Dissertations in Forestry and Natural Sciences › pub › urn_isbn_978-952-61... · 2020-06-30 ·...
Transcript of Dissertations in Forestry and Natural Sciences › pub › urn_isbn_978-952-61... · 2020-06-30 ·...
uef.fi
PUBLICATIONS OF THE UNIVERSITY OF EASTERN FINLAND
Dissertations in Forestry and Natural Sciences
ISBN 978-952-61-3320-1ISSN 1798-5668
Dissertations in Forestry and Natural Sciences
DIS
SE
RT
AT
ION
S | K
AR
LM
AX
RU
TA
RO
| FA
TT
Y A
CID
PR
OF
ILE
S O
F T
HE
ED
IBL
E K
AT
YD
ID, R
US
PO
LIA
... | No
371
KARLMAX RUTARO
FATTY ACID PROFILES OF THE EDIBLE KATYDID, RUSPOLIA DIFFERENS (SERVILLE) (ORTHOPTERA:
TETTIGONIIDAE) AFTER FEEDING ON DIVERSIFIED DIETS
PUBLICATIONS OF THE UNIVERSITY OF EASTERN FINLAND
Rearing of edible insects is seen as one
solution to ensure a sufficient food production for the increasing human population.
A successful mass-rearing programme for edible insects such as the edible katydid, Ruspolia differens, in rural Africa would require affordable but reliable feeds. This
thesis provides novel insights on how feeds influence the fatty acid profiles of R. differens, with emphasis on the essential fatty acids that
are needed for a healthy human diet.
KARLMAX RUTARO
FATTY ACID PROFILES OF THE EDIBLE KATYDID, RUSPOLIA DIFFERENS (SERVILLE)
(ORTHOPTERA: TETTIGONIIDAE) AFTER FEEDING ON DIVERSIFIED DIETS
Karlmax Rutaro
FATTY ACID PROFILES OF THE EDIBLE KATYDID, RUSPOLIA DIFFERENS (SERVILLE)
(ORTHOPTERA: TETTIGONIIDAE) AFTER FEEDING ON DIVERSIFIED DIETS
Publications of the University of Eastern Finland
Dissertations in Forestry and Natural Sciences
No 371
University of Eastern Finland
Joensuu
2020
Academic dissertation
To be presented by permission of the Faculty of Science and Forestry, University of
Eastern Finland
for public examination in the Conference room in the School of Forestry at
Makerere University, Kampala, on March, 26, 2020, at 12 noon
Grano Oy
Jyväskylä, 2020
Editor: Professor Raine Kortet
Distribution: University of Eastern Finland / Sales of publications
www.uef.fi/kirjasto
ISBN: 978-952-61-3320-1 (Print)
ISBN: 978-952-61-3321-8 (PDF)
ISSNL: 1798-5668
ISSN: 1798-5676
ISSN: 1798-5676 (PDF)
Author’s address: Karlmax Rutaro
University of Eastern Finland
Depart. of Environmental and Biological Sciences
P.O. Box 111
80101 JOENSUU, FINLAND
email: [email protected]
Supervisors: Professor Heikki Roininen, Ph.D.
University of Eastern Finland
Depart. of Environmental and Biological Sciences
P.O. Box 111
80101 JOENSUU, FINLAND
email: [email protected]
Anu Valtonen, Ph.D.
University of Eastern Finland
Depart. of Environmental and Biological Sciences
P.O. Box 111
80101 JOENSUU, FINLAND
email: [email protected]
Professor Philip Nyeko, Ph.D.
Makerere University
Depart. of Forestry, Biodiversity and Tourism
P.O. Box 7062 KAMPALA, UGANDA
email: [email protected]
Geoffrey Maxwell Malinga, Ph.D.
Gulu University
Depart. of Biology
P.O. Box 166 GULU, UGANDA
email: [email protected]
Reviewers: Dennis Oonincx, Ph.D
Wageningen University and Research Centre
Animal Nutrition Group
PO 338, 6700AH, Wageningen, the Netherlands
email: [email protected]
Robert Fungo, Ph.D
Makerere University
Depart. of Food Technology and Human Nutrition
P.O. Box 7062
KAMPALA, UGANDA
email: [email protected]
Opponent: John N. Kinyuru, PhD
Jomo Kenyatta University of Agriculture and Technology
Depart. of Food Science and Technology
P.O. Box 62000-00200, Nairobi, Kenya
email: [email protected]
7
Rutaro, Karlmax
Fatty acid profiles of the edible katydid, Ruspolia differens (Serville) (Orthoptera:
Tettigoniidae) after feeding on diversified diets.
Joensuu: University of Eastern Finland, 2020
Publications of the University of Eastern Finland
Dissertations in Forestry and Natural Sciences 2020; 371
ISBN: 978-952-61-3320-1 (print)
ISSNL: 1798-5668
ISSN: 1798-5676
ISBN: 978-952-61-3321-8 (PDF)
ISSN: 1798-5676 (PDF)
ABSTRACT
Consumption of edible insects is seen as a major solution to address the looming
food shortage (due to the increasing human population) and for improving human
nutrition. For example, in Africa and Asia, edible insects have been a traditional
part of the human diet, although with limited documentation. However, the majori-
ty of edible insects in Africa are seasonally harvested from the wild, which unfor-
tunately is unpredictable. Currently, there is growing interest in mass rearing edi-
ble insects to meet the increased food demand and supplement mostly carbohy-
drate-rich diets. A successful mass-rearing programme for edible insects such as the
edible katydid, Ruspolia differens, in rural Africa would require affordable but relia-
ble feed. However, before mass-rearing programmes can commence, there is a great
need to understand accepted feeds and their influence on R. differens nutritional
profiles.
The aim of this dissertation was to investigate how natural (i.e., grass inflo-
rescence) and artificial diets influence the fatty acid content and composition of R.
differens, with emphasis on the essential fatty acids that are needed for a healthy
human diet. Based on earlier studies, R. differens performance is enhanced with
mixed diets. The first objective (study I) was to examine the effect of a diversified
gradient of grass inflorescence diets on the lipid content and fatty acid composition
in R. differens. Here, R. differens sixth instar nymphs were reared on inflorescences
from one grass species or mixtures of inflorescences from two, three or six grass
species for two weeks. The results from this study indicated that the fatty acid
composition and the proportion of essential fatty acids significantly differed among
the diets. The proportion of essential fatty acids was highest in the highly diversi-
fied, six-feed diet but low in less diversified (one-to-three-feed) diets. Total R. dif-
ferens lipid content did not significantly differ among the diets. The nine common
8
fatty acids found across all treatments in this study were (in decreasing order):
palmitic, oleic, palmitoleic, linoleic, stearic, myristic, myristoleic, α-linolenic and
arachidic acid. These findings demonstrated that the R. differens fatty acid composi-
tion can be modified through diet.
The second objective (study II) was to examine the influence of diversified
mixtures of the most accepted natural feeds (grass inflorescences) on the fatty acid
content and composition of R. differens when they are reared from neonatal nymphs
to adults. The results indicated that the contents of saturated, monounsaturated and
polyunsaturated fatty acids, the omega-6/omega-3 ratio and adult body weight did
not differ among insects based on the dietary treatments. However, the composi-
tion of rare (> C20) fatty acids differed significantly among the insects fed on the
six-diet treatment. Furthermore, the omega-6/omega-3 fatty acids ratio was general-
ly low compared to when artificial diet (study III) was used, data that suggest R.
differens reared entirely on grass inflorescences may be suitable for a healthy human
diet.
The third objective (study III) was to assess the influence of diversified lo-
cally sourced, processed and non-processed (artificial) diets on R. differens fatty acid
content and composition. Here, neonatal nymphs were reared on mixtures of six
gradually diversified diets of two, three, four, six, eight or nine feeds. The findings
indicated that the contents of saturated, monounsaturated and polyunsaturated
fatty acids differed significantly among the diets; more diverse diets increased the
polyunsaturated fatty acid content. Furthermore, the omega-6/omega-3 ratio dif-
fered significantly among the diets and between the sexes. R. differens fed on the
four-feed diet had a higher omega-6/omega-3 ratio than those fed on other diets.
Again, the fatty acid composition differed significantly among the diets, and diet
diversification corresponded with the polyunsaturated fatty acid proportions, espe-
cially linoleic acid. The findings of study (III) demonstrated that higher essential
fatty acid levels can be achieved when R. differens is reared on highly diversified
artificial diets.
Overall, the study concluded that the R. differens fatty acid content and
composition was significantly influenced by both grass inflorescences and artificial
diets. The study further revealed that high-quality essential fatty acids needed for
human health can be achieved through dietary manipulations of both grass inflo-
rescence and artificial diets; high essential fatty acid levels are achieved through
highly diversified diets. Highly diversified diets may help balance the ingested
nutrients. Further studies are needed to determine the extent of diet diversification
vis-à-vis the quality of fatty acids, especially essential fatty acids.
9
Universal Decimal Classification: 591.53.063, 591.613, 595.720, 638.4
CAB Thesaurus: insects as food; Orthoptera; Tettigoniidae; Ruspolia differens; nutritive
value; lipids; fatty acids; essential fatty acids; saturated fatty acids; unsaturated fatty acids;
monoenoic fatty acids; polyenoic fatty acids; animal feeding; feeds; diets; diversification;
grasses; inflorescences; manufactured feeds; body weight
Yleinen suomalainen ontologia: hyönteiset; hyönteisruoka; suorasiipiset; hepokatit;
ravintoarvo; lipidit; rasvahapot; omegarasvahapot; ruokinta; rehut; monipuolisuus
10
“Your attitude, not your aptitude, will determine your altitude.” Zig Ziglar
11
ACKNOWLEDGEMENTS
My heartfelt thanks go to my supervisors Professors Heikki Roininen and Philip
Nyeko, Dr. Anu Valtonen and Dr. Geoffrey M. Malinga, first for selecting me
among many to undertake this study and for guiding me this far. Your invaluable
comments have greatly helped to shape this work. Thesis reviewers, Dr. Dennis
Oonincx and Dr. Robert Fungo are greatly thanked for their insights on the thesis.
