Lipid and Fatty Acid Composition of Tree-Growing and Terrestrial Lichens

A comparison of lipid and fatty acid composition was made of the tree-growing lichens Evernia prunastri (L.) Ach., Parmelia saxatilis (L.) Ach. and Hypogymnia physodes (L.) Ach. and the terrestrial species Cetraria islandica (L.) Ach. and Cladonia impexa Harm. In the terrestrial species the total lipid content varied strongly during spring, while the tree-growing species showed much less variation. Phospholipid and sterol content of all lichens was unusually low. Monoglycosyl diglyceride was absent from Parmelia saxatilis. Fatty acids common to higher plants as palmitic, stearic, oleic, linoleic and linolenic acid were invariably present in all lichen species. In addition large quantities of extra-long chain fatty acids like behenic acid, eicosadienoic acid and cyclic aliphatic lichen acids were present in the terrestrial species. The degree of (poly) unsaturation decreased in the order Evernia prunastri, Parmelia saxatilis. Fatty acids common to higher plants as palmitic, stearic, impexa, which decrease was compensated by an increase in extralong chain fatty acids and lichen acids. It is suggested that the lichen acids are of adaptive value for lichen species growing in the terrestrial habitats, which were characterized by extreme diurnal temperature variations. Just as the polyunsaturated fatty acids, lichen acids guarantee at lower temperatures a high flexibility of the membranes involved, at the same time as they are less susceptible to photo-oxidation at the high daytime temperatures.     

Metabolism of Hydrocarbons in Microorganisms

The fatty acid composition of the lipid of yellowfin tuna (Thunnus albacares) caught in two different localities, Philippine Sea (a tropical zone) and the Pacific coast area of Japan (a temperate zone) is described. The total lipids of various organs (dorsal ordinary muscle, ventral ordinary muscle, dark muscle, liver, heart, pyloric cecum, and orbital region) and of the stomach contents were extracted, and the fatty acid comosition was analyzed by gas-liquid chromatography (GLC).

Docosahexaenoic acid (DHA; 22:6n-3) was the major unsaturated fatty acid in the lipid of all organs in the specimens examined from both localities, the mean DHA content accounting for more than 25% (mean ± S.D. of 26.9 ±5.7%) of the total fatty acids. This value is markedly different from the fatty acid profile of other fish species, because, in general, the fatty acid composition of other species is variable and the DHA content is less than 20% of total fatty acids.

Although the mean DHA content of the total fatty acids in the lipid of yellowfin tuna caught in the tropical and temperate zones was markedly higher than that in other fish species, there was a small difference between that in the northern samples (temperate waters, 30.5 ±6.1%) and the southern samples (tropical waters, 25.9 ± 5.2%). It is suggested that this difference may be due to environmental effects, e.g., the fatty acid composition of the lipids of prey organisms, because there is also a small difference between the mean DHA content of northern prey fish (22.7 ±6.1%) and that of southern prey fish (19.2 ±4.0%).     

Lipid content and composition of the Antarctic lamellibranch, Laternula elliptica (King & Broderip) (Anomalodesmata: Laternulidae), in King George Island during an austral summer

