Wild Rabbit Host and Some Parasites Show Trophic-Level Relationships for δ13C and δ15N: A First Report

Abstract

We report the first isotopic study of an animal host-parasite system. Parasitic, intestinal nematodes, Graphidium strigosum and Passalurus ambiguus, were ¹⁵N-enriched relative to their host, the European rabbit Oryctolagus cuniculus, while parasitic cestodes, Cittataenia denticulata and Mosgovoyia pectinata, were ¹⁵N-depleted, suggesting different trophic relationships. Host embryos were more similar in their δ¹³C and δ¹⁵N values to maternal muscle than were any of the parasites. Coprophagy, the direct recycling of food by the rabbit eating its own faeces, did not lead to isotopic differences between stomach contents and faeces, suggesting that the major point for isotopic discrimination in lagomorph nitrogen metabolism is in the animal rather than in the gut. We conclude that bulk δ¹³C and δ¹⁵N can reveal valuable new information about host-parasite relationships, and these could be explored further at the biochemical level using compound-specific isotopic analyses.     

Measuring δ13C values of atmospheric acetaldehyde via sodium bisulfite adsorption and cysteamine derivatisation

δ¹³C values of gaseous acetaldehyde were measured by gas chromatograph–combustion–isotope ratio mass spectrometer (GC–C–IRMS) via sodium bisulfite (NaHSO₃) adsorption and cysteamine derivatisation. Gaseous acetaldehyde was collected via NaHSO₃-coated Sep-Pak^® silica gel cartridge, then derivatised with cysteamine, and then the δ¹³C value of the acetaldehyde–cysteamine derivative was measured by GC–C–IRMS. Using two acetaldehydes with different δ¹³C values, derivatisation experiments were carried out to cover concentrations between 0.009×10^?3 and 1.96×10^?3 mg·l^?1) of atmospheric acetaldehyde, and then δ¹³C fractionation was evaluated in the derivatisation of acetaldehyde based on stoichiometric mass balance after measuring the δ¹³C values of acetaldehyde, cysteamine and the acetaldehyde–cysteamine derivative. δ¹³C measurements in the derivertisation process showed good reproducibility (<0.5 ‰) for gaseous acetaldehyde. The differences between predicted and measured δ¹³C values were 0.04–0.31 ‰ for acetaldehyde–cysteamine derivative, indicating that the derivatisation introduces no isotope fractionation for gaseous acetaldehyde, and obtained δ¹³C values of acetaldehyde in ambient air at the two sites were distinct (?34.00 ‰ at an urban site versus?31.00 ‰ at a forest site), implying potential application of the method to study atmospheric acetaldehyde.     

13C NMR and Fukui function analysis on C82 hydroxylated fullerene through density functional theory

Density functional theory calculations were performed on C₈₂ hydroxylated fullerene. B3LYP and PBE0 functionals with 6-31G** basis set were utilised to get chemical shieldings, chemical shifts and the isotropic Fermi contact coupling on each atomic site. A relation between nuclear magnetic resonance (NMR) properties and reactivity of the molecule, obtained through the electronic Fukui function, was observed. Interestingly, the most stable configurations of OH groups adsorbed on C₈₂ surface were obtained when the hydroxyl groups are adsorbed on deshielded (isotropically and anisotropically) sites. For open-shell systems, a relation between isotropic Fermi contact, spin density and average Fukui function was found, that is, sites with a great amount of Fukui function (analytical and the one obtained through finite difference) and spin density have the largest isotropic Fermi contact coupling data. With the adsorption of the first hydroxyl molecules, spin densities and Fukui functions show preferential sites to adsorb the following OH groups close to previously adsorbed. Additionally, theoretical spectra of chemical shifts of C₈₂(OH)_n (n = 1, 2, 3 and 4) were obtained and they were compared with experimental reports, getting a reasonable comparison. For example, regarding ¹³C NMR chemical shifts obtained in C₈₂OH molecule, 80 ppm (B3LYP) and 79 ppm (PBE0) were calculated on hydroxylated carbon, which is in good agreement with experimental results in C₆₀ fullerols.     

