;?oological Journal of the Linnean Society ( 1988), 93: I07 1 I 2
Amino acid increases in fruit infested by
fruit flies of the family Tephritidae
R. A. I. DREW
Department of Primary Industries, Entomology Branch,
Meiers Road, Indooroopilly, Queensland 4068, Australia
Recezoed June 1987, accepted f o r fiublicatton August 1987
Solanum mauritianum Scop. (wild tobacco) fruit is the major host of the fruit fly Dacus cacuminatus
(Hering), and is a major source of food for the brown pigeon Macropygia phaszanella (Temminck) in
eastern Queensland. Amino acid analyses were undertaken on fruit fly infested and uninfested
S. mauritianum fruits. Infested fruits contained approximately twice the level of protein and essential
amino acids compared to uninfested fruit. This increase is probably due to the plant adding
additional amino acids to infested tissue and the arcompanying growth of bacteria established in
the fruit during oviposition. The infested fruit would provide a valuable source of protein during
the pigeon breeding season.
KEY WORDS:--Fruit fly - amino acids - infestcd fruit - brown pigeon.
CONTENTS
Introduction . . .
Material and Mrthods
Results
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Disrussion . . . .
Acknowledgements
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References
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107
108
109
1I 1
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I12
INTRODUCTION
In the endemic rainforest habitat of tropical/subtropical fruit flies, many fruit
species eaten by vertebrates such as birds (Crome, 1975, 1976; Stocker & Irvine,
1983) are known fruit fly hosts. In a study of the brown pigeon feeding on fruit
of Solanum mauritianum Scop. at Mount Glorious, south-east Queensland (Drew,
1987), more fruit was eaten during the period when the fruit fly, Dacus
cacuminatus (Hering), was breeding in the fruit. The phenology of fruiting in
S. mauritianum and the seasonal variation in fruit fly breeding in this fruit has
been studied in detail by Drew & Hooper (1983).
The importance of protein food to growth in pigeon nestlings was stressed by
Levi (1963) who showed that pigeon ‘milk’ used for feeding young birds
contained up to 59% protein and was rich in B-complex vitamins. In a study of
the fruit feeding pigeons of tropical north Queensland, Crome (1975) noted that
0024-4082/060107 f 0 6 003.00/0
107
0 1988 The Linnean
Society of London
I08
R. A. I . DREW
fruit-eating pigeons ingest higher protein food during the breeding season and
feeding of crop milk to nestlings overcomes the disadvantage of a low-protein
h i t diet. Crome (1975) also found that the brown pigeon usually feeds on low
protein fruit, that truly obligate frugivores are rare, that many frugivorous
pigeons augment their diet with insects as a protein source and that insects fed
to nestlings induce faster growth in the young birds.
The paper reports amino acid analyses of infested and uninfested
S. mauritianum fruit and a discussion on the value of this food source to the brown
pigeon.
MA1 EKIAL AND METHODS
Samples of completely uninfested fruit of S. maurilianum were obtained by
enclosing flower heads in fine gauze cages after pollination. Samples of naturally
infested fruit were obtained by leaving similar size flower heads, on the same
plant, uncaged. One set of samples was taken during a predation study a t
Mount Glorious (Drew, 1987) and a second set was taken from a large plant
growing in Brisbane. T h e fruit samples were picked at the mature ripe stage and
held in an ultra-low deep freeze at -80°C.
Amino acid analyses were carried out by two different methods, one on a n
amino acid autoanalyser and the second using high performance liquid
chromatography (HPLC). Before the analyses were undertaken, the berries
were dissected and the seeds discarded as these are not digested by the birds nor
decayed by bacteria during fruit fly larval development. In infested fruit
samples, the fruit fly larvae and eggs were removed and analyscd together,
separate from the fruit tissue. In case there was a moisture loss in some samples,
the analyses were calculated on a dry weight basis.
In the first set of analyses, 13 infested and 12 uninfested fruits from Mount
Glorious were analysed separately as follows. The separate samples of fruit tissue
and larvae plus eggs were weighed and homogenimd in distilled water (fruit in
2 ml and larvae/eggs in two drops) at room temperature, dried under vacuum
and weighed again. The samples were then hydrolysed by adding constant
boiling point hydrochloric acid (4 ml for fruit, 2 ml for larvae/eggs), sealed
under vacuum at 110°C for 24 h and dried in a vacuum desiccator over P,O,
plus NaOH for 24 h. Citrate buffer (0.2 M, pH 2.0) was added ( 4 ml fruit, 3 ml
larvae/eggs) and the solutions were passed through a millipore filter and 200 p1
of stock norleucine solution (0.0164 g/25 ml water) added. T h e samples were
analysed on a Technicon Autoanalyser using the standard programme for
protein hydrolysates. The amounts of each amino acid, per gram of tissue, were
estimated in nanomoles and number of grams. The sum of the individual amino
acid weights (in grams) was used as an estimate of total protein in each sample.
