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Fatty acid composition and change in Collembola fed differing diets:

identification of trophic biomarkers

P.M. Chamberlaina,b, I.D. Bulla, H.I.J. Blackb, P. Inesonc, R.P. Eversheda,*

aOrganic Geochemistry Unit, Bristol Biogeochemistry Research Centre, School of Chemistry, University of Bristol, Cantock’s Close, Bristol BS8 1TS, UKbCentre for Ecology and Hydrology, Lancaster Environment Centre, Library Avenue, Bailrigg, Lancaster LA1 4AP, UK

cDepartment of Biology, University of York, PO Box 373, York YO10 5WY, UK

Received 5 December 2003; received in revised form 24 November 2004; accepted 27 January 2005

Abstract

To assess the potential of fatty acid (FA) compositions to act as biomarkers in the soil food web, two species of Collembola, Folsomia

candida and Proisotoma minuta, were switched to four possible diets: Cladosporium cladosporioides (a common soil fungus), Panagrellus

redivivus (a bacteria feeding nematode), Zea mays (maize) and Alnus glutinosa (alder). The change in FA content of the Collembola was

observed over the following 39 days. The four diets produced significant shifts in the FA compositions of the Collembola, with P. redivivus

causing the most extreme changes; Collembola fed P. redivivus gained complex FA compositions similar to those of the nematode diet.

Changes in the relative abundances of some FAs were found to follow negative exponential curves, as the components either accumulated in,

or were removed from, the FA pool in the Collembola; abundance half-lives varied between 0.5 and 22.4 days, indicating that Collembolan

FA compositions changed readily with the input of new exogenous components. The results demonstrate that Collembolan FA compositions

are influenced by diet, and that the abundances of FAs such as i15:0, i17:0 and 18:1(n-7) may be used as biomarkers of nematode

consumption by Collembola. In contrast, the C20 polyunsaturated FAs cannot be used as biomarkers for nematode predation as Collembola

possess the ability to biosynthesise high abundances of these compounds when not provided by the diet.

q 2005 Elsevier Ltd. All rights reserved.

Keywords: Diet; Biomarker; Fatty acids; Polyunsaturated; Collembola

1. Introduction

The use of fatty acids (FAs) as trophic biomarkers is

common in aquatic ecosystems (e.g. Nelson et al., 2001;

Auel et al., 2002), but their potential use in soils, for

example in soil food web studies, has not been well

explored. Amongst soil organisms, the FA compositions of

bacteria and fungi have been extensively investigated (e.g.

Zelles, 1999; Madan et al., 2002; Baath, 2003), as have

the FA compositions of nematodes (e.g. Chitwood and

Krusberg, 1981; Tanaka et al., 1996), and there has been

limited, fundamental, research into the FAs of enchytraeids

(Jacob et al., 1991), slugs and snails (Weinert et al., 1993;

Zhu et al., 1994) and earthworms (e.g. Albro et al., 1992;

0038-0717/$ - see front matter q 2005 Elsevier Ltd. All rights reserved.

doi:10.1016/j.soilbio.2005.01.022

* Corresponding author. Tel.: C44 117 9287674; fax: C44 117 9251295.

E-mail address: [email protected] (R.P. Evershed).

Petersen and Holmstrup, 2000). However, there has been

very little study of the FAs of microarthropods such as

Collembola (Stransky et al., 1986; Holmstrup et al., 2002;

Haubert et al., 2004; Ruess et al., 2004) and mites, which are

significant and common components of the soil biological

community (Blakely et al., 2002). Fewer investigators still

have examined the changes in the FA compositions of soil

organisms over time (rare exceptions being Chen et al.

(2001) and Haubert et al. (2004)), or the rates of turnover

of FAs in such organisms. The analytical challenge of

determining the composition of the small quantities of FAs

present in soil organisms, such as the microarthropods, has

also been a hurdle resulting in the lack of previous work.

Fatty acids occur in many forms in organisms. Phospho-

lipid fatty acids (PLFAs) are structural components of cell

membranes, while neutral lipid fatty acids (NLFAs) in

triacylglycerols act as a store of energy and are often the

dominant form in which FAs are found in insects

(Stanley-Samuelson et al., 1988). Fatty acids may also

occur as free components or bound in glycolipids and steryl

Soil Biology & Biochemistry 37 (2005) 1608–1624

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P.M. Chamberlain et al. / Soil Biology & Biochemistry 37 (2005) 1608–1624 1609

fatty acyl esters. Among invertebrates, the focus has been

largely on commercially-important, above-ground

insects and a great deal is known about the composition of

insect FAs which have been shown to vary between species

(Sushchik et al., 2003), life-stage (Ogg and Stanley-Sa-

muelson, 1992), environment (e.g. Joanisse and Storey,

1996) and diet (Geer and Perille, 1977; Hanson et al., 1985).

PLFA compositions change in response to temperature and

moisture conditions (Hazel and Williams, 1990) to ensure

the required fluidity of cell membranes while the relative

abundance of NLFAs are inevitably reduced when an

invertebrate is starved (Renault et al., 2002; Haubert et al.,

2004).

Amongst soil organisms, nematode FAs are known to

change in response to temperature and other conditions

(Tanaka et al., 1996; Abu Hatab and Gaugler, 2001) and the

FA compositions of nematodes are responsive to the FA

compositions of their diet (Abu Hatab et al., 1998; Ruess

et al., 2002). However, there have been few examinations of

the effects of diet on Collembolan FAs (Haubert et al., 2004;

Ruess et al., 2004) despite the wide range of diets (and

therefore FAs) Collembola are known to consume includ-

ing: plant detritus (Takeda and Ichimura, 1983; Ponge,

2000), algae (Vegter, 1983), fungi (e.g. Sadaka-Laulan

et al., 1998), nematodes (Lee and Widden, 1996) and pollen

(Kato, 1995).

In an experiment designed to examine the effects of

different diets on Collembolan total FA compositions with

time, we fed two species of Collembola, Folsomia candida

and Proisotoma minuta, four diets representative of various

components of the soil ecosystem which Collembola

may regularly ingest. The FA compositions of the

Collembola were then examined over the ensuing 39 days.

We hypothesised that: (i) Collembolan FA profiles would

change in response to diet, (ii) that certain dietary FAs

would be directly incorporated into Collembolan FAs, and

(iii) that some of these would therefore have potential value

as trophic biomarkers.

2. Materials and methods

2.1. Experimental design

Diet-switches were carried out in a replicated experiment

with microcosms containing either F. candida (Willem) or

P. minuta (Tullberg) and one of four different foodstuffs:

Cladosporium cladosporioides (Frensen.), Panagrellus

redivivus (Linne, 1767), Zea mays L. (maize) and Alnus

glutinosa L. (alder) leaves.

C. cladosporioides was produced using a modified

Czapek Dox culturing technique with sucrose as the sole

C source. Sucrose (30 g), NaNO3 (3 g), KH2PO4 (1 g),

MgSO4 (0.5 g), KCl (0.5 g) and Fe2SO4 (0.01 g) were

dissolved in 1 l distilled water, autoclaved (15 min at

121 8C) and allowed to cool before inoculation with

C. cladosporioides obtained from the fungal collection

held at Merlewood Research Station, Cumbria, UK. The

inoculated media was shaken for 14 days after which the

fungus was filtered onto glass fibre filter paper (Whatman)

and stored in a Petri dish at 4 8C.

P. redivivus was grown on a substrate of maize meal

(Dunns River Fine Cornmeal, Enco Products Ltd, Hatfield,

Herts, UK). The meal was mixed with double distilled water

(100 ml H2O 100 gK1 maize meal) before being placed in

500 ml glass jars and autoclaved (15 min). After the

substrate had cooled, it was inoculated with P. redivivus

using aseptic techniques. The jars were kept in the dark at

20 8C until required. Nematodes were extracted from the

maize matrix by filtering a solution of distilled water,

nematodes and maize meal through a nylon mesh (90 mm).

The resulting suspension of nematodes was collected from

the bottom of the filter funnel. The nematodes were further

concentrated by centrifugation and excess water removed;

the resultant nematode slurry was added to the experimental

microcosms by pipette.

Maize litter was obtained from Sizergh Farm, near

Kendal, Cumbria, UK, where it was harvested as a fodder

crop. The maize was collected as chopped material prepared

for silage and then air-dried. Alder leaves were collected

from the Gisburn Forest Experiment, Yorkshire, UK and air-

dried for storage. Before use, both plant litters were soaked

overnight in distilled water and then thoroughly rinsed.

F. candida and P. minuta were taken from stock colonies

reared on bakers yeast (Saccharomyces cerevisiae) and

placed in groups of 20 into individual microcosms

comprising small plastic pots (38!65 mm) with a plaster

of Paris and charcoal base (Snider, 1972). The plaster of

Paris bases were soaked in distilled water for 24 h prior to

introduction of the Collembola in order to maintain a high

relative humidity in the microcosms throughout the

experiment. In all cases the Collembola were observed to

be feeding directly on the foodstuffs offered to them.

Microcosms were destructively sampled on days 2, 4, 8, 16

and 39. Collembola from the stock colonies were taken as

day 0 samples. Three replicates of each diet were taken at

each sampling point. Collembola were removed from the

food sources for 2 h prior to freezing to allow complete

passage of ingested foods from the gut.

