Experimental study on the effect of diet on fatty acid and stable isotope profiles of the squid Lolliguncula brevis

Fatty acid and stable isotope analyses have previously been used to investigate foraging patterns of fish, birds, marine mammals and most recently cephalopod species. To evaluate the application of these methods for dietary studies in squid, it is important to understand the degree to which fatty acid and stable isotope signatures of prey species are reflected in the squids' tissue. Four groups of Lolliguncula brevis were fed on prey species with distinctly different fatty acid and stable isotope profiles over 30 consecutive days. One group of squid were fed fish for fifteen days, followed by crustaceans for a further fifteen days. A second and third group were fed exclusively on fish or crustaceans for thirty days. And a fourth group was fed on a mixture of fish and crustaceans for thirty days. Analysis of squid tissue showed that, after 10 days of feeding, fatty acid profiles of squid tended to reflect those of their prey. Squid that fed on a single prey type, i.e. fish or crustacean, showed only minor modifications in fatty acid proportions after the initial change and fatty acid profiles were clearly distinguishable between the two feeding groups. Shifts in fatty acid proportions towards respective prey profiles could clearly be observed in squid the diet of which was swapped after 15 days. Clear differences could also be seen in fatty acid profiles of squid feeding on a mixed diet with trends towards either fish or crustacean fatty acid signatures. Stable isotope signatures of squid tissues clearly distinguished between animals feeding on different diets and supported findings from fatty acid analysis, thus indicating both methods to be viable tools in feeding studies on squid species.     

植物乳杆菌DY6主要抑菌代谢物的分析和鉴定

【背景】被广泛应用于食品和饲料等多个行业的乳酸菌已成为制作生物防腐剂的研究热点。【目的】探究抑菌性能良好的植物乳杆菌DY6的抑菌物质,为其进一步应用提供参考依据。【方法】对植物乳杆菌发酵液中抑菌物质的理化特性进行研究,采用GC-MS分析发酵上清液代谢物,通过多元统计学分析方法推测主要抑菌物质,抑菌物质通过半制备进行初步分离后用GC-MS鉴定。【结果】植物乳杆菌DY6对金黄色葡萄球菌、大肠杆菌、沙门氏菌都有较强的抑制作用。采用不同发酵时间的发酵液作为研究对象,测定发酵上清液的抑菌能力,发酵0-4 h上清液无抑菌能力,发酵至8 h抑菌能力逐步上升,发酵24-48 h发酵上清液抑菌能力趋于稳定,在48 h时抑菌能力最佳,抑菌直径为15.28mm。通过多元统计学分析乳酸菌发酵液差异标志物,发现主要差异物为有机酸(如乳酸、乙酸、丙酸等)和脂肪酸(如辛酸、癸酸等)。经过半制备液相分离发酵上清液得到的抑菌组分,主要有有机酸(如乳酸、乙酸、3-苯基乳酸、苯丙酸等)和脂肪酸(如癸酸、辛酸、壬酸等),另外还有少量的醛类和醇类物质。【结论】确定了植物乳杆菌DY6的抑菌物质主要为有机酸和脂肪酸,为其进一步防腐应用提供了理论基础。     

When season does not matter: summer and winter trophic ecology of Arctic amphipods

Polar marine ecosystems’ functioning is known to be strongly affected by the seasonality of water column production. However, a response of benthic organisms may range from close coupling to total decoupling from seasonal variability of environmental processes, depending on a feeding strategy. In this study, we used a multi-method approach (gut content, lipid and stable isotope analyses) to examine trophic ecology and major food sources of a large set of Arctic sub-littoral amphipods, and to evaluate whether their feeding strategies undergo seasonal changes. The wide range of δ¹⁵N values (5.45-12.43‰) indicates that amphipods form a trophic continuum from primary herbivores to carnivores/scavengers. Three main feeding modes, namely scavenging/predatory, deposit-feeding/predatory and phytodetrivory, were distinguished based on the multivariate analysis of whole fatty acid profiles. Total lipid content was low in all species and included primarily short-term energy reserves of triacylglycerols. In general, amphipods feeding habits appeared to be independent of the seasonal phytodetritial pulses. Low reliance on lipid reserves and lack of major changes in the trophic strategies over time suggest that these crustaceans feed continuously, taking advantage of a variety of food sources that are available year-round in shallow polar waters.     

