Seasonal dynamics of fatty acids in the lipids of water moss <Emphasis Type="Italic">Fontinalis antipyretica</Emphasis> from the Yenisei River

Identification of lipid fatty acids (FA) and studying of their seasonal dynamics in water moss Fontinalis antipyretica from the Yenisei River were carried out by means of gas chromatography-mass spectrometry. FA composition of water moss was notable for a relatively low level of saturated acids and predominance of polyunsaturated acids (PUFA) with double bonds (accounting for more than 30% of total FA) and polyunsaturated acids with double and triple bonds (acetylenic acids, accounting for more than 40% of total FA). Among PUFA, α- and γ-linolenic (18:3ω3 and 18:3ω6), arachidonic (20:4ω6), and eicosapentaenoic (20:5ω3) acids prevailed. Relative content of PUFA from ω3-family was the greatest in spring, and the level of PUFA from ω6-group was essentially the same throughout all the seasons. In the biomass of water moss, we identified seven acetylenic acids; among them octadeca-9,12-dien-6-ynoic (6a,9,12-18:3), octadeca-9,12,15-trien-6-ynoic (6a,9,12,15-18:4), and eicosa-11,14-dien-8-ynoic (8a,11,14-20:3) acids were predominant. For the first time, in the lipids of water moss we identified an acetylenic eicosa-11,14,17-trien-8-ynoic acid (8a,11,14,15-20:4). Relative content of acetylenic acids in the total FA was great throughout the entire period of investigation with the peak accumulation in summer. Owing to a steadily high level in the biomass of water moss and the lack of other producers of these acids in the ecosystem, acetylenic FA are highly specific biochemical markers useful for the investigation of trophic interactions between higher aquatic plants and zoobenthos.     

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.     

Comparison of seasonal dynamics of the essential PUFA contents in benthic invertebrates and grayling Thymallus arcticus in the Yenisei river

Seasonal dynamics of contents of essential polyunsaturated fatty acids (PUFA) in dominant groups of benthic invertebrates: gammarids (Gammaridae, Amphipoda), oligochaetes (Oligochaeta), chironomid larvae (Chironomidae, Diptera) and caddisfly larvae (Trichoptera), and dominant benthivorous fish, Siberian grayling Thymallus arcticus, have been studied in ecosystem of the large Siberian river. During the year of the study most benthic invertebrate taxa showed significant variations in the contents of both C-18 and long chain C-20–22 PUFAs. In contrast, the fish, which consumed the zoobenthos, had no significant seasonal variations in long chain PUFAs' contents. Thereby, the fish, as organisms of relatively higher evolution level than invertebrates, was supposed to have more strict metabolic control of long chain PUFAs' contents. Evidence was obtained that the studied fish species, grayling, may be capable to convert dietary EPA into DHA.     

Seasonal distribution and fatty acid composition of littoral microalgae in the Yenisei River

We studied fatty acid (FA) composition of littoral microalgae in the fast-flowing oligotrophic river, the Yenisei, Siberia, monthly for 3 years. Seasonal dynamics of species composition had similar patterns in all the studied years. In springs, a pronounced dominance of filamentous green algae occurred, in summer and autumn diatoms were abundant, and in late autumn and winter epilithic biofilms consisted primarily of cyanobacteria and detritus. In general, FA composition of the algal periphytic community was dominated by 16:0, 16:1ω7, 20:5ω3, 14:0, and 18:3ω3 throughout the studied period. Several groups of FAs, which had peculiar seasonal dynamics, were differentiated by statistical analysis based on a method of correlation graphs. The seasonal changes in FA composition could be partly explained by the seasonal succession of species composition of the community. Besides, we found that populations of both diatom and green algae grown in summer at a higher water temperature were lower in polyunsaturated fatty acids than those in spring, at a lower temperature. Hence, we suppose that the regular seasonal dynamics of FA composition of the studied littoral microalgae was driven both by changes in species composition and by temperature adaptations of the algal populations. The highest content of essential polyunsaturated FAs, eicosapentaenoic and docosahexaenoic acids, in the spring “psychrophilic” populations of diatoms could make them of the higher nutritive value for zoobenthic primary consumers.     