In the second set of analyses, 12 infested and 12 uninfcsted fruits from
Brisbane were analysed. After separation of seeds the uninfested fruits were
pooled and homogenized together, and similarly for the infested fruits and
larvae plus eggs samples. After the filtering stage above, the amino acids were
derivated with phenylisothiocyanate in pyridine:acetonitrile: triethy1amine:water
(5:10:2:3), drird, redissolved in HPLC solvent and analysed in a Waters HPLC
system controlled by a Digital Professional 350 computer. Four sub-samples of
infested fruit tissue and uninfested fruit tissue, and two sub-samples of the larvae
AMINO ACID CONTENT O F F R U I T FLY INFESTED F R U I T
109
plus eggs were analysed. The amounts of each amino acid per gram of tissue
were estimated in nanomoles. T h e dry weights of each infested fruit, and its
larvae plus eggs, were not taken and consequently the amounts of amino acids
(nanomoles) in infested fruit tissue plus larvae and eggs were not calculated in
these analyses.
RESULTS
The individual fruits of S. mauritianum are c. 10-12 mm diameter, growing in
bunches of c. 10-40. Each fruit contains many very small seeds in the centre,
surrounded by a fleshy layer up to 4 mm thick. As many as 20 fruit fly eggs are
deposited in each fruit and, during the larval development time of c. 7-10 days,
up to six larvae survive to later instar stages.
In the first analysis using the autoanalyser 16 amino acids were recorded,
including nine that are classified essential to animal growth (Table 1).
Tryptophan and cystine are both destroyed by acid hydrolysis and were not
identified in the samples. The concentrations, in nanomoles per gram, for each
amino acid increased from uninfested fruit tissue to infested fruit tissue and
thence to infested fruit tissue plus fruit fly larvae/eggs (Table 1). There was a
40-100% increase in the infested fruit tissue from which eggs and larvae were
removed prior to analysis and a 50-130% increase in the infested fruit tissue
plus eggs/larvae. T h e concentrations, in grams per gram, of each amino acid are
given in Table 2. Based on these weights, the uninfested fruit tissue contained
4.8% protein, the infested fruit tissue 8.5% protein and the infested fruit tissue
plus larvae/eggs 9.5% protein. T h e amino acids that occurred in greatest
quantities in the infested fruit were arginine, asparagine, glutamine, leucine,
lysine and valine. There was no major change with infestation in the relative
abundance of amino acid in the samples analysed (Table 3). Glutamine plus
'I'ABI.E 1. 'I'he amino acid content of uninfested fruit of Solanum mauritianum Scop. and of fruit
infcstcd with Dacus cacurninatus (Hering), and percentage increases in amino acids due to the fruit
fly infestation. Data based on individual fruit samples from Mount Glorious, Queensland
Amino acid
Lysine
Histidine
Arginine
Threonine
Valine
Methionine
Isoleucine
Leucine
Phcnylalaninr
Asparagine
Serine
Clutarnine
Proline
Glyrine
Al a ni 11e
'l'yrosine
Uninfested
fruit tissue
(nrnol g - ' )
30 187
8 862
27 040
21 367
30 88 1
6 823
23 641
36 04 1
15 222
46 372
30717
44 634
28 719
46 198
37 247
8 003
Infested fruit tissur
(larvae removed)
nmol g -
57 961
I9 038
37 993
37 038
57 629
10490
39 469
61 205
24 726
91 024
47 631
85913
47 786
76 706
68 600
13917
'
''{]
increase
92.0
114.8
40.5
73.3
86.6
53.7
70.0
69.8
62.4
96.3
55.1
92.5
66.4
66.0
84.2
73.9
Infested fruit tissur
plus larvae
nmol g - '
yo increase
62 732
20 662
41 595
40 876
63 69 1
11 808
43 439
67 209
27 040
98 674
52 387
99 424
54.105
83817
78 439
I8 549
107.8
133.1
53.8
91.3
106.2
73.1
83.7
86.5
77.6
112.8
70.5
122.8
88.4
81.4
110.6
131.8
R. A. I. DREW
110
TABLE
2. 'The amino acid content (g g - I ) in uninfested fruit of Solanurn rnauritianurn Scop. and in
fruit irifcested with Dams cacuminatus (Hering) and the total protein ("4) in each sample. Data
convcrtcd from Table 1
Uninfrstrd fruit
tissue
Infested fruit tissur
(larvae rrmoved)
0.0039
0.0012
0.0042
0.0022
0.003 I
0.0009
0.0027
0.0041
'l'yroainv
0.0026
0.0026
0.0013
0.0075
0.0026
0.0059
0.0038
0.0058
0.0014
0.0045
0.0070
0.0036
0.0 I20
0.0042
0.0110
0.0047
0.0043
0.0048
0.00'23
Total Protrin ( 1 1 ( , )
4.8
8.5
Amino acid
_..