2.2. Lipid characterisation

Lipids were extracted and analysed as described in

Chamberlain et al. (2004). Briefly, freeze-dried Collembola

and diets were lipid extracted with 2:1 DCM/methanol

(3!2 ml). Lipids were saponified with 0.5 M NaOH in

methanol (70 8C for 90 min), the solution acidified with

0.5 M HCl and the lipids extracted into DCM. Fatty acids

were separated from other lipids on an aminopropyl solid

phase extraction cartridge (Bond Elut NH2, Varian) using

DCM/2-propanol (2:1 v/v) to elute the neutral fraction,

and diethyl ether containing 2% acetic acid to elute the

P.M. Chamberlain et al. / Soil Biology & Biochemistry 37 (2005) 1608–16241610

FAs. Fatty acids were derivatised using boron trifluoride-

methanol (14% w/v, 30 ml, 70 8C, 10 min) to produce fatty

acid methyl esters (FAMEs). The FAME compositions

were determined by gas chromatography (GC) and

compounds identified using gas chromatography/mass

spectrometry (GC/MS). Analytical conditions are described

in detail in Chamberlain et al. (2004).

2.3. Statistical analyses

The absolute concentration of FAs in diets and

Collembola were not determined in this study; FA

compositions are reported as a percentage of total FAs,

commonly referred to as relative abundance. Prior to

statistical analysis FA compositions were arcsine trans-

formed to normalise the distributions. All statistical

analyses were carried out using Statistica (v6.1; StatSoft,

Inc.). Repeated measures analysis of variance (ANOVA)

was used on a single dataset consisting of all Collembolan

relative abundance data to test for significant changes in FA

compositions over time; Tukeys honest significant differ-

ence test was used to determine the significance of changes

in individual components. Changes in the ratios of odd-to-

even chain length FAs and saturated-to-unsaturated FAs

were also analysed using repeated measures ANOVA, with

a post-hoc Tukey test to examine significant changes in

individual Collembola species and diets. Statistica was also

Fig. 1. Partial gas chromatograms of the fatty acid compositions of the four diets; (a

acids are: A 12:0, B 13:0, C 14:0, D 14:1, E i15:0, F a15:0, G 15:0, H i16:0, I 16:0

R 18:1(n-9), S 18:1(n-7), T 18:1(n-5), U 18:2(n-6), V 18:3, W 18:30, X 20:0, Y 20

q 23:0, k 24:0.

used for principle components analysis of the FA

compositions.

3. Results

3.1. Fatty acid compositions of offered diets

The FA compositions of the offered diets are summarised

in Fig. 1 and Tables 1–4. C. cladosporioides (Fig. 1a;

Table 1) exhibited the narrowest range of FAs, containing 7

detectable components, with a composition dominated by

16:0, 18:1(n-9) and 18:2(n-6). P. redivivus (Fig. 1b; Table 2)

contained a particularly wide range of FAs, 28 in total,

including six C20 polyunsaturated fatty acids (PUFAs)

which accounted for 24% of the total FA composition.

Maize (Fig. 1c; Table 3) contained 12 detectable FAs and

like C. cladosporioides, was dominated by 16:0, 18:1 (n-9)

and 18:2(n-6). The latter component alone accounted for

43% of the total FA composition of maize. Alder (Fig. 1d;

Table 4) contained 18 FAs, the most abundant of

which were 16:0 and 22:0. There were significant

differences in the ratios of saturated-to-unsaturated FAs of

the diets (P!0.005). C. cladosporioides, P. redivivus and

maize all exhibited ratios of saturated-to-unsaturated FAs in

the range 0.32–0.41; while the ratio of saturated-to-

unsaturated FAs in alder (2.32) was significantly higher

) C. cladosporioides, (b) P. redivivus, (c) Z. mays and (d) A. glutinosa. Fatty

, J 16:1(n-7), K 16:1(n-5), L 16:2, M i17:0, N 17:0, O 17:1, P i18:0, Q 18:0,

:1, Z 20:2(n-6), a 20:3(n-6), b 20:4(n-6), g 20:3, d 20:4, 3 20:5(n-3), z 22:0,

Table 1

Fatty acid compositions of F. candida and P. minuta fed C. cladosporioides for 39 days from day 0 of the diet-switching experiment

Fatty acid Time (days) Diet

F. candida P. minuta

0 2 4 8 16 39 0 2 4 8 16 39

16:0 12.5 (0.5) 15.1 (0.1) 16.0 (2.6) 17.7 (1.2) 14.4 (3.2) 12.0 (0.5) 15.6 (0.6) 19.2 (1.4) 16.2 (2.9) 20.9 (1.6) 18.7 (1.0) 18.4 (0.5) 18.6 (1.1)

16:1(n-7) 15.6 (1.7) 16.2 (0.7) 11.0 (0.9) 9.2 (0.8) 5.7 (0.5) 2.5 (0.1) 11.6 (2.0) 8.7 (1.3) 6.5 (0.9) 5.8 (0.5) 4.1 (0.5) 3.6 (0.6) 1.1 (0.1)

18:0 13.2 (1.0) 12.5 (0.6) 12.1 (1.6) 14.7 (0.7) 12.7 (3.3) 10.5 (1.3) 18.8 (1.9) 18.8 (0.3) 14.9 (3.2) 18.1 (0.8) 21.2 (0.4) 21.4 (0.7) 5.8 (0.4)

18:1(n-9) 35.9 (0.4) 42.2 (0.3) 43.5 (2.9) 46.4 (0.6) 41.6 (5.4) 36.7 (1.1) 38.0 (1.7) 35.8 (6.1) 37.6 (5.5) 44.8 (1.9) 47.4 (0.9) 44.6 (1.4) 36.8 (0.6)

18:1(n-7) 5.7 (0.2) 5.3 (0.1) 3.8 (0.2) 3.5 (0.2) 2.2 (0.3) 0.9 (0.6) 1.0 (0.2) 1.8 (0.2) 1.8 (0.5) 1.6 (0.1) 1.5 (0.1) 1.5 (0.2) 0.6 (0.1)

18:2(n-6) 1.7 (0.2) 2.5 (0.1) 4.5 (3.1) 1.5 (1.1) 9.7 (6.0) 14.7 (2.0) 4.5 (0.1) 5.7 (3.5) 10.3 (5.5) 3.0 (0.4) 3.1 (0.3) 3.5 (0.9) 31.9 (0.3)

18:3 0 0 0 0 1.1 (1.0) 2.5 (0.4) 0 0 0 0 0 0 4.2 (0.1)

20:4(n-6) 6.0 (1.9) 0 1.8 (3.0) 0 3.7 (3.2) 7.9 (0.2) 8.4 (0.7) 2.4 (4.1) 5.7 (5.0) 0 0 0 0

20:5(n-3) 4.2 (0.3) 0 1.0 (1.8) 0 2.1 (1.8) 4.7 (0.1) 2.1 (0.4) 0.5 (0.8) (0.8) 0 0 0 0

Total C20

PUFAs

10.2 (1.7) 0.4 (0.4) 3.0 (5.2) 0 6.4 (5.5) 14.1 (0.3) 10.1 (1.0) 2.8 (4.9) 6.6 (5.8) 0 0 0 0

Total no. of

fatty acids

19 20 23 21 25 23 15 17 19 15 13 15 7

Sat/unsat

ratioa

0.42 (0.02) 0.46 (0.01) 0.47 (0.10) 0.58 (0.04) 0.47 (0.13) 0.35 (0.01) 0.53 (0.03) 0.73 (0.09) 0.56 (0.14) 0.78 (0.05) 0.76 (0.03) 0.83 (0.04) 0.33 (0.01)

Odd/even

ratiob

0.025

(0.002)

0.027

(0.003)

0.027

(0.005)

0.034

(0.005)

0.029

(0.008)

0.027

(0.003)

0.015

(0.002)

0.026

(0.002)

0.029

(0.004)

0.039

(0.009)

0.031

(0.006)

0.048

(0.004)

0.005

(0.001)

Fatty acid compositions are mean percentages of total FAs (SD) and nZ3. All components present at O2% abundance during the experiment are shown.a Ratio of saturated-to-unsaturated fatty acids.b Ratio of odd-to-even carbon number fatty acids.