Seasonal changes in the content of lipids,fatty acids,and pigments in brown alga <Emphasis Type="Italic">Costaria costata</Emphasis>

We compared the content of total lipids, particular lipid classes, fatty acids (FAs), and pigments in the brown alga Costaria costata [Turn.] Saund (Laminariaceae) in different seasons: during algal active life (April–June) and in the beginning of their degradation (the end of July). Lipids comprised only a small part of algal extractable compounds (10.9–13.4%). Their higher content was observed in May, in the period of alga preparation to sporogenesis. Polar lipids, glyceroglycolipids (GL) and phospholipids (PL), comprised a great part of total lipids in spring months and June, whereas neutral lipids, in July. GL predominated in polar lipids in spring and summer. The highest content of GL was observed in May and PL in April. Storage lipids comprised a great part of lipids in July. The content of sterols was the highest in April and May. In summer months, the content of sterols decreased and remained on unchanged level until thallus degradation. Polyunsaturated FAs (PUFAs) comprised the most part of FAs. Their highest content was observed in April. The main part of PUFAs were those of ω-3 series. In July, the level of these PUFA decreased substantially. The levels of ω-6 PUFAs were approximately similar in spring and summer months. The lowest content of monounsaturated FAs was detected in April; in May and July; the relative content of these FAs increased sharply. We also detected seasonal changes in the content of pigments and the ratios between them.     

Thraustochytrid Marine Protists: Production of PUFAs and Other Emerging Technologies

Thraustochytrids, the heterotrophic, marine, straminipilan protists, are now established candidates for commercial production of the omega-3 polyunsaturated fatty acid (ω-3 PUFA), docosahexaenoic acid (DHA), that is important in human health and aquaculture. Extensive screening of cultures from a variety of habitats has yielded strains that produce at least 50% of their biomass as lipids, and DHA comprising at least 25% of the total fatty acids, with a yield of at least 5 g L⁻¹. Most of the lipids occur as triacylglycerols and a lesser amount as phospholipids. Numerous studies have been carried out on salinity, pH, temperature, and media optimization for DHA production. Commercial production is based on a fed batch method, using high C/N ratio that favors lipid accumulation. Schizochytrium DHA is now commercially available as nutritional supplements for adults and as feeds to enhance DHA levels in larvae of aquaculture animals. Thraustochytrids are emerging as a potential source of other PUFAs such as arachidonic acid and oils with a suite of PUFA profiles that can have specific uses. They are potential sources of asataxanthin and carotenoid pigments, as well as other lipids. Genes of the conventional fatty acid synthesis and the polyketide-like PUFA synthesis pathways of thraustochytrids are attracting attention for production of recombinant PUFA-containing plant oils. Future studies on the basic biology of these organisms, including biodiversity, environmental adaptations, and genome research are likely to point out directions for biotechnology explorations. Potential areas include enzymes, polysaccharides, and secondary metabolites.     

Changes in the fatty acid composition of blood cell membranes in children with inflammatory diseases

Fatty acid composition of erythrocyte and leukocyte membranes has been studied in children (with normal body mass and obesity) with inflammatory diseases of the gastrointestinal tract and children with bronchial asthma in comparison with basically healthy children. Fifty seven children aged from 7 to 14 years were examined: 13 with inflammatory diseases of the gastrointestinal tract (IDGIT) (eosophagitis, gastroduodenitis, stomach ulcer), 25 with obesity stages (I–III) complicated by IDGIT, 9 with bronchial asthma and 10 basically healthy children. The study revealed that both IDGIT and bronchial asthma caused significant and similar changes in fatty acid composition of cell membranes. These included accumulation of ω3 eicosapentaenoic acid (EPA) and the decrease of docosahexaenoic acid (DHA); this phenomenon observed in both erythrocyte and leukocyte membranes suggests a common feature of the detected changes in fatty acid composition of cell membranes in inflammation. There was a significant decrease in the level of membrane ω6 polyunsaturated fatty acids (PUFA), first of all arachidonic acid and total ω6 PUFA. Consequently, EPA accumulation in membranes may be a compensatory response to low dietary arachidonic acid supply and/or its increased loss for the synthesis of pro-inflammatory eicosanoids (prostaglandins, leukotriens, thromboxans) during inflammatory process.     