To the various ‘anonymous’ reviewers and journal editors, thank you for your
comments some a bit harsh, but very insightful. I feel proud that my publications
already have been cited severally.
I thank the administration of the Department of Environmental and Biolog-
ical Sciences, University of Eastern Finland, Joensuu for providing a good working
environment during my stay at Joensuu and for coordinating the study activities
while in Uganda. In addition, I wish to thank the Uganda National Council of Sci-
ence and Technology (UNCST) for permission to conduct this study and the Mak-
erere University Agricultural Research Institute, Kabanyolo (MUARIK) for provid-
ing laboratory space.
Also, I extend my gratitude to Makerere University Council through the of-
fice of the Vice Chancellor for offering me a study leave and providing me other
related support whenever needed throughout the study period. To my colleagues
at the department of Biochemistry and Sports science, especially the HOD Dr. Peter
Vuzi, thank you for the support. Dr. Joseph Kyambadde, Dean SBS, together with
Professor JYT. Mugisha, the Principal, CONAS, your constant follow ups on my
progress gave this work focus, resulting in its record time completion. I really ap-
preciate your support.
I ‘am thankful to my colleagues, VJ. Lehtovaara and R. Opoke for helpful
comments during the writing of the manuscripts, on which this thesis is based.
Robert, our overnight field and laboratory ‘visits’ have not gone to the waste, and
coming this far amidst challenges well known to you confirms that ‘’faith is the only
antidote for failure’’. VJ. Lehtovaara, thank you for ice skiing lessons during the visit
to your summer cottage. The whole experience of skiing and walking on a frozen
lake is still alive and fresh in my mind, kiitos. Furthermore, my gratitude goes to
Mirja Roininen for her hospitality during my visit to her home, and Dr. Jaakko Ha-
verinen for introducing me to many places within Joensuu and for being a wonder-
ful housemate. For this, I say kiitos. Ms. Tuula Toivanen, thank you very much for
the care and for quickly fixing financial issues, whenever approached.
Lastly, I ’am grateful to my family especially my dear wife for her kind
love, patience, and for taking good care of the children during several long and
short absences both within and out of the country in pursuit of this study. To my
12
children, Jo, Gabi, Esther and Jysen you have been the source of strength, some-
times through your jokes and the unending ‘homework issues at times disrupting
my own’, but your ‘necessary disruption’ always relaxed my mind amidst the
tough journey this was. I could not give up, because in me, I knew that completing
this thesis ’’wasn’t about me, but us’’, and I want you to draw your current and
future strength from this triumph.
Funding for this study was provided by the Academy of Finland (grant no
14956) and Bugbox Limited supported fatty-acid analysis in Estonia. Emeritus Pro-
fessor Heikki Roininen, and Mr. Erlend Sild, thank you so much for the logistical
support.
Kampala, January 2020
Karlmax Rutaro
13
LIST OF ABBREVIATIONS
ANOVA Analysis of variance
BAME Bacterial acid methyl ester
CVD Cardiovascular diseases
DHA Docosahexaenoic acid
FA Fatty Acids
FAME Fatty acid methyl ester
FAO Food Agriculture Organization
FID Flame ionization detector
GC-MS Gas chromatography-mass spectrometry
LC-PUFA Long chain polyunsaturated fatty acid
MUFA Monounsaturated fatty acid
n-3 Omega-3 fatty acids
n-6 Omega-6 fatty acids
NADPH Nicotinamide Adenine Dinucleotide Phosphate (reduced)
NMDS Non-metric multidimensional scaling
PEG Poly ethylene glycol
PERMDISP Permutational analysis of multivariate dispersions
PUFA Polyunsaturated fatty acid
SFA Saturated fatty acid
SIMPER Similarity of percentages analysis
14
15
LIST OF ORIGINAL PUBLICATIONS This thesis is based on data presented in the following articles, referred to by the
Roman Numerals I-III.
I Rutaro K, Malinga GM, Lehtovaara VJ, Opoke R, Valtonen A, Kwetegyeka J,
Nyeko P, Roininen H. (2018). The fatty acid composition of edible
grasshopper Ruspolia differens (Serville) (Orthoptera: Tettigoniidae) feeding
on diversifying diets of host plants. Entomological Research, 48: 490-498.
II Rutaro K, Malinga GM, Opoke R, Lehtovaara VJ, Nyeko P, Roininen H,
Valtonen A. (2018). Fatty acid content and composition in edible grasshopper,
Ruspolia differens feeding on mixtures of natural food plants. BMC Research
Notes, 11: 687.
III Rutaro K, Malinga GM, Opoke R, Lehtovaara VJ, Omujal F, Nyeko P,
Roininen H, Valtonen A. (2018). Artificial diets determine fatty acid
composition in edible grasshopper Ruspolia differens (Orthoptera:
Tettigoniidae). Journal of Asia-Pacific Entomology, 21: 1342-1349.
The above publications have been included at the end of this thesis with their copyright
holders’ permission.
16
17
AUTHOR’S CONTRIBUTION The author participated in the planning and design of all the three studies (I-III)
alongside the supervisors and took a leading role in data collection. He was also
responsible for analyzing the data in all papers (I-III) with the assistance of co-
authors and wrote the first drafts of all the manuscripts with subsequent inputs
from co–authors.
18
19
CONTENTS
ABSTRACT ........................................................................................................... 7 ACKNOWLEDGEMENTS ...................................................................................11 1 INTRODUCTION ..........................................................................................21
1.1 THE EDIBLE KATYDID RUSPOLIA DIFFERENS ...................................21 1.2 WHAT DETERMINES THE FATTY ACID COMPOSITION OF EDIBLE
INSECTS? ................................................................................................22 1.3 FATTY ACID BIOSYNTHESIS IN INSECTS ...........................................23
1.3.1 Fatty acids ....................................................................................23 1.3.2 Fatty acid biosynthesis .................................................................25 1.3.3 Lipids ............................................................................................27 1.3.4 Fat body ........................................................................................28
1.4 AIMS OF THE PRESENT STUDY ...........................................................28 1.5 STUDY HYPOTHESES ...........................................................................29
2 MATERIALS AND METHODS .....................................................................31 2.1 STUDY AREA ..........................................................................................31 2.2 EXPERIMENTAL SET-UP .......................................................................31 2.3 LIPID AND FATTY ACID ANALYSIS .......................................................32 2.4 STATISTICAL ANALYSES ......................................................................32
3 RESULTS AND DISCUSSION .....................................................................35 3.1 EFFECT OF DIVERSIFIED DIETS ON R. DIFFERENS LIPID CONTENT
AND FATTY ACID COMPOSITION .........................................................35 3.2 DIVERSIFIED DIETS ALTER THE N-6/N-3 FATTY ACID RATIO IN R.
DIFFERENS .............................................................................................37 3.3 INFLUENCE OF SEX ON THE R. DIFFERENS FATTY ACID
COMPOSITION ........................................................................................38 3.4 BODY WEIGHT OF R. DIFFERENS WAS NOT INFLUENCED BY GRASS
INFLORESCENCE DIET .........................................................................38 4 CONCLUSIONS AND FUTURE PROSPECTS ...........................................41 5 BIBLIOGRAPHY ..........................................................................................43
20
21
1 INTRODUCTION
1.1 THE EDIBLE KATYDID RUSPOLIA DIFFERENS
Consumption of edible insects is seen as a major solution to address the looming
food shortage due to the increasing human population (van Huis et al., 2013)—
projected to be 9.7 billion by 2050 (United Nations, 2019)—and for improving hu-
man nutrition (Shantibala et al., 2014). For example, in Africa and Asia, edible in-
sects are a traditional part of the human diet. Globally, approximately 2000 edible
insect species are documented (Ramos‐Elorduy, 1997; Jongema, 2017). Most belong
to six orders: Lepidoptera (butterflies and moths), Coleoptera (beetles), Isoptera
(termites), Hymenoptera (ants, bees and wasps), Hemiptera (the true bugs) and
Orthoptera (katydids, crickets and grasshoppers; Bukkens, 1997; Dobermann et al.,
2017).
The katydid Ruspolia differens (Serville) (Orthoptera: Tettigoniidae), with
common names such as ‘the edible grasshopper’, ‘the African edible bush cricket’,
‘nsenene’, ‘senesene’ and ‘Nshonkonono’ (Siulapwa et al., 2014), is a popular edible
insect in sub-Saharan Africa. It has the potential to mitigate the nutritional and eco-
nomic challenges of vulnerable communities (van Huis et al., 2013; Siulapwa et al.,
2014; Mmari et al., 2017). Its geographical distribution includes tropical Africa and
some Indian Ocean islands (Bailey & McCrae, 1978; Massa, 2015). They occur in
eight colour morphs (Bailey & McCrae, 1978; Nyeko et al., 2014), mainly in tropical
grasslands and open bushvelds, and are mostly nocturnal (Nonaka, 2009; Matojo &
Hosea, 2013). In the wild, R. differens feeds on a range of grass and sedge species
(predominantly Panicum maximum, Brachiaria ruziziensis, Chloris gayana, Hyparrhenia
rufa, Cynodon dactylon, Sporobolus pyramidalis and Pennisetum purpureum; Opoke et
al., 2019). Furthermore, they prefer anthers or the setting seed at the 'milk stage' of
crops such as rice, sorghum, millet and maize (Bailey & McCrae, 1978; McCrae,
1982). In captivity, R. differens can accept a wide range of diets, including grass
leaves and inflorescences (Valtonen et al., 2018) and seeds or flours of rice seed,
finger millet and sorghum. They can also consume wheat bran, chicken super feed
egg booster, germinated finger millet, simsim cake, crushed dog biscuit pellets,
dried blood, Lucerne meal and a high protein cereal meal (Brits & Thornton, 1981;
Nyeko et al., 2014; Malinga et al., 2018a).
