Fatty Acid Profiles Of Neutral Lipids Research Articles

Earthworm invasion shifts trophic niches of ground-dwelling invertebrates in a North American forest

Earthworms are invading soil communities worldwide, and their actions as decomposers and ecosystem engineers are vastly impacting many ecosystem functions. In the northern regions of North America, invasive earthworms are often functionally distinct from the native invertebrate fauna and, thus, typically occupy empty trophic niches in soil food webs. Nevertheless, they can affect the co-occurring soil invertebrate communities in multiple indirect ways. Particularly, the redistribution and removal of litter resources can affect feeding interactions of soil biota that channel up to higher trophic levels, such as predators, causing shifts across all components of the soil food web, which are hard to investigate. To study trophic shifts in earthworm-invaded soil communities, we used ground predators as model organisms since they occupy high trophic levels and connect different energy channels in soil food webs. We used stable isotope (13C and 15N) and fatty acid analyses as complementary tools to describe the trophic levels and basal resources of consumers that were impacted by earthworm invasion, specifically examining the trophic niches and resources available to ground-dwelling invertebrates of a northern aspen forest. The distinct trophic niches of invertebrate species were affected significantly by earthworm invasion. Shifts in neutral lipid fatty acid profiles as well as decreases in animal Δ13C and Δ15N signatures indicated changes in basal resources and trophic levels, respectively. Furthermore, we observed a trend of greater intra-specific and less inter-specific variation in fatty acid profiles of soil organisms following earthworm invasion. Notably, shifts in marker fatty acids of ground-dwelling invertebrates were opposite to the changes observed in soil microbial communities, suggesting de-coupling of soil microbial and ground arthropod food-web compartments. Overall, our study revealed a systemic effect of invasive earthworms on ground-dwelling invertebrates. Earthworms presumably consumed a considerable amount of resources, such as litter and, thus, incorporated them in the soil food web, which was, as a basal resource, not available in the food web free of earthworms. Overall, the ground-dwelling invertebrates have adapted (changed their trophic function) which could explain the balancing of potential environmental changes that are caused by invasive earthworms. This observation potentially explains why these species are dominant in the studied forest and resist earthworm invasion. Future studies should investigate if altered litter availability also causes shifts in soil biodiversity in invaded forests, which is assumed but rarely directly tested to date.

Bottom-up effects of fungicides on tadpoles of the European common frog (Rana temporaria).

Biodiversity is under pressure worldwide, with amphibians being particularly threatened. Stressors related to human activity, such as chemicals, are contributing to this decline. It remains, however, unclear whether chemicals exhibiting a fungicidal activity could indirectly affect tadpoles that depend on microbially conditioned leaf litter as food source. The indirect effect of fungicides (sum concentration of a fungicide mixture composed of azoxystrobin, carbendazim, cyprodinil, quinoxyfen, and tebuconazole: 100 µg/L) on tadpoles was assessed relative to leaf litter colonized by microbes in absence of fungicides (control) and a worst‐case scenario, that is leached leaf litter without microbial colonization. The quality of leaf litter as food for tadpoles of the European common frog (Rana temporaria) was characterized through neutral lipid fatty acid profiles and microbial sum parameters and verified by sublethal responses in tadpoles (i.e., feeding rate, feces production, growth, and fatty acid composition). Fungicides changed the nutritious quality of leaf litter likely through alterations in leaves’ neutral lipid fatty acid profiles (i.e., changes in some physiologically important highly unsaturated fatty acids reached more than 200%) in combination with a potential adsorption onto leaves during conditioning. These changes were reflected by differences in the development of tadpoles ultimately resulting in an earlier start of metamorphosis. Our data provide a first indication that fungicides potentially affect tadpole development indirectly through bottom‐up effects. This pathway is so far not addressed in fungicide environmental risk assessment and merits further attention.

Conversion of rainforest to oil palm and rubber plantations alters energy channels in soil food webs.