Is the fatty acid composition of Daphnia galeata determined by the fatty acid composition of the ingested diet?

1. The fatty acid (FA) composition of Daphnia galeata and their algal food was analysed and showed many similarities, however, some significant differences were also found in the relative abundance of the FA C16 : 4ω3 and docosahexaenoic acid (DHA). Their relative abundances were much lower in daphnids than in their algal diet.
2. When daphnids were fed three distinct emulsion particles with DHA : eicosapentaenoic acid (EPA) ratios of c. 0.7, 2 and 4, the final DHA : EPA ratio in the daphnids always favoured EPA. The increase of the food DHA : EPA ratio resulted in a minor increase of DHA (to c. 2%). Feeding the animals on emulsion particles with increasing ratios of DHA : EPA, caused a minor ( c. 2%) increase of DHA level but EPA levels remained high ( c. 10%).
3. When labelled with [¹⁴C]linoleic acid and [¹⁴C]linolenic acid daphnids showed low conversion of both essential FA into C20 polyunsaturated fatty acids (PUFAs). This low conversion activity might explain the importance of C20 PUFAs as dietary compounds in the food of Daphnia.
4. The results indicate the insignificance of DHA and C16 : 4ω3 for daphnids. As EPA can be derived from C18 : 3ω3 it is not strictly essential, although it might be a significant factor in food quality for Daphnia.     

Antarctic microorganisms as source of the omega-3 polyunsaturated fatty acids

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are long-chain polyunsaturated fatty acids (PUFAs) that belong to the omega-3 group. They are essential fatty acids found in phospholipid of cell membranes. There is strong evidence that these nutrients may also favorably modulate many diseases. Primary sources of omega-3 PUFAs in the human diet are fish and fish-derived products. The fishing industry worldwide, however, is becoming unable to satisfy the growing demand for these PUFAs. A promising cost-effective alternative source of PUFAs is bacterial production. We identified 40 Antarctic marine bacterial isolates by 16S rRNA gene sequence analysis. Fifteen genera in three phyla were represented in the collection. Isolates were tested for ability to produce EPA using a method in which their ability to reduce 2,3,5-triphenyltetrazolium chloride (TTC) is determined and by gas chromatography coupled to mass spectrometry (GC–MS). All isolates could reduce TTC, and GC–MS analysis showed that four produced EPA and that six produced DHA. We show for the first time that isolates identified as Cellulophaga, Pibocella and Polaribacter can produce EPA and DHA, only DHA or only EPA, respectively. One isolate, Shewanella sp. (strain 8-5), is indicated to be a good candidate for further study to optimize growth and EPA production. In conclusion, a rapid method was tested for identification of new EPA producing strains from marine environments. New EPA and DHA producing strains were found as well as a potentially useful PUFA production strain.     