R. differens is particularly valuable due to its fats. Its fat content is 47-49%
based on dry weight (Kinyuru et al., 2010), and it is rich in essential polyunsaturat-
ed fatty acids, i.e., linoleic acid (29.5-31.2%) and α-linolenic acid (3.2-4.2% of the
total fatty acid content). Previous studies on both wild harvested (Kinyuru et al.,
2010; Opio, 2015; Fombong et al., 2017) and laboratory-reared R. differens
(Lehtovaara et al., 2017) demonstrated that the species also contains palmitic acid
(11-35%), stearic acid (5-12%) and oleic acid (19-45%). The R. differens fatty acid con-
22
tent and composition can be modified through diet (Lehtovaara et al., 2017); this
manipulation can produce high‐quality fatty acids, including essential fatty acids
for humans (van Huis et al., 2013). Additionally, R. differens is rich in both macro-
and micronutrients. On a dry weight basis, it contains 35-37% protein, 2.6-2.8% ash,
3.9-4.9% fibre as well as 259.7-370.6 mg/100 g potassium, 121.0-140.9 mg/100 g
phosphorous and 13.0-16.6 mg/100 g iron, among others (Kinyuru et al., 2010).
Despite its enormous potential in sub-Saharan Africa, utilisation of this ed-
ible katydid is currently based on wild harvesting (Mmari et al., 2017). R. differens
are harvested from the wild when they swarm, usually during peaks in rainy sea-
sons (i.e., April-May and November-December; Bailey & McCrae, 1978; Okia et al.,
2017). This practice of seasonal R. differens harvesting is generally unpredictable
(Okia et al., 2017). Consequently, there is a great need to develop mass-rearing
methods for this species to improve food and nutrition security in rural African
communities and prevent overexploitation due to wild harvesting (Agea et al.,
2008; Kinyuru et al., 2010; Kelemu et al., 2015). However, suitable diet mixtures for
mass rearing developed from commonly available local African feeds are not well
understood (but see Malinga et al., 2018a, 2018b).
This study evaluated the influence of a diversified gradient of locally sourced
artificial and natural (tropical grass inflorescence) diets in Uganda, on R. differens
fatty acid content and composition. The diversified feed gradients were studied
because R. differens is known to benefit from diet mixing (Malinga et al., 2018b).
Generally, diet mixing is considered beneficial to insect growth and development
because it allows for a better balance of nutrients (Miura & Ohsaki, 2004a; Unsicker
et al., 2008). Diet mixing could also be beneficial in mass-rearing conditions where
insects are offered feeds that they would not encounter in nature. In R. differens, diet
mixing improves performance, including shortened developmental time, increased
fresh adult weight and improved female fecundity (Malinga et al., 2018b).
However, the effect of diversifying locally sourced diets on R. differens fatty acid
content and composition is not well understood.
1.2 WHAT DETERMINES THE FATTY ACID COMPOSITION OF EDIBLE INSECTS?
The nutritional composition of edible insects is largely determined by the insects’
diet (Barker et al., 1998; Oonincx & van der Poel, 2011; Komprda et al., 2013; Alves
et al., 2016; Adámková et al., 2017; Lehtovaara et al., 2017), although other factors
such as the insect species, developmental stage, rearing conditions, sex and meta-
bolic activity are also important determinants (Yang, Siriamornpun, & Li, 2006;
Oonincx et al., 2015; van Broekhoven et al., 2015; Pino Moreno & Ganuly, 2016;
Sönmez et al., 2016). For example, in a study by Lehtovaara et al. (2017), R. differens
supplied with different diet ingredients that varied in their fat, protein and carbo-
hydrate contents greatly differed in their fatty acid composition. The diets used in
23
Lehtovaara et al. (2017) were designed from linseed, sunflower, sesame seed, oat,
sugar beet fibre, fructose, coconut flour, rice flour, wheat flour, maize starch,
TetraMin (aquarium) fish food, casein, wheat germ, pea protein and milk whey.
Additionally, earlier studies by Oonincx et al. (2015) and van Broekhoven et al.
(2015) that used Argentinian cockroaches and edible mealworms, namely Tenebrio
molitor L., Zophobas atratus and Alphitobius diaperinus, also found that the nutrient
composition, including fatty acids, greatly differs when the insects are reared on
formulated artificial diets. The diets were formulated from by-products of food
manufacturing and bioethanol production, including organic by-products from
beer brewing, bread/cookie baking and potato stem peelings.
Sex is another major factor that influences fatty acid composition. Lease
and Wolf (2011) showed that female insects have higher lipid and/or fatty acid
conents compared to males and varying fatty acid composition (Subramanyam &
Cutkomp, 1987). These differences are attributed to sexual dimorphism that results
in physiological and reproductive differences (Subramanyam & Cutkomp, 1987;
Zhou et al., 1995). The females lay eggs, and as such may require certain fatty acids
in greater proportions than their male counterparts. For example, oleic acid is
thought to play an important role in egg laying (Sönmez et al., 2016).
1.3 FATTY ACID BIOSYNTHESIS IN INSECTS 1.3.1 Fatty acids
Fatty acids are of basic significance in living organisms due to their roles in meta-
bolic energy storage, cell and bio-membrane structure and regulatory physiology,
among others (Stanley-Samuelson et al., 1988, and references therein). Fatty acids
are an important lipid component, and in nature, they exist in combination with
glycerol to form triglycerides (Figure 1). Fatty acids consist of a straight chain (rep-
resented by R in Figure 1), usually with an even number of carbon atoms, including
hydrogen atoms with a carboxyl group (―COOH) at one end. They are categorised
based on the carbon-to-carbon bonds, the nature of which results in saturated and
unsaturated fatty acids. If all the carbon-carbon bonds are single, the fatty acid is
saturated, but if any of the bonds is double or triple, the fatty acid is unsaturated.
Unsaturated fatty acids are further subdivided into monounsaturated and polyun-
saturated fatty acids. Monounsaturated fatty acids contain only one double bond,
while polyunsaturated fatty acid structure contain two or more double bonds.
24
Figure 1. Generalised structure of a fatty acid molecule; R refers to an aliphatic chain.
Polyunsaturated fatty acids (PUFAs) are further categorised as omega-3 and
omega-6 fatty acids. Omega-3 fatty acids are characterised by a double bond three
atoms away from the terminal methyl group. Comparatively, omega-6 fatty acids
have the last double bond six carbons from the omega (methyl) end of the fatty acid
molecule. Both omega-3 and omega-6 fatty acids are classified as essential fatty
acids to animals (including insects). They can only be obtained from dietary
sources, although a few insect species can biosynthesise their own (Cripps,
Blomquist, & de Renobales, 1986; Stanley-Samuelson et al., 1988). α-linolenic and
linoleic acids are the most common omega-3 and omega-6 fatty acids, respectively,
and can be metabolised into other fatty acids, such as eicosapentaenoic (EPA) and
docosahexaenoic (DHA) acids (from omega-3) and arachidonic acid (ARA) from
omega-6 (Figure 2; Stanley-Samuelson et al., 1988). In humans, the balance between
omega-3 and omega-6 is an important determinant for brain development and in
decreasing the risk for coronary heart disease (CHD), hypertension, cancer, diabe-
tes, arthritis and other autoimmune and neurodegenerative diseases (Simopoulos,
2002, 2010). In insects, the balance between omega-3 and omega-6 fatty acids (i.e.,
omega-6/omega-3 ratio of approximately 1-2) enhances olfaction and cognitive
functions, as observed in Apis mellifera (Arien, Dag, & Shafir, 2018). A study by
Hixson et al. (2016) found that the appropriate balance of omega-3 and omega-6
fatty acids is crucial for adult metamorphosis and wing development in the cabbage
white butterfly (Pieris rapae). Furthermore, the lack of PUFA in the developing in-
sect is associated with impaired pupal eclosion (Turunen, 1974; Stanley-Samuelson
et al., 1988). An insufficient PUFA quantity in the diet retards growth; however,
supplementation of the diet with linseed oil, which is high in α-linolenic acid, can
reverse that condition (Turunen, 1974; Komprda et al., 2013).
25
Figure 2. Structures of omega-3 and omega-6 fatty acids, as developed through ChemDraw
Ultra 8.0 software (A = α-linolenic acid, B = eicosapentaenoic acid, C = docosahexaenoic
acid, D = linoleic acid, E = arachidonic acid).
