre-oviposition period, lower daily weight gain and fecundity were found for the diet-fed females compared to those fed on E. kuehniella eggs throughout the life span. The adult food source had no significant effect on longevity and fertility. Lower amino acid and fatty acid contents (in particular C16:1 and C18:3n-3) were found for the prepupae and newly emerged females obtained from diet-reared larvae compared to controls. Deficiencies in fatty acids C16:1 and C18:3n-3 were also observed in females obtained from E. kuehniella egg-reared larvae and fed on diet from adult emergence. The analyses of the foods showed deficiencies in artificial diet, especially for some amino and fatty acids. The results suggest a non-optimal composition of the artificial diet and some possibilities for its improvement. However, this polyphagous predator could be reared from first instar larvae to fully reproductive adults on a pork liver-based artificial diet.