In the last decades, lowland tropical rainforest has been converted in large into plantation systems. Despite the evident changes above ground, the effect of rainforest conversion on the channeling of energy in soil food webs was not studied. Here, we investigated community‐level neutral lipid fatty acid profiles in dominant soil fauna to track energy channels in rainforest, rubber, and oil palm plantations in Sumatra, Indonesia. Abundant macrofauna including Araneae, Chilopoda, and Diplopoda contained high amounts of plant and fungal biomarker fatty acids (FAs). Lumbricina had the lowest amount of plant, but the highest amount of animal‐synthesized C20 polyunsaturated FAs as compared to other soil taxa. Mesofauna detritivores (Collembola and Oribatida) contained high amounts of algal biomarker FAs. The differences in FA profiles between taxa were evident if data were analyzed across land‐use systems, suggesting that soil fauna of different size (macro‐ and mesofauna) are associated with different energy channels. Despite that, rainforest conversion changed the biomarker FA composition of soil fauna at the community level. Conversion of rainforest into oil palm plantations enhanced the plant energy channel in soil food webs and reduced the bacterial energy channel; conversion into rubber plantations reduced the AMF‐based energy channel. The changes in energy distribution within soil food webs may have significant implications for the functioning of tropical ecosystems and their response to environmental changes. At present, these responses are hard to predict considering the poor knowledge on structure and functioning of tropical soil food webs.

Unveiling community patterns and trophic niches of tropical and temperate ants using an integrative framework of field data, stable isotopes and fatty acids.

BackgroundThe use and partitioning of trophic resources is a central aspect of community function. On the ground of tropical forests, dozens of ant species may be found together and ecological mechanisms should act to allow such coexistence. One hypothesis states that niche specialization is higher in the tropics, compared to temperate regions. However, trophic niches of most species are virtually unknown. Several techniques might be combined to study trophic niche, such as field observations, fatty acid analysis (FAA) and stable isotope analysis (SIA). In this work, we combine these three techniques to unveil partitioning of trophic resources in a tropical and a temperate community. We describe patterns of resource use, compare them between communities, and test correlation and complementarity of methods to unveil both community patterns and species’ niches.MethodsResource use was assessed with seven kinds of bait representing natural resources available to ants. Neutral lipid fatty acid (NLFA) profiles, and δ15N and δ13C isotope signatures of the species were also obtained. Community patterns and comparisons were analyzed with clustering, correlations, multivariate analyses and interaction networks.ResultsResource use structure was similar in both communities. Niche breadths (H′) and network metrics (Q and H2′) indicated similar levels of generalization between communities. A few species presented more specialized niches, such as Wasmannia auropunctata and Lasius fuliginosus. Stable isotope signatures and NLFA profiles also indicated high generalization, although the latter differed between communities, with temperate species having higher amounts of fat and proportions of C18:1n9. Bait use and NLFA profile similarities were correlated, as well as species’ specialization indices (d′) for the two methods. Similarities in δ15N and bait use, and in δ13C and NLFA profiles, were also correlated.DiscussionOur results agree with the recent view that specialization levels do not change with latitude or species richness. Partition of trophic resources alone does not explain species coexistence in these communities, and might act together with behavioral and environmental mechanisms. Temperate species presented NLFA patterns distinct from tropical ones, which may be related to environmental factors. All methods corresponded in their characterization of species’ niches to some extent, and were robust enough to detect differences even in highly generalized communities. However, their combination provides a more comprehensive picture of resource use, and it is particularly important to understand individual niches of species. FAA was applied here for the first time in ant ecology, and proved to be a valuable tool due to its combination of specificity and temporal representativeness. We propose that a framework combining field observations with chemical analysis is valuable to understand resource use in ant communities.