1.3.2 Fatty acid biosynthesis
The majority of insects can biosynthesise de novo certain fatty acids (de Renobales,
Cripps, Stanley-Samuelson, Jurenka, & Blomquist, 1987a; Stanley-Samuelson et al.,
1988 and references therein; Blomquist, Borgeson, & Vundla, 1991). This process is
achieved through a series of reactions (Figure 3) that involve the conversion of sug-
ars and other carbohydrates into fatty acids. When excess carbohydrates are availa-
ble, the pyruvate generated through glycolysis is used to produce acetyl coenzyme
A (acetyl-CoA). Subsequently, the carboxylation of acetyl-CoA through acetyl-CoA
carboxylase forms malonyl-CoA, which is used to form fatty acids, notably a 16-
carbon palmitic acid, using the fatty acid synthase enzyme complex in the presence
of the reduced nicotinamide adenine dinucleotide phosphate (NADPH). Palmitic
acid (C16:0) can then be elongated (through elongase enzymes), into stearic acid
26
(C18:0). The action of desaturases on C18:0 generates oleic acid (C18:1; Downer &
Matthews, 1976; Stanley-Samuelson et al., 1988; Visser et al., 2017). There are some
exceptions to these processes. In some insects, such as the order Diptera, lauric acid
(C12:0) and myristic acid (C14:0) are generated from acetyl CoA (Stanley-
Samuelson et al., 1988). However, some insect species that lack the Δ12 desaturase
enzyme in the biosynthetic pathway are unable to biosynthesise certain fatty acids,
particularly linoleic acid (C18:2; Cripps et al., 1986; de Renobales et al., 1987a;
Stanley-Samuelson et al., 1988). The lack of and inability to biosynthesise certain
fatty acids (such as linoleic acid) leads to the differences in fatty acid composition
observed among insect species such as Musca domestica, Acyrthosiphon pisum and
Blatella germanica (Blomquist et al., 1982; Beenakkers et al., 1985; Stanley-Samuelson
et al., 1988). Notably, in most insect species, fatty acids are fairly similar in qualita-
tive terms, with palmitic, stearic, oleic, linoleic and α-linolenic acids among the
common fatty acids (Stanley-Samuelson et al., 1988; Ogg et al., 1993). However,
there are exceptions; for example, most dipterans are associated with high propor-
tions of palmitoleic acid (C16:1), and some aphids have high myristic acid (C14:0)
proportions, whereas coccids are characterised by high capric acid (C10:0) and lau-
ric acid (C12:0) contents (Stanley-Samuelson et al., 1988, and references therein).
27
Figure 3. Schematic representation of fatty acid biosynthesis; adapted from Takahashi
(2018).
1.3.3 Lipids
Lipids are biological molecules that are soluble in non-polar solvents. In addition to
fatty acids, they include phospholipids, sterols, sphingolipids and terpenes, among
others (Fahy, Cotter, Sud, & Subramaniam, 2011). They provide the energy source
for numerous body processes and act as a source of essential fatty acids (Stanley-
Samuelson et al., 1988; Raksakantong et al., 2010). Lipids are also used for the
transportation and absorption of fat-soluble vitamins and nutrients, as well as the
synthesis of hormones, cellular membrane, structural elements in cells and vital
organ protection (Haunerland, 1997). Lipids are further classified as neutral (tri-
glycerides), which constitute approximately 90% of the total lipid component,
phospholipids (7%) and glycolipids (3%; Turunen, 1974; Kinyuru et al., 2010). In
insects, lipids are generally stored in the fat body, an organ equivalent to the liver
and adipose tissues in vertebrates (Arrese et al., 2001; Azeez, Meintjes, &
Chamunorwa, 2014).
28
1.3.4 Fat body
The fat body is a large, multifunctional organ that is distributed throughout the
insect body, from the terminal abdominal segment to the head capsule (Downer &
Matthews, 1976; Arrese & Soulages, 2010). The fat body is in a close contact with the
hemolymph for easy exchange of metabolites (Downer & Matthews, 1976). Lipids
form the major fat body component; more than 90% are triglycerides (Downer &
Matthews, 1976; Kinyuru et al., 2010). Functionally, the fat body exhibits marked
biosynthetic and metabolic activity, and it plays an essential role in energy storage
and utilisation, as well as excess nutrient storage (Arrese et al., 2001; Azeez et al.,
2014).
The fat body achieves its function through lipogenesis, which results in the
synthesis of triglyceride from diglyceride units as precursors (Arrese et al., 2001).
The precursor diglyceride units can be formed from a number of pathways, i.e.,
phosphatidic acid produced by the glycerophosphate pathway, the monoacylglyc-
erol pathway, degradation of phospholipids or triglyceride diacylation catalysed by
lipases (Arrese et al., 2001; Canavoso et al., 2001; Arrese & Soulages, 2010). The
diglyceride is further esterified through a diacylglycerol acyltransferase in a reac-
tion catalysed by the fatty-acyl-CoA to yield a triglyceride molecule.
When required, the fatty acids stored in the fat body are either mobilised to
provide energy to flight muscles or used for maintenance of metabolic activities for
other insect tissues, including the fat body itself (Downer & Matthews, 1976; Arrese
et al., 2001). This use can be achieved through mobilisation of diglycerides,
trehalose or proline (Arrese & Soulages, 2010). Mobilisation requires fat-body-based
triglyceride lipases (TG-lipase), which catalyse triglyceride hydrolysis. TG-lipases
include insect adipose triglyceride lipase and triglyceride lipase (Arrese & Soulages,
2010, and references therein). The lipids are mobilised and utilised to directly
support flight. This phenomenon has been demonstrated in a number of insect
species, including R. differens (Karuhize, 1972), and for the synthesis of trehalose
and proline (used for ready energy provision) as well as during starvation,
embryogenesis and the immune response (Arrese et al., 2001; Arrese & Soulages,
2010).
1. 4 AIMS OF THE PRESENT STUDY
The goal of this study was to assess how diversified natural diets that included the
inflorescences of selected grass species (i.e., B. ruziziensis, Setaria megaphylla, Setaria
sphacelata, Echinochloa pyramidalis, P. purpureum, C. gayana, E. indica and P. maxi-
mum), as well as artificial diets (formulated from rice seed head, finger millet seed
head, wheat bran, superfeed chicken egg booster, sorghum seed head, germinated
finger millet, simsim cake, crushed dog biscuit pellet and shea butter) influenced
29
the fatty acid content and composition of the edible katydid R. differens, one of the
most nutritionally and economically important edible insects in Africa.
The specific objectives were:
1. To evaluate the effect of diet, represented by a diversified gradient of natu-
ral host plants, on the lipid content and fatty acid composition in R. differens
sixth instar nymphs harvested from the wild and reared for two weeks
(study I).
2. To evaluate the effect of diet, represented by a diverse gradient of natural
host plants, on the content and fatty acid composition in R. differens indi-
viduals, when reared from neonatal nymphs to adults (study II).
3. To assess the influence of diet, represented by a diverse gradient of locally
sourced, processed and non-processed artificial diets, on the fatty acid con-
tent and composition of R. differens (study III).
1.5 STUDY HYPOTHESES
The study hypotheses were:
1. If R. differens are fed on a multi-species diet, the fatty acid content of the in-
sects will be higher than when fed on a less-diversified diet. Similar to oth-
er generalist herbivores, a multi-species diet might allow for ‘compulsive’
switching behaviour (Bernays, Bright, Howard, Raubenheimer, &
Champagne, 1992; Bernays & Bright, 1993) in R. differens. The phenomenon
would result in eating diverse food with more variable nutrient sources, in-
cluding fatty acids and other constituent nutrients (e.g., proteins and car-
bohydrates), than when fed on a mono-species diet.
2. Diet diversification will lead to differences in the fatty acid composition
among R. differens. More diversified diets will offer a more variable fatty ac-
id formulation compared to less diversified diets and thus promote differ-
ences in the R. differens fatty acid composition. Diversified diets will also
lead to alterations in fat content, because this measure reflects the diet fat
content (Turunen, 1974; Stanley-Samuelson et al., 1988; Lease & Wolf, 2011;
Malinga et al., unpublished manuscript).
3. The fatty acid content and composition will be influenced by R. differens
sex, regardless of the dietary levels of the diversified diet, because insects
exhibit sexual dimorphism in their lipid and fatty acid metabolism
(Turunen, 1974; Arrese & Soulages, 2010).
30
31
2 MATERIALS AND METHODS
This section provides a general outline of the materials and methods. A detailed
methodology is provided in the original papers I-III, which are attached.
2.1 STUDY AREA
Ruspolia differens used in this work originated from a wild population of the farm-
lands in and around the Makerere University Agricultural Research Institute
(MUARIK), Uganda. MUARIK is located in central Uganda, approximately 20 km
north of Kampala; it lies at 0°27'03.0"N and 32°36'42.0"E, with an average altitude of
1,200 m above sea level (asl). MUARIK has a wet-and-dry climate typical of tropical
regions. The mean annual rainfall (1,160 mm) is distributed bi-modally from March
to June and September to November each year (Tenywa et al., 2000). While the rest
of the insects were hatched and reared to maturity over the course of the experi-
ments at the Animal Science Laboratory, MUARIK (II-III), for study I, sixth instar
nymphs were harvested from the fields prior to using them in experiments. In
study I, fresh samples were used, and for II and III, the samples were freeze-dried
prior to fatty acid analysis. For study I, the analysis was performed at Kyambogo
University and Makerere University, Uganda. For studies II and III, the analysis
was performed at the Bio-Competence Centre of Healthy Dairy Products, Tartu,
Estonia (Accreditation EN ISO/IEC 17025:2005).
