Incorporation of Cestrum parquii (Solanaceae) Leaves in an ... - Iresa

Incorporation of Cestrum parquii (Solanaceae) Leaves in an
Artificial Diet Affected Larval Longevity and Gut Structure of
the Desert Locust Schistocerca gregaria
Mohamed Ammar, Département de Protection des Plantes et Maladies Post-récolte,
Institut National Agronomique de Tunisie, 1082 Cité Mahrajène, Tunisia, and
Sabrine N’cir, Direction Générale de la Protection et du Contrôle de la Qualité des
Produits Agricoles, Ministère de l’Agriculture et des Ressources Hydrauliques, 59
Avenue Alain Savary 1002 Tunis
____________________________________________________________________________
ABSTRACT
Ammar, M. and N’cir, S. 2008. Incorporation of Cestrum parquii (Solanaceae) Leaves in an
Artificial Diet Affected Larval Longevity and Gut Structure of the Desert Locust Schistocerca
gregaria. Tunisian Journal of Plant Protection 3: 27-34.
In laboratory, desert locust Schistocerca gregaria was fed with Cestrum parquii (Solanaceae) leaves
which are appreciated by this insect despite their toxic properties. Light microscopy observations revealed
that the foregut structure of the 5 th stage is modified at cuticular intima level where no exuvial space
could be seen up to 7 days of treatment. By the 9 th day of treatment, this space started to appear but no
new cuticle intimae were observed as in the case of the control. The height of the epithelial cells and the
thickness of muscular layers are reduced significantly. At midgut level, C. parquii eliminated
extracellular micro-organisms by intoxication. The food digestion by epithelial cells was precociously
achieved. On day 5, a proliferation of intra-cellular microorganisms was observed and then decreased on
day 7 to disappear on day 9 following plant toxin accumulation. In the controls, proliferation of intracellular
microorganisms was not observed before day 9.
Key-words: Cestrum parquii, gut, microorganisms, Schistocerca gregaria
____________________________________________________________________________
Plagues of desert locust, Schistocerca
gregaria, have been recognized as a threat
to agricultural production in North Africa
(12). Because of the difficulty to predict
locust outbreaks, the concerned countries
used to apply pollutant chemicals for
locust control (9). As an alternative and in
order to preserve the environment, these
countries tend presently to apply
preventive control methods based on the
Corresponding author: M. Ammar
ammar.med@inat.agrinet.tn
Accepted for publication 9 May 2008
use of components considered as safe for
the ecosystem (11).
Within this control concept, some
plant extracts including those of Olea
europea in Tunisia (3), Eucalyptus
gomphocephala in Algeria (8) and
Azadirachta indica in Mauritania (4) were
tested against desert locust larvae. All
these plant extracts revealed toxic effects
on locust larvae and were considered as
effective in the control of S. gregaria.
Some recent works investigating the
effect of Cestrum parquii (Solanaceae)
leaves on insects show the cytotoxical
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Vol. 3, No. 1, 2008

activity of this plant at foregut and gastric
caeca level (6, 1). This cytotoxical activity
was confirmed by Kammoun et al. (10) by
electronic microscope observation on
human sperm.
The aim of this work is to determine
the effects of C. parquii leaf powder
incorporated in an artificial diet on the
longevity of the treated desert locust larvae
and their excrement dry weight and to
assess its effect on fore- and mid-gut
structures at the cytological level.
MATERIALS AND METHODS
Batches of 20 locust larvae in 5 th
instars from a desert locust mass rearing
conducted in laboratory were fed with a
2% C. parquii leaf powder artificial diet
(14). The control larvae were fed with a
2% cabbage flour powder.
Longevity (days)
16
14
12
10
8
6
4
2
0
Daily mortality and excrement are
recorded during 9 days (life of the 5 th
instars larvae). Excrements are dried in 40°
C drying oven during 48 hours before
weighing.
Larvae are dissected on day 5, 7 and 9
to collect guts. Samples of guts were fixed
in Bouin and then embedded in paraffin
and 7 µm layers were stained in Patay (11)
for light microscopy observations.
RESULTS
Effect on longevity. The effect of C.
parquii on larval longevity was first
observed on day 4 and increased on day 9
(Fig. 1). At this stage, the control larvae
moult whereas most of the treated larvae
died following moulting difficulties.
