Impact of feeding and starvation on the lipid metabolism of the Arctic pteropod Clione limacina

Feeding and starvation experiments were carried out with Clione limacina sampled in Kongsfjorden (Svalbard, Arctic) during summer 2002. Dry mass and lipid mass, lipid class and fatty acid compositions were analysed. Specimens of C. limacina used for the feeding study had a mean length of 25 mm, a dry mass (DM) of 13.7 mg, and a moderate lipid content of 12.1%DM. Animals were allowed to ingest only one individual of its exclusive prey, Limacina helicina which had 8.0 mm in diameter, 21.4 mg DM and 8.7% lipid of ash-free DM. Five days after feeding, the dry mass of C. limacina had increased from 13.7 to 25.3 mg which corresponds to an uptake of about 80% of the ash-free DM (14.3 mg) of L. helicina. Lipid mass increased from 1.5 to 3.9 mg which is almost two times more the ingested lipid from L. helicina (1.2 mg lipid). Thus, the major portion of lipids was synthesised de novo by C. limacina from non-lipid compounds. These lipids were triacylglycerols (TAG) and 1-O-alkyldiacylglycerol ethers (DAGE), increasing from low proportions of 6.1% and 5.7% to 42.3% and 25.8%, respectively. Considerable de novo synthesis was observed for the monounsaturated fatty acids 16:1(n − 7), 17:1(n − 8), 18:1(n − 9), and 18:1(n − 7) and the alkyl moiety 16:0. The increase in the polyunsaturated fatty acids 22:6(n − 3), 20:5(n − 3), and 18:4(n − 3) corresponded with the amount available by ingestion of L. helicina, supporting that C. limacina is not able to synthesise polyunsaturates. After 15 days of digestion, dry mass and lipids dropped almost back to the initial values.During the 100-day starvation experiment, two groups of animals were separately considered as storage lipid-rich and lipid-poor animals because of their large differences in the amount and proportion of TAG and DAGE. Storage lipid-rich C. limacina were only found until day 50, whereas lipid-poor animals were present throughout the experiment. In the lipid-rich specimens, the levels of TAG were about twice that of DAGE. The proportions of TAG decreased considerably during the 50 days of starvation (from 48.3% to 25.1% of total lipid). DAGE, varying between 16.5% and 20.5%, showed only a small decrease. The lipid-poor animals survived 100 days of starvation, exhibiting low initial amounts and proportions of storage lipids which were nearly exhausted at the end. In all C. limacina specimens, the total lipid content remained almost constant showing that lipid and non-lipid components were simultaneously utilised. This implies that body shrinkage may be an important adaptation to long-term starvation. Based on these results, it is possible to estimate the potential survival period of lipid-rich C. limacina under food limitation. A model, which considers maturity and reproduction (egg production), reveals that lipid-rich specimens might be able to survive up to 260 days without food.     

Exceptional long-term starvation ability and sites of lipid storage of the Arctic pteropod <Emphasis Type="Italic">Clione limacina</Emphasis>

The Arctic pteropod Clione limacina was collected in Kongsfjorden, Svalbard, in mid June 2004, to study the lipid metabolism within the sites of lipid storage structures during long-term starvation. Animals survived in an aquarium without any food for nearly 1 year (356 days). Size, number of lipid droplets, dry and lipid mass, lipid class and fatty acid compositions of C. limacina were determined and separately analysed for the digestive gland and the remaining integument. During the starvation period, animals shrunk from 22.4 to 12 mm in length on average, and the number of lipid droplets decreased from 1,600 to 1,000 per animal. Dry mass (DM) and total lipid mass both dropped by about 80% from day 200 to the end. The lipid content as percentage DM of the total organism did not decrease significantly ranging from 43.8 to 32.3%DM. The lipid content of the trunk was moderate with about 20%DM. The digestive gland was very rich in lipids with more than 70%DM throughout the experiment and is the major site of lipid metabolism and storage. Triacylglycerols (TAG) decreased, in the total organism, from high initial levels of 62.6 to 43% of total lipid at the end. In contrast, the proportions of 1-O-alkyldiacylglycerols [diacylglycerol ethers (DAGE)] remained almost constant, varying between 20.4 and 28.4%. In the digestive gland, TAG ranged from 60.3 to 64.8% and DAGE from 23.6 to 32.2% from day 200 to the end of the experiment. TAG and DAGE of the trunk were most likely located in the lipid droplets and were almost depleted at the end of starvation. Besides their function as lipid deposit DAGE may also act as protecting substance against bacterial and fungal infections. During the first 200 days of starvation, the fatty acid compositions showed only small variations. Thereafter, fatty acids typical for storage lipids decreased in all body compartments. In adaptation to long periods of food scarcity, C. limacina has evolved various strategies as body shrinkage, utilisation of body constituents not essential for survival, a very low metabolism and slow lipid consumption.     