2.2 EXPERIMENTAL SET-UP
To test whether a diverse gradient of natural plants as a food source (I & II) affected
fatty acid content and composition, in study I, we reared R. differens individuals on
four dietary treatments. These treatments included one, or mixtures of two, three,
or six host plant inflorescences for two weeks after wild sixth instar harvesting. In
study II, we reared individuals on six dietary treatments that consisted of one, or
mixtures of two, three, five, six or eight host plant inflorescences from neonate
nymphs to adults (II). In both cases, freshly opened host plant inflorescences were
used. In study III, the effect of mixtures of locally sourced artificial diets on R. dif-
ferens fatty acid content and composition was investigated by rearing neonatal indi-
viduals to maturity on six levels of gradually diversified diets of two, three, four,
six, eight or nine feeds. The diets were formulated from rice seed head, finger millet
seed head, wheat bran, superfeed chicken egg booster, sorghum seed head, germi-
nated finger millet, simsim cake, crushed dog biscuit pellet and shea butter. In all
the studies, the insects were reared in the laboratory (temperature 22–28°C, 12 h
light:12 h dark photoperiod and relative humidity 50–60%) using transparent flat-
bottom plastic jars (1,000 mL, Thermopak Limited, Nairobi) that measure 12.5 cm
32
(diameter) × 8 cm (height). For study I, one male and one female were reared to-
gether in each jar for two weeks, whereas in studies II and III, neonatal nymphs
were reared singly per jar for 2-4 months. Moistened tissue paper was provided as
a source of water, and food was provided ad libitum, with regular replenishment
every 3-4 days. Upon maturity, the insects were harvested and frozen at -80°C
(studies II and III) until use in fatty acid analysis. For fatty acid and statistical anal-
ysis in study I, 30 individuals—four male and four female R. differens from each diet
treatment, except in treatment one (three males) and treatment two (three fe-
males)—were analysed, in addition to eight fresh samples (i.e., four males and four
females) collected from the wild. For studies II and III, a total of 30 individuals—
five from each diet treatment—were used.
2.3 LIPID AND FATTY ACID ANALYSIS
Lipid extraction in study I followed the method of Folch et al. (1957). The fatty acid
composition was determined using gas chromatography-mass spectrometry (GC-
MS; Agilent 6890-version N.05.05, GC-System, Santa Clara, CA, USA) fitted with an
electronic pressure control and mass selective detection (ionising energy, 70 eV;
temperature, 250°C) analysis. The fatty acids were identified in the samples using a
standard mixture and mass spectrometry and quantified using an internal standard
(C19:0). In experiments II and III, fatty acid analysis followed a direct transesterifi-
cation method (Sukhija & Palmquist 1988), with minor modifications (Lehtovaara et
al. 2017). Fatty acid methyl esters (FAMEs) were analysed on an Agilent 6890A GC
(Agilent Technologies Inc.), equipped with a flame ionisation detector (FID) detec-
tor and an autosampler. In all cases, the fatty acid peak areas were quantified using
ChemStation chromatography software, and the relative amounts of each fatty acid
were calculated based on their relative retention times and peak areas. Values are
expressed as a percentage (%) of the total analysed fatty acids and as content (mg
fatty acid per g R. differens dry weight).
2.4 STATISTICAL ANALYSES
For all studies, analysis of variance (ANOVA) and permutational multivariate
analysis of variance (PERMANOVA) were applied. ANOVA models (type III sums
of squares) were fitted in SPSS (IBM SPSS Statistics, version 23) to test whether the
content of SFAs, MUFAs, PUFAs or omega-6/omega-3 (n-6/n-3) fatty acid ratio of R.
differens were explained by diet and sex (fixed factors) or their interaction (studies II
and III). The PUFA content, n-6/n-3 ratio and MUFA content (study III) were natu-
ral log or square root transformed to improve normality prior to analysis. In study
III, Duncan’s post hoc test was used for pairwise comparisons, because for some
variables, the more conventional pairwise Tukey test (used in studies I and II) was
too conservative to detect any significant differences (Williams & Abdi, 2010), even
33
when ANOVA indicated significant differences among the diets. PERMANOVA
was performed to test for differences in fatty acid compositions (fatty acid propor-
tions) among diets, between the sexes and the interaction between these two factors
using type III sums of squares and 999 permutations (Anderson, 2001). A permuta-
tional analysis of multivariate dispersions (PERMDISP) was also conducted to as-
sess the degree of variability in the relative fatty acid proportions among samples in
each treatment and to test the dispersions within factor groups based on deviations
from the group centroids (Anderson, Gorley, & Clarke, 2008). Furthermore, a simi-
larity percentage analysis (SIMPER; Clarke & Gorley, 2006) was performed to iden-
tify which fatty acids contributed most to differences in fatty acid composition
among the diets. Non-metric multidimensional scaling (NMDS), with 50 restarts,
was applied to visualise fatty acid patterns among individuals fed with different
diet treatments. In all cases, Bray-Curtis was used as a measure of similarity. As a
response dataset, the proportions of each fatty acid out of the total fatty acid con-
tent in study I, and those with levels of 0.05% and above in a sample in studies II
and III, were used in the multivariate analysis. In study III, PERMANOVA was run
using both untransformed and forth-root transformed fatty acid proportional data
sets (the latter lessens the influence of the most common fatty acids and emphasises
the rare fatty acids). Branched chain (iso/anteiso) fatty acids (studies II and III) were
combined before inclusion in the analysis. PRIMER-E version 6.0 and PERMANO-
VA+ add-on were used for multivariate statistical analyses.
34
35
3 RESULTS AND DISCUSSION
3.1 EFFECT OF DIVERSIFIED DIETS ON R. DIFFERENS LIPID CONTENT AND FATTY ACID COMPOSITION
The study I results demonstrated that when wild sixth instar R. differens nymphs
were reared for two weeks, the fatty acid composition significantly differed among
the individuals fed with distinct natural host plant diets (for diet formulation, see
Table 1; study I). However, when R. differens were reared from neonatal nymphs to
adults, the fatty acid content and composition was not significantly different among
individuals fed with different diets (see Table 1; study II). The reason for this dis-
crepancy is unclear. However, it could be due to seasonal differences in the food
quality in diet mixtures offered to R. differens (i.e., study I was performed during
the wet season in November, whereas study II was executed in March during the
dry season). Food quality and the nutrient levels in grass species vary or fluctuate
with seasons due environmental factor variations, e.g., nutrient availability, solar
radiation, temperature and water deficiency, even when forages are harvested at
the same maturity stage (Buxton, 1996; Warly, Fariani, Ichinohe, & Fujihara 2004).
However, a study by Guil-Guerrero and Rodriguez-Garcia (1999) argued that most
plants are very similar in their fatty acid compositions, especially in leaf tissues, but
may differ in other constituent nutrients (e.g., proteins and carbohydrates) and
other physical characteristics such as plant tissue toughness. These combined fac-
tors could influence the palatability of the diet offered to R. differens, and this phe-
nomenon may have affected nutrient accumulation, including the fatty acids. In
study I, the insects were harvested as wild sixth instar nymphs with relatively well-
developed mandibles that they could possibly use to chew any offered grass type.
Comparatively, in study II, the growing nymphs were less developed and had
more fragile mandibles (Miura & Ohsaki, 2004b). Additionally, restriction in ac-
ceptance of plant species diets due to lack of experience, as suggested by Jermy
(1987), could have led to non-utilisation of some of the offered feeds. A recent study
by Opoke et al. (2019) showed that P. maximum is the preferred host for the young-
est R. differens nymphs. This finding suggests that in study II, the growing nymphs
may have only utilised a limited range of feeds from the mixture, a factor that
would underlie the similarity in their fatty acid profiles. Several studies (Turunen,
1974; Oonincx & van der Poel, 2011; Komprda et al., 2013; Lehtovaara et al., 2017)
argue that insect fatty acid profiles often reflect dietary fatty acids.
Study III results demonstrated that when R. differens individuals were fed
over the full life cycle (neonatal nymph to adult), a diversified gradient of local
(processed and unprocessed) artificial feeds in Uganda (see Table 1 for diet formu-
lations) strongly modified fatty acid content and composition. In particular, the
PUFA content was approximately 3.5-fold higher in R. differens that received the
36
most compared to the least diversified diet. Several reasons may explain the high
PUFA levels in the most diversified (eight- and nine-feed) diets. For example, the
highly diversified diets contained shea butter and simsim seed cake, both of which
are generally rich in PUFAs (Shea butter, 6–8%; simsim cake, 22–46% of the total
fatty acid content; Okullo et al., 2010; Honfo et al., 2014; Gharby et al., 2017). Thus,
R. differens possibly incorporated the dietary PUFAs, a phenomenon that may have
led to the observed high PUFA levels compared to the low PUFA levels in R. dif-
ferens offered the least diversified diets (Table 1; study III). This assertion of incor-
poration of unaltered dietary fatty acids into body tissues is also shared with a pre-
vious R. differens study (Lehtovaara et al., 2017) and in other edible insects, includ-
ing the mealworm Tenebrio molitor (Dreassi et al., 2017) and migratory locusts Lo-
custa migratoria L. (Oonincx & van der Poel, 2011). In the present study, the PUFA
content in R. differens fed with mixtures of artificial feed diet was 10% of the total fat
content, whereas in individuals offered the most diversified natural diet and in the
wild harvested individuals, it was 17% and 21%, respectively (see study I). In the
wild, herbivorous insects can exhibit complementarity effects as well as ‘compul-
sive’ switching on a wide range of plant species (Bernays et al., 1992; Unsicker et al.,
2008). This behaviour may allow accumulation of higher fatty acid levels, in partic-
ular PUFAs, compared to when the insects are offered a limited range of feeds in
artificial diets. Therefore, for fast growth and PUFA accumulation during mass
rearing, diet switching (i.e., the act of alternate feeding on a variety of food types in
polyphagous individuals; see Bernays et al., 1992) between the natural and artificial
diets is suggested. Diet switching can be advantageous to polyphagous insects,
because mixing foods increases the quality of the overall diet through improved
nutrient balance (Bernays et al., 1992; Bernays & Bright, 1993; Bernays, Bright,
Gonzalez, & Angel, 1994).