Wild Rabbit Host and Some Parasites Show Trophic-Level Relationships for δ(13)C and δ(15)N: A First Report

Abstract We report the first isotopic study of an animal host-parasite system. Parasitic, intestinal nematodes, Graphidium strigosum and Passalurus ambiguus, were (15)N-enriched relative to their host, the European rabbit Oryctolagus cuniculus, while parasitic cestodes, Cittataenia denticulata and Mosgovoyia pectinata, were (15)N-depleted, suggesting different trophic relationships. Host embryos were more similar in their δ(13)C and δ(15)N values to maternal muscle than were any of the parasites. Coprophagy, the direct recycling of food by the rabbit eating its own faeces, did not lead to isotopic differences between stomach contents and faeces, suggesting that the major point for isotopic discrimination in lagomorph nitrogen metabolism is in the animal rather than in the gut. We conclude that bulk δ(13)C and δ(15)N can reveal valuable new information about host-parasite relationships, and these could be explored further at the biochemical level using compound-specific isotopic analyses.     

Characterisation of spatial variability and patterns in tree and soil δ13C at forested sites in eastern Canada

Wholistic isotopic studies provide a necessary foundation on which to build conceptual understanding of ecosystem development processes and provide the basis for further isotopic studies at a site or within an ecophysiological region. This study seeks to broadly characterise δ¹³C spatial variability and spatial patterns within soils and canopy tissues at five forest research sites in eastern Canada. We observe consistent and predictable patterns of leaf δ¹³C variation within trees and a consistent offset between woody and leafy tree tissues. Patterns are similar for both hardwoods and softwoods, but overall hardwoods had canopies that were more depleted in ¹³C. Soil carbon δ¹³C enrichment occurred with depth and appeared to vary according to site soil texture. Upper soil δ¹³C was intermediate between leaves and woody tissues, whereas deeper soil values suggested important contributions from more enriched tree tissues, such as persistent woody debris and possibly roots. The relationship between aboveground and belowground signatures suggests functional or developmental differences between study sites.     

Measuring δ13C of atmospheric air with non-dispersive infrared spectroscopy

The potential use of non-dispersive infrared spectroscopy for measuring δ¹³C in air is demonstrated. This technique has already been successfully established for breath test analyses in medical diagnostics, where the CO₂ concentration ranges from 1 to 5 vol.% in the exhaled breath of vertebrates. For breath tests, the sensitivity and accuracy has been improved to reach a standard deviation of 0.2 ‰ (delta-value). Further adjustments were necessary to improve the sensitivity of the instrument at concentration levels typical of atmospheric air. The long-term stability is given by a standard deviation of 0.35 ‰ for CO₂ concentrations of about 400 ppm with signal averaging over 60 s.     

The Effect of Diet Quality on δ13C and δ15N in the Tissues of Locusts,Locusta migratoria L

Abstract

Locust nymphs were raised from hatching to adult locusts on either seedling wheat (C₃) or maize (C₄), to determine whether relative enrichments/depletions of ¹⁵N and ¹³C within body tissues are influenced by diet. The maize contained less hexose sugars and protein per gram than wheat.

The isotopic spacing between the food and the whole insect was found to differ between the two diets. The lower quality maize diet showed an overall +5.1‰ enrichment in δ¹⁵N compared to + 2.8‰ for wheat, possibly due to increased fractionation due to protein recycling.

The maize diet resulted in increased depletion in lipid and trehalose and depletion in chitin relative to diet. The results for both δ¹⁵N and δ¹³C suggest that substrate recycling was occurring on the low quality maize diet. Therefore diet quality determines the enrichment/depletion in δ¹⁵N and δ¹³C within organisms.     