Total lipid content, lipid classes and fatty acid composition were studied in various tissues of the Antarctic clam Laternula elliptica in an early austral summer. A histological examination of the gonads revealed that most of the clams examined were spawning or ready to spawn. Lipid content was highest in gills (14.9% of tissue dry weight), followed by gonads (10.9%) and digestive glands (9.9%), and averaged 8.2% for the soft tissues. The overall lipid contents were relatively low compared to temperate bivalves at a similar reproductive stage. Lipid class composition in the total lipid of L. elliptica was quite similar to those of most marine bivalves at lower latitudes, being dominated by triacylglycerols (19.3–41.4% of total lipids) and phospholipids (18.9–28.3%) in most of the organs. Large amounts of triacylglycerol deposits in non-reproductive tissues, particularly in siphon and gill, indicate a potential role of lipid as maintenance energy reserve, although the low lipid contents suggest that lipid may not serve as an energy reserve for any food-limited periods. Fatty acid composition in L. elliptica was also typical of marine bivalves with predominance of 16:0 (26%) and 20:5n-3 (18%) acids. Total fatty acids from the soft tissues showed a moderate level of unsaturation (50.6%), and about 35% of the total fatty acids were polyunsaturated. These values were not significantly different from, or even lower than those of marine bivalves in warmer waters. However, the content of 20:5n-3 (18.2% of total fatty acids), which dominated n-3 polyunsaturated fatty acids, was similar to those reported for other marine bivalve species in temperate waters. The fatty acid composition of L. elliptica reflected dietary input of some microalgal species. The nanoflagellates Cryptomonas spp., which were reportedly rich in 16:0, 18:3n-3 and 20:5n-3, predominated in the water column during the present investigation. Accepted: 19 June 1999     

HIGH POLYUNSATURATED FATTY ACID LEVELS IN TWO SUBTROPICAL MACROALGAE,CLADOSIPHON OKAMURANUS AND CAULERPA LENTILLIFERA1

The lipid and fatty acid compositions in two edible subtropical algae (the brown alga Cladosiphon okamuranus Tokida and the green alga Caulerpa lentillifera J. Agardh) were determined to clarify their lipid characteristics and nutritional values. Glycolipids and phospholipids were the major lipid classes, with significant levels of triacylglycerols. Polyunsaturated fatty acids (PUFA) were the major fatty acids of both algae. The lipid class composition and major fatty acids were similar in both the algal species, irrespective of wild and cultured specimens. Typical n‐6 PUFA, such as 18:2n‐6 (linoleic acid) and 20:4n‐6 (arachidonic acid), occurred in characteristically high levels in both of the algae. High levels of n‐3 PUFA were measured in all lipid classes of both species without 22:6n‐3 (docosahexaenoic acid), 18:3n‐3, 18:4n‐3, and 20:5n‐3 (eicosapentaenoic acid) for Cl. okamuranus; and 16:3n‐3, 18:3n‐3, and 20:5n‐3 for Ca. lentillifera. The finding suggests that the green algal species, which mainly biosynthesizes short‐chain (C₁₆ and C₁₈) PUFA, differs from that of the brown alga, which is capable of biosynthesizing high 20:5n‐3 levels. The PUFA levels in glycolipids of the two algal species comprised up to 60%, even though they are subtropical marine species. High n‐6 PUFA levels in the algal lipids probably influence the significant levels of n‐6 PUFA in herbivorous fishes, because the n‐6 PUFA levels in marine fish lipids are generally undetectable or negligible.     

Understanding the trophic role of the Antarctic ctenophore,Callianira antarctica,using lipid biomarkers

To better understand the trophic role of ctenophores in Antarctica during austral fall and winter, a major species of cydippid ctenophore, Callianira antarctica, was collected during April/May (fall) and August/September (winter) 2002 in the vicinity of Marguerite Bay. Lipid content, lipid classes, fatty acids, fatty alcohols and sterols were analyzed in animals, together with lipid biomarkers in krill and copepod species representing potential ctenophore prey. Lipid content in ctenophores collected in winter was slightly higher than from animals in fall (4.8 and 3.5% of dry weight, respectively). Polar lipids were the dominant lipid class in ctenophores, accounting for over half of the lipid content, with significant amounts of free fatty alcohols (more than 10% of total lipid content) detected. Lipid-class composition, however, differed significantly between seasons, with significant amounts of neutral lipid (wax esters and triacylglycerols) only detected in animals from fall. Although the dominant lipid classes in ctenophores varied between fall and winter, individual lipids (i.e., fatty acids, alcohols and sterols) showed only minor changes between seasons. Specifically, long-chain polyunsaturated fatty acids [20:5(n-3) and 22:6(n-3)] found in high abundance in larval krill were also elevated in ctenophores collected in winter. Very high amounts of monounsaturated fatty alcohols, particularly 20:1(n-9) and 22:1(n-11), known to be important components of wax esters in calanoid copepods, were also observed. Multivariate analysis using the suite of lipids found indicated that copepods are an important diet item for ctenophores in the study area. Results further suggest that C. antarctica feed actively year-round, with larval krill providing a food resource during austral winter.     