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Table 2

Fatty acid compositions of F. candida and P. minuta fed P. redivivus for 39 days from day 0 of the diet-switching experiment

Fatty acid Time (days) Diet


0 2 4 8 16 39 0 2 4 8 16 39

i15:0 0.5 (0.1) 2.8 (0.4) 3.4 (0.1) 5.9 (1.3) 5.2 (0.1) 6.0 (0.2) 0 1.5 (0.8) 1.9 (0.6) 3.3 (0.4) 4.4 (0.6) 5.5 (0.2) 8.2 (0.3)

16:0 12.5 (0.5) 10.2 (1.0) 8.6 (0.3) 8.7 (2.0) 6.7 (0.4) 4.6 (0.4) 14.6 (0.6) 9.6 (0.7) 8.4 (0.5) 7.9 (0.4) 8.2 (0.2) 5.4 (0.2) 2.7 (0.1)

16:1(n-7) 15.6 (1.7) 8.3 (2.0) 6.1 (0.2) 5.1 (1.0) 3.4 (0.2) 2.6 (0.2) 10.8 (2.0) 7.1 (1.8) 4.9 (0.5) 3.4 (0.1) 2.6 (0.2) 1.9 (0.1) 1.6 (0.1)

i17:0 0.7 (0.1) 1.3 (0.2) 1.8 (0.1) 2.9 (0.8) 2.3 (0.1) 2.8 (0.1) 0 1.4 (0.1) 2.0 (0.1) 2.9 (0.2) 3.8 (0.2) 4.8 (0.1) 5.2 (0.2)

18:0 13.2 (1.0) 9.9 (0.5) 10.3 (0.9) 13.5 (3.5) 11.1 (0.5) 10.0 (0.5) 17.6 (1.8) 13.1 (2.2) 14.0 (0.3) 14.0 (0.8) 14.9 (0.2) 11.3 (0.1) 6.4 (0.1)

18:1(n-9) 35.9 (0.4) 22.9 (4.3) 17.3 (0.3) 16.7 (3.4) 13.5 (0.2) 11.9 (1.0) 36.6 (1.7) 20.6 (0.3) 16.8 (0.5) 13.7 (0.7) 13.3 (0.7) 9.1 (0.3) 5.3 (0.1)

18:1(n-7) 5.7 (0.2) 11.1 (0.9) 12.6 (0.1) 15.3 (3.3) 13.4 (0.2) 12.5 (0.3) 2.3 (0.2) 9.7 (0.3) 10.6 (0.2) 11.6 (0.4) 10.4 (0.2) 14.1 (0.3) 17.7 (0.4)

18:2(n-6) 1.7 (0.2) 8.7 (1.2) 11.0 (0.1) 9.3 (3.8) 13.5 (0.4) 13.4 (0.4) 4.2 (0.1) 13.0 (0.1) 13.6 (0.1) 13.5 (0.6) 11.9 (0.3) 14.7 (0.3) 20.8 (0.3)

18:3 0 1.0 (0.2) 1.4 (0.1) 1.2 (0.7) 1.5 (0.1) 1.0 (0.1) 0 1.1 (0.1) 1.0 (0.1) 0.9 (0.2) 0.7 (0.1) 0.7 (0.1) 2.7 (0.1)

20:2(n-6) 0 1.3 (0.1) 1.8 (0.1) 1.7 (0.7) 2.1 (0.1) 1.7 (0.5) 0 1.6 (0.1) 1.9 (0.1) 2.1 (0.1) 1.6 (0.1) 2.7 (0.1) 4.7 (0.1)

20:3(n-6) 0 1.9 (0.3) 2.5 (0.1) 1.7 (1.3) 2.6 (0.1) 2.3 (0.2) 0 1.4 (0.2) 1.7 (0.3) 1.5 (0.1) 1.0 (0.1) 1.4 (0.1) 5.5 (0.2)

20:4(n-6) 6.0 (1.9) 8.2 (0.4) 10.3 (0.3) 7.2 (6.7) 11.7 (0.3) 15.3 (0.5) 7.9 (0.7) 12.3 (1.1) 14.9 (0.4) 16.5 (0.9) 18.3 (0.3) 18.8 (0.5) 8.4 (0.4)

20:5(n-3) 4.2 (0.3) 4.2 (0.5) 5.8 (0.2) 3.4 (3.4) 6.3 (0.3) 8.1 (0.1) 2.0 (0.3) 3.0 (0.2) 3.3 (0.1) 3.2 (0.3) 3.0 (0.2) 3.5 (0.1) 4.5 (0.2)

Total C20

PUFAs

10.2 (1.7) 15.7 (1.8) 20.5 (0.5) 14.1 (11.9) 22.7 (0.7) 27.4 (0.5) 10.1 (1.0) 18.3 (1.6) 21.8 (0.8) 23.3 (1.4) 24.0 (0.6) 26.4 (0.6) 24.2 (0.8)

Total no. of

fatty acids

19 28 28 28 28 28 15 23 24 24 24 24 28

Sat/unsat

ratioa

0.43 (0.02) 0.36 (0.02) 0.37 (0.01) 0.52 (0.20) 0.38 (0.02) 0.34 (0.02) 0.53 (0.03) 0.37 (0.03) 0.38 (0.02) 0.42 (0.03) 0.50 (0.03) 0.40 (0.01) 0.32 (0.01)

Odd/even

ratiob

0.025

(0.002)

0.051

(0.006)

0.070

(0.002)

0.110

(0.032)

0.089

(0.004)

0.104

(0.004)

0.01

(0.01)

0.04

(0.01)

0.05

(0.01)

0.07

(0.01)

0.10

(0.01)

0.12

(0.01)

0.17

(0.01)


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Table 3

Fatty acids compositions of F. candida and P. minuta fed Z. mays for 39 days from day 0 of the diet-switching experiment

Fatty acids Time (days) Diet


0 2 4 8 16 39 0 2 4 8 16 39

16:0 12.5 (0.5) 18.9 (1.1) 18.0 (0.1) 18.0 (0.4) 11.9 (1.0) 12.4 (1.2) 15.1 (0.6) 17.8 (1.0) 18.3 (2.0) 17.7 (1.0) 18.9 (1.6) 26.7 (2.2) 22.6 (0.2)

16:1(n-7) 15.6 (1.7) 7.1 (0.8) 4.7 (0.5) 3.3 (0.3) 2.7 (1.1) 2.3 (0.7) 11.1 (2.1) 12.3 (2.1) 8.5 (1.7) 6.3 (0.6) 4.3 (1.6) 1.2 (0.1) 0.8 (0.1)

18:0 13.2 (1.0) 13.2 (0.3) 13.3 (0.2) 13.2 (0.1) 11.6 (1.9) 15.0 (1.2) 18.2 (1.9) 17.9 (2.0) 21.2 (2.9) 19.0 (2.5) 27.8 (4.0) 49.3 (3.5) 2.8 (0.3)

18:1(n-9) 35.9 (0.4) 34.1 (0.7) 33.1 (0.8) 34.9 (1.5) 31.4 (2.3) 39.8 (0.9) 37.7 (1.8) 36.5 (3.2) 35.6 (1.8) 32.9 (1.3) 28.6 (5.2) 15.4 (4.0) 20.4 (0.5)

18:1(n-7) 5.7 (0.2) 3.3 (0.3) 2.6 (0.2) 2.6 (0.1) 2.4 (0.7) 2.6 (0.5) 2.4 (0.2) 3.9 (0.4) 4.5 (0.3) 3.3 (0.1) 2.8 (0.1) 2.0 (0.4) 0.9 (0.1)

18:2(n-6) 1.7 (0.2) 10.5 (2.3) 10.8 (1.4) 11.2 (1.4) 18.2 (8.1) 8.3 (1.0) 4.3 (0.1) 3.7 (0.6) 4.1 (1.6) 6.5 (1.2) 6.6 (1.0) 0 43.1 (0.7)

18:3 0 1.2 (0.1) 1.7 (0.2) 1.5 (0.2) 2.1 (0.7) 0.9 (0.5) 0.6 (0.1) 0 2.5 (0.5) 0 0 0 5.5 (0.2)

20:4(n-6) 6.0 (1.9) 4.3 (0.7) 6.8 (0.1) 6.2 (1.7) 8.6 (0.3) 8.0 (1.4) 8.2 (0.7) 0.9 (1.6) 1.6 (1.4) 6.0 (2.9) 1.3 (2.2) 0 0

20:5(n-3) 4.2 (0.3) 1.9 (0.4) 3.4 (0.1) 3.2 (0.3) 5.2 (1.1) 3.8 (0.3) 2.1 (0.4) 0.2 (0.3) 0.1 (0.2) 1.5 (1.0) 0.3 (0.5) 0 0

Total C20

PUFAs

10.2 (1.7) 6.9 (1.1) 11.1 (0.1) 10.3 (0.9) 10.0 (8.7) 12.4 (1.8) 10.1 (1.0) 1.1 (1.9) 1.8 (1.5) 7.4 (3.9) 1.6 (2.7) 0 0

Total no. of

fatty acids

19 20 19 19 19 19 15 18 17 17 18 10 12

Sat/unsat

ratioa

0.42 (0.02) 0.55 (0.02) 0.53 (0.01) 0.53 (0.01) 0.36 (0.07) 0.47 (0.07) 0.53 (0.03) 0.63 (0.01) 0.74 (0.15) 0.67 (0.1) 1.05 (0.28) 4.23 (1.33) 0.41 (0.02)

Odd/even

ratiob

0.025

(0.002)

0.018

(0.002)

0.020

(0.001)

0.020

(0.004)

0.027

(0.001)

0.043

(0.018)

0.015

(0.002)

0.034

(0.003)

0.041

(0.010)

0.036

(0.008)

0.046

(0.009)

0.039

(0.003)

0.023

(0.012)


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Table 4

Fatty acids compositions of F. candida and P. minuta fed A. glutinosa for 39 days from day 0 of the diet-switching experiment

Fatty acids Time (days) Diet


0 2 4 8 16 39 0 2 4 8 16 39

14:0 1.3 (0.1) 1.4 (0.2) 1.3 (0.3) 1.4 (0.3) 1.2 (0.1) 0.6 (0.2) 1.8 (0.2) 1.3 (0.3) 1.5 (1.0) 1.5 (0.1) 1.0 (1.2) 0 2.6 (0.2)

15:0 0.3 (0.1) 0.4 (0.1) 0.6 (0.1) 1.1 (0.4) 1.2 (0.1) 0.6 (0.1) 0.8 (0.2) 0.9 (0.2) 1.0 (0.1) 1.9 (0.9) 0.8 (0.4) 0 5.4 (1.5)