Effects of 3-thia fatty acids on feed intake, growth, tissue fatty acid composition, beta-oxidation and Na+,K+-ATPase activity in Atlantic salmon

Atlantic salmon (Salmo salar) with an initial mass of 86 g were reared in 12 °C seawater for 8 weeks to a final average mass of 250 g. The fish were fed fish meal and fish oil-based diet supplemented with either 0%, 0.3% or 0.6% of tetradecylthioacetic acid (TTA), a 3-thia fatty acid. The specific growth rate (SGR) decreased with increasing dietary dose of TTA. The SGR of the group fed 0% of TTA (Control) was 1.8; that of the group fed 0.3% of TTA (TTA-L) was 1.7, and that of the group fed 0.6% of TTA (TTA-H) was 1.5. The mortality increased with increased dietary dose of TTA. The mitochondrial β-oxidation capacity in the liver of fish fed the TTA diets was 1.5 to 2 times higher than that of the Control fish. TTA supplementation caused substantial changes in the fatty acid compositions of the phospholipids (PL), triacylglycerols (TAG) and free fatty acids (FFA) of gills, heart and liver. The percentages of n−3 fatty acids, particularly 22:6 n−3, increased in fish fed diets containing TTA, while the percentage of the saturated FAs 14:0 and 16:0 in the PL fractions of the gills and heart decreased. The sum of monounsaturated FAs in the PL and TAG fractions from liver was significantly higher in fish fed diets containing TTA. TTA itself was primarily incorporated into PL. Two catabolic products of TTA (sulphoxides of TTA) were identified, and these products were particularly abundant in the kidney. TTA supplementation had no significant effect on the activity of the membrane-bound enzyme Na⁺,K⁺-ATPase.     

Total lipid and fatty acid compositions of <Emphasis Type="Italic">Lertha sheppardi</Emphasis> (Neuroptera: Nemopteridae) during its main life stages

Total lipid and the fatty acid compositions of phospholipid and triacylglycerol fractions, prepared from eggs, 3^rd instars of larvae, pupae, male and female adults of Lertha sheppardi, were analyzed by gas chromatography and gas chromatography-mass spectrometry. The effect of diet (adults’ nutrition) on fatty acid composition of L. sheppardi adults was also investigated. Total lipid of L. sheppardi considerably increased in adults compared with immature stages. There was a significant decrease in total lipid level in larval stage in contrast with egg stage. Qualitative analysis revealed the presence of 14 fatty acids during all stages. The major components were C16 and C18 saturated and unsaturated components which are ubiquitous to most animal species. In addition to these components, one odd-chain (C17:0) and prostaglandin precursor fatty acids were found. The fatty acid profiles of phospholipids and triacylglycerols were substantially different. In phospholipid fraction, monounsaturated fatty acids were the major proportion of fatty acids in both sex of adults and pupae, whereas polyunsaturated fatty acids were the most dominant fatty acids in eggs and 3^rd instars. Results of triacylglycerol fraction revealed that fatty acid composition of eggs had higher level of C16:1, C18:0 and C18:3n-3 content than that of 3^rd instars and pupae, which suggests accumulation of energetic and structural reserve materials during embryonic development. At more advanced developmental stages, mainly in adult females, the amount of C16:1 increased once again, which may be related to the need for accumulation of sufficient energy and of carbon reservoir in the developing new vitellum. Percentages of C18:1 were significantly high in adult stages compared to other stages. These findings indicate that the accumulation and consumption of fatty acids fluctuate through different development stages. Diet did not effect the fatty acid composition of L. sheppardi adults.     