.
~.
~~~
Lysinr
Histidinr
Arginiric
Thrronine
Valinr
Methioriinc
Isolrucinr
Lcucinc
I'tlcrlylalariinc
Asparaginr
Sc ri ne
Glntamine
Prolinc
Glycinc
Alaninr
0.0022
0.006 I
0.0027
0.0057
o.nw8
Irifrstrd fruit tissur
plus larvae
~____~_
o.no8 I
0.0028
0.0065
o.0042
0.0064
n.oo 16
0.0050
0.0076
o.m9
0.0 130
0.0046
0.0127
0.0053
0.0047
0.0055
o.0030
9.5
glutamic acid, asparagine plus aspartic acid, glycine, alanine, lysine, valine and
leucine were detected in higher levels than the other amino acids.
In the analyses based on HPLC, 14 amino acids were recorded (Table 4).
Rrginine and threonine curves overlapped on the printout and thus could not be
estimated and total protein contents were not calculated. There were some
unexplained differences in individual amino acid levels between experiments
which differed in both environmental conditions and analytical methodology.
However eight amino acids showed similar or higher percentage increases, in
infested fruit over uninfested fruit, to those in the first analysis, viz. alanine,
'I'ABLE 3 . Relativc ;hiridarice of each amino acid (:I;, of total) present in uninfcstcd fruit of
Solanurn rnauritianurn Scop. and in fruit infested with Dacus cacurninatus (Hering). Data calculated
from that in Table 2
Amino acid
~
.~
.._
_
..
I.ysinc
Histidine
A rgi n i n r
'l'lirruninr
Valinc
.Methioninc
Isulcuciiir
Leucinc
Phenylalaninc
Asparaginr
Serine
Glutarnine
Prrilint.
Glyciric
.Manine
'l'ymsirir
~
Uninlcstcd h i t
tissue
Infested fruit tissue
8. I
2.5
8.7
4.6
6.4
I .o
5.6
8.5
'1.6
12.6
5.6
11.8
5.8
5.4
5.4
2.7
8.8
3.0
6.9
4.5
6.8
I .6
5.3
8.2
4.2
14.1
8.0
4.1
13.7
4.9
12.9
5.5
5.0
5.6
2.7
13.4
5.6
5.0
5.8
3.2
(larvaca rrmovrd)
Inlistcd l i u i t tissiit.
plus larvae
~
~~~~
~~
~~~
8.5
3.0
6.8
4.4
6.7
1.7
5.3
4.8
-
AMINO ACID C O N T E N T OF F R U I T FLY INFESTED FRUIT
Ill
TABLE
4. T h e a m i n o acid content in uninfested fruit of Solanum mauritzunum Scop. a n d i n fruit
infested with Uucus ruruminutu ( H c r i n g ) , a n d percentage increases i n a m i n o acids d u e t o fruit fly
infestation. D a t a based o n 12 fruits of e a c h statc from Brisbane
Amino arid
Lysine
Histidine
Valine
Mcthionine
Isolcucinr
Lrucine
Phenylalanine
Asparagine
Serine
Glutamine
Proline
Glycine
Alarrine
'Iyrosine
Infestrd fruit tissue
(larvae removed)
Uninfested
fruit tissue
(rrmol g - ' j
nmol g - '
yo increase
Larvae plus eggs
(nniol g- ' j
7 446
13 990
31 996
8 624
I 7 634
27 870
12339
32819
29 199
41 805
34 009
33 972
41 161
10 356
12 063
25 322
55 704
I2 843
34 095
55 193
21 844
53 495
38 026
66 052
58 933
48 003
76 987
20 302
62.0
81.0
74.1
48.9
93.4
98.0
77.0
63.0
30.2
58.0
73.3
41.3
87.0
96.0
63 593
34 157
93.546
16 344
67 283
113.116
51 515
73.514
103.946
140 101
78 101
123 633
172 305
32 770
isoleucine, leucine, methionine, phenylalanine, proline, tyrosine and valine
(Table 4). T h e samples of larvae plus eggs possessed high levels of all amino
acids (Table 4).