The results of these studies (I-III) showed that palmitic, stearic, oleic, linole-
ic and α-linolenic acids contributed > 90% of the total fatty acids across all dietary
treatments. These fatty acids were also found to be the most common in previous
studies that analysed composite samples of R. differens harvested from the wild
(Kinyuru et al., 2010; Opio, 2015; Fombong et al., 2017). The reason for this similari-
ty is unclear, but it might be related to de novo biosynthesis (Stanley-Samuelson et
al., 1988). In study III, oleic acid was exceptionally the most predominant fatty acid
(43-53% of the total fatty acid content across the dietary treatments), and this find-
ing could be attributed to oleic-acid-rich cereal feeds, such as rice and wheat
(Weihrauch & Matthews, 1977), that formed a major diet component for R. differens
in this study.
Finally, the results revealed that the lipid content was not altered when R.
differens was offered the different grass inflorescence diets (study I). The results in
study I suggest that R. differens lipid requirements may be fulfilled even with sim-
ple diets. Animals, and particularly insects, utilise lipids for various morphogenetic
and physiological functions, including flight (Karuhize, 1972; Downer & Matthews,
37
1976). In Bailey and McCrae (1978), the fat content of individuals harvested from
swarming R. differens varied from 26-29 g/100 g (based on wet weight) compared to
10 g/100 g in the study I (i.e., the R. differens harvested after two weeks on diet
treatments). However, a study by Lehtovaara, Roininen, and Valtonen (2018) noted
that R. differens weight continues to increase and could be up to 50% higher approx-
imately 10 days after adult moulting. This observation suggests that R. differens
continue to accumulate lipids in its fat body, a phenomenon that increases weight
after maturity is attained. Thus, leveraging the nutritional benefits of R. differens
during mass-rearing requires maintaining the insects after they reach maturity.
However, the lack of differences in the lipid content despite the diets in study I
could be attributed to the insects being confined in the rearing jars with reduced
movements and other energy-consuming processes. It is also possible that lipid
content differences could appear with further maturation, especially as they reach
their reproductive roles.
3.2 DIVERSIFIED DIETS ALTER THE N-6/N-3 FATTY ACID RATIO IN R. DIFFERENS
The results indicated that the n-6/n-3 fatty acid ratio was influenced by the diet
(studies I-III). When R. differens was fed with grass inflorescences, the n-6/n-3 fatty
acid ratio was reduced, i.e., 4.1-6.6 (study I; Table 3) and 1.45-2.03 (study II; Table
2). Several studies demonstrated that reduced n-6/n-3 fatty acid ratio is favourable
for both human health and insect growth and development. In humans, a reduced
n-6/n-3 fatty acid ratio (< 5) is important for brain development and decreasing the
risk for CHD, hypertension, cancer, diabetes, arthritis and other autoimmune and
neurodegenerative diseases (Simopoulos, 2002, 2010). For insects, a reduced n-6/n-3
fatty acid ratio is associated with better olfaction and cognitive functions, adult
metamorphosis, wing development and improved pupal eclosion (Turunen, 1974;
Stanley-Samuelson et al., 1988; Hixson et al., 2016; Arien, Dag, & Shafir, 2018).
On the contrary, when R. differens was reared on an artificial diet, the n-6/n-
3 fatty acid ratio was generally high and variable (range: 14-36; see study III, Table
2). In study III, the n-6/n-3 fatty acid ratio was unusually high compared to the rati-
os reported in studies I and II. This finding, however, suggests that the offered arti-
ficial feeds may contain higher levels of n-6 relative to n-3 fatty acids. The feed
combinations in study III (see Table I) comprised mostly cereals or cereal-based
feeds, all of which contain higher n-6 fatty acid levels (Weihrauch & Matthews,
1977). The n-6 fatty acids from the cereals were possibly incorporated into R. dif-
ferens tissues, a process that would result in the high n-6/n-3 fatty acid ratio. A high
n-6/n-3 fatty acid ratio has also been reported in a study by Lehtovaara et al. (2017),
where R. differens was reared on artificial diets with manipulated fatty acid, carbo-
hydrate and protein contents. Overall, on the basis of the n-6/n-3 fatty acid ratio, to
produce healthy food for humans, it would be important to rear R. differens with
38
grass-inflorescence-based diets or develop artificial diets supplemented with n-3-
rich feeds to balance the high n-6 fatty acids associated with the cereal-based diets.
3.3 INFLUENCE OF SEX ON THE R. DIFFERENS FATTY ACID COMPOSITION
The study showed that sex affected the R. differens fatty acid composition. The com-
positional differences observed between male and female R. differens could be the
result of sexual dimorphism, as reported for insects species from other families
(Subramanyam & Cutkomp, 1987). Females lay eggs, and thus they likely require
greater proportions of certain fatty acids (such as oleic acids) compared to their
male counterparts, as observed in Acanthoscelides obtectus (Sönmez et al., 2016). To
satisfy such physiological requirements, the different sexes may have consumed
different amounts of feeds, a phenomenon that would ultimately modify the overall
fatty acid proportions in their tissues.
3.4 BODY WEIGHT OF R. DIFFERENS WAS NOT INFLUENCED BY GRASS INFLORESCENCE DIET
In contrast to the study hypothesis, adult R. differens weight was not affected by
grass inflorescence diets (study I & II), although the reasons behind these data are
unclear. However, these findings corroborate the results from a related study that
also offered R. differens a grass inflorescence diet (Malinga et al., unpublished data
set). In a related study that used artificial diets (Malinga et al., 2018b), R. differens
weight was on average 0.40-0.65 g, compared to the weight in R. differens offered
the natural diets of 0.33-0.45 g and 0.41-0.45 g in study I and II, respectively. A pre-
vious study by Lehtovaara et al (2017) found that the final R. differens weight dif-
fered significantly among diet treatments when individuals were fed with artificial
diets with varied fat, protein and carbohydrate contents. These study findings sug-
gest that artificial feeds possibly offer R. differens better and more varied nutrients
compared to natural diets. However, based on the previous study by Lehtovaara et
al. (2018), R. differens individuals can achieve up to 50% higher weight approximate-
ly 10 days after final moulting compared to if they are harvested immediately after
adult moulting. Thus, the low weights observed in studies I and II may have result-
ed from early R. differens harvesting, which according to Lehtovaara et al. (2018) is a
limitation for this part of this study.
Furthermore, the study showed that more diversified diets resulted in R.
differens with relatively higher weights than those fed on single or less diversified
diets (studies I and II). In more diversified diets, the insects are considered to be
nutritionally advantaged due to diet complementation (Hagele & Rowell-Rahier,
1999; Miura & Ohsaki, 2004a; Unsicker et al., 2008). Indeed, many generalist and
specialist herbivores are known to perform best when offered a mixed rather than
39
less-diversified or single-food diet (Miura & Ohsaki, 2004a; Unsicker et al., 2008;
Malinga et al., 2018b). Nevertheless, in some cases, as highlighted by Hägele &
Rowell-Rahier (1999), some insects can perform well on less-diverse diets. Accord-
ing to Loveridge (1973), insect weight is largely determined by the offered diet.
Overall, the findings in this study suggest that the quality of the grass inflorescence
diets offered to the insects (in studies I and II) was inferior and could not build a
heavy fat body compared to the artificial diets (Malinga et al., 2018b).
40
41
4 CONCLUSIONS AND FUTURE PROSPECTS
This thesis investigated the influence of diversified diets that contained selected
artificial components and grass inflorescences on the fatty acid content and compo-
sition of R. differens. The results provide new knowledge on the effect of a diversi-
fied diet on fatty acid content and composition in R. differens. This information will
be useful when designing rearing methods and technology for this edible insect.
The main conclusions and the future prospects from this study are summarised
below.
1. R. differens fatty acid content and composition can be influenced by diet.
Thus, using plants (grass inflorescences) and artificial diets, it is possible to
produce R. differens with elevated fatty acid levels, including the preferred
high-quality essential fatty acids that are important in human health.
2. The study I results further showed that it is possible to rear R. differens har-
vested in the wild as sixth instar nymphs and modify their fatty acid com-
position based on mixtures of its natural diet (grass inflorescences).
3. Furthermore, the study III results revealed that when fed from neonatal
nymph to adult, a diversified gradient of local artificial feeds strongly mod-
ified the fatty acid content and composition in R. differens.
4. The most common fatty acids in R. differens included palmitic, stearic, oleic,
linoleic and α-linolenic acids, which collectively contributed > 90% of the
total fatty acids irrespective of diet treatment.
5. The lipid content was not altered when R. differens is offered the grass inflo-
rescence diet (study I).
6. The n-6/n-3 fatty acid ratio in R. differens was influenced by the diet.
7. Despite being offered similar diets, there were notable proportional differ-
ences in fatty acids among female and male R. differens.
8. Finally, adult R. differens weight was not affected by host plant inflo-
rescence diets.
Overall, the study provides important information regarding the influence of diver-
sified diets on the fatty acid content and composition in R. differens. This infor-
mation will be useful for designing nutritious feeds for future R. differens mass-
rearing programmes. However, additional studies are recommended to establish
the extent of diet diversification vis-à-vis the quality of fatty acids, especially the
essential fatty acids.
42
43
5 BIBLIOGRAPHY
Adámková A., Mlček J., Kouřimská L., Borkovcová M., Bušina T., Adámek M., Bednářová M.
& Krajsa J. 2017. Nutritional potential of selected insect species reared on the island of
Sumatra. International Journal of Environmental Research and Public Health 14: 521.