16:0 13.9 (1.0) 14.4 (1.4) 14.4 (1.3) 13.8 (1.0) 10.5 (0.5) 10.0 (0.4) 27.2 (0.4) 24.8 (2.6) 24.4 (2.1) 25.2 (0.6) 18.0 (2.1) 10.2 (1.6) 26.6 (0.4)

16:1(n-7) 15.6 (0.4) 16.9 (0.6) 14.7 (0.2) 12.5 (1.7) 8.5 (1.2) 6.0 (2.7) 8.4 (4.6) 7.0 (1.0) 5.6 (0.9) 3.9 (0.6) 1.8 (1.0) Trace 1.3 (0.1)

16:2 Trace 0.3 (0.1) 0.5 (0.1) 1.1 (0.2) 1.0 (0.3) 0.8 (0.3) 0 0.8 (0.5) 1.1 (0.2) 1.5 (0.1) 2.8 (0.2) 0 0.6 (0.1)

17:0 0.3 (0.1) 0.5 (0.1) 0.7 (0.1) 1.1 (0.2) 1.2 (0.1) 0.9 (0.4) 1.6 (0.1) 2.2 (1.2) 4.8 (0.9) 4.7 (0.4) 3.1 (0.2) 0 0.5 (0.1)

18:0 11.2 (1.2) 12.7 (1.1) 16.0 (0.6) 17.3 (1.6) 14.6 (0.5) 20.2 (4.0) 29.8 (2.3) 30.3 (1.9) 26.8 (3.0) 27.0 (1.6) 31.8 (6.2) 30.6 (5.5) 6.0 (0.1)

18:1(n-9) 38.0 (0.3) 38.6 (0.8) 38.9 (1.8) 36.8 (1.9) 32.9 (0.9) 33.4 (1.4) 16.5 (2.2) 24.6 (2.8) 23.2 (1.0) 19.9 (2.0) 17.4 (1.0) 13.0 (1.4) 9.4 (0.2)

18:1(n-7) 5.6 (0.1) 6.6 (0.4) 7.2 (0.4) 7.6 (0.3) 6.5 (0.7) 3.6 (2.5) 5.2 (4.8) 4.0 (0.7) 5.0 (0.3) 5.7 (0.5) 6.1 (1.0) 4.3 (0.5) 1.7 (0.1)

18:2(n-6) 1.7 (0.1) 1.3 (0.7) 0.7 (0.2) 0.7 (0.1) 1.9 (0.1) 1.4 (0.9) 1.8 (0.8) 0 0 0 4.0 (0.7) 3.0 (0.4) 9.7 (0.2)

18:3 0.5 (0.1) 0.3 (0.1) 0.3 (0.1) 0.6 (0.1) 0.9 (0.1) 0.6 (0.1) 0 0 0 0 0 1.5 (0.4) 6.8 (0.3)

20:0 0.3 (0.1) 0.4 (0.1) 0.7 (0.1) 1.2 (0.4) 0.8 (0.1) 1.8 (2.3) 0 0 0 0 2.2 (0.8) 4.2 (1.0) 9.1 (0.3)

20:1 0.6 (0.1) 0.7 (0.1) 1.3 (0.1) 1.7 (0.2) 1.4 (0.2) 3.6 (3.6) 1.4 (0.5) 0 0 0 3.4 (0.1) 18.3 (2.5) 0

20:4(n-6) 5.1 (0.3) 2.7 (2.2) 0 0 8.2 (2.1) 11.3 (2.8) 0 0 0 0 0 7.1 (0.4) 0

20:5(n-3) 2.9 (0.2) 1.3 (1.4) 0 0 6.0 (0.4) 7.0 (1.6) 0 0 0 0 0 0 0

22:0 0 0 0 0 0 0 0 0 0 0 0 0 12.6 (0.2)

24:0 0 0 0 0 0 0 0 0 0 0 0 0 4.8 (1.0)

Total C20

PUFAs

8.1 (0.1) 4.0 (3.6) 0.5 (0.5) 0 14.2 (2.4) 17.8 (3.6) 0 0 0 0 0 0 0

Total no. of

fatty acids

20 19 19 17 19 20 16 13 15 15 17 12 18

Sat/unsat

ratioa

0.40 (0.01) 0.45 (0.06) 0.54 (0.05) 0.63 (0.09) 0.48 (0.01) 0.56 (0.17) 1.05 (0.28) 1.53 (0.18) 1.48 (0.12) 1.78 (0.12) 1.73 (0.18) 0.89 (0.22) 2.32 (0.05)

Odd/even

ratiob

0.016

(0.001)

0.021

(0.002)

0.036

(0.004)

0.056

(0.013)

0.046

(0.001)

0.069

(0.072)

0.512

(0.130)

0.052

(0.013)

0.128

(0.011)

0.164

(0.004)

0.144

(0.026)

0.047

(0.014)

0.083

(0.015)


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than the other diets (P!0.005). The ratios of odd-to-even

chain length FAs of the diets were also significantly

different between diets (P!0.005); post-hoc comparisons

showed that P. redivivus and alder possessed significantly

higher ratios of odd-to-even FAs than maize and

C. cladosporioides, and that the ratios of odd-to-even FAs

of P. redivivus and alder were also significantly different to

each other.

3.2. Collembolan fatty acid compositions

3.2.1. Collembola switched to C. cladosporioides

Relative to day 0, a wider range of FAs was detected in

F. candida fed C. cladosporioides on all other days, despite

the narrower range of FAs present in the diet (Table 1).

However, these additional components were present only at

low relative abundances. The abundance of 16:1(n-7) in the

FA pool fell significantly (P!0.001) during the experiment,

as did the abundance of 18:1(n-7) (P!0.01); the reduced

abundances of these FAs reflected their low abundance

in the C. cladosporioides diet. Conversely, 18:2(n-6)

increased in abundance significantly (P!0.001) during

the experiment, reflecting the high abundance of this FA in

the diet. The 18:0 component was maintained at higher

proportions of total FAs in F. candida compared to the diet

while 16:0 and 18:1(n-9) remained at abundances similar to

those of the diet throughout the experiment. The PUFAs

20:4(n-6) and 20:5(n-3) were observed sporadically during

the experiment but were not detected in C. cladosporioides.

There were no significant differences in the ratio of

saturated-to-unsaturated FAs of F. candida during the

experiment, which remained similar to the saturated-to-

unsaturated FA ratio of the diet. Similarly, the ratio of odd-

to-even chain length FAs did not change significantly during

the experiment, and remained higher than that of the diet.

The range of FAs observed in P. minuta fed

C. cladosporioides was less than that observed in

F. candida. In P. minuta, 18:0 was maintained at higher

proportions of total FAs relative to the diet, while 16:0 and

18:1(n-9) remained relatively constant in abundances

similar to the diet. As in F. candida, 16:1(n-7) fell

significantly (P!0.005) in relative abundance over time

while 18:2(n-6) increased significantly (P!0.005) from

4.5% on day 0 to 10.3% on day 4 but remained around 3%

for the remainder of the experiment. The PUFAs 20:4(n-6)

and 20:5(n-3) were observed in P. minuta on days 0–4 only.

There were no significant changes in the ratios of saturated-

to-unsaturated and odd-to-even FAs in P. minuta.

3.2.2. Collembola switched to P. redivivus

A greater range of FAs was observed in Collembola fed

P. redivivus than for any other diet, reflecting the wide range

of FAs in the nematode diet (Table 2). Significant (all P!0.01) increases in abundance were observed in i15:0, i17:0,

18:1(n-7), 18:2(n-6) and 18:3. All these components were

present in the dietary FA composition at relatively high

abundances. However, significant decreases were observed

in some components present in F. candida in high

abundances on day 0, particularly 16:0 (P!0.001),

16:1(n-7) (P!0.001) and 18:1(n-9) (P!0.001), reflecting

the lower abundance of these components in the diet relative

to their abundance in F. candida on day 0. Increases in the

concentrations of C20 PUFAs were also observed in

F. candida; on day 0 PUFAs accounted for 10.7% of the

total FA composition but by day 39 they amounted to 27.4%

of the total FA complement. However, these differences

were not significant. There were no significant differences in

the ratio of saturated-to-unsaturated FAs in F. candida over

time and the saturated-to-unsaturated FA ratio of the diet

was not significantly different to the ratio of saturated-to-

unsaturated FAs in F. candida (t-test, P!0.17) on day 39.

The ratio of odd-to-even chain length FAs increased

significantly (P!0.005) from 0.02 on day 0 to 0.1 on day

39 but the ratio of odd-to-even FAs in the diet was still

significantly greater (t-test, P!0.005) than that of

F. candida on day 39.

Similar effects were observed in P. minuta fed

P. redivivus. The FAs i15:0, i17:0, 18:1(n-7) and

18:2(n-6) all rose in abundance significantly (P!0.005)

during the experiment. Conversely, the abundances of 16:0,

16:1(n-7) and 18:1(n-9) fell significantly (P!0.005) during

the experiment. The proportion of C20 PUFAs in the FA

pool increased from 10.1% on day 0 to 28.5% on day 39.

There were no significant changes in the ratio of saturated-

to-unsaturated FAs in P. minuta fed nematodes. However,

the ratio of odd-to-even chain length FAs increased

significantly (P!0.005) from 0.01 to 0.12 during the

experiment; the ratio on day 39 was significantly lower (t-

test, P!0.05) than that of the diet. All changes in

Collembola FA compositions reflected the abundance of

the corresponding dietary components.