DISCUSSION
During oviposition, fruit flies insert bacteria together with the eggs into the
host fruit. T h e subsequent growth of the bacterial colony appears to be
important to the developing larvae which always remain and feed in the
bacterial 'soup' (Courtice & Drew, 1984). T h e similarities in amino acid
composition between uninfested and infested fruit tissue lead one to suspect that
the plant is adding additional amino acids to the latter. This is, perhaps, a
process to repair damaged tissue. T h e marked increase in amino acid levels in
the fruit accompanying fruit fly infestation probably enhances the bacterial
growth. In turn, the bacteria most likely provide essential nutrients such as
amino acids and vitamins for the developing fruit fly larvae.
Recent studies (Drew, 1987) showed that the breeding season of the brown
pigeon coincides with the time of maximum fruit abundance on S. maurilinnum
and the peak level of infestation in the ripe fruit by the fruit fly D.cacuminatus.
There is 1 0 0 ~ infestation
0
of fruit at this peak and also more fruit is eaten by the
birds at that time. Crome (1975) noted that the breeding season of fruit pigeons
coincided with the period of peak fruiting of food plants and that ripe fruit (the
stage infested by fruit fly) is the one always selected for food.
The increased levels of amino acids in the infested fruit would be of value to
the pigeons, particularly during the breeding season. T h e high level of protein
i n the pigeon crop 'milk' for feeding the newly hatched young, and the
subsequent protein food required for the growing birds, could be obtained from
protein rich food such as fruit fly infested fruit.
Frugivorous birds have a longer nesting time than non-frugivores and
consequently are subjected to greater predation pressure (Morton, 1973). This
I12
K. A. 1. DREW
nest predation imposes strong selection pressure against birds using fruit as the
sole source of food for nestlings and many frugivores seek insects, at that time, as
an important protein supplement. The growth rate of young nestlings depends
on the rate at which the adult birds can provide essential amino acids (Morton,
1973). Fruit fly infested fruit of S. mauritianum would assist in providing this
dietary factor to the brown pigeon, and similar infested fruit in the rainforests
probably provides a valuable food source to a wide range of fruit eating
vertebrate animals.
ACKNOWLEDGEMENTS
Miss J. Bright, Department of Primary Industries, Brisbane, assisted in the
field sampling and amino acid analyses; the analyses were supervised by Dr J.
de Jersey, Department of Biochemistry, University of Queensland. This
assistance is gratefully acknowledged.
REFERENCES
COUK'I'IC:E, A. C. & DREW, K. A. I . , 1984. Bacterial regulation of abundance in tropical fruit flies
(Diptera: Tcphritidae). Auttmlian Zuulugist, 21: 251-268.
CROME, F. H. J.? 1975. 'I'he ecology of fruit pigeons in tropical northcrrr Queensland. Australian Wild&
Research, 2: 155-185.
CROME, E'. H. J., 1976. Some observations on the biology of the cassowary in northern Queensland. The
Emu, 76: 8-14.
1)K EM', K . A. I . , 1987. Reduction in fruit fly ('l'cphritidae: Dacinae) populations in their endcrnic. raiiifoi-rst
habitat by fi.u~ivctrtri~s
wrtebratrs. Austrdian Journaf qf<uoolu~y, 35: 283 288.
DREW, R. A. I . & HOOPER, G. H . S., 1983. Populations studies of fruit flies (Diptera: Trphritidae) in
south-east Queensland. Oeculogia (Berlin), 56: 153-159.
LEVI, W.M., 1963. 'The Pigeon. Sumter, South Carolina: Levi Publishing Company.
M O R T O N , F,. S., 1973. O n thr evolutionary advantages and disadvantages of fruit eating i n tl-opical birds.
il nimcau .hniurnli.tt, 107: 8-22.
STOCKEK, G . C. & IKVINE, A. K., 1983. Seed dispersal by
owarics (Casuarius casuarius) in north
Queensland rainforests. Bzulrupzca, 15: 170 176.