Lipid compositions in diatom Conticribra weissflogii under static and aerated culture conditions

The diatom Conticribra weissflogii is a microalga with high nutrition value, rich in docosahexaenoic acids (DHA) and eicosapentaenoic acids (EPA). In order to study the effect of culture conditions on the changes of lipid compositions, the intact lipid structural profiles and fatty acids in C. weissflogii were monitored under static and aerated culture conditions. The results showed that, lipids identified in C. weissflogii were neutral lipid triacylglycerols (TAG), betaine lipid diacylglycerylcarboxy‐N‐hydroxymethyl‐choline (DGCC), phosphatidylcholine (PC) and four classes of photosynthetic glycerolipids. The profiles of lipid metabolites of C. weissflogii were different between two culture modes, with the following characteristics under aerated conditions: TAGs increased significantly, whereas the levels of sulfoquinovosyl diacylglycerol (SQDG), monogalactosyldiacylglycerol (MGDG), and DGCC decreased. Furthermore, higher contents of EPA‐rich TAG and EPA/DHA‐rich DGCC were detected at the end of stationary phase, while EPA/DHA‐rich PC, EPA‐rich MGDG and EPA‐rich digalactosyldiacylglycerol (DGDG) were obtained in the exponential phase under static conditions. Meanwhile, the contents of almost all classes of the essential fatty acids (EFAs)‐enriched lipids increased at onset of stationary phase under aerated conditions. Taken together, given that the high levels of EFAs are required for artificial rearing of marine organisms, aeration is critically important for increasing the production rate and the contents of EFA molecules and therefore increasing the nutritional value of the microalgae.     

Molecular and Functional Analysis of Three Fatty Acyl-CoA Reductases with Distinct Substrate Specificities in Copepod Calanus finmarchicus

The marine copepod Calanus finmarchicus constitutes the substantial amount of biomass in the Arctic and Northern seas. It is unique in that this small crustacean accumulates a high level of wax esters as carbon storage which is mainly comprised of 20:1n−9 and 22:1n−11 alcohols (Alc) linked with various kinds of fatty acids, including n−3 polyunsaturated fatty acids. The absence of 20:1n−9 Alc and 22:1n−11 Alc in diatoms and dinoflagellates, the primary food sources of copepods, suggests the existence of de novo biosynthesis of fatty alcohols in C. finmarchinus. Here, we report identification of three genes, CfFAR1, CfFAR2, and CfFAR3, coding for fatty acyl-CoA reductases involved in the conversion of various fatty acyl-CoAs to their corresponding alcohols. Functional characterization of these genes in yeast indicated that CfFAR1 could use a wide range of saturated fatty acids from C18 to C26 as substrates, CfFAR2 had a narrow range of substrates with only very-long-chain saturated fatty acid 24:0 and 26:0, while CfFAR3 was active towards both saturated (16:0 and 18:0) and unsaturated (18:1 and 20:1) fatty acids producing corresponding alcohols. This finding suggested that these three fatty acyl-CoA reductases are likely responsible for de novo synthesis of a series of fatty alcohol moieties of wax esters in C. finmarchicus.     

Cellular Lipid and Fatty Acid Compositions of Burkholderia pseudomallei Strains Isolated from Human and Environment in Viet Nam