Morphological and Chemical Differentiation between Tunisian Populations of Pinus halepensis,Pinus brutia,and Pinus pinaster

The lipid fraction of seeds from different pine species and populations was studied regarding total lipid content, fatty acid profile and vitamin E composition. The investigated seeds contained a high percentage of lipid (13.6 to 31.5 %). Lipid fractions were found to be rich in vitamin E, which varied significantly among species and populations. P. halepensis (Ph−Hn) showed the highest content of vitamin E (256.3 mg/kg of seeds) and the uppermost content of α-tocopherol (44 mg/kg). However, P. halepensis (Ph−Kas) was the richest in γ-tocopherol (204.9 mg/kg). Lipid fractions had a low content of δ-tocopherol (1.2 to 3.6 mg/kg. The highest content of γ-tocotrienol (∼18 %) was determined for P. halepensis (Ph−Dc and Ph−Hn). Thirteen fatty acids were identified by GC-FID with significant variation between the investigated species. The linoleic acid was the major fatty acid followed by oleic acid and palmitic acid. The chemical differentiation among species for the composition of fatty acids and vitamin E was confirmed by PCA. Significant correlations were observed between the content of vitamin E and fatty acids and ecological parameters of P. halepensis populations.     

Total lipid and fatty acid composition of seaweeds for the selection of species for oil‐based biofuel and bioproducts

We investigated the potential of seaweeds as feedstock for oil‐based products, and our results support macroalgae (seaweeds) as a biomass source for oil‐based bioproducts including biodiesel. Not only do several seaweeds have high total lipid content above 10% dry weight, but in the brown alga Spatoglossum macrodontum 50% of these lipids are in the form of extractable fatty acids. S. macrodontum had the highest fatty acid content (57.40 mg g^?1 dw) and a fatty acid profile rich in saturated fatty acids with a high content of C18:1, which is suitable as a biofuel feedstock. Similarly, the green seaweed Derbesia tenuissima has high levels of fatty acids (39.58 mg g^?1 dw), however, with a high proportion of PUFA (n‐3) (31% of total lipid) which are suitable as nutraceuticals or fish oil replacements. Across all species of algae the critical parameter of fatty acid content (measured as fatty acid methyl esters, FAME) was positively correlated (R² = 0.67) with total lipid content. However, the proportion of fatty acids to total lipid decreased markedly with total lipid content, generally between 30% and 50%, making it an inaccurate measure of the potential to identify seaweeds suitable for oil‐based bioproducts. Finally, we quantified within species variation of fatty acids across locations and sampling periods supporting either environmental effects on quantitative fatty acid profiles, or genotypes with specific quantitative fatty acid profiles, thereby opening the possibility to optimize the fatty acid content and quality for oil production through specific culture conditions and selective breeding.     

Fatty Acid Compositions of Triglyceride and Phospholipid from Candida tropicalis Grown on n-Alkanes

The content of total cellular lipid of Candida tropicalis grown on a mixture of n-alkanes (C₁₀–C₁₈) was about 20% of the dry cell weight at the exponential growth phase and 14% at the early stationary phase. Phospholipid corresponded to approximately 70 % of the total lipid independent of the growth phases. The composition of cellular lipid classes did not change significantly during the growth. On the other hand, a drastic time-course change in fatty acid composition was observed. The proportion of odd-chain fatty acids, one of the most specific cellular components of the yeast grown on the n-alkane mixture, increased in both phospholipid and triglyceride along with the yeast growth. In the meantime, the proportion of polyunsaturated fatty acids varied markedly during the course of cultivation, showing a peak at the early growth phase. The high content of polyunsaturated fatty acids at the early stages of growth correlated to the contents of these acids in phospholipid rather than in triglyceride.     