3.2.3. Collembola switched to Z. mays

The total number of FAs detected in F. candida fed

maize did not change during the experiment although the

relative abundances of some FAs did change significantly.

The abundance of 18:2(n-6) changed significantly (P!0.001) from 1.7% on day 0 to 18.2% on day 16 before

falling to 8.3% on day 39, reflecting the high abundance of

18:2(n-6) in maize. Conversely, the significant reductions in

the proportions of 16:1(n-7) (P!0.005) reflected the low

abundance of this component in the diet. The proportions of

16:0 in F. candida were generally lower than those of 16:0

in the diet, while the abundances of 18:0 and 18:1(n-9) were

higher than those of the corresponding dietary components.

The abundances of the PUFAs 20:4(n-6) and 20:5(n-3) were

relatively constant throughout the experiment despite their

absence from the diet. There were no significant changes in

the ratio of saturated-to-unsaturated and odd-to-even FAs in

F. candida. Both the ratios of saturated-to-unsaturated and

odd-to-even FAs of the collembola were similar to those of

the maize diet.


Post-hoc comparisons of the FA compositions of

P. minuta fed maize demonstrated that samples taken on

day 39 were significantly different (P!0.005) to those on

all other days. On day 39, almost half the FA composition

was attributable to one component (18:0) and no PUFAs

were detected. This led to the extremely high ratio of

saturated-to-unsaturated FAs observed which was signifi-

cantly different (P!0.005) to those observed on all other

sampling days. Excluding day 39, the abundance of 16:0 in

P. minuta was maintained at proportions similar to that of

the diet while 18:0 and 18:1(n-9) were maintained at higher

abundances in the Collembola relative to those of the diet.

During the experiment, the abundance of 16:1(n-7) fell

significantly (P!0.005) from 11.1 to 1.2%. However, the

abundance of 18:2(n-6) in P. minuta did not increase over

time despite the high abundance of this component in the

diet. There were no significant changes in the ratio of odd-

to-even chain length FAs of P. minuta, and the ratio on day

39 was not significantly different to that of the diet (t-test,

P!0.05).

3.2.4. Collembola switched to A. glutinosa

The range of FAs observed in F. candida fed alder

changed little during the diet-switch experiment, although

the abundances of the some FAs did change significantly

over time. Significant decreases in the abundance of

16:1(n-7) (P!0.005) were observed. The 18:0 and

18:1(n-9) components of F. candida were maintained at

higher proportions than the same components in the diet,

while 16:0 was consistently lower in abundance in F.

candida than the corresponding dietary FA. The PUFAs

20:4(n-6) and 20:5(n-3) were observed in F. candida at the

beginning and end of the experiment, despite their absence

from the diet, while the long chain FAs 22:0 and 24:0 were

not detected in F. candida despite their presence in the diet

in relatively high abundances. The ratio of saturated-to-

unsaturated FAs of F. candida did not change significantly

with time and was consistently lower than that of the diet.

There were also no significant differences over time in the

ratio of odd-to-even chain length FAs in F. candida

consuming alder.

The FAs of P. minuta fed alder were qualitatively

different on day 39 to those on all other days. In particular,

many of the components present at low abundances on days

0–16 were entirely absent on day 39 and the 20:1 component

exhibited a high abundance of 18.3% which was

Table 5

Total abundances of C20 PUFAs in F. candida and P. minuta fed the four diets f

C. cladosporioides P. redivivus

F. candida 4.48cq 18.83a

p

P. minuta 1.77eq 21.31d

p

Data are means of percent total FAs. Superscripts refer to comparisons within C

letters represent significant differences (ANOVA; P!0.05).

significantly higher than on all other days (P!0.005).

During the experiment the 16:1(n-7) component fell in

abundance significantly (P!0.001), from 8.4% on day 0 to

only trace levels on day 39, while 16:0 fell in abundance

significantly in the latter part of experiment (P!0.005).

Consistently higher proportions of the 18:0 and 18:1(n-9)

components were found in P. minuta relative to the alder

diet. The PUFA 20:4(n-6) was only detected on day 39

while 20:5(n-3) was not detected at all in P. minuta fed

alder. There were no significant differences over time in the

ratio of saturated-to-unsaturated FAs of P. minuta,

although all ratios were lower than that of the saturated-

to-unsaturated FA ratios of the diet. There were significant

differences over time in the ratio of the odd-to-even

chain length FAs of P. minuta (P!0.05); post-hoc

comparisons showed that the ratio on day 0 was signifi-

cantly higher (P!0.05) than for all other days.

3.2.5. Occurrence of C20 PUFAs in Collembola

The four diets significantly affected the abundance of C20

PUFAs in both Collembolan species (Table 5; P!0.05);

post-hoc comparisons demonstrate that the P. redivivus diet

resulted in a significantly higher C20 PUFA content than all

other diets. In F. candida, feeding on C. cladosporioides and

alder resulted in the lowest PUFA contents, while the maize

diet resulted in intermediate abundances of the PUFAs. In

P. minuta, abundances of PUFAs when fed C. cladospor-

ioides, maize and alder were low and not significantly

different among the diets. However, P. minuta fed

P. redivivus displayed a 10-fold increase in the abundance

of C20 PUFAs relative to P. minuta fed the other diets.

Regardless of the diet, P. minuta exhibited significantly

higher ratios of saturated-to-unsaturated (P!0.005) and

odd-to-even (P!0.005) FAs relative to F. candida.

3.2.6. Rate of change of FA compositions

The relative abundance of many Collembolan FAs

changed during the diet-switch experiment. Many of these

changes were exhibited as a gradual increase or decrease

over time or fluctuations about a mean value. However for

some FAs the rate of change of abundance could be

quantified by fitting negative exponential equations to the

data. For example, in all diet-switches the abundances of

16:1(n-7) decreased over time (Fig. 2) and could be fitted to

such equations. Half-lives of the 16:1(n-7) abundance

changes varied between 1.4 and 13.1 days, and ANOVA

or 39 days

Z. mays A. glutinosa

9.49br 5.81c

t

2.22es 1.33e

u

ollembolan species, subscripts refer to comparisons within diets. Different

Fig. 2. Changes in the relative concentrations of 16:1 (n-7) in all diet-switch experiments. Data are percentages of total fatty acids GSD (nZ3).


of the rate coefficient in the equations demonstrated that the

rates of change of this FA in F. candida were significantly

affected by the diets (P!0.005). However, the rates of

change of 16:1 (n-7) in P. minuta were not significantly

different between diets (P!0.3). In the nematode diet-

switches, the changes in abundance of most major FAs, with

the exception of 18:0, could be fitted to negative exponential

equations (Figs. 3 and 4). The half-lives of FA abundance

changes varied between 1.2 and 22.4 days in F. candida, and

0.5 and 7.7 days in P. minuta, and the rate of change of

Collembolan FA abundance was not related to the FA

composition of the diet (R2Z0.27, P!0.3). The rates of

change of abundance of i15:0, 16:0, i17:0 and 20:4 (n-6)

were all significantly different (Tukey, PO0.05) between

the two species, but the species exhibiting the greater rate of

change varied between FAs.

3.2.7. PCA of Collembolan fatty acid compositions

The FAs of the Collembola sampled on day 39 (the final

day) of the experiment were subjected to principle

components analysis (Figs. 5 and 6). The FAs derived

from both species of Collembola fed the differing diets

clustered separately using the PCA scores, indicating that

the effects of each diet on FA compositions was different

and consistent across all replicates. The first three axes

(Fig. 5) accounted for 36.0, 20.1 and 15.0%, respectively, of

the variation in the FA compositions and therefore together

accounted for 71.1% of the total variance. PC1 was mainly

described by the FAs which exhibited high abundances in

Collembola fed P. redivivus (Fig. 6) with negative

contributions from the n-alkanoic FA components. PC2

was mainly described by components that exhibited less

than 5% of the FA composition on day 39, i.e. 18:1(n-5),

20:0 and 20:1, with negative contributions from 16:1(n-7).

4. Discussion

4.1. Dietary FA compositions

The four diets represent a broad range of FA compo-

sitions. In total, 33 different FAs were detected in the diets,

although only 9 FAs were common to all; the abundances of

16:0, 18:1(n-9), 18:1(n-7), 18:2(n-6) and the C20 PUFAs

were particularly variable between diets. In our study, a total

of 30 FAs were detected in P. redivivus while other soil

nematodes have been reported to contain 13–22 individual

FAs (Sivapalan and Jenkins, 1966; Holz et al., 1999; Ruess

et al., 2002). For earlier work especially, this increase in

diversity of FAs is most likely due to the improved detection

limits and resolution facilitated by modern gas chromato-

graphic techniques. Sivapalan and Jenkins (1966) reported

that the FA compositions of P. redivivus was dominated by

18:1 and 18:2 in abundances (16.3 and 20.7%, respectively)

similar to those reported here. C20 PUFAs, especially

20:4(n-6) and 20:5(n-3), are often major components of

nematode FAs (Tanaka et al., 1996; Chen et al., 2001).

However, in contrast to other studies on P. redivivus

(Sivapalan and Jenkins, 1966), no FAs were observed

eluting after 20:5(n-3) in our work. The C20 PUFAs were

not present in the fungal, maize and alder diets. The

observed FA compositions of maize is similar to that

reported by Woodbury et al. (1998), but as far as can be

ascertained, there have been no reports of the FA

Fig. 3. Changes in the relative concentrations of the major fatty acids of F. candida fed a diet of P. redivivus. Data are percentages of total fatty acids GSD

(nZ3).


compositions of A. glutinosa or C. cladosporioides. The

lipid content of laboratory-grown fungi is dependent upon

the culture conditions (Griffiths et al., 2003) and since C.

cladosporioides was cultured on a matrix consisting of only

one C source, sucrose, all FAs present in the

C. cladosporioides must be the result of fungal biosynthesis.

The wide range of FAs present in these diets demonstrates

that Collembola in the soil are likely to be exposed to a wide

variety of FAs as they forage.