Altered essential fatty acid metabolism and composition in rat liver, plasma, heart and brain after microalgal DHA addition to the diet

To investigate the effect of docosahexaenoic acid (DHA) without other highly unsaturated fatty acids (HUFA) on n-3 and n-6 essential fatty acid (EFA) metabolism and fatty acid composition in mammals, a stable isotope tracer technique was used in adult rats fed diets with or without 1.3% of algal DHA in a base diet containing 15% of linoleic acid and 3% of alpha-linolenic acid over 8 weeks. The rats were administered orally a mixed oil containing 48 mg/kg body weight of deuterated linoleic and alpha-linolenic acids and euthanized at 4, 8, 24, 96, 168, 240, 360 and 600 h after administration of the isotopes. Fatty acid compositions and the concentrations of deuterated precursors and their respective metabolites were determined in rat liver, plasma, heart and brain as a function of time. DHA, docosapentaenoic acid and eicosapentaenoic acid in the n-3 EFA family were significantly increased in all organs tested in the DHA-fed group, ranging from 5% to 200% greater in comparison with the control group. The accumulation of the metabolites, deuterated-DHA and deuterated-docosapentaenoic acid n-6 was greatly decreased by 1.5- to 2.5-fold in the dietary DHA group. In summary, feeding preformed DHA led to a marked increase in n-3 HUFA content of rat organs at the expense of n-6 HUFA and also prevented the accumulation of newly synthesized deuterated end products. This is the first study which has isolated the effects of DHA on the de novo metabolism on both the n-6 and n-3 EFA pathways.     

Trophic ecology of adult male Odonata. I. Dietary niche metrics by foraging guild,species, body size,and location

1. Information on the dietary niches of adult odonates is sparse, as they are highly mobile and evasive animals, which makes them difficult to observe in their natural habitat. Moreover, there is a lack of knowledge on how varying behavioural traits of odonates relate to phenomena like niche partitioning. 2. This study investigated niche partitioning amongst odonate species, foraging guilds and size classes in a riverine system in the Eastern Cape province of South Africa. A combination of stable isotope and fatty acid‐based niches was used to infer odonate feeding. 3. Both fatty acid and stable isotope‐based niches showed that there was niche separation amongst odonates that forage in flight (fliers) and those that forage from a perch (perchers), amongst odonates of different size classes (damselflies, medium‐ and large‐sized dragonflies), and amongst species, although varying levels of niche overlap were observed in each case. 4. Niche sizes of odonates varied between an upstream and a downstream site. Generally greater niche overlap was recorded at the narrow upstream site (associated with low insect emergence rates) than the wider downstream site (associated with high insect emergence rates), indicating that a greater degree of resource sharing occurred at the upstream site where aquatic food was less abundant. 5. The findings of this study suggest that dietary niches of odonates can be influenced by foraging guild, body size, and/or environmental conditions, and additional study in a variety of regions is recommended to determine the greater applicability of these findings.     

The composition of fatty acids and stable isotopes in the detritophage <Emphasis Type="Italic">Acila insignis</Emphasis> (Gould, 1861) (Bivalvia: Nuculidae): Searching for markers of a microbial food web

The fatty acid composition and stable isotope ratios of carbon, nitrogen, and sulfur were analyzed in the protobranch bivalve Acila insignis, a selective detritophage inhabiting subtidal sand sediments of Vostok Bay (Sea of Japan). Soft tissues of A. insignis contained abnormally high concentrations of the polyunsaturated arachidonic acid, 20: 4(n-6), and a rare monounsaturated fatty acid 20: 1(n-13), which distinguishes this species from other bivalves. The high concentrations of these fatty acids in A. insignis, together with the low values of σ³⁴S and the high values of σ¹³C and σ¹⁵N, are probably a result of feeding on the microbial food web.     