Effects of storage and handling on neutral lipid fatty acid profiles of two woodlice (Isopoda, Crustacea) species differing in size

Neutral lipid fatty acid (NLFA) analysis is a promising tool to investigate energy fluxes and basal resources of soil animal communities. This study aimed at investigating the effect of common handling and storage procedures in soil animal ecology on the NLFA composition and marker NLFAs. First, we tested the effect of the method of killing (by freezing and by drowning in diethylene glycol mixed with water; 1:1) on NLFA composition of the woodlouse Oniscus asellus. Additionally, we inspected the effect of two reference methods (direct freezing at −20 °C and storage in methanol at −80 °C with evaporating methanol prior to lipid extraction) after 4 and 12 months on the NLFA profile of O. asellus. We investigated the effect of the collection solution used in heat extraction of soil animals (water and glycol), storage fluids (saltwater, glycerine, ethanol and methanol) and storage time (4 and 12 months) on NLFA composition and common marker NLFAs of two Isopoda species differing in body size. The NLFA composition and marker fatty acids (FAs) did not differ between the methods of killing and between the two reference treatments but the amount of saturated FAs and the saturated-to-unsaturated FA ratio generally increased after 12 months indicating oxidation processes. Generally, the collection solution was of minor importance, whereas storage fluid and storage time strongly affected NLFA patterns. The NLFA profile of the larger species O. asellus was affected by storage in methanol and ethanol and to some extent in saltwater, while the NLFA profile of the smaller Trichoniscus pusillus was affected by each of the treatments. Notably, however, marker FAs of O. asellus and T. pusillus were not significantly affected by storing in glycerine even after 12 months in O. asellus. Therefore, if animals need to be stored prior to NLFA analysis for sorting and identification, storage in glycerine is advisable.

Dietary Flax Oil Enriches Adipose Tissue Phospholipids in Long Chain n‐3 PUFA and Reduces Adiposity

Consumption of diets enriched in long‐chain omega‐3 polyunsaturated fatty acids (LC n‐3 PUFA) has been associated with reduced adiposity and metabolic benefits in humans and animals, including poultry. Avians express unique elongase enzymes that, relative to humans, enhance their capacity to produce eicosapentaenoic acid (EPA, 20:5, n‐3) and docosahexaenoic acid (DHA, 22:6, n‐3) from alpha‐linolenic acid (ALA; 18:3, n‐3). We tested the hypothesis that enriching adipose tissue in ALA would reduce adiposity in broiler chickens by activating lipid‐responsive nuclear receptors and upregulating expression of genes involved in fatty acid oxidation, comparable to what we have previously found for fasting (Ji et al., 2012). Cobb 500 broiler chicks were fed isocaloric diets containing either 8% flaxseed oil (flax) or 8% lard from hatch to 21 days of age (DS1), or from 21‐42 days of age (DS2). Adipose neutral lipid fatty acid profiles reflected the dietary fat composition. Both EPA and DHA were undetectable in adipose phospholipids (PL) from the lard group but were present in birds consuming flax, while arachidonic acid was increased in PL of the lard group. In both DS1 and DS2, flax diets significantly (p<0.05) reduced adiposity and abdominal adipose weight, with no effect on body weight. Plasma non‐esterified fatty acid (NEFA) levels were significantly lower in flax vs. lard birds in both studies (p=0.0062, DS1 and p=0.014, DS2). Despite the significant reduction in adiposity, we did not find evidence for upregulation of genes involved in fatty acid oxidation based on QPCR of abdominal adipose tissue. In conclusion, these studies demonstrate that dietary enrichment in ALA reduces adiposity, but the mechanisms remain to be determined.

Expression of fatty acyl desaturase and elongase genes, and evolution of DHA:EPA ratio during development of unfed larvae of Atlantic bluefin tuna ( Thunnus thynnus L.)

