Polyunsaturated fatty acids in zooplankton: variation due to taxonomy and trophic position

1. Food quality has major effects on the transfer of energy and matter in food webs, and essential long‐chained polyunsaturated fatty acids (PUFAs) can affect the quality of phytoplankton as food. In a study of oligotrophic lakes in north‐western Sweden, we investigated the fatty acid composition of four planktonic cladocerans and two calanoid copepods, representing herbivorous and carnivorous species. We also collected seston samples. 2. The proportions of long‐chain PUFAs in the organisms increased with their increasing trophic position. Thus, both their quality as food for other organisms, as well as their requirement for fatty acids (FAs), differed among taxa and depended on their trophic position. 3. We found taxon‐specific differences in the FA composition of zooplankton that were not related to sestonic FA composition. This implies that the variation in zooplankton FA composition is constrained by phylogenetic origin, life history characteristics, or both. 4. The cladoceran taxa contained 12–23% eicosapentaenoic acid (EPA) but only 0.9–2.1% docosahexaenoic acid (DHA) of the total FA content. In contrast, the calanoid copepods contained 7–11% EPA and 14–21% DHA. Thus, our results show that differences in the PUFA content among zooplankton species could have repercussions for both food web structure and function.     

Taxonomic differences in the essential fatty acid composition of groups of freshwater zooplankton relate to reproductive demands and generation time

1. Marked differences were observed in the total fatty acid concentrations and essential fatty acid (EFA) distributions of co-existing freshwater copepods and cladocerans in four large lake systems (lakes Michigan, Erie, Ontario and Champlain) over two growing seasons. These patterns appeared independent of lake seston EFA composition.
2. Compared to the cladocerans, calanoid and cyclopoid copepods contained significantly higher concentrations of total fatty acids and docosahexaenoic acid (DHA), an EFA abundant in fish. Calanoids and cladocerans contained similar levels of eicosapentaenoic acid (EPA), but cladocerans showed EPA : DHA ratios consistently greater than those of the available seston food source. Alpha-linolenic acid was most abundant in the herbivorous cladocerans, Daphnia and Holopedium , while the highest concentrations of arachidonic acid were found in the predatory cladocerans, Bythotrephes longimanus and Leptodora kindtii .
3. The distinct EFA accumulation patterns between cladoceran and copepod zooplankton suggest metabolic regulation of certain EFAs to meet the particular physiological demands and ecological strategies of these different zooplankton groups. Cladocerans may accumulate EPA directly from their diet, or through transformation of dietary materials to facilitate rapid somatic growth and enhance reproduction due to their short generation time. In contrast, copepods may retain DHA to increase their cell membrane fluidity in order to remain active over the winter due to their longer generation time and life cycle.
4. Consistent EFA differences between zooplankton groups may have implications regarding the somatic growth and reproductive success of different zooplankton taxa as well as the nutritional value of various zooplankton groups for larval and planktivorous fish.     

Fatty acid composition of Cladocera and Copepoda from lakes of contrasting temperature

相似文献   

A comparison of the trophic transfer of fatty acids in freshwater plankton by cladocerans and calanoid copepods

1. Analyses of zooplankton fatty acid (FA) composition in laboratory experiments and samples collected from lakes in New Zealand spanning a wide gradient of productivity were used to assess the extent to which FAs might infer their diet. We used the cladocerans, Daphnia and Ceriodaphnia, and the calanoid copepod, Boeckella, as test organisms, and monocultures of cryptophytes, chlorophytes and cyanobacteria as food. Based on reproductive success, cryptophytes were the highest food quality, chlorophytes were intermediate and cyanobacteria the poorest. 2. Several FA groups were highly correlated between zooplankton and their diets. They were monounsaturated fatty acids (MUFAs), and ω3 and ω6 polyunsaturated fatty acids (PUFAs) for cladocerans, and saturated fatty acids (SAFAs) and ω3 PUFAs for copepods. Several FAs varied significantly less in the zooplankton than in their monoculture diets, e.g. MUFAs in Daphnia, and ω3 and ω6 PUFAs in Ceriodaphnia, despite clear dietary dependency for these FAs. 3. Zooplankton collected from lakes in New Zealand had more eicosapentaenoic acid (EPA) (Daphnia), more highly unsaturated ω3 and ω6 FAs (C₂₀, C₂₂; Daphnia, Ceriodaphnia, Boeckella) and less ω3 C₁₈ PUFAs (Daphnia, Ceriodaphnia, Boeckella) and ω6 C₁₈ PUFAs (Daphnia, Ceriodaphnia) than measured in the same species reared on phytoplankton in the laboratory. 4. Analyses of FA composition of seston and freshwater zooplankton globally showed that, in general, zooplankton had a significantly higher proportion of arachidonic acid and EPA than seston, and copepods also had a higher percentage of docosahexaenoic acid than seston. 5. These results suggest that zooplankton selectively incorporate the most physiologically important FAs. This could be a consequence of preferential assimilation, selective feeding on more nutritious cells or locating and feeding within higher food quality food patches.     