Cold hardening induces transfer of fatty acids between polar and nonpolar lipid pools in the Arctic collembollan Megaphorura arctica

Cold hardiness in the Arctic Collembola Megaphorura arctica (Tullberg), formerly Onychiurus arcticus, has been the subject of extensive studies over the last decade. This species employs an unusual strategy known as cryoprotective dehydration to survive winter temperatures as low as ?25 °C. To expand knowledge of cryoprotective dehydration in M. arctica, the present study investigates how a reduction in ambient temperature affects the fatty acid composition of the total body lipid content along with polar (mainly membrane phospholipids) and nonpolar (mainly triacylglycerols) lipids. Most ectothermic animals compensate for changes in fluidity by regulating fatty acid composition, a process often described as homeoviscous adaptation. In M. arctica, changes in the fatty acid composition of total body lipid content during cold treatment are only moderate, with no clear pattern emerging. However, the levels of unsaturated fatty acids in the polar lipids increase with cold exposure, largely attributable to 16 : 1(n? 7), 18 : 1(n? 9), 18 : 3(n? 6) and 18 : 3(n? 3), whereas unsaturated fatty acid levels in the nonpolar lipids correspondingly decrease. These results suggest a reallocation of fatty acids between the two lipid pools as a response to a temperature reduction of 6 °C. Because of hypometabolism, a characteristic of cold adaptation, such a mechanism could be less energy demanding than de novo synthesis of fatty acids and may comprise part of an adaptive homeostatic response.     

Lipid quality of the diatoms Skeletonema costatum and Navicula gregaria from the South Atlantic Coast (Argentina): evaluation of its suitability as biodiesel feedstock

Since the fatty acid ester profile of a given biofuel is relatively consistent with the source’s fatty acid profile, the properties of the biodiesel produced from a particular feedstock exhibit predictable quality. Thus, lipid fractions and the fatty acid composition of stationary growth-phase cultures of the local strains of the diatoms Skeletonema costatum and Navicula gregaria were analysed to evaluate their suitability as biodiesel feedstock. Total lipid content was 20.83 pg cell⁻¹ in S. costatum and 19.17 pg cell⁻¹ in N. gregaria. Neutral lipids were the main fraction of total lipids in both species, accounting for ca. 65% and 76%, respectively. S. costatum was predominant in saturated fatty acids (SFAs; 43.48 %) and monounsaturated fatty acids (MUFAs; 40.11%), while N. gregaria was predominant in MUFAs (54.85%), followed by SFAs (33.42%). In S. costatum, the main fatty acids in neutral lipid fraction were myristic, palmitic, palmitoleic and oleic acids, while the main ones in N. gregaria were palmitic and palmitoleic acids. The oils extracted from these species presented linolenic acid contents within biodiesel’s quality specifications. However, in neutral lipid fraction both species showed eicosapentaenoic acid levels higher than the required limit. The lipid quality analysed in both species suggests that a biodiesel derived from these oils may present an acceptable cetane number, but likely poor cold-flow properties. This baseline information is useful for future research tending to find more suitable conditions in order to improve oil yield. In addition, both estuarine species neither compete with agriculture for food nor require farmland nor fresh water.     

A quantitative analysis of microalgal lipids for optimization of biodiesel and omega‐3 production

The lipid characteristics of microalgae are known to differ between species and change with growth conditions. This work provides a methodology for lipid characterization that enables selection of the optimal strain, cultivation conditions, and processing pathway for commercial biodiesel production from microalgae. Two different microalgal species, Nannochloropsis sp. and Chlorella sp., were cultivated under both nitrogen replete and nitrogen depleted conditions. Lipids were extracted and fractionated into three major classes and quantified gravimetrically. The fatty acid profile of each fraction was analyzed using GC–MS. The resulting quantitative lipid data for each of the cultures is discussed in the context of biodiesel and omega‐3 production. This approach illustrates how the growth conditions greatly affect the distribution of fatty acid present in the major lipid classes and therefore the suitability of the lipid extracts for biodiesel and other secondary products. Biotechnol. Bioeng. 2013; 110: 2096–2104. © 2013 Wiley Periodicals, Inc.     