Fatty acids in anopheline mosquito larvae and their habitats

Larvae of the three important Central American malaria vectors, Anopheles albimanus, An. vestitipennis, and An. darlingi, are found in distinctly different habitats broadly defined by hydrology and aquatic vegetation, but little is known about the actual food quality and quantity of these habitats. Polyunsaturated fatty acids (PUFA) are of special interest, because mosquitoes require 20:5ω3 (EPA), 20:4ω6 (ARA), and 22:6ω3 (DHA) and without an adequate supply of these PUFAs they are not able to complete their life cycle. We collected samples of larvae and their corresponding habitats and analyzed their fatty acid (FA) composition to reveal if there are any species‐specific and habitat‐specific differences in FA composition, and if habitat FA differences can be linked to differences in the mosquito FA pattern and, ultimately, mosquito performance. We also assessed how FA of wild larvae compare to the laboratory‐reared larvae. Habitats were generally low in essential PUFAs and there were no significant differences among the FA composition of habitat samples. There were significant differences in FA composition of larvae. An. darlingi contained significantly higher amounts of FA, specifically a higher content of ω‐6 PUFA, represented mainly by the linoleic acid (18:2ω‐6). Large differences were found between field‐collected and laboratory‐reared An. vestitipennis larvae, especially in the content of PUFAs. The laboratory‐reared larvae contained significantly more of the total FA, ω3 PUFA, and MUFA. The laboratory‐reared larvae contained three to five times more essential PUFAs, EPA, and DHA. However, there were no differences in the total dry weight of the 4^th instar larvae between the wild vs laboratory‐reared larvae. Total FA in both larvae and habitats of An. albimanus and An. darlingi were positively correlated with the concentration of particulate organic carbon and nitrogen (POC, PON) in their respective habitats, but no such correlation was found for An. vestitipennis. PUFA are a good indicator of nutritional quality, although factors controlling the success of anopheline development from larval habitats are likely to be more complex and would include the presence of predators, pathogens, and toxins as interacting factors.     

Comparative Analysis of Content of Omega-3 Polyunsaturated Fatty Acids in Food and Muscle Tissue of Fish from Aquaculture and Natural Habitats

Two fish species reared in aquaculture (pink salmon Oncorhynchus gorbuscha and whitefish Coregonus lavaretus) and ten fish species from natural habitats (whitefish C. lavaretus, tugun Coregonus tugun, broad whitefish Coregonus nasus, least cisco Coregonus sardinella, vendace Coregonus albula, boganid charr Salvelinus boganidae, charr Salvelinus alpinus complex, northern pike Esox lucius, sharp-snouted lenok Brachymystax lenok, and taimen Hucho taimen) have been studied. The content of two long-chain polyunsaturated omega-3 fatty acids (PUFAs), eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA), in the muscle tissue of the fish and in their food (intestine contents) are compared. In the aquacultures of whitefish and pink salmon, the total content of EPA and DHA is significantly higher in feed than in the muscle tissue of the fish, which indicates losses of PUFA in the two-link food chain of the aquaculture during their transfer to the upper trophic level. EPA and DHA losses in aquaculture, which are confirmed by numerous literature data, mean an inefficient usage of the available sources of PUFAs and the aggravation of the global deficit of these biochemicals in the human diet. A study of natural fish populations reveals the accumulation of EPA and DHA in their biomass compared to food in many cases, although opposite phenomena are also observed. An assumption on the presence of an optimal, physiologically adequate species-specific level of PUFA in the fish muscle tissue has been made based on our data and literature data. If the level of PUFAs in the muscles is lower than optimal, their accumulation (bioaccumulation) from food and/or de novo synthesis are observed. When the optimal level is exceeded, the content of EPA and DHA in biomass approaches maximum species-specific values; however, part of these PUFAs entering from food is not digested or is catabolized. According to the obtained data, the species of the order Salmoniformes have an optimal level of 2 to 6 mg/g of wet weight. It has been found that in aquaculture approaching to maximum values of EPA + DHA content was accompanied by their losses (scattering) in the food chains, while in natural ecosystems the maximum values of PUFA content in the fish biomass are achieved by their accumulation from the lower trophic level. Boganid charr S. boganidae had the highest content of EPA + DHA in the muscle tissue among all known fish species (32.78 mg/g of wet weight).     