The effect of different fish feed compositions on δ13C and δ15N signatures of sea bass and its potential value for tracking mariculture-derived nutrients

Increasing demand for fish and seafood calls for an expansion of aquaculture production. At the same time, the status of the marine environment must not be jeopardised. Stable isotopes are potential markers for tracking feed-based nutrient flows from aquaculture into marine biota. Here, we demonstrate how four experimental diets (main protein components: fishmeal, soya protein concentrate, wheat gluten, and Jatropha kernel meal) and a commercial diet induce characteristic δ¹³C and δ¹⁵N signals in sea bass (Dicentrarchus labrax) during nine weeks of laboratory feeding under replicate conditions. The plant-protein-based diets containing wheat gluten and soya, and the commercial feed consistently induced the largest isotopic differentiation of the fish, both from the feed source and from the pre-experimental condition. The large difference of the fish on plant-protein-based diets compared to the range of natural isotopic variation in the macrozoobenthos of the North Sea lends support to the idea that plant-based feeds are suitable for tracing mariculture-derived organic matter under practical conditions. The commercial feed had a similar effect as the experimental feeds and would be a cost-effective option for an offshore aquaculture experiment.     

Measuring δ(13)C values of atmospheric acetaldehyde via sodium bisulfite adsorption and cysteamine derivatisation

δ(13)C values of gaseous acetaldehyde were measured by gas chromatograph-combustion-isotope ratio mass spectrometer (GC-C-IRMS) via sodium bisulfite (NaHSO(3)) adsorption and cysteamine derivatisation. Gaseous acetaldehyde was collected via NaHSO(3)-coated Sep-Pak(?) silica gel cartridge, then derivatised with cysteamine, and then the δ(13)C value of the acetaldehyde-cysteamine derivative was measured by GC-C-IRMS. Using two acetaldehydes with different δ(13)C values, derivatisation experiments were carried out to cover concentrations between 0.009×10(-3) and 1.96×10(-3)?mg·l(-1)) of atmospheric acetaldehyde, and then δ(13)C fractionation was evaluated in the derivatisation of acetaldehyde based on stoichiometric mass balance after measuring the δ(13)C values of acetaldehyde, cysteamine and the acetaldehyde-cysteamine derivative. δ(13)C measurements in the derivertisation process showed good reproducibility (<0.5?‰) for gaseous acetaldehyde. The differences between predicted and measured δ(13)C values were 0.04-0.31?‰ for acetaldehyde-cysteamine derivative, indicating that the derivatisation introduces no isotope fractionation for gaseous acetaldehyde, and obtained δ(13)C values of acetaldehyde in ambient air at the two sites were distinct (-34.00?‰ at an urban site versus-31.00?‰ at a forest site), implying potential application of the method to study atmospheric acetaldehyde.     

A robust and fast method of sampling and analysis of δ13C of dissolved inorganic carbon in ground waters

The stable carbon isotopic composition of dissolved inorganic carbon (δ¹³C_DIC) is traditionally determined using either direct precipitation or gas evolution methods in conjunction with offline gas preparation and measurement in a dual-inlet isotope ratio mass spectrometer. A gas evolution method based on continuous-flow technology is described here, which is easy to use and robust. Water samples (100–1500 μl depending on the carbonate alkalinity) are injected into He-filled autosampler vials in the field and analysed on an automated continuous-flow gas preparation system interfaced to an isotope ratio mass spectrometer. Sample analysis time including online preparation is 10 min and overall precision is 0.1 ‰. This method is thus fast and can easily be automated for handling large sample batches.     

Field-based cavity ring-down spectrometry of δ13C in soil-respired CO2

Measurement of soil-respired CO₂ at high temporal resolution and sample density is necessary to accurately identify sources and quantify effluxes of soil-respired CO₂. A portable sampling device for the analysis of δ¹³C values in the field is described herein.