Utilization of endogenous lipid by the isolated perfused rat heart

1. The lipids of the rat heart have been studied with regard to amount, classes present and fatty acid composition of free fatty acids, triglycerides and phospholipids. Myocardial lipid contained 300μmoles of total fatty acid/g. dry wt. of which only 2–4μmoles were free; the remainder was esterified, chiefly as phospholipid. Neutral esters, of which triglyceride was the principal form, made up 15% of the total fatty acids. 2. When normal hearts were perfused with a nutrient-free medium until exhaustion, the triglyceride concentration declined from 43 to 13μmoles/g. dry wt. The content of phospholipids, partial glycerides and cholesteryl esters did not change. When the lipids of the rat heart were labelled with [1-¹⁴C]palmitate before perfusion with non-nutrient medium, radioactivity disappeared from the triglyceride, diglyceride and free fatty acid fractions, but not from the phospholipid or other ester classes. 3. These experiments support the view that only a small fraction of the total cardiac lipid, principally triglycerides and to a smaller extent diglycerides, is available as a source of fuel in the absence of exogenous substrate.     

Fatty acid composition of vitellogenin from four teleost species

The fatty acid compositions of vitellogenin and liver from cod (Gadus morhua), rainbow trout (Oncorhynchus mykiss), turbot (Scophthalmus maximus) and wolffish (Anarhichas lupus) were determined. Vitellogenin was isolated from plasma of estradiol-17-treated fish by precipitation with EDTA-Mg²⁺ and distilled water or by high-performance ion-exchange chromatography. In all investigated species, vitellogenin contained 16–18% (w/w) lipid, in which polyunsaturated fatty acids, predominantly 20:5 (n-3) and 22:6 (n-3), comprised about 50% of the total fatty acids. The proportions of saturated, monounsaturated, polyunsaturated and (n-3) fatty acids in vitellogenin of the different species were generally similar, although the relative content of specific fatty acids was distinctive for each species. The distribution of fatty acids in total lipids of vitellogenin was highly consistent among individual females of each species. In contrast, liver fatty acid composition varied considerably, both within and between species. Altogether, the differences in the fatty acid composition of vitellogenin and liver from each species indicate that a specific selection of fatty acids occurs during the lipidation of vitellogenin.Abbreviations BHT butylated hydroxytoluene - E-17 estradiol-17 - EDTA ethylenedinitrilo tetra-acetic acid disodium salt dihydrate - FA fatty acids - FAME fatty acid methyl esters - HDL high density lipoproteins - PUFA polyunsaturated fatty acids - SD standard deviation - TLC thin-layer chromatography - VHDL very high density lipoproteins - VLDL very low density lipoproteins - v/v volume per volume - w/v weight per volume - w/w weight per weight     

Lipid content and fatty acid distribution in tissues from Portuguese dogfish, leafscale gulper shark and black dogfish

The lipid characterization in tissues from the three deep-sea sharks leafscale gulper shark (Centrophorus squamosus), Portuguese dogfish (Centroscymnus coelolepis) and black dogfish (Centrocyllium fabricii) captured at Hatton Bank in the North Atlantic were examined. The objective was to determine the lipid content and the fatty acid composition in different tissues. In addition, the fatty acid composition in tissues and species was compared. The tissues examined were pancreas, heart, kidney, stomach, spleen and liver. The lipid content was high in liver (40–50%) and ranged from 1% to 5% in the other tissues. The dominant fatty acids were C16:0, C18:1 (n-9), C18:1 (n-7) and C22:6 (n-3) in all tissues. All tissues had a high content of unsaturated fatty acids.     