Successful high‐level accumulation of fish oil omega‐3 long‐chain polyunsaturated fatty acids in a transgenic oilseed crop

Omega‐3 (also called n‐3) long‐chain polyunsaturated fatty acids (≥C20; LC‐PUFAs) are of considerable interest, based on clear evidence of dietary health benefits and the concurrent decline of global sources (fish oils). Generating alternative transgenic plant sources of omega‐3 LC‐PUFAs, i.e. eicosapentaenoic acid (20:5 n‐3, EPA) and docosahexaenoic acid (22:6 n‐3, DHA) has previously proved problematic. Here we describe a set of heterologous genes capable of efficiently directing synthesis of these fatty acids in the seed oil of the crop Camelina sativa, while simultaneously avoiding accumulation of undesirable intermediate fatty acids. We describe two iterations: RRes_EPA in which seeds contain EPA levels of up to 31% (mean 24%), and RRes_DHA, in which seeds accumulate up to 12% EPA and 14% DHA (mean 11% EPA and 8% DHA). These omega‐3 LC‐PUFA levels are equivalent to those in fish oils, and represent a sustainable, terrestrial source of these fatty acids. We also describe the distribution of these non‐native fatty acids within C. sativa seed lipids, and consider these data in the context of our current understanding of acyl exchange during seed oil synthesis.     

In humans, the seasonal variation in poly-unsaturated fatty acids is related to the seasonal variation in violent suicide and serotonergic markers of violent suicide

BACKGROUND: Depression is accompanied by a depletion of n-3 poly-unsaturated fatty acids (PUFAs). There is also a negative correlation between suicide and fish-oil intake (rich in n-3 PUFAs) across different countries. Both depression and suicide show a seasonal variation and are related to disorders in the serotonergic system. AIMS: The present study was carried out to determine if there is a seasonal variation in the PUFA fractions in serum phospholipids and whether there are significant relationships between lowered n-3 PUFA status and the seasonal variation in the number of suicide deaths and serotonergic markers of suicide. METHODS: We took monthly blood samples during 1 calendar year from 23 healthy volunteers and analyzed the PUFA composition in serum phospholipids and related those data to the annual variation in the mean weekly number of suicides for Belgium and the Bmax [3H]-paroxetine binding to platelets in the same 23 subjects. RESULTS: Significant annual rhythms were detected in the long-chain PUFAs only, i.e. arachidonic acid (C20: 4n-6; AA), eicosapentaenoic acid (C20: 5n-3; EPA), and docosahexaenoic acid (C22: 6n-3; DHA). There was a significant correlation between the changes over the last 2 weeks in AA and EPA and the mean weekly number of violent, but not nonviolent, suicide deaths in Belgium. There was a significant correlation between the PUFAs, AA and DHA, and the Bmax [3H]-paroxetine binding to platelets. CONCLUSIONS: Our results show that there is a true seasonality in long-chain PUFAs, such as AA, EPA and DHA. The results suggest that the seasonality in PUFAs may be related to the incidence of violent suicide and the expression of the serotonin transporter complex.     

Dietary supplementation with docosahexaenoic acid, but not eicosapentaenoic acid, dramatically alters cardiac mitochondrial phospholipid fatty acid composition and prevents permeability transition

Treatment with the ω-3 polyunsaturated fatty acids (PUFAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) exerts cardioprotective effects, and suppresses Ca²⁺-induced opening of the mitochondrial permeability transition pore (MPTP). These effects are associated with increased DHA and EPA, and lower arachidonic acid (ARA) in cardiac phospholipids. While clinical studies suggest the triglyceride lowering effects of DHA and EPA are equivalent, little is known about the independent effects of DHA and EPA on mitochondria function. We compared the effects of dietary supplementation with the ω-3 PUFAs DHA and EPA on cardiac mitochondrial phospholipid fatty acid composition and Ca²⁺-induced MPTP opening. Rats were fed a standard lab diet with either normal low levels of ω-3 PUFA, or DHA or EPA at 2.5% of energy intake for 8 weeks, and cardiac mitochondria were isolated and analyzed for Ca²⁺-induced MPTP opening and phospholipid fatty acyl composition. DHA supplementation increased both DHA and EPA and decreased ARA in mitochondrial phospholipid, and significantly delayed MPTP opening as assessed by increased Ca²⁺ retention capacity and decreased Ca²⁺-induced mitochondria swelling. EPA supplementation increased EPA in mitochondrial phospholipids, but did not affect DHA, only modestly lowered ARA, and did not affect MPTP opening. In summary, dietary supplementation with DHA but not EPA, profoundly altered mitochondrial phospholipid fatty acid composition and delayed Ca²⁺-induced MPTP opening.     