The concentration of n-3 long-chain polyunsaturated fatty acids (LC-PUFA) in neural tissues is known to be crucial for effective prey capture from the time of first feeding in marine fish larvae. Furthermore, tissues of tunids, including Atlantic bluefin tuna, have relatively high levels of DHA (docosahexaenoic acid, 22:6n-3) and a high ratio of DHA:EPA (eicosapentaenoic acid; 20:5n-3) compared to most other species. Although the lipid biochemistry underpinning the high DHA:EPA ratio in tuna is unclear, it has been generally assumed that they must selectively accumulate and retain DHA in their tissues. In the present study, we investigated lipid and fatty acid metabolism during early development of Atlantic bluefin tuna and determined the changes in lipid content, lipid class composition and total, phospholipid and neutral lipid fatty acid profiles in unfed larvae during yolk sac utilization. In addition, we studied the LC-PUFA biosynthesis pathway by quantifying expression of fatty acyl desaturase and elongase genes. To this end, we cloned and functionally characterized two cDNAs by heterologous expression in yeast, showing them to code for a Δ6 desaturase and Elovl5 elongase, respectively, that could both be involved in the conversion of EPA to DHA. The level of DHA was maintained, but the proportion of EPA declined, and so the DHA:EPA ratio increased in bluefin tuna larvae during yolk sac utilization. Although this could be the result of relative retention of DHA during a period of generally high fatty acid oxidation and utilization, there was also a great increase in desaturase and elongase expression with larval development. This suggests that increased activity of these enzymes is important for the normal development of tuna larvae related to the provision of adequate DHA for the formation of biomembranes, particularly in neural (brain and eye) tissues.

Fatty acid patterns as biomarker for trophic interactions: Changes after dietary switch and starvation

Fatty acid (FA) analysis is becoming increasingly important for investigating trophic interactions in soil food webs. FA profiles of neutral lipids are affected by diet, and the occurrence and amount of certain FAs can reflect feeding strategies. However, to draw conclusions on feeding strategies in the field it is necessary to know physiological parameters of fatty acid metabolism such as the detection time and storage period of FAs. In this study we investigated the chronological change of FA biomarkers in the Collembola Heteromurus nitidus when switched between different food sources: leaves (Tilia europaea), a fungus (Chaetomium globosum) and two bacteria (Stenotrophomonas maltophilia, Bacillus amyloliquefaciens). Additionally, we followed the change of bacterial FA biomarkers during starvation. After 14 days of food deprivation bacterial FAs were still detectable in a sufficient amount to use them as dietary markers. Switching diet experiments demonstrated that FAs typical for a specific diet are already present after one day and are still detectable after 14 days of feeding on a different food source, suggesting that FA analysis can integrate the food choice of Collembola over a longer period of time, in contrast to snapshot methods such as gut content analysis.

Comparison of the fatty acid profile of muscle neutral lipids and phospholipids of up-river anadromous sea lamprey (<i>Petromyzon marinus</i> L.) from three Portuguese river basins

Composition of fatty acid profile of muscle neutral lipids (NL) and phospholipids (PL) of sea lamprey that enter the Portuguese rivers Minho, Tagus and Guadiana during their non-trophic spawning migration was analysed. The fatty acid profile exhibited differences in the percentage among NL and PL and between river basins. Similarities were found in the fatty acid profile of NL. Monounsaturated fatty acids (MUFA) were the most representative, followed by saturated fatty acids (SFA) and finally by polyunsaturated fatty acids (PUFA). Monoenic 16:1 and 18:1ω9 formed a considerable percentage of total fatty acids, followed by SFA 14:0 and 16:0. EPA and DHA were the dominant PUFA fatty acids. In terms of NL, the fatty acid that contributed for the discrimination between the three river basins was 18:1ω7. Individuals from the Minho river basin exhibited a different fatty acid profile of PL characterised by a low PUFA percentage when compared with lampreys from the Tagus and Guadiana river basins. Muscle PL fraction showed that the two monoenes, 16:1 and 18:1ω9, occurred at high percentage, followed by 16:0 and 14:0 (SFA). Among PUFA, DHA was the most representative fatty acid. The fatty acids that contributed to the separation between the three river basins were 16:0, 18:4ω3 and 24:1ω9. Although the results point in the direction of a possible difference between the fatty acid composition of the NL and PL fractions in the muscle samples from the three river basins, further studies, especially in tissues where fatty acid composition will be less sensitive to diet and environmental factors, are necessary to confirm this hypothesis.