The lipid compositions of high-Antarctic notothenioid fish species with different life strategies

Lipid and fatty acid compositions of five notothenioid fishes from the Antarctic Weddell and Lazarev Seas were investigated in detail with regard to their different modes of life. The pelagic Aethotaxis mitopteryx was the lipid-richest species (mean of 61.4% of dry mass, DM) followed by Pleuragramma antarcticum (37.7%DM). The benthopelagic Trematomus lepidorhinus had an intermediate lipid content of 23.2%DM. The benthic Bathydraco marri (20.8%DM) and Dolloidraco longedorsalis (14.5%DM) belonged to the lipid-poorer species. Triacylglycerols were the major lipid class in all species. Important fatty acids were 16:0, 16:1(n-7), 18:1(n-9), 18:1(n-7), 20:5(n-3) and 22:6(n-3). The enhanced proportions of the long-chain monounsaturated fatty acids, 20:1 and 22:1, in the lipid-rich pelagic fishes clearly reflected the ingestion of the two copepod species, Calanoides acutus and Calanus propinquus, which are the only known Antarctic zooplankters rich in these fatty acids. Although wax esters are the major storage lipid in many prey species, they were absent in all notothenioid fishes studied. Thus, wax esters ingested with prey are probably converted to triacylglycerols via fatty acids or metabolised by the fishes. The enhanced lipid accumulation with increasingly pelagic lifestyle has energetic advantages, especially with regard to improved buoyancy. It is still unknown to what extent these lipids are utilised as energy reserves, since it has been suggested that not only the benthic but also the pelagic Antarctic fishes are rather sluggish, with a low scope for activity and hence low metabolic requirements. Accepted: 14 May 2000     

Lipid and Fatty Acid Composition in the Flesh of an Edible Marine Fish: Amadi (Coilia reynaldi)

Amadi is a small sized edible marine fish species (Coilia reynaldi) under the order-Clupeiformes. It is important for principal lipids and in particular for highly unsaturated fatty acids which have potential biomedical benefits. Among the lipid classes, phospholipids were found to be the most predominant constituents than the glycolipid and neutral lipid in Amadi. Twenty six fatty acids were quantified by open tube gas–liquid chromatography. Dominant fatty acids in this fish are Palmitic acid (C_16:0), Stearic acid (C_18:0), Oleic acid (C_18:1n?9), Myristic acid (C_14:0), Palmitoleic acid (C_16:1), Docosahexanoic acid (C_22:6n?3), Pentadecanoic acid (C_15:0), and Eicosatetraenoic acid (C_20:4n?3). Fatty acid deficiency in fish species is indicated by the presence of C_20:3n?9 acid. It is absent in this fish.The content of DHA and EPA are maximum in amount in neutral lipid than other lipid classes.     

Content of arachidonic and eicosapentaenoic acids in polar lipids from Gracilaria (Gracilariales,Rhodophyta)

Fatty acid composition, especially the distribution of eicosapolyenoic acids in several species of Gracilaria, was analyzed in relation to their taxonomy. The species have been grouped into two types based on distribution of these polyenoic acids: Type 1, which contains palmitic, oleic and arachidonic acids as the major components, and Type II, which contains eicosapentaenoic acid in addition to Type I fatty acids. Octadecapolyenoic acids were detected only in trace amounts in each Type. A similar remarkable difference also was observed in the fatty acid composition of lipid classes. The major component of eicosapolyenoic acids in Type I was arachidonic acid in all lipid classes. In Type II, eicosapentaenoic acid was the major component in monogalactosyl diacylglycerol, digalactosyl diacylglycerol, sulfoquinovosyl diacylglycerol and phosphatidylglycerol. Arachidonic and eicosapentaenoic acids were contained in large amounts in Type II phosphatidylcholine. Grouping of Gracilaria species into Type I and Type II is not entirely consistent with morphological and taxonomic features, but the difference in fatty acid composition is likely due to genetic rather than to environmental factors.     