Nucleic Acid Content in Crustacean Zooplankton: Bridging Metabolic and Stoichiometric Predictions

Metabolic and stoichiometric theories of ecology have provided broad complementary principles to understand ecosystem processes across different levels of biological organization. We tested several of their cornerstone hypotheses by measuring the nucleic acid (NA) and phosphorus (P) content of crustacean zooplankton species in 22 high mountain lakes (Sierra Nevada and the Pyrenees mountains, Spain). The P-allocation hypothesis (PAH) proposes that the genome size is smaller in cladocerans than in copepods as a result of selection for fast growth towards P-allocation from DNA to RNA under P limitation. Consistent with the PAH, the RNA:DNA ratio was >8-fold higher in cladocerans than in copepods, although ‘fast-growth’ cladocerans did not always exhibit higher RNA and lower DNA contents in comparison to ‘slow-growth’ copepods. We also showed strong associations among growth rate, RNA, and total P content supporting the growth rate hypothesis, which predicts that fast-growing organisms have high P content because of the preferential allocation to P-rich ribosomal RNA. In addition, we found that ontogenetic variability in NA content of the copepod Mixodiaptomus laciniatus (intra- and interstage variability) was comparable to the interspecific variability across other zooplankton species. Further, according to the metabolic theory of ecology, temperature should enhance growth rate and hence RNA demands. RNA content in zooplankton was correlated with temperature, but the relationships were nutrient-dependent, with a positive correlation in nutrient-rich ecosystems and a negative one in those with scarce nutrients. Overall our results illustrate the mechanistic connections among organismal NA content, growth rate, nutrients and temperature, contributing to the conceptual unification of metabolic and stoichiometric theories.     

Browning reduces the availability—but not the transfer—of essential fatty acids in temperate lakes

相似文献   

Lake trophic state and the limnological effects of omnivorous fish

Ecologists have hypothesized that planktivorous fish have greater effects on the plankton and water quality of oligotrophic lakes than eutrophic lakes. We tested this hypothesis in a tank-mesocosm experiment of factorial design in which five biomass levels of filter-feeding omnivorous gizzard shad (Dorosoma cepedianum) were cross-classified with two levels of lake trophic state achieved by filling tank-mesocosms with water and plankton transported by truck from two lakes with different trophic states. The presence of gizzard shad significantly increased total phosphorus, primary productivity, chlorophyll, and particulate phosphorus (PP) 2–20 and 20–200 μm and significantly decreased Secchi depth, cladocerans, copepods and PP > 200 μm. The effects of gizzard shad on chlorophyll, Secchi depth, cladocerans, copepods and PP 2–20 and > 200 μm were dependent on lake trophic state and most intense in the eutrophic lake system. This experiment suggests that filter-feeding omnivorous fish interact synergistically with trophic state so that the limnological effects of omnivorous fish become more intense with increased eutrophication.     

Plasticity of vertical distribution of crustacean zooplankton in lakes with varying levels of water colour

Zooplankton that are vulnerable to predation by planktivorousfish typically remain in deeper, darker water during the day.Vertical position may be affected by profiles of temperatureand oxygen concentration, but light levels are thought to becritically important. Water transparency in temperate lakesis strongly dependent on the concentration of dissolved organiccarbon (DOC). Therefore, different patterns of zooplankton verticalposition might be expected in lakes that vary in their levelof DOC. The importance of three factors (light, temperatureand oxygen) that might affect vertical position of major zooplanktongroups was evaluated in 10 small lakes located in central Ontario.The lakes, encompassing a wide range of water colour, were sampledin May, June and August of 2000. Small cladocerans were foundto be always higher in the water column than large cladocerans,while copepods were deeper. Small cladocerans had a weak responseto the predictive factors, but copepods and large cladoceranswere strongly affected. The vertical position of copepods wasconsistently dependent solely on Secchi depth. Surprisingly,for large cladocerans, temperature gradient was decisive inMay and June, and only in August was water transparency themost important variable. Overall, water transparency, as determinedby level of water colour, was the most important variable but,depending on taxonomic group and time of year, temperature andoxygen were also major determinants of vertical position.     