CO₂ accumulated in a soil chamber was batch sampled sequentially in four gas bags and analysed by Wavelength-Scanned Cavity Ring-down Spectrometry (WS-CRDS). A Keeling plot (1/[CO₂] versus δ¹³C) was used to derive δ¹³C values of soil-respired CO₂. Calibration to the δ¹³C Vienna Peedee Belemnite scale was by analysis of cylinder CO₂ and CO₂ derived from dissolved carbonate standards. The performance of gas-bag analysis was compared to continuous analysis where the WS-CRDS analyser was connected directly to the soil chamber.

Although there are inherent difficulties in obtaining absolute accuracy data for δ¹³C values in soil-respired CO₂, the similarity of δ¹³C values obtained for the same test soil with different analytical configurations indicated that an acceptable accuracy of the δ¹³C data were obtained by the WS-CRDS techniques presented here. Field testing of a variety of tropical soil/vegetation types, using the batch sampling technique yielded δ¹³C values for soil-respired CO₂ related to the dominance of either C₃ (tree, δ¹³C=?27.8 to?31.9 ‰) or C₄ (tropical grass, δ¹³C=?9.8 to?13.6 ‰) photosynthetic pathways in vegetation at the sampling sites. Standard errors of the Keeling plot intercept δ¹³C values of soil-respired CO₂ were typically<0.4 ‰ for analysis of soils with high CO₂ efflux (>7–9 μmol m^?2 s^?1).     

Diurnal variability of δ13C and δ18O of atmospheric CO2 in the urban atmosphere of Kraków,Poland

This article presents the results of measurements of the isotopic composition and concentration of atmospheric carbon dioxide, performed on air samples from Kraków (Southern Poland) in different seasons of the year. A simple isotope mass balance model has been applied to determine the contributions of different sources of CO₂ to the urban atmosphere of Kraków city: the latitudinal/regional background, biospheric contributions and anthropogenic emissions. The calculations show that during the summer and early autumn the dominant contribution to local CO₂ peaks is the biosphere, making up to 20% of atmospheric CO₂ during the nocturnal temperature inversion in the lower troposphere. During early spring and winter, anthropogenic emissions are the main local source.     

Effect of different lipid extraction methods on δ13C of lipid and lipid-free fractions of fish and different fish feeds

For many ecological applications of stable carbon isotope techniques, it is necessary to separate the lipid and lipid-free fractions. The effect of different lipid extraction methods on the isotope signature of the remaining lipid-free matter as well as the lipid fraction was tested. A hot extraction form of the Soxhlet method using petrol-ether was compared with two liquid-liquid extraction methods for lipid determination described by Bligh and Dyer and Smedes. Solid samples of fish and different natural food items were subjected to extraction and the carbon isotope ratios in lipid and lipid-free matter determined by IRMS. All methods were suitable for lipid extraction from all samples analysed here and did not cause biologically relevant differences (>1) in carbon isotopic ratios, except the Bligh and Dyer extraction method using chloroform which caused systematic errors for δ ¹³C when applied to diatoms.     

δ2H, δ13C and δ18O from whole wood, α-cellulose and lignin methoxyl groups in Pinus sylvestris: a multi-parameter approach

Novel tree ring parameters – δ¹³C and δ²H from methoxyl groups – have been developed to reconstruct palaeoclimate. Tests with δ¹³C and δ¹⁸O derived from whole wood and cellulose samples, however, indicated differences in the isotopic composition and climate signal, depending on the extracted wood component. We assess this signal dependency by analysing (i) δ¹³C and δ¹⁸O from whole wood and cellulose and (ii) δ¹³C and δ²H from methoxyl groups, using Pinus sylvestris L. growing near Altenkirchen (Germany). Results indicate significant correlations among the time series derived from whole wood, cellulose, and lignin methoxyl groups. Compared with the whole wood samples, δ¹³C from methoxyl groups showed a different and overall lower response to climate parameters. On the other hand, δ²H from methoxyl groups showed high correlations with temperature and was also correlated with ring width, indicating its potential as a temperature proxy. Isotope time series with the highest correlation with climatic parameter were: (i) whole wood and cellulose δ¹³C with growing season precipitation and summer temperature; (ii) methoxyl groups with spring precipitation; (iii) whole wood and cellulose δ¹⁸O correlates with annual evapotranspiration and water balance; and (iv) methoxyl group δ²H with spring temperatures. These findings reveal that multiple climate elements can be reconstructed from different wood components and that whole wood proxies perform comparably to cellulose time series.     