Viet nam is known as an endemic area of melioidosis but its etiologic agent originated in Viet nam was not extensively studied. For the first time, we analyzed the cellular lipid and fatty acid compositions of 15 Vietnamese isolates of Burkholderia pseudomallei, 10 from humans and 5 from the environment. Cellular lipid compositions were analyzed by two-dimensional thin-layer chromatography on silica gel G plates. Cellular fatty acid methyl esters were analyzed by gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS). The major lipids in all the isolates were phosphatidylglycerol (PG), two forms of phosphatidylethanolamine (PE-1 and PE-2), and two forms of ornithine-containing lipid (OL-1 and OL-2). PE-1 contained non-hydroxy fatty acids at both sn-1 and ?2 positions, while PE-2 possessed 2-hydroxy fatty acids and non-hydroxy fatty acids in a ratio of 1: 1. Since snake venom phospholipase A₂ digestion of PE-2 liberated 2-hydroxy fatty acids, it was confirmed that these acids are at the sn-2 position of glycerol moiety. In both OL-1 and OL-2, amide-linked fatty acid was 3-hydroxy palmitic acid (3-OH-C16: 0), while ester-linked fatty acids were non-hydroxy acids in OL-1 and 2-hydroxy acids in OL-2. The total cellular fatty acid compositions of the test strains were characterized by the presence of 2-hydroxy palmitic (2-OH-C16: 0), 2-hydroxy hexadecenoic (2-OH-C16: 1), 2-hydroxy octadecenoic (2-OH-C18: 1), 2-hydroxy methylene octadecanoic (2-OH-C19CPA), 3-hydroxy myristic (3-OH-C14: 0) and 3-hydroxy palmitic (3-OH-C16: 0) acids. There were significant differences in the concentration of hexadecenoic (C16: 1), methylene hexadecanoic (C17CPA), octadecenoic (C18: 1) and methylene octadecanoic (C19CPA) acids among the Vietnamese isolates of B. pseudomallei. However, no significant difference was observed in cellular lipid and fatty acid components between strains of human and environmental origins.     

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.     

Poles Apart: The “Bipolar” Pteropod Species Limacina helicina Is Genetically Distinct Between the Arctic and Antarctic Oceans

The shelled pteropod (sea butterfly) Limacina helicina is currently recognised as a species complex comprising two sub-species and at least five “forma”. However, at the species level it is considered to be bipolar, occurring in both the Arctic and Antarctic oceans. Due to its aragonite shell and polar distribution L. helicina is particularly vulnerable to ocean acidification. As a key indicator of the acidification process, and a major component of polar ecosystems, L. helicina has become a focus for acidification research. New observations that taxonomic groups may respond quite differently to acidification prompted us to reassess the taxonomic status of this important species. We found a 33.56% (±0.09) difference in cytochrome c oxidase subunit I (COI) gene sequences between L. helicina collected from the Arctic and Antarctic oceans. This degree of separation is sufficient for ordinal level taxonomic separation in other organisms and provides strong evidence for the Arctic and Antarctic populations of L. helicina differing at least at the species level. Recent research has highlighted substantial physiological differences between the poles for another supposedly bipolar pteropod species, Clione limacina. Given the large genetic divergence between Arctic and Antarctic L. helicina populations shown here, similarly large physiological differences may exist between the poles for the L. helicina species group. Therefore, in addition to indicating that L. helicina is in fact not bipolar, our study demonstrates the need for acidification research to take into account the possibility that the L. helicina species group may not respond in the same way to ocean acidification in Arctic and Antarctic ecosystems.     

The effect of the entomopathogenic fungus Conidiobolus coronatus on the composition of cuticular and internal lipids of Blatta orientalis females

The composition of cuticular and internal lipids in females of the cockroach Blatta orientalis L. exposed to the entomopathogenic fungus Conidiobolus coronatus is investigated. The compositions of the fatty acids, n‐alkanes, alcohol, sterols and methyl esters in the lipids are chemically characterized. Although contact with virulent colonies of the fungus does not induce insect mortality, significant changes in the lipid profiles, both cuticular and internal, are found. The cuticular extracts of a control group of B. orientalis females contain 24 compounds varying in carbon chain length from C6 to C22. The main cuticular fatty acids identified are: C16:1, C16:0, C18:1 and C18:0_. The cuticular lipids of B. orientalis females after exposure to C. coronatus contain only 14 free fatty acids from C8 to C20. The highest concentrations identified are C16:0, C18:2 and C18:1. Analysis by gas chromatography‐mass spectrometry identifies the presence of a homologous series of n‐alkanes containing from 25 to 31 carbon atoms. In the case of the insects after fungal exposure, the content of the n‐alkanes in the cuticular lipid is two‐fold higher compared with the controls. Of the cuticular lipids, 11 alcohols are found, ranging from C12:0 to C20:0. There is no presence of alcohols in the internal lipids of the control B. orientalis females and in all of the extracts from the B. orientalis females after fungal exposure. In the samples analyzed, the most common sterol is cholesterol. This is present in the cuticular lipids and the internal lipids of all of the insects sampled. The cuticular and internal lipids of females contain five fatty acid methyl esters, ranging in size from C15 to C19.     