Do phosphorus requirements for RNA limit genome size in crustacean zooplankton?

As for most other organisms, genome size in zooplankton differs widely. This may have a range of consequences for growth rate, development, and life history strategies, yet the causes of this pronounced variability are not settled. Here we propose that small genome size may be an evolutionary consequence of phosphorus (P) allocation from DNA to RNA under P deficiency. To test this hypothesis we have compared the two major groups of zooplankton, copepods and cladocerans, that have overlapping niches and body size. Relative to the cladocerans, copepods have a more complex life history and a lower mass-specific P content, while cladocerans tend to have higher P and RNA contents and higher specific growth rates and frequently experience P-limited growth, likely due to a shortage of P for ribosome synthesis. Cladocerans also generally have smaller genomes than copepods (1C = 0.17-0.63 pg DNA.cell-1 vs. 1C = 0.10-10 pg DNA.cell-1). Furthermore, cladocerans have a higher slope of the relationship of body size with DNA content (1.5 vs. 0.28 in copepods) and present almost 15-fold higher RNA:DNA ratios (24.8 in cladocerans vs. 1.6 in copepods). Hence, small genome size in cladocerans could reflect an evolutionary pressure towards "efficient" genomes to conserve a key element needed to maximize growth rate. We do not claim that this is a universal cause of genome size variability, but propose that streamlining of genomes could be related to P conservation rather than energy conservation. This could be relevant for a range of organisms that may suffer P-limited growth rates.     

An evaluation of the diet of <Emphasis Type="Italic">Mysis relicta</Emphasis> using gut contents and fatty acid profiles in lakes with and without the invader <Emphasis Type="Italic">Bythotrephes longimanus</Emphasis> (<Emphasis Type="Italic">Onychopoda,Cercopagidae</Emphasis>)

Diets of Mysis relicta from four lakes in central Ontario that had been invaded by Bythotrephes longimanus and three lakes that had not been invaded were investigated using gut content analysis and fatty acid (FA) composition. Gut content analysis of M. relicta revealed a high incidence of cannibalism in all lakes, and consumption of B. longimanus and native zooplanktivorous midges in the genus Chaoborus in lakes where these were present. Cladocera other than B. longimanus were present in the guts of all M. relicta examined except those from Bernard Lake, the lake with the most B. longimanus. In that lake, B. longimanus was the most frequent diet item. Copepod remains were found in 60–100% of M. relicta guts with the lowest frequency occurring in Bernard Lake. Fatty acids (FA) that contributed strongly to the variation in FA composition in M. relicta, as revealed by a principal component analysis, were C16:0 (palmitic acid), C16:1n7 (palmitoleic acid), C18:1n9c (oleic acid), C20:4n6 (arachidonic acid), C20:5n3 (eicosapentaenoic acid), and C22:6n3 (docosahexaenoic acid). Significant differences in FA amount and composition of M. relicta were found between invaded and non-invaded lakes, and among lakes within these groups. Generally, M. relicta in non-invaded lakes had higher concentrations of C16:0, C18:1n9c, C18:2n6c (linoleic acid), C18:3n3 (α-linolenic acid) and C20:4n6, while M. relicta in invaded lakes had higher concentrations of C22:6n3. Two of the non-invaded lakes had lower water transparency, as measured by Secchi depth, which may be the reason why mysids and abundant populations of Chaoborus spp. could be found in the water column during the day. However, differences in FA profiles and gut contents of M. relicta between invaded and non-invaded lakes are consistent with competition for Cladocera in the presence of the invader rather than pre-existing differences among lakes. We conclude that the diet of M. relicta is affected by the invasion of B. longimanus.     