Agea J.G., Biryomumaisho D., Buyinza M. & Nabanoga G.N. 2008. Commercialisation of
Ruspolia nitidula (Nsenene grasshoppers) in central Uganda. African Journal of Food
Agriculture Nutrition and Development 8: 319-332.
Alves A.V., Sanjinez-Argandoña E.J., Linzmeier A.M., Cardoso C.A.L. & Macedo M.L.R.
2016. Food value of mealworm grown on Acrocomia aculeata pulp flour. PLOS ONE
11: e0151275.
Anderson M., Gorley R.N. & Clarke R.K. 2008. Permanova+ for Primer: Guide to software
and statistical methods. PRIMER-E, Plymouth, UK.
Anderson M.J. 2001. A new method for non‐parametric multivariate analysis of variance.
Austral Ecology 26: 32-46.
Arien Y., Dag A. & Shafir S. 2018. Omega-6: 3 ratio more than absolute lipid level in diet
affects associative learning in honey bees. Frontiers in Psychology 9: 1-8.
Arrese E.L., Canavoso L.E., Jouni Z.E., Pennington J.E., Tsuchida K. & Wells M.A. 2001. Lipid
storage and mobilization in insects: current status and future directions. Insect
Biochemistry and Molecular Biology 31: 7-17.
Arrese E.L. & Soulages J.L. 2010. Insect fat body: energy, metabolism, and regulation. Annual
Review of Entomology 55: 207-225.
Azeez O. I., Meintjes R. & Chamunorwa J.P. 2014. Fat body, fat pad and adipose tissues in
invertebrates and vertebrates: the nexus. Lipids in Health and Disease 13: 1-13.
Bailey W.J. & McCrae A.W.R. 1978. The general biology and phenology of swarming in the
East African tettigoniid Ruspolia differens (Serville) (Orthoptera). Journal of Natural
History 12: 259-288.
Barker D., Fitzpatrick M.P. & Dierenfeld E.S. 1998. Nutrient composition of selected whole
invertebrates. Zoo Biology 17: 123-134.
Beenakkers A.M.T., Van der Horst D.J. & Van Marrewijk W.J.A. 1985. Insect lipids and
lipoproteins, and their role in physiological processes. Progress in Lipid Research 24: 19-
67.
Bernays E. & Bright K.L. 1993. Mechanisms of dietary mixing in Grasshoppers: A review.
Comparative Biochemistry and Physiology 104A: 125-131.
Bernays E.A., Bright K., Howard J.J., Raubenheimer D. & Champagne D. 1992. Variety is the
spice of life: frequent switching between foods in the polyphagous grasshopper
Taeniopoda eques Burmeister (Orthoptera : Acrididae ). Animal Behaviour 44: 721-731.
Bernays E.A., Bright K.L., Gonzalez N. & Angel J. 1994. Dietary mixing in a generalist
herbivore: tests of two hypotheses. Ecology 75: 1997-2006.
Blomquist G.J., Borgeson C.E. & Vundla M. 1991. Polyunsaturated fatty acids and
eicosanoids in insects. Insect Biochemistry 21: 99-106.
Blomquist G.J., Dwyer L.A., Chu A.J., Ryan R.O. & de Renobales M. 1982. Biosynthesis of
linoleic acid in a termite, cockroach and cricket. Insect Biochemistry 12: 349-353.
Brits J.A. & Thornton C.H. 1981. On the biology of Ruspolia differens (Serville)(Orthoptera:
Tettigoniidae) in South Africa. Phytophylactica 13: 169-174.
44
Bukkens S.G.F. 1997. The nutritional value of edible insects. Ecology of Food and Nutrition 36:
287-319.
Buxton D.R. 1996. Quality-related characteristics of forages as influenced by plant
environment and agronomic factors. Animal Feed Science and Technology 59: 37-49.
Canavoso E., Jouni Z.E., Karnas K.J., James E. & Wells M.A. 2001. Fat metabolism in insects.
Annual Review of Nutrition 21: 23-46.
Clarke K.R. & Gorley R.N. 2006. PRIMER v6: User Manual/Tutorial. Primer-E, Plymouth.
Cripps C., Blomquist, G. J. & de Renobales, M. 1986. De novo biosynthesis of linoleic acid in
insects. Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism 876: 572–580.
de Renobales M., Cripps C., Stanley-Samuelson D.W., Jurenka R.A. & Blomquist G.J. 1987.
Biosynthesis of linoleic acid in insects. Trends in Biochemical Sciences 12: 364-366.
Dobermann D., Swift, J.A. & Field L.M. 2017. Opportunities and hurdles of edible insects for
food and feed. Nutrition Bulletin 42: 293-308.
Downer R.G.H. & Matthews J.R. 1976. Patterns of lipid distribution and utilisation in insects.
American Zoologist 16: 733-745.
Dreassi E., Cito A., Zanfini A., Materozzi L., Botta M. & Francardi V. 2017. Dietary fatty acids
influence the growth and fatty acid composition of the yellow mealworm Tenebrio
molitor (Coleoptera: Tenebrionidae). Lipids 52: 285-294.
Fahy E., Cotter D., Sud M. & Subramaniam S. 2011. Lipid classification, structures and tools.
Biochimica et Biophysica Acta 1811: 637-647.
Fombong F., Van Der Borght M. & Vanden Broeck J. 2017. Influence of freeze-drying and
oven-drying post blanching on the nutrient composition of the edible insect Ruspolia
differens. Insects 8: 102.
Gharby S., Harhar H., Bouzoubaa Z., Asdadi A., El Yadini A. & Charrouf Z. 2017. Chemical
characterization and oxidative stability of seeds and oil of sesame grown in Morocco.
Journal of the Saudi Society of Agricultural Sciences 16: 105-111.
Guil-Guerrero J.L. & Rodriguez-Garcia I. 1999. Lipid classes, fatty acids, and carotenes of the
leaves of six edible wild plant. European Food Research and Technology 209: 313-316.
Hägele B.F. & Rowell-Rahier M. 1999. Dietary mixing in three generalist herbivores: nutrient
complementation or toxin dilution? Oecologia 119: 521-533.
Haunerland N.H. 1997. Transport and utilization of lipids in insect flight muscles.
Comparative Biochemistry and Physiology 117B: 475-482.
Hixson S.M., Shukla K., Campbell L.G., Hallett R.H., Smith S.M., Packer L. & Arts M.T. 2016.
Long-chain omega-3 polyunsaturated fatty Acids have developmental effects on the
crop pest, the cabbage white butterfly Pieris rapae. PLOS ONE 11: e0152264.
Honfo F.G., Akissoe N., Linnemann A.R., Soumanou M. & Van Boekel M.A.J.S. 2014.
Nutritional composition of shea products and chemical properties of shea butter: a
review. Critical Reviews in Food Science and Nutrition 54: 673-686.
Jermy T. 1987. The role of experience in the host selection of phytophagous insects. In
Perspectives in chemoreception and behavior (pp. 143-157). Springer.
Jongema Y. 2017. Worldwide list of recorded edible insects. https://www. wur.
nl/upload_mm/8/a/6/0fdfc700-3929-4a74-8b (2017): 69-f02fd35a1696_Worldwide.
Karuhize G.R. 1972. Utilization of fat reserve substances by Homorocoryphus (Orthoptera:
Tettigoniidae) during flight. Comparative Biochemistry 43: 563-569.
Kelemu S., Niassy S., Torto B., Fiaboe K., Affognon H., Tonnang H., Maniania N.K. & Ekesi
S. 2015. African edible insects for food and feed : inventory , diversity, commonalities
and contribution to food security. Journal of Food and Feed 1: 103-119.
45
Kinyuru J.N., Kenji G.M., Muhoho S.N. & Ayieko M. 2010. Nutritional potential of longhorn
grasshopper (Ruspolia differens) consumed in Siaya district, Kenya. Journal of
Agriculture, Science and Technology 12: 32-46.
Komprda T., Zorníková G., Rozíková V., Borkovcová M. & Przywarová A. 2013. The effect of
dietary Salvia hispanica seed on the content of n-3 long-chain polyunsaturated fatty
acids in tissues of selected animal species, including edible insects. Journal of Food
Composition and Analysis 32: 36-43.
Lease H.M. & Wolf B.O. 2011. Lipid content of terrestrial arthropods in relation to body size,
phylogeny, ontogeny and sex. Physiological Entomology 36: 29-38.
Lehtovaara V.J., Roininen H. & Valtonen A. 2018. Optimal temperature for rearing the edible
Ruspolia differens (Orthoptera: Tettigoniidae). Journal of Economic Entomology 111: 2652-
2659.
Lehtovaara V.J., Valtonen A., Sorjonen J., Hiltunen M., Rutaro K., Malinga G.M., Nyeko P. &
Roininen H. 2017. The fatty acid contents of the edible grasshopper Ruspolia differens
can be manipulated using artificial diets. Journal of Insects as Food and Feed 3: 253-262.
Loveridge J.P. 1973. Age and the changes in water and fat content of adult laboratory-reared
Locusta migratoria migratorioides R. and F. Rhodesian Journal of Agriculture Research 11:
130-143.
Malinga G.M., Valtonen A., Lehtovaara V.J., Rutaro K., Opoke R., Nyeko P. & Roininen H.
2018a. Diet acceptance and preference of the edible grasshopper Ruspolia differens
(Orthoptera: Tettigoniidae). Applied Entomology and Zoology 53: 229-236.
Malinga G.M., Valtonen A., Lehtovaara V.J., Rutaro K., Opoke R., Nyeko P. & Roininen H.
2018b. Mixed artificial diets enhance the developmental and reproductive performance
of the edible grasshopper, Ruspolia differens (Orthoptera: Tettigoniidae). Applied
Entomology and Zoology 53: 237-242.