An assessment of the reproductive biology of the Marico barb Barbus motebensis from the upper Groot Marico catchment,South Africa

Temporal changes in fatty acid composition and δ¹⁵N, δ¹³C stable isotope values of the phytobenthos growing on artificial clay substrates under natural conditions over a 28-day period at an upstream and a downstream site in the Kowie River near Grahamstown were investigated in 2012. High concentrations of diatom markers 16:1ω7 and 20:5ω3 fatty acids were recorded, especially at the downstream site, reflecting the importance of diatoms in contributing to the phytobenthos communities at that station. After day 7 at the downstream site the average δ¹⁵N value of the phytobenthos was lighter, gradually increasing by ～2‰ and ～5‰ overall to heavier values on day 28. At the upstream site there were no significant changes (<1‰ increase) in δ¹⁵N values of the phytobenthos over time. Stable nitrogen (δ¹⁵N) and carbon (δ¹³C) signatures in the phytobenthos communities were significantly different between sites (one-way ANOVA; p < 0.001). The stable isotope values and fatty acid concentrations of phytobenthos at the downstream site were different to those of the phytobenthos at the upstream site, and they changed concurrently with changes in the phytobenthos community structure. At the downstream site there was a strong correlation of the δ¹⁵N of phytobenthos with nitrates (R = 0.56) and time (weeks; R = 0.81). However, the fatty acids were not specific enough to characterise the composition of phytobenthos communities. Other biomarker methods, such as stable isotopes and microscopic examination of the communities, were found to be useful. The results from this relatively small-scale tile experiment indicate the complexity of changes in fatty acid composition and δ¹⁵N, δ¹³C stable isotope values of a phytobenthos community. Stable isotope and fatty acid composition can be successfully used to map changes in phytobenthos composition and carbon and nitrogen flow patterns along a river continuum.     

Stable Isotope and Signature Fatty Acid Analyses Suggest Reef Manta Rays Feed on Demersal Zooplankton

Assessing the trophic role and interaction of an animal is key to understanding its general ecology and dynamics. Conventional techniques used to elucidate diet, such as stomach content analysis, are not suitable for large threatened marine species. Non-lethal sampling combined with biochemical methods provides a practical alternative for investigating the feeding ecology of these species. Stable isotope and signature fatty acid analyses of muscle tissue were used for the first time to examine assimilated diet of the reef manta ray Manta alfredi, and were compared with different zooplankton functional groups (i.e. near-surface zooplankton collected during manta ray feeding events and non-feeding periods, epipelagic zooplankton, demersal zooplankton and several different zooplankton taxa). Stable isotope δ¹⁵N values confirmed that the reef manta ray is a secondary consumer. This species had relatively high levels of docosahexaenoic acid (DHA) indicating a flagellate-based food source in the diet, which likely reflects feeding on DHA-rich near-surface and epipelagic zooplankton. However, high levels of ω6 polyunsaturated fatty acids and slightly enriched δ¹³C values in reef manta ray tissue suggest that they do not feed solely on pelagic zooplankton, but rather obtain part of their diet from another origin. The closest match was with demersal zooplankton, suggesting it is an important component of the reef manta ray diet. The ability to feed on demersal zooplankton is likely linked to the horizontal and vertical movement patterns of this giant planktivore. These new insights into the habitat use and feeding ecology of the reef manta ray will assist in the effective evaluation of its conservation needs.     

Combined stable‐isotope and fatty‐acid analyses demonstrate that large wood increases the autochthonous trophic base of a macroinvertebrate assemblage

相似文献   

Influence of the marine feeding area on the muscle and egg fatty‐acid composition of Atlantic salmon Salmo salar spawners estimated from the scale stable isotopes

Fatty acids in muscle tissue and eggs of female Atlantic salmon Salmo salar spawners were analysed to evaluate the dietary quality of their final feeding areas in the Baltic Sea. The final likely feeding area was identified by comparing stable carbon and nitrogen isotope composition of the outermost growth region (final annulus) of scales of returned S. salar with that of reference S. salar caught from different feeding areas. Some overlap of stable‐isotope reference values among the three areas, in addition to prespawning fasting, decreased the ability of muscle tri‐acylglycerols to discriminate the final likely feeding area and the area's dietary quality. Among three long‐chained polyunsaturated fatty acids, docosahexaenoic acid (DHA; 22:6n‐3), eicosapentaenoic acid (EPA; 20:5n‐3) and arachidonic acid (ARA; 20:4n‐6), the proportions of ARA in total lipids of spawning S. salar muscle and eggs showed a significant negative correlation with increasing probability of S. salar having returned from the Baltic Sea main basin (i.e. the Baltic Sea proper). The results suggest that ARA in muscle and eggs is the best dietary indicator for dietary characteristics of final marine feeding area dietary characteristics among S. salar in the Baltic Sea.     