Relative Sensitivity Distribution of Freshwater Planktonic Crustaceans to Trace Metals

Cladocerans and copepods are common inhabitants of ponds and lakes, but assessments of the toxic effects of chemicals on aquatic organisms are often based mainly on toxicity data for cladocerans of the genus Daphnia. The paucity of toxicity data for copepods and other species of cladocerans raised the question whether toxicity data derived primarily from daphniids can be extrapolated to protect other planktonic organisms. In this study, we address this question by systematically comparing between the sensitivities of cladocerans and copepods to the metals Cd, Cu, Pb, Ni, and Zn using the species sensitivity distributions. Our results indicate that cladocerans are consistently more sensitive than copepods to Cd and Cu. Most importantly, sensitivities of D. magna, D. pulex, and Ceriodaphnia dubia, the three most commonly tested cladocerans, to these metals are higher than those of most copepod species and fall within the range of those exhibited by other cladocerans. C. dubia, a cladoceran with relatively small body size, is more sensitive to all metals than most other cladoceran species. Our results imply that water quality criteria of trace metals derived from datasets dominated by Daphnia are likely also protective to copepods and most other cladocerans.     

Larger zooplankton in Danish lakes after cold winters: are winter fish kills of importance?

Winter fish kills can be intense under ice in shallow lakes, and have cascading effects on the food web and ultimately on lake water clarity. In maritime Western Europe, winters are usually mild, but occasional colder periods may also have strong effects on lake fish communities. Global warming may have disproportionate effects by delaying freezing and shortening the period of ice coverage. We studied differences in zooplankton (cladocerans, copepods, and rotifers): phytoplankton biomass, zooplankton community structure, and individual body size among 37 Danish lakes of various depths, chemical characteristics, and trophy, by comparing four winters of different severity (mean winter temperatures ranging from −1.19°C in 1996 to +2.9°C in 1995). We found that crustacean mean body sizes were significantly larger in the summer following a severely cold winter. The zooplankton communities in the summer after a cold winter had a significantly larger proportion of larger-bodied species and taxa. Phytoplankton biomass, expressed as chlorophyll-a (chl-a), was lower and zooplankton herbivory (chl-a:TP index), higher, in the summer after the severely cold winter of 1995/1996. All these effects were stronger in shallow lakes than in deep lakes. Changes in zooplankton during summer 1996, compared with other years, were likely caused by fish kills under ice during the preceding severe winter of 1995–1996. Fish kills due to under ice oxygen depletion would be expected to occur earlier and be more complete in the shorter water columns of shallow lakes. With climate change, severe winters are predicted to become less frequent and the winters to be milder and shorter. In general, this is likely to lead to higher winter survival of fish, lower zooplankton grazing of phytoplankton the following summer and more turbid waters, particularly in shallow eutrophic lakes.     

Seasonal changes in European whitefish muscle and invertebrate prey fatty acid composition in a subarctic lake

相似文献   

Calcium content of crustacean zooplankton and its potential role in species distribution

SUMMARY 1. The occurrence and species composition of crustacean zooplankton in Norwegian lakes was related to ambient Ca concentrations, pH, total phosphorus and chlorophyll a , and to the presence/absence of other zooplankters and a planktivorous fish (roach: Rutilus rutilus ).
2. Ambient Ca concentrations appeared to influence the distribution of Daphnia species: Daphnia longispina often occurred in Ca-rich lakes with low fish-predation pressure while the smaller Daphnia cristata often occurred in opposite conditions.
3. Body Ca contents were measured in zooplankters from a wide range of localities, to examine Ca requirements and thus the potential for Ca-limitation of common species.
4. All Daphnia species had relatively high specific Ca contents [ranging from 0.8 to 4.4% Ca dry weight (DW)⁻¹] compared with other cladocerans and also copepods (ranging from 0.1 to 0.4% Ca DW⁻¹). Within the Daphnia genus, the specific Ca content increased with increasing body size of the species, and thus the large-bodied species had especially high Ca demands.
5. Because of their high Ca demands, species of Daphnia could be competitively disadvantaged in softwater lakes relative to less Ca-demanding species.     