Liver conversion of docosahexaenoic and arachidonic acids from their 18-carbon precursors in rats on a DHA-free but α-LNA-containing n-3 PUFA adequate diet

The long-chain polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3), and arachidonic acid (AA, 20:4n-6), are critical for health. These PUFAs can be synthesized in liver from their plant-derived precursors, α-linolenic acid (α-LNA, 18:3n-3) and linoleic acid (LA, 18:2n-6). Vegetarians and vegans may have suboptimal long-chain n-3 PUFA status, and the extent of the conversion of α-LNA to EPA and DHA by the liver is debatable. We quantified liver conversion of DHA and other n-3 PUFAs from α-LNA in rats fed a DHA-free but α-LNA (n-3 PUFA) adequate diet, and compared results to conversion of LA to AA. [U-(13)C]LA or [U-(13)C]α-LNA was infused intravenously for 2h at a constant rate into unanesthetized rats fed a DHA-free α-LNA adequate diet, and published equations were used to calculate kinetic parameters. The conversion coefficient k(?) of DHA from α-LNA was much higher than for AA from LA (97.2×10(-3) vs. 10.6×10(-3)min(-1)), suggesting that liver elongation-desaturation is more selective for n-3 PUFA biosynthesis on a per molecule basis. The net daily secretion rate of DHA, 20.3μmol/day, exceeded the reported brain DHA consumption rate by 50-fold, suggesting that the liver can maintain brain DHA metabolism with an adequate dietary supply solely of α-LNA. This infusion method could be used in vegetarians or vegans to determine minimal daily requirements of EPA and DHA in humans.     

Modulation of cyclin D1 and early growth response factor-1 gene expression in interleukin-1beta-treated rat smooth muscle cells by n-6 and n-3 polyunsaturated fatty acids.

The proliferation of smooth muscle cells (SMC) is a key event in the development of atherosclerosis. In addition to growth factors or cytokines, we have shown previously that n-3 polyunsaturated fatty acids (PUFAs) act in opposition to n-6 PUFAs by modulating various steps of the inflammatory process. We have investigated the molecular mechanisms by which the incorporation of the n-6 PUFA, arachidonic acid, increases the proliferation of rat SMC treated with interleukin-1beta, while the n-3 PUFAs eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), elicit no mitogenic response. Incorporation of EPA or DHA into SMC, which are then activated by interleukin-1beta to mimic inflammation, decreases promoter activity of the cyclin D1 gene and phosphorylation of the retinoblastoma protein. Together, our data demonstrate that n-3 effects are dependent on the Ras/Raf-1/extracellular signal regulated kinase (ERK)/mitogen-activated protein kinase pathway, and that down-regulation of the cyclin D1 promoter activity is mediated by the specific binding of the early growth response factor-1. Finally, we have shown that the incorporation of EPA and DHA also increased the concentration of caveolin-1 and caveolin-3 in caveolae, which correlated with n-3 PUFA inhibition of SMC proliferation through the mitogen-activated protein kinase pathway. We provide evidence indicating that, in contrast to n-6 PUFAs, n-3 PUFAs exert antiproliferative effects on SMC through the mitogen-activated protein kinase/ERK pathway.     