Massa B. 2015. Taxonomy and distribution of some katydids (Orthoptera Tettigoniidae) from
tropical Africa. ZooKeys 524: 17-44.
Matojo N.D. & Hosea K.M. 2013. Phylogenetic relationship of the longhorn grasshopper
Ruspolia differens Serville (Orthoptera: Tettigoniidae) from northwest Tanzania based
on 18S ribosomal nuclear sequences. Journal of Insects 2013: 1-5.
McCrae A.W.R. 1982. Characteristics of swarming in the african edible bush-cricket Ruspolia
differens (Serville)(Orthoptera, Tettigonioidea). Journal of the East Africa Natural History
178: 1-5.
Miura K. & Ohsaki N. 2004a. Diet mixing and its effect on polyphagous grasshopper
nymphs. Ecological Research 19: 269-274.
Miura K. & Ohsaki N. 2004b. Relationship between physical leaf characteristics and growth
and survival of polyphagous grasshopper nymphs, Parapodisma subastris (Orthoptera:
Catantopidae). Population Ecology 46: 179-184.
Mmari M.W., Kinyuru J.N., Laswai H.S. & Okoth J.K. 2017. Traditions, beliefs and
indigenous technologies in connection with the edible longhorn grasshopper Ruspolia
differens (Serville 1838) in Tanzania. Journal of Ethnobiology and Ethnomedicine 13: 60.
Nonaka K. 2009. Feasting on insects. Entomological Research 39: 304-312.
Nyeko P., Nzabamwita P.H., Nalika N., Okia C.A., Odongo W. & Ndimubandi J. 2014.
Unlocking the potential of edible insects for improved food security, nutrition and
adaptation to climate change in the Lake Victoria basin. Kampala, Uganda.
46
Ogg C.L., Meinke L.J., Howard R.W. & Stanley-Samuelson D.W. 1993. Phospholipid and
triacylglycerol fatty acid compositions of five species of Diabrotica (insecta: coleoptera:
chrysomelidae). Comparative Biochemistry and Physiology-Part B 105: 69-77.
Okia C.A., Odongo W., Nzabamwita P., Ndimubandi J., Nalika N. & Nyeko P. 2017. Local
knowledge and practices on use and management of edible insects in Lake Victoria
basin, East Africa. Journal of Insects as Food and Feed 3: 83-93.
Okullo J.B.L., Omujal F., Agea J.G., Vuzi P.C., Namutebi A., Okello J.B.A. & Nyanzi S.A.
2010. Physico-chemical characteristics of Shea butter (Vitellaria paradoxa CF Gaertn.)
oil from the Shea district of Uganda. African Journal of Food, Agriculture, Nutrition and
Development 10.
Oonincx D.G.A.B., van Broekhoven S., van Huis A. & van Loon J.J.A. 2015. Feed conversion,
survival and development, and composition of four insect species on diets composed
of food by-products. PLOS ONE 10: e0144601.
Oonincx D.G.A.B. & van der Poel A.F.B. 2011. Effects of diet on the chemical composition of
migratory locusts ( Locusta migratoria ). Zoo Biology 30: 9-16.
Opio, M. 2015. Abundance and nutritional compositions of Ruspolia differens polymorphs
from Masaka Uganda. Makerere University.
Opoke R., Nyeko P., Malinga G.M., Rutaro K., Roininen H. & Valtonen A. 2019. Host plants
of the non‐swarming edible bush cricket Ruspolia differens. Ecology and Evolution 9: 3899-
3908.
Pino Moreno J.M. & Ganuly A. 2016. Determination of fatty acid content in some edible
insects of Mexico. Journal of Food and Feed 2: 37-42.
Raksakantong P., Meeso N., Kubola J. & Siriamornpun S. 2010. Fatty acids and proximate
composition of eight Thai edible terricolous insects. Food Research International 43: 350-
355.
Ramos‐Elorduy J. 1997. Insects: A sustainable source of food? Ecology of Food and Nutrition 36:
247-276.
Shantibala T., Lokeshwari R.K. & Debaraj H. 2014. Nutritional and antinutritional
composition of the five species of aquatic edible insects consumed in Manipur, India.
Journal of Insect Science 14.
Simopoulos A.P. 2002. The importance of the ratio of omega-6/omega-3 essential fatty acids.
Biomedicine and Pharmacotherapy 56: 365-379.
Simopoulos A.P. 2010. The omega-6 / omega-3 fatty acid ratio: health implications. Nutrition–
Sante’ 17: 267-275.
Siulapwa N., Mwambungu A., Lungu E. & Sichilima W. 2014. Nutritional value of four
common edible insects in Zambia. International Journal of Science and Research 3: 876-884.
Sönmez E., Güvenç D. & Gülel A. 2016. The changes in the types and amounts of fatty acids
of adult Acanthoscelides obtectus (Coleoptera: Bruchidae ) in terms of age and sex.
Internation Journal of Fauna and Biological Studies 3: 90-96.
Stanley-Samuelson D.W., Jurenka R.A., Cripps C., Blomquist G.J. & de Renobales M. 1988.
Fatty acids in insects: Composition, metabolism, and biological significance. Archives of
Insect Biochemistry and Physiology 5: 1-33.
Subramanyam B. & Cutkomp L. 1987. Total lipid and fatty acid composition in male and
female larvae of Indian meal moth and almond moth (Lepidoptera: Pyralidae). Great
Lakes Entomologist 20: 10.
Takahashi H. 2018. Association between arachidonic acid and chicken meat and egg flavor ,
and their genetic regulation. Japan Poutry Science Association 55: 163-171.
47
Tenywa M.M., Zake J.Y.K., Sessanga S., Majaliwa J.G.M., Kawongolo J.B. & Bwamiki D. 2000.
Changes in water infiltration along a catena prior to mechanised clearing operations
and after two cropping seasons. African Crop Science Journal 8: 233-242.
Turunen S. 1974. Metabolism and function of fatty acids in a phytophagous lepidopteran.
Annales Zoologici Fennici 11: 170-184.
United Nations. 2019. World Population Prospects 2019: Highlights. New York (US): United
Nations Department for Economic and Social Affairs.
Unsicker S.B., Oswald A., Köhler G. & Weisser W.W. 2008. Complementarity effects through
dietary mixing enhance the performance of a generalist insect herbivore. Oecologia 156:
313-324.
Valtonen A., Malinga G.M., Junes P., Opoke R., Lehtovaara V.J., Nyeko P. & Roininen H.
2018. The edible Ruspolia differens (Orthoptera: Tettigoniidae: Conocephalinae), is a
selective feeder on the inflorescences and leaves of grass species. Entomologia
Experimentalis et Applicata 166: 592-602.
van Broekhoven S., Oonincx D.G.A.B., van Huis A. & van Loon J.J.A. 2015. Growth
performance and feed conversion efficiency of three edible mealworm species
(Coleoptera: Tenebrionidae) on diets composed of organic by-products. Journal of Insect
Physiology 73: 1-10.
van Huis A., van Itterbeeck J., Klunder H., Mertens E., Halloran A., Muir G. & Vantomme P.
2013. Edible insects. Future prospects for food and feed security. FAO Forestry Paper.
Rome: UNFAO.
Visser B., Willett D.S., Harvey A. & Alborn H.T. 2017. Concurrence in the ability for lipid
synthesis between life stages in insects. Royal Society Open Science 4: 1-8.
Warly L., Fariani A., Ichinohe T. & Fujihara T. 2004. Seasonal changes in nutritive value of
some grass species in west sumatra , Indonesia. Asian-Australasian Journal of Animal
Sciences 17: 1663-1668.
Weihrauch J.L. & Matthews R.H. 1977. Lipid content of selected cereal grains and their
milled and baked products. Cereal Chemistry 54: 444-453.
Williams L.J. & Abdi H. 2010. Post-Hoc Comparisons. In In Neil Salkind (Eds.), Encyclopedia
of Research Design. Thousand Oaks, CA: Sage pp. 1-12.
Yang L.F., Siriamornpun S. & Li D. 2006. Polyunsaturated fatty acid content of edible insects
in Thailand. Journal of Food Lipids 13: 277-285.
Zhou X., Honek A., Powell W. & Carter N. 1995. Variations in body length, weight, fat
content and survival in Coccinella septempunctata at different hibernation sites.
Entomologia Experimentalis et Applicata 75: 99-107.
uef.fi
PUBLICATIONS OF THE UNIVERSITY OF EASTERN FINLAND
Dissertations in Forestry and Natural Sciences
ISBN 978-952-61-3320-1ISSN 1798-5668
Dissertations in Forestry and Natural Sciences
DIS
SE
RT
AT
ION
S | K
AR
LM
AX
RU
TA
RO
| FA
TT
Y A
CID
PR
OF
ILE
S O
F T
HE
ED
IBL
E K
AT
YD
ID, R
US
PO
LIA
... | No
371
KARLMAX RUTARO
FATTY ACID PROFILES OF THE EDIBLE KATYDID, RUSPOLIA DIFFERENS (SERVILLE) (ORTHOPTERA:
TETTIGONIIDAE) AFTER FEEDING ON DIVERSIFIED DIETS
PUBLICATIONS OF THE UNIVERSITY OF EASTERN FINLAND
Rearing of edible insects is seen as one
solution to ensure a sufficient food production for the increasing human population.
A successful mass-rearing programme for edible insects such as the edible katydid, Ruspolia differens, in rural Africa would require affordable but reliable feeds. This
thesis provides novel insights on how feeds influence the fatty acid profiles of R. differens, with emphasis on the essential fatty acids that
are needed for a healthy human diet.
KARLMAX RUTARO