Determination of food sources of marine invertebrates from a subtidal sand community using analyses of fatty acids and stable isotopes

The fatty acid compositions and stable isotope ratios of carbon, nitrogen, and sulfur were analyzed in the bivalve mollusks Mactra chinensis, Pandora pulchella, Felaniella usta, and Megangulus zyonoensis, the polychaete Chaetopterus cautus, and the main sources of organic matter in a subtidal sand bottom community in Vostok Bay (Sea of Japan). The fatty acid composition and stable isotope ratios of some bivalves is likely to be indicative of substantial inputs from benthic microalgae and an important role of microbial food chains. Only the filter-feeding polychaete C. cautus showed similarity in these characteristics to suspended particulate organic matter synthesized by phytoplankton. It is suggested that the contribution of benthic microalgae to the diet of a consumer organism, inferred solely from the carbon stable isotope analysis, can be significantly overestimated.     

Characterizing the feeding habits of the testate amoebae Hyalosphenia papilio and Nebela tincta along a narrow "fen-bog" gradient using digestive vacuole content and 13C and 15N isotopic analyses

Population dynamics and feeding habits of the testate amoebae Nebela tincta and Hyalosphenia papilio were studied along a short "fen" to "bog" gradient in a Sphagnum-dominated mire (Jura, France). Samples were collected in living "top segments" (0-3 cm) and early declining "bottom segments" (3-6 cm) of Sphagnum fallax peat. Observations of digestive vacuole content and stable isotope analyses ((13)C and (15)N) were used to establish the feeding behavior of both testate amoeba species. Owing to their vertical distribution, the feeding habit of H. papilio was described from top segments, and that of N. tincta from bottom segments. Among identified food sources, those most frequently ingested by N. tincta were spores and mycelia of fungi (55%), microalgae (25%) and cyanobacteria (8.5%). For H. papilio, the most frequently ingested prey were ciliates (55%) and microalgae (35%). Nonmetric Multidimensional Scaling analysis clearly demonstrated that the two species did not have the same feeding habit along the "fen-bog" gradient, and furthermore that a significant spatial split exists in the feeding behavior of H. papilio. Additionally, isotope analyses suggested that H. papilio and N. tincta did not have the same trophic position in the microbial food web, probably resulting from their different feeding strategies.     

Unravelling the complex structure of forest soil food webs: higher omnivory and more trophic levels

Food web topologies depict the community structure as distributions of feeding interactions across populations. Although the soil ecosystem provides important functions for aboveground ecosystems, data on complex soil food webs is notoriously scarce, most likely due to the difficulty of sampling and characterizing the system. To fill this gap we assembled the complex food webs of 48 forest soil communities. The food webs comprise 89 to 168 taxa and 729 to 3344 feeding interactions. The feeding links were established by combining several molecular methods (stable isotope, fatty acid and molecular gut content analyses) with feeding trials and literature data. First, we addressed whether soil food webs (n = 48) differ significantly from those of other ecosystem types (aquatic and terrestrial aboveground, n = 77) by comparing 22 food web parameters. We found that our soil food webs are characterized by many omnivorous and cannibalistic species, more trophic chains and intraguild‐predation motifs than other food webs and high average and maximum trophic levels. Despite this, we also found that soil food webs have a similar connectance as other ecosystems, but interestingly a higher link density and clustering coefficient. These differences in network structure to other ecosystem types may be a result of ecosystem specific constraints on hunting and feeding characteristics of the species that emerge as network parameters at the food‐web level. In a second analysis of land‐use effects, we found significant but only small differences of soil food web structure between different beech and coniferous forest types, which may be explained by generally strong selection effects of the soil that are independent of human land use. Overall, our study has unravelled some systematic structures of soil food‐webs, which extends our mechanistic understanding how environmental characteristics of the soil ecosystem determine patterns at the community level.     