Embryonic and larval development and fatty‐acid profile of Epinephelus marginatus spawned in captivity: tools applied to captive rearing

Development, ontogeny of the digestive system and the fatty‐acid (FA) profile, were analysed during development of Epinephelus marginatus. Larvae were analysed 7 and 17 days post fertilization (dpf) to evaluate fatty‐acid profile and morphological variables, respectively. Epinephelus marginatus larvae have relatively slow development of digestive structures, but were able to capture, ingest and digest prey by 5 dpf. Eggs were composed of high percentages of polyunsaturated fatty acids (PUFA) in phospholipids. The percentage of n3 PUFAs was higher than n6, especially docosahexaenoic acid (DHA), which exhibited higher levels compared with other marine species during the first 3 days of development, both in terms of phospholipids and triglycerides. The larvae present a high content of docosahexaenoic acid–eicosapentaenoic acid (DHA–EPA) and, during this phase, live food of small size was required (copepods or SS‐strain Brachionus rotundiformes), enriched with DHA–EPA. These results may guide future studies on the contribution of FAs required during this stage of the life cycle of E. marginatus, to advance knowledge of the use of these FAs throughout ontogeny and contribute to the culture of this species commercial production or restocking.     

Effect of frozen storage on fatty acid composition of the different tissues of four scombrid and one dussumeriid species

In the current study, the effect of frozen storage at ?18°C was evaluated on fatty acid composition of different body parts (liver, muscle tissue, and viscera) of narrow‐barred Spanish mackerel (Scomberomorus commerson, Lacépède, 1800), longtail tuna (Thunnus tonggol, Bleeker, 1851), kawakawa (Euthynnus affinis, Cantor, 1849), king mackerel (Scomberomorus guttatus, Bloch & Schneider, 1801), and rainbow sardine (Dussumieria acuta, Valenciennes, 1847) caught in the Persian Gulf. Changes in saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), polyunsaturated fatty acids (PUFAs), eicosapentaenoic acid plus docosahexaenoic acid/palmitic acid (EPA+DHA/C16), ω3 PUFA/ω6 PUFA (ω3/ω6), and polyunsaturated fatty acids/saturated fatty acids (PUFA/SFA) were investigated during a 6‐month period. A decrease in unsaturated fatty acids, particularly PUFAs (60–100%) as well as ω3/ω6, EPA+DHA/C16 (polyene index) and PUFA/SFA ratios, indicated a decrease in the nutritional values of the samples.     

Particulate fatty acids in two small Siberian reservoirs dominated by different groups of phytoplankton

SUMMARY 1. We studied the composition of fatty acids (FAs) in the seston from two small freshwater reservoirs (Bugach and Lesnoi) with distinct periodicity of domination by cyanobacteria and eukaryotic algae during the growth season.
2. The diatoms in the both reservoirs were characterised by a high content of 14:0 and C16 unsaturated acids, whereas that of the essential FA 20:5ω3 [eicosapentanoic acid (EPA)] was low. The correlation between this polyunsaturated FA (PUFA) and diatom biomass was not significant in either reservoir. The percentage of 20:5ω3 in seston significantly correlated with the biomass of euglenophyta in Bugach and dinophyta in Lesnoi. Hence the diatoms, usually referred as a valuable food for zooplankton, were not an important source of the essential PUFA in these systems.
3. The dominant cyanobacteria in Bugach, and the green algae in Lesnoi, both contained the same marker acids: 18:3ω3 and 18:2ω6. Hence, a discrimination between these two phytoplanktonic groups on the basis of FA biomarkers may be difficult in some cases.
4. We found no significant correlation between the content of 20:5ω3 in seston and the biomass of the dominant daphniids in either reservoir. This is contrary to expectations, based on the literature, that EPA is generally important. Rather, the biomass of the two dominant Daphnia species in Bugach correlated strongly with the content of 18:3ω3 in the seston. The cyanobacteria were a probable source of this ω3 FA for Daphnia . We conclude that EPA is not always important for Daphnia populations although, in such cases, some other PUFA (e.g. 18:3ω3) might be related to their growth.