Effects of temperature and life stage on the fatty acid composition of Collembola

Fatty acid (FA) analysis is used as a promising tool to investigate trophic interactions in soil food webs. The FA profile of neutral lipids in consumers is affected by the diet, and the occurrence and amount of certain FAs can reflect feeding strategies. We investigated the lipid composition of the Collembola Folsomia candida, Heteromurus nitidus and Protaphorura fimata with the fungus Chaetomium globosum as food source. The impact of environmental temperature and life stage was assessed, with special respect to linoleic acid (18:2ω6,9) as a marker FA for fungal feeding. In all Collembola species the ratio of C16/C18 in neutral lipid fatty acids (NLFAs) increased with decreasing temperature. In the NLFAs of F. candida and H. nitidus the Unsaturation Index and the amount of 18:2ω6,9 decreased with temperature, whereas in P. fimata effects were the opposite. The composition of phospholipid fatty acids (PLFAs) differed between species, but was little affected by temperature. The degree of unsaturation in NLFAs increased with the age of Collembola, mainly due to higher amounts of 18:2ω6,9 and a lower proportion of 18:1ω9. The biomarker linoleic acid represented over 20% of FAs in all fungal feeding Collembola. Despite considerable influence of temperature and life stage on its proportion, the amount was always higher than in individuals reared on other diets. This suggests that linoleic acid can serve as marker for fungal feeding independent of such physiological variations in Collembola.

Improvement of a solid phase extraction method for analysis of lipid fractions in muscle foods

The most used method for muscle lipid fractionation into major lipid classes was modified for improving its separation efficiency. Extracted lipids from a masseter muscle of one Iberian pig were separated into neutral lipids (NL), free fatty acids (FFA) and polar lipids (PL) using aminopropyl minicolumns, following the extensively used method of Kaluzny et al. [1] (old method-OM-) and a method based on that, developed by Pinkart et al. [2] with some (modifications modified method–MM). Obtained lipid classes were further analysed by TLC and lipid fractions were identified. TLC evidenced the presence of a certain amount of PL in the NL fraction obtained with the OM. On the other hand, using the MM only an almost undetectable presence of PL was evidenced in the NL fraction. Fatty acid composition of NL, PL and FFA obtained with each method was studied by gas chromatography. Fatty acid profile of NL was strongly influenced by the separation method used. Thus, NL obtained using the OM showed higher amounts of saturated fatty acids (SFA) and polyunsaturated fatty acids (PUFA) and lower of monounsaturated fatty acids (MUFA) than those obtained using the MM. Moreover, NL obtained using the OM showed the presence of fatty alcohols, constituents of phospholipids (PhL) absent or present only in trace amounts in acylglycerols. This profile reflects the coelution of PL in the NL fraction. Fatty acid profile of FFA and PL fractions was also influenced by the solid phase extraction (SPE) method used, but to a lesser extent.

Physico-chemical characteristics of M. Longissimus dorsi from three lines of free-range reared Iberian pigs slaughtered at 90 kg live-weight and commercial pigs: a comparative study

Longissimus dorsi muscles from three lines of Iberian pig and those from commercial pigs were analysed in order to evaluate their quality for fresh consumption. Iberian pigs were reared in a natural outdoor production system with access to grass, while m. Longissimus dorsi from commercial pigs were procured from a local slaughterhouse. Iberian pigs’ Longissimus dorsi showed a higher fat ( P<0.05) and lower phospholipid contents (g PL/g fat; P<0.05) than Longissimus dorsi from commercial pigs. Iberian pigs’ Longissimus dorsi muscles had a higher content of haem iron ( P<0.05) than those from commercial pigs and consequently m. Longissimus dorsi exhibited a redder colour (higher a*-value) that diverged less from the true red axis (lower hue value; P<0.05) than those from commercial pigs which resulted paler (higher L*-value; P<0.05). Total fat and neutral lipid fatty acid profiles showed higher percentages of palmitic, oleic, total saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) m. Longissimus dorsi of Iberian pigs than in the commercial ones ( P<0.05). m. Longissimus dorsi from the commercial pigs contained higher proportions of polyunsaturated fatty acids and a higher n-6/n-3 ratio value ( P<0.05).