Mesograzer identity,not host algae,determines consumer stable isotope ratios

Species-specific foraging habits or feeding preferences influence the overall trophic functioning in consumer assemblages. We set out to assess the in situ trophic diversity in a mesograzer assemblage (isopods, amphipods and gastropods) associated with marine littoral macroalgae. More specifically, we set out to establish whether stable isotope ratios of carbon (δ¹³C) and nitrogen (δ¹⁵N) are dependent on primary consumer identity or expressed in relation to the identity of the algal host, i.e. the habitat of the consumer. Consumer locations in bivariate isotope space revealed significant differences among grazer taxa, but no effect of the algal host. This suggests that grazer-specific foraging is more important in driving the qualitative range of feeding in the consumer assemblage than host diversity per se within a macrohabitat, such as a bay or a lagoon. The stable isotope ratios of the mesoherbivores were in line with expectations based on the known feeding ecology of the grazers. However, the trophic diversity suggested by stable isotope analysis implies that even an established concept such as the mesograzer guild may encompass simplifications in terms of functional group membership.     

Trophodynamics of Southern Ocean pteropods on the southern Kerguelen Plateau

Pteropods are a group of small marine gastropods that are highly sensitive to multiple stressors associated with climate change. Their trophic ecology is not well studied, with most research having focused primarily on the effects of ocean acidification on their fragile, aragonite shells. Stable isotopes analysis coupled with isotope‐based Bayesian niche metrics is useful for characterizing the trophic structure of biological assemblages. These approaches have not been implemented for pteropod assemblages. We used isotope‐based Bayesian niche metrics to investigate the trophic relationships of three co‐occurring pteropod species, with distinct feeding behaviors, sampled from the Southern Kerguelen Plateau area in the Indian Sector of the Southern Ocean—a biologically and economically important but poorly studied region. Two of these species were gymnosomes (shell‐less pteropods), which are traditionally regarded as specialist predators on other pteropods, and the third species was a thecosome (shelled pteropod), which are typically generalist omnivores. For each species, we aimed to understand (a) variability and overlap among isotopic niches; and (b) whether there was a relationship between body size and trophic position. Observed isotopic niche areas were broadest for gymnosomes, especially Clione limacina antarctica, whose observed isotopic niche area was wider than expected on both δ¹³C and δ¹⁵N value axes. We also found that trophic position significantly increased with increasing body length for Spongiobranchaea australis. We found no indication of a dietary shift toward increased trophic position with increasing body size for Clio pyramidata f. sulcata. Trophic positions ranged from 2.8 to 3.5, revealing an assemblage composed of both primary and secondary consumer behaviors. This study provides a comprehensive comparative analysis on trophodynamics in Southern Ocean pteropod species, and supports previous studies using gut content, fatty acid and stable isotope analyses. Combined, our results illustrate differences in intraspecific trophic behavior that may be attributed to differential feeding strategies at species level.     

Revisiting “what do tadpoles really eat?” A 10‐year perspective

相似文献   

Manipulating membrane Fatty Acid compositions of whole plants with tween-Fatty Acid esters

This paper describes a method for manipulating plant membrane fatty acid compositions without altering growth temperature or other conditions. Tween-fatty acid esters carrying specific fatty acids were synthesized and applied to various organs of plants growing axenically in glass jars. Treated plants incorporated large amounts of exogenous fatty acids into all acylated membrane lipids detected. Fatty acids were taken up by both roots and leaves. Fatty acids applied to roots were found in leaves, while fatty acids applied to leaves appeared in both leaves higher on the plant and in roots, indicating translocation (probably in the phloem). Foliar application was most effective; up to 20% of membrane fatty acids of leaves above the treated leaf and up to 40% of root membrane fatty acids were exogenously derived. Plants which took up exogenous fatty acids changed their patterns of fatty acid synthesis such that ratios of saturated to unsaturated fatty acids remained essentially unaltered. Fatty acid uptake was most extensively studied in soybean (Glycine max [L.] Merr.), but was also observed in other species, including maize (Zea mays L.), mung beans (Vigna radiata L.), peas (Pisum sativum L.), petunia (Petunia hybrida L.) and tomato (Lycopersicon esculentum Mill.). Potential applications of this system include studying internal transport of fatty acids, regulation of fatty acid and membrane synthesis, and influences of membrane fatty acid composition on plant physiology.     