4.2. Collembolan FA compositions

The FA compositions of Collembola are a little-studied

area. Stransky et al. (1986) identified 29 FAs in the field-

derived specimens of Tetrodontophora bielanensis while

Holmstrup et al. (2002) and Ruess et al. (2004) reported 14

and 11–21 FAs in various Collembolan species, respectively.

In our work, 13–28 FAs were detected in F. candida

and P. minuta with the range of components depending upon

diet; this was similar to the previous reports. Holmstrup et al.

(2002) investigated the phospholipid and neutral lipid FAs of

F. candida under varying moisture regimes and found a shift

towards greater unsaturation in the PLFAs of drought-

acclimatised individuals but little change in the NLFAs.

Since the neutral fraction comprised 89% of the total FAs, the

change in the total FAs content upon droughting was small.

Similarly, Haubert et al. (2004) starved the Collembolan

Protaphorura fimata and established that whilst the NLFA

content of the Collembola fell the NLFAs were equally

metabolised so the overall FA composition remained

relatively unchanged. The NLFAs represent the major FA

pool in Collembola; even in P. fimata starved for 28 days the

NLFAs accounted for ca. 90% of the total FAs. We have

previously reported the total FA compositions of F. candida

and P. minuta fed continuously on a diet of bakers yeast

(Chamberlain et al., 2004) and demonstrated that

Fig. 4. Changes in the relative concentrations of the major fatty acids of P. minuta fed a diet of P. redivivus. Data are percentages of total fatty acids GSD

(nZ3).


the composition did not change significantly with time.

However, changing the diet in the current work caused

significant changes in the FA compositions of both

Collembolan species as observed for F. candida, P. fimata

and Heteromurus nitidus fed a range fungal and nematode

diets (Ruess et al., 2004). Some components present in low

abundance in Collembola, such as i15:0 and i17:0, are

characteristic of bacterial FAs and are likely derived from gut

bacteria (Jantzen and Bryn, 1985). However, all other

components are derived from Collembolan lipids since the

guts were empty of food when FAs were extracted.

Fatty acids in invertebrates can either be directly

assimilated from the diet or biosynthesised by the consumer

(Canavoso et al., 2001) although it is energetically

favourable to directly incorporate dietary lipid and catabo-

lise dietary carbohydrate (Pond, 1981). Therefore, if

changes in individual FA abundances can be directly linked

to the abundance of FAs in the diet, there is a strong case for

the direct assimilation of these dietary components. For

example, in our work the abundances of 16:1(n-7) in each of

the four offered diets were under 2% and since there was a

gradual reduction of 16:1(n-7) in Collembola in all diet

switches, it is probable that the Collembola did not

biosynthesise significant proportions of this component.

The high abundance of this FA in the diet on day 0 is likely

due to the high abundance in the initial bakers yeast diet

(32–37%; Chamberlain et al., 2004) again consistent with

direct assimilation from the diet. Similar trends were

observed in 18:1(n-7) in F. candida fed C. cladosporioides

and Z. mays, where the abundance of this component fell in

response to low abundances in the diet. The opposite trend

was observed in F. candida fed nematodes where the

proportion of 18:1(n-7) more than doubled during the

experiment. This was consistent with a high input of this

Fig. 5. Principle components analysis showing variation in the fatty acid compositions of F. candida and P. minuta fed the four offered diets after 39 days of

consumption.


component from the diet. The components 16:1(n-7) and

18:1(n-7), along with other components of the nematode

diet which were incorporated into the Collembola, such as

i15:0 and i17:0, therefore appear to be FAs the Collembola

are capable of assimilating if available but do not

biosynthesise in high abundance if absent from the diet.

However, i15:0 and i17:0 are also present in gut bacteria,

Fig. 6. Individual fatty acid loading plot of the first two eigenva

and the identification of low abundances of these com-

ponents in Collembolan extracts is more likely due to these

bacteria than to nematode consumption. However, high

abundances of these FAs should be indicative of nematode

predation. Ruess et al. (2004) also identified 20:1(n-7) and

20:1(n-9) as biomarkers of nematode consumption since

these FAs were only found in Collembola fed these diets.

lues (PC1 and PC2) of the principle components analysis.


However, 20:1 is also present in F. candida and P. minuta

feeding on alder, probably through desaturation of the large

abundances of dietary 20:0. Caution is therefore advisable

in using these FAs, present in only low relative concen-

trations in Collembola, as biomarkers of specific diets until

further studies have clarified the factors causing their

presence in Collembolan FAs.

The FA 18:2(n-6) is a biochemical precursor of 18:3(n-6)

and 20:4(n-6) and is an essential FA for many, but not all,

invertebrates (Blomquist et al., 1991; Weinert et al., 1993).

The presence of 18:2(n-6) on day 0, albeit at low

abundances, is evidence for the biosynthesis of this FA in

Collembola, since it was not present in the initial yeast diet

(Chamberlain et al., 2004). High abundances of 18:2(n-6) in

the C. cladosporioides, P. redivivus and maize diets caused

significant increases in the abundance of this FA in

F. candida consistent with the direct incorporation of this

component. However, the relatively high abundance of

18:2(n-6) in alder did not cause an increase in the proportion

of this component in F. candida, demonstrating that even if

a particular FA is present in the diet it may not be directly

incorporated to abundances similar to those of the diet. This

was also the case in P. minuta, where high dietary

abundance of 18:2(n-6) in P. redivivus resulted in increased

abundances in the Collembola; high dietary proportions in

the other three diets did not consistently produce high

concentrations in the consumers.

Direct incorporation of FAs is also likely to contribute to

those Collembolan FAs that did not change in abundance

during the diet-switch experiments. In such components, the

concentration of a particular FA would be the result of a

combination of direct incorporation from the diet and

biosynthesis either from acetate or via modification of other

FAs (Canavoso et al., 2001). In our experiments, dietary

abundances of 18:0 and 18:1(n-9) were generally lower than

those of the Collembola, consistent with biosynthesis and

resulting in increased abundances of these FAs within the

Collembola. Both F. candida and P. minuta fed maize

biosynthesised high proportions of 18:0 likely from dietary

18:1(n-9) and 18:2(n-6). However, P. minuta maintained

higher proportions of 18:0 in tissue FAs than F. candida. It

is possible that P. minuta prefers to store FAs as C18

unsaturated and monounsaturated components rather than

C18 PUFAs since 18:2(n-6) has a specialised function as a

C20 PUFA precursor although the precise reasons for these

observations remains unclear. The Collembolan 16:0

component generally exhibited abundances equal to or

lower than those of the diet such that the diet could have

supplied all the 16:0 observed in the Collembola with no

biosynthetic contribution from the consumers. In the

nematode diet switch, the abundances of 16:0 in Collembola

decreased over time in response to low dietary abundances

indicating that the Collembola, when fed nematodes, did not

biosynthesise high amounts of 16:0. This strongly contrasts

with 18:0 and 18:1(n-9) in Collembola fed nematodes which

were maintained at abundances greater than those of the diet

throughout the experiment.

4.3. C20 PUFAs in Collembola

Collembola have been shown to be more closely related

to crustacea than to insects (Nardi et al., 2003). The

occurrence of high abundances of C20 PUFAs in Collem-

bola, already reported by Holmstrup et al. (2002) and

Chamberlain et al. (2004) and expanded here for a range of

different diets, is further evidence for the differentiation of

Collembola and insects since terrestrial insects generally do

not biosynthesise such high abundances of PUFAs (Stan-

ley-Samuelson et al., 1988). Crustacea, however, often

contain very high abundances of PUFAs (Graeve et al.,

2001). Our results indicate that Collembola biosynthesise

high abundances of 20:4(n-6) and 20:5(n-3) and that

Collembolan PUFA abundances may be affected by those

of the diet. However, Ruess et al. (2004) reported no

20:5(n-3) in F. candida, H. nitidus and P. fimata but low

abundances of 20:2(n-6) and 20:3(n-6) in some individuals.

Therefore, 20:5(n-3) may not always be present when C20

PUFAs are detected. Not surprisingly, of the four offered

diets the nematode diet produced the highest abundances of

C20 PUFAs in Collembola since 24% of the FA profile of

nematodes was comprised of these components. However,

the remaining three diets, which did not contain C20 PUFAs,

all produced higher abundances of these components in F.

candida than in P. minuta. The reason for the lower

abundances of PUFAs in P. minuta is not clear although it is

likely to be related to differing metabolism in the two

species.

4.4. FA compositions of Collembola fed nematodes

The changes in the Collembolan FA composition in

response to the nematode diet were particularly striking.