Tissue-specific δ13C in ancient and modern tropical seabirds and flying fish in the Xisha Islands,South China Sea

We analyzed ¹³C characteristics in samples of bird bones, feathers, eggshell carbonate and membrane from modern specimens of red-footed booby (Sula sula) as well as fish muscle, scales, and bones from its predominant food source, flying fish (Exocoetus volitans), and muscle from its secondary food source squid (Loligo chinensis), as well as in ancient sub-fossil samples of seabird and flying fish at the Xisha Islands, South China Sea. δ¹³C is tissue-specific in both seabirds and flying fish due to the variance in turn-over among the tissues and differences in the type and content of amino acids across a diverse range of tissues. The δ¹³C discrimination factors also differed significantly among the various tissues between tropical seabirds and their prey. A Suess effect, caused by fossil fuel combustion and the emission of carbon with fewer ¹³C isotopes, was observed in the bird and fish tissue from ancient to modern time. Our study provides a multiple variability index for δ¹³C in organisms along a food chain, and verifies that tissue-specific ¹³C analysis is essential to identify diet and species and thus is a valuable tool for research on tropical seabird ecology.     

The Effect of Diet Quality on δ(13)C and δ(15)N in the Tissues of Locusts, Locusta migratoria L

Abstract Locust nymphs were raised from hatching to adult locusts on either seedling wheat (C(3)) or maize (C(4)), to determine whether relative enrichments/depletions of (15)N and (13)C within body tissues are influenced by diet. The maize contained less hexose sugars and protein per gram than wheat. The isotopic spacing between the food and the whole insect was found to differ between the two diets. The lower quality maize diet showed an overall +5.1‰ enrichment in δ(15)N compared to + 2.8‰ for wheat, possibly due to increased fractionation due to protein recycling. The maize diet resulted in increased depletion in lipid and trehalose and depletion in chitin relative to diet. The results for both δ(15)N and δ(13)C suggest that substrate recycling was occurring on the low quality maize diet. Therefore diet quality determines the enrichment/depletion in δ(15)N and δ(13)C within organisms.     

Comparison of δ13C and δ18O from cellulose,whole wood,and resin-free whole wood from an old high elevation Pinus uncinata in the Spanish central Pyrenees*

δ¹³C and δ¹⁸O values from sapwood of a single Pinus uncinata tree, from a high elevation site in the Spanish Pyrenees, were determined to evaluate the differences between whole wood and resin-free whole wood. This issue is addressed for the first time with P. uncinata over a 38-year long period. Results are also compared with published isotope values of α-cellulose samples from the same tree. The differences in δ¹³C and δ¹⁸O between whole wood and resin-free whole wood vary within the analytical uncertainty of 0.3 and 0.5?‰, respectively, indicating that resin extraction is not necessary for sapwood of P. uncinata. Mean differences between cellulose and whole wood are 0.9?‰ (δ¹³C) and 5.0?‰ (δ¹⁸O), respectively. However, further analyses of different species and other sites are needed to evaluate whether the findings reported here are coherent more generally.     

High-resolution solid-state 13C14N and 13C15N heteronuclear correlation spectroscopy

Two-dimensional heteronuclear correlation spectroscopy is applied to coupled carbon and nitrogen nuclei in single crystals of amino acids and peptides. High resolution is available because the spectra have the carbon chemical shift along one frequency axis and the nitrogen chemical shift (and the second-order quadrupole shift in the case of ¹⁴N) along the second frequency axis. These two-dimensional spectra enable direct measurements of resonance frequencies and dipole-dipole couplings that are useful in providing information about the structure, dynamics, and spectral characteristics of molecules.