DGAT1 from the arachidonic-acid-producing microalga <Emphasis Type="Italic">Lobosphaera incisa</Emphasis> shows late gene expression under nitrogen starvation and substrate promiscuity in a heterologous system

We report the identification and characterization of an acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1)-encoding gene from the green oleaginous microalga Lobosphaera incisa (SAG 2468), a prolific photosynthetic producer of the n-6 very long chain polyunsaturated fatty acid (VLC-PUFA), arachidonic acid. The gene expression pattern of LiDGAT1 in L. incisa cells showed a weak increase in mRNA abundance in the course of nitrogen starvation under low light; however, LiDGAT1 expression was significantly upregulated with the progression of N-starvation under high light. Heterologous expression of LiDGAT1 in the neutral lipid-deficient mutant H1246 of Saccharomyces cerevisiae complemented the mutant phenotype and demonstrated an excelling TAG production compared to the yeast endogenous DGAT gene (DGA1). The TAG that formed in the LiDGAT1-expressing H1246 cells contained higher proportions of C16:0 and C18:0 fatty acids, suggesting that at least in a heterologous system, lacking PUFA biosynthesis, the enzyme seems to favor saturated over monounsaturated fatty acids. LiDGAT1 expression prompted an incorporation of several tested exogenous C18 PUFA and C20 VLC-PUFA into TAG. LiDGAT1-driven activity mediated the incorporation of either n-3 or n-6 VLC-PUFA, supplied as substrates for the TAG assembly; however, somewhat of a preference for 18:3n-3 over 20:4n-6 was demonstrated by lipidomics analysis. A structure-functional analysis of LiDGAT1 revealed that the N-terminal Pleckstrin homology (PH) domain is important but not essential for TAG generation in the yeast expression system. Deletion of the PH domain led to decreased TAG formation and ARA incorporation into TAG in yeast. Remarkably, we found the PH domain to be present in the DGAT1 of a number of chlorophytes, in a charophyceaen multicellular alga, in two diatoms and in the liverwort Marchantia polymorpha, but absent from those of red algae, higher plants and animals. Our findings indicate the promiscuity of LiDGAT1 for VLC-PUFA and suggest a specific role for this enzyme in the neutral lipid metabolism of L. incisa that needs to be further investigated by molecular engineering approaches.     

Patterns of variation in the lipid class and fatty acid composition of Nannochloropsis oculata (Eustigmatophyceae) during batch culture

Changes in the lipid and fatty acyl compositions of the marine microalga Nannochloropsis oculata Droop were examined during a batch culture growth cycle. During the early phase of batch culture the cellular proportion of triacylglycerols (TAG) increased. This was in addition to the increases in TAG observed in many microalgal species in the stationary-phase. Concomitant increases in the relative proportions of both saturated and monounsaturated fatty acids and decreases in the proportion of polyunsaturated fatty acids in total lipid were also associated with this phase. The separated individual lipid classes were found to have characteristic fatty acyl compositions. The relative proportion of lipid per cell, the relative proportions of the individual lipid classes and the fatty acyl compositions of the individual classes were all subject to variability during the growth cycle. The changing total lipid fatty acyl composition of N. oculata was found to be determined by the proportion of the total lipid present as TAG. The data suggest that the changes observed in the fatty acyl composition of N. oculata are a result of the partitioning of photosynthetically fixed carbon between polar and neutral lipid class biosynthesis and fatty acyl desaturation and elongation pathways. The effect of such a partitioning of carbon is discussed in relation to the effects of environmental variables and growth phase upon the balance of lipid class and polyunsaturated fatty acids (PUFA) synthesis in marine microalgae.     