Targeted quantitative analysis of fatty acids in atherosclerotic plaques by high sensitivity liquid chromatography/tandem mass spectrometry

The quantitative analysis of fatty acid composition in atherosclerotic plaques provides a way to monitor the underlying etiology of atherosclerosis. Previously, the method of choice for analyzing fatty acids in biological samples was gas chromatography/mass spectrometry (GC/MS); however, recent developments in electrospray ionization (ESI)/liquid chromatography (LC)/tandem mass spectrometry have made it a superior alternative. Previous research has largely focused on global analyses of intact lipids rather than more targeted analysis of the fatty acids themselves. We have now developed a targeted, stable isotope dilution LC-electrospray ionization/multiple reaction monitoring/MS method for the quantitative analysis of 10 fatty acids (myristic, palmitic, stearic, oleic, linoleic, alpha-linolenic, gamma-linolenic, arachidonic, eicosapentaenoic, and docosahexaenoic acids) using their trimethylaminoethyl ester (TMAE) derivatives to improve sensitivity. The method was validated, had a detection limit in the fmol range, and was used in the analysis of fatty acids in atherosclerotic plaques from carotid arteries.     

Impact of feeding and short-term temperature stress on the content and isotopic signature of fatty acids,sterols, and alcohols in the scleractinian coral <Emphasis Type="Italic">Turbinaria reniformis</Emphasis>

This study assesses the combined effect of feeding and short-term thermal stress on various physiological parameters and on the fatty acid, sterol, and alcohol composition of the scleractinian coral Turbinaria reniformis. The compound-specific carbon isotope composition of the lipids was also measured. Under control conditions (26°C), feeding with Artemia salina significantly increased the symbiont density and chlorophyll content and the growth rates of the corals. It also doubled the concentrations of almost all fatty acid (FA) compounds and increased the n-alcohol and sterol contents. δ¹³C results showed that the feeding enhancement of FA concentrations occurred either via a direct pathway, for one of the major polyunsaturated fatty acid (PUFA) compounds of the food (18:3n-3 FA), or via an enhancement of photosynthate transfer (indirect pathway), for the other coral FAs. Cholesterol (C₂₇Δ⁵) was also directly acquired from the food. Thermal stress (31°C) affected corals, but differently according to their feeding status. Chlorophyll, protein content, and maximal photosynthetic efficiency of photosystem II (PSII) decreased to a greater extent in starved corals. In such corals, FA concentrations were reduced by 33%, (especially C16, C18 FAs, and n-3 PUFA) and the sterol content by 27% (especially the C₂₈∆^5,22 and C₂₈∆⁵). The enrichment in the δ¹³C signature of the storage and structural FAs suggests that they were the main compounds respired during the stress to maintain the coral metabolism. Thermal stress had less effect on the lipid concentrations of fed corals, as only FA levels were reduced by 13%, with no major changes in their isotope carbon signatures. In conclusion, feeding plays an essential role in sustaining T. reniformis metabolism during the thermal stress.     

Feeding habits may explain the morphological uniqueness of brown bears on Etorofu Island,Southern Kuril Islands in East Asia

The brown bear (Ursus arctos) population on Etorofu Island, Southern Kuril Islands, has several unique morphological features: (1) the presence of white‐pelage bears within the population and (2) a larger body size than bears on a larger neighbour island, Hokkaido Island. Nevertheless, little ecological information is available about Etorofu brown bears. In the present study, we reveal the unique feeding habits of Etorofu brown bears and suggest that their unique morphological features and diet are related. The feeding habits of brown bears on Etorofu Island were assessed using carbon, nitrogen, and sulfur stable isotope analysis, and their feeding habits were compared with those of bears on the eastern side of Hokkaido Island. According to the stable isotope analysis, the dependence on salmon is great for bears on Etorofu but only slight for bears on Hokkaido. Our results suggest that the feeding habits of Etorofu brown bears may explain their unique morphological features because a white pelage colour confers an advantage when catching salmon, and a carnivorous diet can make their body size larger. The variation in feeding habits can be an important driver of the speciation and evolution of animals.