Seasonal variations in the lipid and fatty acid composition of the euphausiid Meganyctiphanes norvegica from the Ligurian Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 186:199-210 (1999) - doi:10.3354/meps186199 Seasonal variations in the lipid and fatty acid composition of the euphausiid Meganyctiphanes norvegica from the Ligurian Sea Patrick Mayzaud*, Patti Virtue, Eric Albessard Observatoire Océanologique, Océanographie Biochimique et Ecologie, ESA-CNRS 7076, BP 28, 06230 Villefranche-sur-Mer, France *E-mail: mayzaud@ccrv.obs-vlfr.fr ABSTRACT: Lipid and fatty acid composition of the northern krill Meganyctiphanes norvegica from the Mediterranean Sea were studied with respect to sex and season. Detailed composition of the lipid classes is reported for both males and females during the spring reproductive season and the late summer non-reproductive season. Both sexes showed similar lipid structure, with neutral lipids dominated by triacylglycerols. Polar lipids were dominated by phosphatidylcholine. Fatty acid compositions of both polar lipids and triacylglycerols showed little change with sex or season. Polar lipids were dominated by HUFA (20:5n-3 or EPA and 22:6n-3 or DHA) as well as palmitic and oleic acid. Neutral lipid fatty acid profiles were dominated by 22:6(n-3) and palmitic acid, with a significant contribution of oleic, myristic, stearic and vaccenic acids as well as 20:5(n-3). Seasonal changes in total lipids showed maximum accumulation in early summer and minimum levels in early winter. Changes in fatty acid composition appeared related to the succession of populations with varying levels of triacylglycerols, as illustrated by the contrast between the early winter and spring periods in a correspondence analysis. Increased proportions of myristic, palmitoleic and 18:4(n-3) acids during the spring period are characteristic of the triglyceride fraction while the main descriptor of the winter period is DHA, which is the key constituent of the polar lipids. Comparison with literature data illustrated the clear decrease in lipid content of northern krill with latitude and the specific nature of the seasonal pattern recorded in the Ligurian Sea. The regional variability in fatty acid composition and the significance of fatty acids as potential markers of feeding behaviour are discussed in relation to the omnivorous character of M. norvegica. KEY WORDS: Northern krill · Lipids · Ligurian Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 186. Publication date: September 17, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Fatty Acid Composition of Neutral Lipid Energy Reserves in Infective Juveniles of Entomopathogenic Nematodes

The fatty acid composition of neutral lipids from infective juveniles (IJs) of Steinernema carpocapsae strain All, S. riobravis strain Biosys 355, S. feltiae strain UK76, and S. glaseri strain NC stored in distilled water at 25°C was determined. Newly emerged IJs of all four species had similar neutral lipid fatty acid profiles and of the 18 fatty acids identified, C18:1n−9 (43–49 mol %), C16:0 (18–23%), C18:2n−6 (8–14%) and C18:0 (4–8%) were the most abundant. Unsaturated fatty acids predominated, with about 50% being monoene and 14–22% polyene; the unsaturation index ranged from 91.6 in S. glaseri to 111.6 in S. carpocapsae. The fatty acid composition of the total lipid and the free fatty acid fraction mirrored that of the neutral lipids. During storage, the relative levels (%) of C16:0, C18:0, and C18:1n−9 in the neutral lipids declined significantly, suggesting they were preferentially utilised.