Biosynthesis of fatty acids and triacylglycerols by 2,6,10,14-tetramethyl pentadecane-grown cells of Nocardia globerula 432

Nocardia globerula strain 432 was able to synthesize triacylglycerols (TAG) during cultivation on 2,6,10,14-tetramethyl pentadecane (pristane) under nitrogen-limiting conditions. Within these cells, 4,8,12-trimethyl tridecanoic acid was the major fatty acid detected. Fatty acids with an odd number of carbon atoms and minor amounts of even-numbered fatty acids were also observed. Experiments carried out with acrylic acid, an inhibitor of beta-oxidation, suggested that odd-numbered fatty acids such as C15:0, C17:0 and 10-methyl C17:0 were synthesized de novo using propionyl-CoA, the beta-oxidation product, as precursor. Although N. globerula 432 incorporated mainly straight chain fatty acids into TAG, the branched fatty acid 4,8,12-trimethyl tridecanoic acid also appeared, to some extent, in the acylglycerols. The importance of TAG biosynthesis by pristane-grown cells of N. globerula strain 432 is discussed.     

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     

Mesozooplankton beneath the summer sea ice in McMurdo Sound,Antarctica: abundance,species composition,and DMSP content

The summer Phaeocystis antarctica bloom increases under-ice phytoplankton biomass in McMurdo Sound, Antarctica. The magnitude of mesozooplankton grazing on this bloom is unknown, and determines whether this production is available to the pelagic food web. We measured mesozooplankton abundance and body content of dimethylsulfoniopropionate (DMSP) during the McMurdo Sound austral summer (2006 and 2006–2007). Abundance varied from 20 to 4,500 ind. m⁻³ (biomass 0.02–274.0 mg C m⁻³), with peaks in mid-December and late-January/February. Abundance was higher but total zooplankton biomass lower in our study compared to previous reports. Copepods and the pteropod Limacina helicina dominated the zooplankton in both abundance and biomass. DMSP was detected in all zooplankton groups, with highest concentrations in copepod nauplii and L. helicina (95 and 54 nmol mg⁻¹ body C, respectively). Experiments suggested that L. helicina obtains DMSP by directly grazing on P. antarctica, which often accumulates to high biomass under the summer sea ice in McMurdo Sound.     

Effect of Conidiobolus coronatus on the Cuticular and Internal Lipid Composition of Tettigonia viridissima Males

Conidiobolus coronatus is an entomopathogenic fungus which has a potential as a biological control agent of insects. The cuticular and internal lipid composition of infected and noninfected Tettigonia viridissima males were analyzed by GC/MS. A total of 49 compounds were identified in the infected and noninfected males, including fatty acids, fatty acid methyl esters (FAMEs), n‐alkanes, alcohols, sterols, and other organic compounds. The most abundant components of the cuticular and internal lipids of the insects were fatty acids. After exposure to C. coronatus, the cuticular lipids of the T. viridissima males contained 17 free fatty acids from C(8) to C(22), while the cuticular lipids of the noninfected insects contained only 15 fatty acids from C(12) to C(24). The cuticular and internal lipids of both the infected and the noninfected males also contained five FAMEs from C(15) to C(19), seven n‐alkanes from C(25) to C(34), five alcohols from C(16) to C(25), five sterols, and the following six other organic compounds: azelaic acid, phenylacetic acid, glutaric acid, benzoic acid, sebacic acid, and glycerol. The compounds which were present only in the cuticular lipids of the infected males could be due to fungal infection.     

Synergistic effects of ocean acidification and warming on overwintering pteropods in the Arctic

Ocean acidification and warming will be most pronounced in the Arctic Ocean. Aragonite shell‐bearing pteropods in the Arctic are expected to be among the first species to suffer from ocean acidification. Carbonate undersaturation in the Arctic will first occur in winter and because this period is also characterized by low food availability, the overwintering stages of polar pteropods may develop into a bottleneck in their life cycle. The impacts of ocean acidification and warming on growth, shell degradation (dissolution), and mortality of two thecosome pteropods, the polar Limacina helicina and the boreal L. retroversa, were studied for the first time during the Arctic winter in the Kongsfjord (Svalbard). The abundance of L. helicina and L. retroversa varied from 23.5 to 120 ind m^?2 and 12 to 38 ind m^?2, and the mean shell size ranged from 920 to 981 μm and 810 to 823 μm, respectively. Seawater was aragonite‐undersaturated at the overwintering depths of pteropods on two out of ten days of our observations. A 7‐day experiment [temperature levels: 2 and 7 °C, pCO₂ levels: 350, 650 (only for L. helicina) and 880 μatm] revealed a significant pCO₂ effect on shell degradation in both species, and synergistic effects between temperature and pCO₂ for L. helicina. A comparison of live and dead specimens kept under the same experimental conditions indicated that both species were capable of actively reducing the impacts of acidification on shell dissolution. A higher vulnerability to increasing pCO₂ and temperature during the winter season is indicated compared with a similar study from fall 2009. Considering the species winter phenology and the seasonal changes in carbonate chemistry in Arctic waters, negative climate change effects on Arctic thecosomes are likely to show up first during winter, possibly well before ocean acidification effects become detectable during the summer season.     