1 2 3 4 5 6 7 8 9
Age (days)
C. parquii leaves Control
Fig. 1. Effect of C. parquii treatment on the longevity of S. gregaria larvae according to the age.
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Vol. 3, No. 1, 2008

Effect on excrement weight. Fig. 2
shows the lack of anti-appetence toward
fresh C. parquii leaves of locust larvae at
the beginning of food intake. At day 3, a
toxic effect was observed within the
Mean excrement weight (g)
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
treated larvae resulting in larval mortality.
This toxic effect becomes significant by
day 6, which generally corresponds to the
moulting stage of the locust.
1 2 3 4 5 6 7 8 9
Age (days)
C. parquii leaves Control
Fig. 2. Effect of C. parquii treatment on individual excrement dry weight of S. gregaria larvae according to the age.
Effect on foregut structure. From
plate 1 (A and B), it appears that on the 5 th
day, the epithelium is recovered by cuticle
intimae for treated larvae as in the case of
the control. By the 7 th day, the cuticle
intimae appears to be thinner in the treated
larvae (plate 1, C and D). Plate 1 (F)
revealed that exuvial space and new
cellular intimae were very conspicuous in
the control larvae. While intact epithelial
cells and thick muscular layers were
observed in the control with a clear
separation between the new and the old
intimae, very disturbed thin and non
separated layers were seen in the treated
larvae with important signs of cell damage
(plate 1, E and F).
Effect on midgut structure. The
development of intra-cellular
microorganisms was observed earlier
within treated larvae (day 5) as compared
to control larvae (day 9) (plate 2, A and F).
In fact, from plate 2 (B and D) it is
apparent that microorganisms did not
appear at days 5 and 7, as in the untreated
control. By contrast, numerous apparently
health microorganisms were detected in
the C. parquii fed larvae at day 5, but
never at day 7 and 9. The number of these
microorganisms was significantly reduced
and they revealed evident signs of
intoxication and degeneration as indicated
by the presence of pycnotic nuclei (plate 2,
C and E).
We notice that epithelium structure
does not show yet difference between
treated ant control insects midgut, due
probably to the fact that cellular
development occurs after this digestion
phase.
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Plate 1. Light microscope photographs of S. gregaria larval foregut structure after 5, 7, and 9 days of C. parquii
leaves treatment
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Plate 2. Light microscope photographs of S. gregaria larval midgut structure after 5, 7, and 9 days of C. parquii
leaves treatment.
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DISCUSSION
In concordance with these
observations, our previous results (2)
showed that the rates of total and soluble
proteins in the cuticle increased at the end
of the 5 th stage of desert locust larvae fed
with C. parquii leaves and accumulated
in the cuticle following protease
inhibition effect. These investigations
showed also that the cuticle was modified
at the external integument level. The
same authors concluded that in the lack of
exuvial liquid at apolysis, the reabsorbing
process is disturbed and the exuviation
does not occur.
Previous studies indicated that under
normal conditions, the extracellular
microorganisms inhibit the digestion
enzymes in the midgut (13). Once the
nutrient needs of these microorganisms
are achieved, the inhibition is stopped and
degradation products are absorbed by gut
cells. At this stage, intra-cellular
microorganisms use these products in
order to achieve the digestion process
(13).
In the case of C. parquii treated
larvae, therefore, extracellular
microorganisms seem to be destroyed by
C. parquii saponins (3). The inhibition of
digestion enzymes is observed earlier and
on day 5 the intra-cellular
microorganisms use the nutrients
absorbed by intestinal cells for their
further digestion. In the presence of
saponins, these intra-cellular
microorganisms degenerate and show
pycnotic nuclei on day 7. Investigations
about the identification of chemical
structure of active substances,
demonstrate that these compounds are
steroids saponins (steroid aglycone linked
to oligosaccharide chain) (5).
ACKNOWLEDGMENTS
This research was supported by funds ECproject
« Development of a strategy for locust
control, starting from new developments in insect
endocrinology ». We thank Dr M. Chérif and H.
Ben Salah for the revision of the manuscript.