The compositions of both species and the ratios of odd-to-

even carbon number FAs, grew to mirror those of the diet

during the experiment. Additionally, individual compounds

present in the nematode diet were observed in Collembolan

FAs at abundances similar to the diet. This reveals the

surprising plasticity of the FA profile of Collembola with a

nematode diet although the reason for the very different

response of the Collembola to this diet is not clear. We did

not explore the partitioning of the FAs into different

biochemical fractions but these observations suggest that

the substantial change in FA composition is due to direct

input of dietary FAs into NLFAs, rather than PLFAs, since

the functioning of PLFAs is closely related to their

molecular structure and hence PLFA content is tightly

regulated by the organism (Hazel and Williams, 1990;

Holmstrup et al., 2002). Ruess et al. (2004) also fed

nematodes to Collembola but did not observe the same

modifications to Collembolan FA compositions. This was

mainly due to the contrasting FA compositions of the


nematodes used which mostly did not contain high

abundances of i15:0, i17:0 and 18:1(n-7). Consumption of

the nematode species that did contain the latter two FAs

resulted in elevated proportions of these compounds in

Collembola NLFAs, consistent with direct incorporation

from the diet. However, high abundances of 20:4(n-6) in

nematodes did not result in elevated abundances of this

component in the Collembola, unlike in our study. Further

work on other species that consume nematodes is therefore

necessary to establish whether these substantial shifts in the

FA composition are exhibited in other Collembola and

indeed in other invertebrates, consuming nematodes.

4.5. Rate of change of FA compositions

The significant changes in abundance observed in some

FAs (i.e. 16:1(n-7) in all switches and most major FAs in the

nematode switches (Figs. 2–4)) could be described using

negative exponential equations. This is not unexpected since

other researchers have demonstrated that the metabolism of

radiolabelled FFAs in insect haemolymph follows similar

negative exponential patterns (Downer and Chino, 1985;

Soulages and Wells, 1994; Atella et al., 2000). However,

whilst turnover of FFAs in haemolymph occurs in ca. 1 h,

turnover of FAs in diacylglycerol takes up to 10 h (Downer

and Chino, 1985). Since NLFAs are energy storage

molecules turnover times of these components would be

expected to be much longer still. Absolute turnover rates of

these FAs cannot be derived from the equations presented

since the FAs were not simply turning over; rather, they

were accumulating in, or being removed from, the

Collembolan lipid pool. However, the identification of

abundance changes that could be fitted to negative

exponential equations implies that these components were

being added to, or being removed from, the Collembolan

lipid pool strictly according to their presence in or absence

from the diet. This contrasts with, for example, 18:0 in

Collembola fed nematodes (Figs. 3 and 4); the abundances

of this component did not change significantly (Tukey, P!0.15) during the experiment, consistent with physiological

regulation of this FA by the Collembola.

Upon starvation, the absolute NLFA content of Collem-

bola is reduced rapidly over the first 14 days of starvation

(Haubert et al., 2004) and there is complete C turnover in

Collembolan FAs in ca. 30–40 days (Chamberlain et al.,

2004). The present results concur with those previously and

give some indication as to the period over which the FA

compositions of Collembola would be expected to change,

given a change in diet. In our study, half-lives varied

between 0.5 and 22.4 days demonstrating that, for

Collembola, the FA profile only represents the dietary

input and Collembolan biosynthesis of recent days and that

some components may appear and disappear, due to a

change in diet, at much greater rates than others. The factors

affecting the rates of change of FA abundances are as yet not

clear but are likely to include physiological differences

between the two species, and the lipid content of the diet.

4.6. Identification of FA trophic biomarkers

The changes in Collembolan FA compositions, as shown

by consideration of both individual FAs and PCA, indicate

that FA profiles do offer a means of elucidating trophic

preferences in Collembola although the FA content is

generally not simply related to that of the diet. In the PCA,

the main effect was the abundance of nematode-derived FAs

(i15:0, i17:0 and the PUFAs) which was not surprising given

the high input of dietary FAs directly into Collembolan

lipids when nematodes were consumed. Ruess et al. (2002)

concluded, also using PCA, that the FA compositions of

nematodes are affected by the FA content of their fungal

diets although no specific compounds were able to function

as biomarkers since all the various fungal diets did not

contain unique FAs. In our work, the offered diets contained

a much wider range of FAs and it would be possible, for

example, to use i15:0, i17:0 and 18:1(n-7) as biomarker

compounds for nematode predation since these compounds

only occurred at high abundance in the nematode diet and

when P. redivivus was consumed the abundance of these

particular FAs rose in the Collembola to abundances similar

to those of the diet. Components such as 20:4(n-6) and 20:5

(n-3), present at high abundance in the nematodes, could

not, however, be used as biomarkers for nematode predation

since it is clear from the present results that Collembola

biosynthesise these compounds in high abundance when not

present in the diet. The proportion of 18:2(n-6) could

potentially be used as a biomarker since it is evident that

Collembola biosynthesise only low abundance of this FA if

not present in the diet and that high abundances of this

component in Collembolan FAs are the result of incorpor-

ation from the diet. However, since not all high dietary

abundances of 18:2(n-6) result in high abundances in the

Collembola (e.g. in P. minuta, and F. candida when fed

alder) the impact of each diet on Collembolan FA profiles

must first be determined.

The high abundances of C20 PUFAs in Collembola also

has implications for the analysis of whole-soil FAs. Chen et

al. (2001) suggested that analyses of such components could

be useful as biomarkers for nematodes in soils as long as

insects and other soil dwelling invertebrates, which until

recently were thought to contain C20 PUFAs at low

abundances, could be removed from the samples prior to

extraction. The results presented here make this qualifica-

tion even more important since Collembola can contain

considerably higher abundances of C20 PUFAs than

previously realised. Even if only the PLFA fraction of soil

extracts is considered, Collembola could still represent a

significant contribution of FAs to this pool, since Holmstrup

et al. (2002) demonstrated that when fed bakers yeast, C20

PUFAs comprise 24% of the total PLFAs of F. candida.

Therefore careful removal of invertebrates such as


Collembola will be necessary before using PUFAs as

biomarkers for nematodes.

4.7. Conclusions

On the basis of the results presented here, we must re-

emphasise the conditions that must be fulfilled if

particular FAs are to be used as biomarkers in trophic

studies: (i) the FA compositions of the possible diets must

each contain unique compounds in relatively high

abundances, (ii) these compounds must be either absent

from, or only minor components of, those FAs biosynthe-

sised by the consumer, and (iii) these compounds must be

assimilated into the consumer FA composition as intact

molecules at significant abundance when the diet is

consumed. It is not sufficient to assume that if a particular

FA is present in a diet this compound will be assimilated

unchanged into the lipids of the consumer. These

considerations suggest that, prior to choice experiments,

FA components of a consumer fed on single diets must be

analysed in order to determine the FAs biosynthesised by

the organism and the effect of exogenous compounds on

FA compositions. Simply obtaining invertebrates from the

soil and analysing their FA composition, without a

thorough analysis of dietary FAs, is unlikely to yield

usable dietary information.

In summary, Collembola both directly assimilated from

the diet and biosynthesised FAs, although the pathways of

biosynthesis were not determined. Collembolan FA com-

positions were modified by all offered diets and the

nematode diet caused the largest changes. Biomarkers

for nematode consumption were identified, and the FA 18:2

(n-6) may also function in F. candida as a biomarker for

diets containing high abundances of this component

although not all diets rich in 18:2(n-6) produced elevated

proportions of this FA in this species. Our results indicate

that the influences of dietary FA compositions on Collem-

bolan FA compositions are complex and that a thorough

understanding of the impact of diet FAs on consumer FA

profiles is essential when using FAs as biomarkers in soil

food web studies.

Acknowledgements

This study was undertaken while PMC was in receipt

of a NERC CASE studentship. The use of the NERC

Mass Spectrometry facilities is gratefully acknowledged.

Margaret Hurley is thanked for statistical analysis and

advice.

References

Abu Hatab, M., Gaugler, R., 2001. Diet composition and lipids of in vitro-

produced Heterorhabditis bacteriophora. Biological Control 20, 1–7.

Abu Hatab, M., Gaugler, R., Ehlers, R.U., 1998. Influence of culture

method on Steinernema glaseri lipids. Journal of Parasitology 84, 215–

221.

Albro, P.W., Schroeder, J.L., Corbett, J.T., 1992. Lipids of the earthworm

Lumbricus terrestris. Lipids 27, 136–143.

Atella, G.C., Arruda, M., Masuda, H., Gondim, K.C., 2000. Fatty acid

incorporation by Rhodnius prolixus midgut. Archives of Insect

Biochemistry and Physiology 43, 99–107.

Auel, H., Harjes, M., da Rocha, R., Stubing, D., Hagen, W., 2002. Lipid

biomarkers indicate different ecological niches and trophic relation-

ships of the Arctic hyperiid amphipods Themisto abyssorum and T.

libellula. Polar Biology 25, 374–383.

Baath, E., 2003. The use of neutral lipid fatty acids to indicate the

physiological conditions of soil fungi. Microbial Ecology 45, 373–383.

Blakely, J.K., Neher, D.A., Spongberg, A.L., 2002. Soil invertebrate and

microbial communities, and decomposition as indicators of polycyclic

aromatic hydrocarbon contamination. Applied Soil Ecology 21, 71–88.

Blomquist, G.J., Borgeson, C.E., Vundla, M., 1991. Polyunsaturated fatty

acids and eicosanoids in insects. Insect Biochemistry 21, 99–106.

Canavoso, L.E., Jouni, Z.E., Karnas, K.J., Pennington, J.E., Wells, M.A.,

2001. Fat metabolism in insects. Annual Review of Nutrition 21, 23–46.

Chamberlain, P.M., Bull, I.D., Black, H.I.J., Ineson, P., Evershed, R.P.,

2004. Lipid content and carbon assimilation in Collembola: impli-

cations for the use of compound-specific carbon isotope analysis in

animal dietary studies. Oecologia 139, 325–335.