Seven Decades of Change in the Zooplankton (s.l.) of the Nile Delta Lakes (Egypt), with Particular Reference to Lake Borullus

Around the 1930s, the zooplankton (and benthos) of the Nile delta lakes, and Lake Borullus in particular, had a mixed, eutrophic facies, with marine and mesohaline elements dominant for about eight months per year, and freshwater species taking over during the four months of the Nile flood. After the Aswan dam became operational, this regime changed: a steady supply of agricultural drainage water of Nilotic origin consistently freshened the delta. Thus, except in the immediate vicinity of their outlet to the sea, the lakes became almost fresh. Only during the rare and short‐lived (one‐three weeks) occasions when Aswan closes in winter, marine water is sucked in, and along with it, a saline fauna temporarily becomes re‐established in the east and centre of lake Borullus, and presumably of the other delta lakes as well. This marine fauna remained the same over 70+ years of observations. The freshwater component, in contrast, partly nilotic, partly mediterranean, changed deeply over time. First, the fraction of species from temporary waters disappeared, as well as (among copepods and cladocerans) all large‐bodied species. Several cladocerans and copepods with a euro‐mediterranean range appeared and diluted the pre‐existing Afrotropical fauna. The abundance of small cladocerans and, especially, rotifers increased by a factor ten or more. This latter change is believed to reflect two pressures. In a first phase, a re‐arrangement of the lake's fish fauna (a top down force) occurred. Freshwater fish replaced marine diadromic species, and their predation pressure on the zooplankton preferentially removed large‐bodied prey. In a second phase, increased agricultural drainage caused eutrophication (a bottom‐up force) and larger filtrators (cladocerans, some copepods) began to be replaced by small filtrators (rotifers). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Milk in the island of Chole [Tanzania] is high in lauric, myristic, arachidonic and docosahexaenoic acids, and low in linoleic acid reconstructed diet of infants born to our ancestors living in tropical coastal regions

BACKGROUND: We need information on the diet on which our genes evolved. OBJECTIVE: We studied the milk fatty acid [FA] composition of mothers living in the island of Chole [Tanzania, Indian Ocean]. These mothers have high intakes of boiled marine fish and coconut, and consume plenty amount of fruits and vegetables. DESIGN: The outcome was compared with three fish-eating tribes living along Tanzanian freshwater lakes [Kerewe, Nyakius, Nyiramba], four tribes living in the Tanzanian inland [Hadzabe, Maasai, Sonjo, Iraqw] and our milk FA database. RESULTS: Milk from Chole contained high levels of 12:0 [20.17 g%], 14:0 [21.19], 12:0/14:0 ratio [0.92 g/g], arachidonic acid [AA, 0.50 g%] and docosahexaenoic acid [DHA, 0.73], but low levels of linoleic acid [LA, 4.23]. The combination of a high medium chain fatty acid [MCFA; 相似文献   

Fatty acids as organic markers for the study of trophic relationships in littoral cladoceran communities of a pond

The fatty acid (FA) composition of zooplankton and paniculatematter (including phytoplankton) associated with the submergedvegetation of a pond shoreline was analysed by gas chromatography.The FA of paniculate matter was characterized by fluctuatingproportions of polyunsaturated FA (PUFA), comprising between31.7 and 51.1% of total FA and originating from phytoplankton.Important levels of bacterial FA (branched 15:0 and 17:0) anddetrital FA (17:0, 17:1) were also detected. Littoral zooplanktonwas dominated by two cladocerans: Eurycercus lametlatus andSimocephalus velulus. Their triacyglycerol fatty acids (TAG-FA)were characterized by PUFA (18:2(n-6), 18:3(n-3). 20:5(n-3))originating in phytoplankton and periphytic algae, and alsoby bacterial and detrital odd-numbered FA. An unusual unsaturatedFA (22:2(n-6)) was detected in the trophic web. It was incorporatedinto cladoceran polar lipids, together with long 22-carbon FAof (n-6) series. Unsaturation of polar lipids was inverselycorrelated with water temperature in both cladocerans. The influenceof dietary FA on the composition of polar lipid FA is also considered.     