The density of odontocete integument depends on blubber lipid composition and temperature

Cetacean integument serves many functional roles, including contribution to whole body buoyancy. The blubber of the integument of different cetacean species contains varying concentrations of triacylglycerols (TAG) and wax esters (WE); generally, these lipid classes have different densities. Integument can also experience a wide range of temperatures during a dive, so its density may change with depth. The goals of this study were to measure integument density and isolated blubber lipid density in three deep‐diving odontocete species (n = 3–4)—short‐finned pilot whales (Globicephala macrorhynchus), pygmy sperm whales (Kogia breviceps), and Gervais' beaked whales (Mesoplodon europeaus)—at different temperatures (6°C–35°C), and to relate these densities to lipid content and composition. Kogia and Mesoplodon integument and isolated lipids had high WE content (78.7–99.5 wt%) and were less dense (by 1.7%–9.3%) than those of Globicephala, which were composed predominately of TAG. Generally, densities increased as temperature decreased. Changes in integument densities mirrored those of isolated lipid densities, suggesting that blubber lipids are largely responsible for the buoyant properties of cetacean integument. These data demonstrate that the contribution of the integument to whole body density depends on lipid class and temperature, and therefore may provide useful, species‐specific correction factors for diving energetics models.     

Fatty acid and alcohol composition of the small polar copepods,Oithona and Oncaea: indication on feeding modes

The fatty acid and alcohol compositions of the Antarctic copepods Oithona similis, Oncaea curvata, Oncaea antarctica and the Arctic Oncaea borealis were determined to provide the first data on their lipid biochemistry and to expand the present knowledge on their feeding modes and life-cycle strategies. All these tiny species contained high amounts of wax esters (on average 51.4–86.3% of total lipid), except females of Oithona similis (15.2%). The fatty-acid composition was clearly dominated by 18:1(n-9), especially in the wax-ester-rich Oncaea curvata (79.7% of total fatty acids). In all species, 16:0 and the polyunsaturated fatty acids 20:5(n-3) and 22:6(n-3), which are structural components of all membranes, occurred in significant proportions. The dominant fatty alcohols were 14:0 and 16:0. In Oncaea antarctica and Oncaea borealis, the 20:1(n-9) and 22:1(n-11) alcohols and, to a lesser extent, the corresponding fatty acids were also found in high proportions. This indicates carnivorous feeding, although de novo biosynthesis cannot be excluded. The variable composition might be due to a wider range of food items and parasitic feeding. Typical trophic marker fatty acids for phytoplankton ingestion occurred only in small amounts, which suggests that the species were feeding on particles such as detritus or aggregates and not on living phytoplankton. From the compositional data of fatty acids and alcohols, it can be concluded that feeding behaviour of all species is omnivorous and/or carnivorous.     

Fatty acid and lipid analysis of the house cricket,Acheta domesticus

The fatty acid content and composition of the house cricket Acheta domesticus have been investigated in entire insects at different developmental stages and in selected organs of male and female adults. We have also determined the fatty acid composition of the various lipid classes within extracts of the organs of adult female insects. Fatty acids were analysed by capillary gas chromatography or mass spectrometry as their methyl esters (FAMEs) after direct transesterification of insect material or separated lipid classes.The major esterified fatty acids in all extracts were palmitate (C_16:0), stearate (C_18:0), oleate (C_18:1) and linoleate (C_18:2). Levels of esterified fatty acid varied considerably between organs but the fatty acid compositions showed only small variations. The levels of polyunsaturated fatty acids of the C₁₈ series were considerably higher in phospholipid fractions than in other lipid classes. Triacylglycerols formed the major lipid class in ovaries, fat-body and newly-laid eggs, whereas diacylglycerols and phospholipid predominate in the haemolymph. Triacylglycerols, phospholipids, diacylglycerols and free fatty acids were all found in significant amounts in the gut tissue.