Chen, J., Ferris, H., Scow, K.M., Graham, K.J., 2001. Fatty acid

composition and dynamics of selected fungal-feeding nematodes and

fungi. Comparative Biochemistry and Physiology B—Biochemistry

and Molecular Biology 130, 135–144.

Chitwood, D.J., Krusberg, L.R., 1981. Diacyl, alkylacyl and alkenylacyl

phospholipids of the nematode Turbatrix aceti. Comparative Biochem-

istry and Physiology B—Biochemistry and Molecular Biology 69, 115–

120.

Downer, R.G.H., Chino, H., 1985. Turnover of protein and diacylglycerol

components of lipophorin in insect hemolymph. Insect Biochemistry

15, 627–630.

Geer, B.W., Perille, T.J., 1977. Effects of dietary sucrose and environmen-

tal temperature on fatty acid synthesis in Drosophila melanogaster.

Insect Biochemistry 7, 371–379.

Graeve, M., Dauby, P., Scailteur, Y., 2001. Combined lipid, fatty acid and

digestive tract content analyses: a penetrating approach to estimate

feeding modes of Antarctic amphipods. Polar Biology 24, 853–862.

Griffiths, R.G., Dancer, J., O’Neill, E., Harwood, J.L., 2003. Effect of

culture conditions on the lipid composition of Phytophthora infestans.

New Phytologist 158, 337–344.

Hanson, B.J., Cummins, K.W., Cargill, A.S., Lowry, R.R., 1985. Lipid

content, fatty acid composition, and the effect of diet on fats of aquatic

insects. Comparative Biochemistry and Physiology B—Biochemistry

and Molecular Biology 80, 257–276.

Haubert, D., Haggblom, M.M., Scheu, S., Ruess, L., 2004. Effects of fungal

food quality and starvation on the fatty acid composition of

Protaphorura fimata. Comparative Biochemistry and Physiology

138B, 41–52.

Hazel, J.R., Williams, E.E., 1990. The role of alterations in membrane lipid

composition in enabling physiological adaptation of organisms to their

physical environment. Progress in Lipid Research 29, 167–227.

Holmstrup, M., Hedlund, K., Boriss, H., 2002. Drought acclimation and

lipid composition in Folsomia candida: implications for cold shock,

heat shock and acute desiccation stress. Journal of Insect Physiology 48,

961–970.

Holz, R.A., Troth, K., Atkinson, H.J., 1999. The influence of potato cultivar

on lipid content and fecundity of Bolivian and British populations of

Globodera rostochiensis. Journal of Nematology 31, 357–366.

Jacob, J., Hanssen, H.P., Ziemsen, B., Brockmeyer, V., Willig, S., 1991.

Chemical composition of lipids in populations and species of


Enchytraeus (Annelida, Oligochaeta) and Tisbe (Arthropoda, Crusta-

cea). Zeitschrift Fur Zoologische Systematik Und Evolutionsforschung

29, 373–380.

Jantzen, E., Bryn, K., 1985. Whole-cell and lipopolysaccharide fatty acids

and sugars of gram-negative bacteria, in: Goodfellow, M.,

Minnikin, D.E. (Eds.), Chemical Methods of Bacterial Systematics.

Academic Press, London, pp. 145–171.

Joanisse, D.R., Storey, K.B., 1996. Fatty acid content and enzymes of fatty

acid metabolism in overwintering cold-hardy gall insects. Physiological

Zoology 69, 1079–1095.

Kato, M., 1995. The Aspidistra and the Amphipod. Nature 377, 293.

Lee, Q., Widden, P., 1996. Folsomia candida, a ‘fungivorous’ collembolan,

feeds preferentially on nematodes rather than soil fungi. Soil Biology

and Biochemistry 28, 689–690.

Madan, R., Pankhurst, C., Hawke, B., Smith, S., 2002. Use of fatty acids for

identification of AM fungi and estimation of the biomass of AM spores

in soil. Soil Biology and Biochemistry 34, 125–128.

Nardi, F., Spinsanti, G., Boore, J.L., Carapelli, A., Dallai, R., Frati, F.,

2003. Hexapod origins: monophyletic or paraphyletic?. Science 299,

1887–1889.

Nelson, M.M., Mooney, B.D., Nichols, P.D., Phleger, C.F., 2001. Lipids of

Antarctic Ocean amphipods: food chain interactions and the occurrence

of novel biomarkers. Marine Chemistry 73, 53–64.

Ogg, C.L., Stanley-Samuelson, D.W., 1992. Phospholipid and triacylgly-

cerol fatty acid compositions of the major life stages and selected tissues

of the tobacco hornworm Manduca sexta. Comparative Biochemistry

and Physiology B—Biochemistry and Molecular Biology 101, 345–351.

Petersen, S.O., Holmstrup, M., 2000. Temperature effects on lipid

composition of the earthworms Lumbricus rubellus and Eisenia

nordenskioeldi. Soil Biology and Biochemistry 32, 1787–1791.

Pond, C.M., 1981. Storage, in: Townshend, C.R., Calow, P. (Eds.),

Physiological Ecology: an Evolutionary Approach to Resource Use.

Blackwell, London, pp. 190–219.

Ponge, J.F., 2000. Vertical distribution of Collembola (Hexapoda) and their

food resources in organic horizons of beech forests. Biology and

Fertility of Soils 32, 508–522.

Renault, D., Hervant, F., Vernon, P., 2002. Comparative study of the

metabolic responses during food shortage and subsequent recovery at

different temperatures in the adult lesser mealworm, Alphitobius

diaperinus (Coleoptera: Tenebrionidae). Physiological Entomology

27, 291–301.

Ruess, L., Haggblom, M.M., Zapata, E.J.G., Dighton, J., 2002. Fatty acids

of fungi and nematodes—possible biomarkers in the soil food chain?.

Soil Biology and Biochemistry 34, 745–756.

Ruess, L., Haggblom, M.M., Langel, R., Scheu, S., 2004. Nitrogen isotope

ratios and fatty acid composition as indicators of animal diets in

belowground systems. Oecologia 139, 336–346.

Sadaka-Laulan, N., Ponge, J.F., Roquebert, M.F., Bury, E.,

Boumezzough, A., 1998. Feeding preferences of the collembolan

Onychiurus sinensis for fungi colonizing holm oak litter

(Quercus rotundifolia Lam.). European Journal of Soil Biology 34,

179–188.

Sivapalan, P., Jenkins, W.R., 1966. Phospholipid and long-chain fatty acid

composition of the nematode Panagrellus redivivus. Proceedings of the

Helminthological Society of Washington 33, 149–157.

Snider, R.J., 1972. Laboratory observations on the biology of Folsomia

candida (Willem) (Collembola: Isotomidae). Revue D’ecologie et de

Biologie du Sol 10, 103–124.

Soulages, J.L., Wells, M.A., 1994. Metabolic fate and turnover rate of

hemolymph free fatty acids in adult Manduca sexta. Insect Biochem-

istry and Molecular Biology 24, 79–86.

Stanley-Samuelson, D.W., Jurenka, R.A., Cripps, C., Blomquist, G.J.,

Derenobales, M., 1988. Fatty acids in insects—composition, metab-

olism, and biological significance. Archives of Insect Biochemistry and

Physiology 9, 1–33.

Stransky, K., Trka, A., Budesinsky, M., Streibl, M., 1986. Lipidic

compounds from the extract of the Springtail Tetrodontophora

bielanensis (Waga). Collection of Czechoslovak Chemical Communi-

cations 51, 948–955.

Sushchik, N.N., Gladyshev, M.I., Moskvichova, A.V., Makhutoba, O.N.,

Kalachova, G.S., 2003. Comparison of fatty acid composition in major

lipid classes of the dominant benthic invertebrates of the Yenisei river.

Comparative Biochemistry and Physiology B—Biochemistry and

Molecular Biology 134B, 111–122.

Takeda, H., Ichimura, T., 1983. Feeding attributes of 4 species of

collembola in a pine forest soil. Pedobiologia 25, 373–381.

Tanaka, T., Ikita, K., Ashida, T., Motoyama, Y., Yamaguchi, Y.,

Satouchi, K., 1996. Effects of growth temperature on the fatty acid

composition of the free-living nematode Caenorhabditis elegans.

Lipids 31, 1173–1178.

Vegter, J.J., 1983. Food and habitat specialization in coexisting Springtails

(Collembola, Entomobryidae). Pedobiologia 25, 253–262.

Weinert, J., Blomquist, G.J., Borgeson, C.E., 1993. De novo biosynthesis of

linoleic acid in 2 non-insect invertebrates—the land slug and the garden

snail. Experientia 49, 919–921.

Woodbury, S.E., Evershed, R.P., Rossell, J.B., 1998. Purity assessments

of major vegetable oils based on d13C values of individual fatty acids.

Journal of the American Oil Chemists Society 75, 371–379.

Zelles, L., 1999. Fatty acid patterns of phospholipids and lipopolysacchar-

ides in the characterisation of microbial communities in soil: a review.

Biology and Fertility of Soils 29, 111–129.

Zhu, N., Dai, X.N., Lin, D.S., Connor, W.E., 1994. The lipids of slugs and

snails—evolution, diet and biosynthesis. Lipids 29, 869–875.

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