Fasting triacylglycerol status, but not polyunsaturated/saturated fatty acid ratio, influences the postprandial response to a series of oral fat tolerance tests

Elevated postprandial lipemia is emerging as a risk factor for obesity-related chronic diseases, such as type 2 diabetes and cardiovascular disease, and is associated with alterations in several metabolic biomarkers of disease. Our goal was to examine the effects of specific polyunsaturated/saturated fatty acid (P/S) ratios on postprandial triacylglycerol (TAG) concentrations and metabolic biomarkers in men with different fasting TAG concentrations through a series of oral fat tolerance tests (OFTT) consisting solely of emulsified lipid. Otherwise healthy men with high (>1.69 mmol/L) fasting TAG (HTAG, n=8) and low fasting TAG (LTAG, n=8) underwent three OFTTs with specific P/S ratios of 0.2, 1.0 and 2.0, respectively, and a total lipid load of 1 g/kg subject body mass. All subjects received each treatment separated by at least 1 week. Postprandial plasma TAG fatty acid composition reflected fatty acids present in the OFTT. All other metabolic responses were independent of the P/S ratio ingested. An accelerated increase in postprandial TAGs was observed in HTAG compared to LTAG. Interleukin (IL)-6 and soluble intercellular adhesion molecule (sICAM)-1 were significantly elevated in HTAG at baseline (P<.05). IL-6 increased significantly following each OFTT (P<.05) in both groups. Postprandial glucose and CRP were significantly exaggerated (P<.05) in HTAG. Overall, HTAG subjects had an accelerated postprandial TAG response and increased concentrations of several inflammatory markers following an OFTT, in the absence of an insulin response. However, P/S ratio had no influence on postprandial lipid and inflammatory parameters.     

Isolation of quizalofop-resistant mutants of Nannochloropsis oculata (Eustigmatophyceae) with high eicosapentaenoic acid following N-methyl-N-nitrosourea-induced random mutagenesis

Nannochloropsis oculata was subjected to N-methyl-N-nitrosourea-induced mutagenesis under the selection pressure of quizalofop, a known inhibitor of acetyl-CoA carboxylase (ACCase) activity with the objective of generating genetically tractable mutants with altered fatty acid metabolism. Two mutants, QUIZ1 and QUIZ2, with stable resistance to quizalofop were isolated and partially characterized. The growth properties and morphology of the mutants appeared identical with the parent strain. However thermo-tolerance was observed in the mutants. Enhanced resistance to quizalofop suggested the presence of herbicide resistant isoforms of ACCase. In vitro assays for ACCase activity showed that ACCase in the wild strains was much more sensitive to quizalofop than the mutant strains. Gas chromatographic analysis of fatty acids revealed that the mutant strains were rich in polyunsaturated fatty acids (n– 3PUFAs), as well as total fatty acid contents; this was accompanied by a concomitant increase in triacylglycerol (TAG) followed by linoleic acid (18:2), arachidonic acid (20:4 n– 6) and EPA (20:5 n– 3). These results suggest that an increased substrate pool (malonyl-CoA) (due to increased specific activity of ACCase) in the mutant strains in vivo and in vitro may have led to the increased TAG accumulation. Random mutagenesis was shown to be a good tool to manipulate PUFAs and EPA in Nannochloropsis. The strains developed will be useful in understanding fatty acid metabolism using genetic and biochemical approaches and also for their direct use in mariculture.