Differential Impacts of Copepods and Cladocerans on Lake Seston,and Resulting Effects on Zooplankton Growth

In an enclosure study in Schöhsee, a small mesotrophic lake in Northern Germany, the impact of copepods and daphniids on the seston community was studied. In general, these two guilds differ in their feeding behaviour. Copepods actively select their food, with a preference for larger particles, whereas most cladocerans are unselective filter-feeders. In this study we investigate how the impact of the two different grazers affects zooplankton growth. We combine results obtained in the laboratory with results measured in situ in the enclosures. Copepods and cladocerans were cultured on seston from enclosures that were inhabited by density gradients of copepods or daphniids. We observed that Daphnia grew faster on seston that was pre-handled by copepods than on seston that was pre-handled by daphniids, and that somatic growth decreased with increasing densities of daphniids in the enclosures. In contrast, we observed no differences in development rates for copepods grown on the different media. The population growth rates of Daphnia in the Daphnia treatments were determined in the enclosures. Growth differences in both somatic- and population growth of Daphnia were correlated to food quality aspects of the seston. In the laboratory we found that Daphnia growth was correlated with several fatty acids. The strongest regression was with the concentration of 20:43 (r ²= 0.37). This particular fatty acid also showed the highest correlation with growth after normalisation of the fatty acids to the carbon content of the enclosures (r ²= 0.33). On the other hand, in the enclosure the population growth correlated most to the particulate nitrogen content (r ²= 0.78) and only to the N:C ratio, when normalised to carbon (r ²= 0.51).     

δ15N of zooplankton species in subarctic lakes in northern Sweden: effects of diet and trophic fractionation

1. To assess the use of stable nitrogen isotopes (δ¹⁵N) for reconstructing trophic relationships in planktonic food webs, crustacean zooplankton species and pelagic dissolved and particulate matter were analysed in 14 subarctic lakes in northern Sweden. The lakes are situated along an altitudinal gradient and show a substantial variation in nutrient content and energy mobilization by bacterioplankton and phytoplankton. 2. The δ¹⁵N of dissolved and particulate matter was comparatively low, suggesting efficient N recycling and low losses of depleted N from the pelagic zone of these unproductive lakes. 3. Copepods had a systematically higher δ¹⁵N than cladocerans, with an average difference of 3.1–4.9‰ within lakes, implying different trophic positions of the two groups. Comparisons of nitrogen pools and energy fluxes suggest that the low cladoceran δ¹⁵N was a result of feeding on bacteria. 4. The difference in δ¹⁵N between copepods and cladocerans declined with decreasing bacterioplankton production among lakes, due either to increasing trophic isotope fractionation or decreasing relative importance of bacteria in the diet of cladocerans.     

Fatty acid content of the dorsal muscle—an indicator of fat quality in freshwater fish

In 56 samples of freshwater fish, most were low in fat, ≤ 5% of dry weight (D.W.), and the sum of all fatty acids (ΣFA) was about 2% of D.W. Trout, whitefish, and grayling had the highest content of the long-chained FA. of ω3 type, EPA and DHA (1·7–2·6% of D.W.). Two large, low-fat pikes with ΣFA of about12–3% of D.W. and a medium-fat whitefish had the highest ω3/ω6 ratios, 8–9, whereas the fattiest fishes, eels from two lakes and the Baltic (ΣFA =17–26% of D.W.) had lower ω3/ω6 ratios, 1·1–1·8 (ω3 and ω6 FA are two important series of FA). The results indicate that ΣA controls the content of saturated FA (SAFA) and monounsaturated FA (MUFA), whereas the polyunsaturated FA (PUFA) was independent of ΣFA after a break point of about 10%ΣFA of D.W. The P/S ratio (PUFA/SAFA) and the PUFA/ΣFA ratio decreased with increased ΣFA, whereas the ω3/ω6 ratio showed no clear correlation to ΣFA. The difference in fatty acid patterns lay between low-fat and high-fat fishes, rather than between marine and freshwater fishes. The variation, both within and between species of the separate FA is small in fish with similar ΣFA content. Also, low-fat and medium-fat fishes tend to be more dietarily favourable than high-fat fishes, when considering the latest criteria for high nutritional value to humans. Abbreviations used in the text: FA, fatty acids; ΣFA, sum of all FA; AA, arachidonic acid (20 : 4ω6); EPA, eicosapentaenoic acid (20 : 5ω3); DHA, docosahexaenoic acid (22 : 6ω3); SAFA, saturated fatty acids; MUFA, monounsaturated fatty acids; PUFA, polyunsaturated fatty acids; D.W., dry weight; F.W. fresh weight; CV, coefficient of variation; ω3 FA, series of PUFA with the first double bond located at carbon number 3; ω6 FA, series of PUFA with the first double bond located at carbon number 6. The fatty acids are described by three numbers, x:ywz, where x=number of carbon atoms, y=number of double bonds, and z=position of the first double bond counted from the methyl end of the molecule.