___________________________________________________________________________
RESUME
Ammar M. et N’cir S. 2008. Incorporation des feuilles de Cestrum parquii (Solanaceae) dans un
milieu artificiel affecte la longévité et la structure du tube digestif du criquet pèlerin Schistocerca
gregaria. Tunisian Journal of Plant Protection 3: 27-34.
Au laboratoire, le criquet pèlerin Schistocerca gregaria a été nourri par les feuilles de Cestrum parquii
(Solanacées) qui sont appréciées par cet insecte malgré leurs propriétés toxiques. Au microscope
photonique, la structure de l’intestin antérieur du 5 ème stade larvaire est modifiée au niveau de l’intima
cuticulaire qui montre l’absence de l’espace exuvial jusqu’au 7 ème jour du traitement. Au 9 ème jour, il
commence à se former sans que les nouvelles intima cuticulaires n’apparaissent, par contre, elles sont
déjà formées chez le témoin. Les cellules épithéliales diminuent de la hauteur et les couches
musculaires deviennent moins épaisses. Au niveau de l’intestin moyen, le C. parquii détruit les
microorganismes extracellulaires par intoxication. La digestion du bol alimentaire par le tissu épithélial
se fait précocement. Au 5 ème jour, nous observons une prolifération des microorganismes
intracellulaires qui diminue au 7 ème jour pour s’estomper au 9 ème jour suite à une accumulation des
toxines végétales. Chez le témoin, la prolifération des microorganismes intracellulaires ne se manifeste
qu’à l’âge de 9 jours.
Mots clés : Cestrum parquii, intestin, microorganismes, Schistocerca gregaria
___________________________________________________________________________
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Vol. 3, No. 1, 2008

___________________________________________________________________________
ﺀﺍﺫﻐﻝﺍ
ﻲﻓ
( ﺕﺎﻴﻨﺎﺠﻨﺫﺎﺒ)
Cestrum parquii
ﻲﻝﺎﺠﻝﺍ ﻙﺴﻤﻝﺍ ﻕﺍﺭﻭﺃ
. 2008
ﺹﺨﻠﻤ
. ﺭﻴﺼﻨ ﻥﻴﺭﺒﺎﺼﻭ
ﺩﻤﺤﻤ ،ﺭﺎﻤﻋ
Tunisian Journal of Plant Protection 33
Vol. 3, No. 1, 2008
لﺎﺨﺩﺇ
. ﺎﻫﺩﻨﻋ ﻲﻌﻤﻝﺍ ﺔﻴﻨﺒﻭ Schistocerca gregaria ﻱﻭﺍﺭﺤﺼﻝﺍ ﺩﺍﺭﺠﻝﺍ
ﺕﺎﻗﺭﻴ ﺭﻴﻤﻌﺘ ﻲﻓ ﺭﺜﺅﺘ
ﻲﻋﺎﻨﻁﺼﻻﺍ
Tunisian Journal of Plant Protection 3: 27-34.
Cestrum parquiiﻲﻝﺎﺠﻝﺍ
ﻙﺴﻤﻝﺍ ﻕﺍﺭﻭﺄﺒ
Schistocerca gregaria
ﻱﻭﺍﺭﺤﺼﻝﺍ ﺩﺍﺭﺠﻝﺍ
ﺔﻴﺫﻐﺘ
،ﺭﺒﺨﻤﻝﺍ ﻲﻓ
ﺔﻴﻨﺒ ﻲﻓ ﹰﺍﺭﻴﻐﺘ ﻲﺌﻭﻀﻝﺍ ﺭﻬﺠﻤﻝﺍ ﺕﺎﻅﺤﻼﻤ ﺕﺭﻬﻅﺃ . ﺔﻓﻭﺭﻌﻤﻝﺍ ﺔﻴﻤﺴﻝﺍ
ﺎﻬﺼﺌﺎﺼﺨ ﻡﻏﺭ ﺓﺭﺸﺤﻝﺍ
ﺎﻫﺫﺒﺤﺘ
ﻲﺘﻝﺍ ( ﺕﺎﻴﻨﺎﺠﻨﺫﺎﺒ)
ﻡﻭﻴﻝﺍ ﻰﺘﺤ ﻲﺨﻼﺴﻨﻻﺍ لﺌﺎﺴﻝﺍ ﺏﺎﻴﻏ ﻊﻤ ﺔﻤﻴﻤﺤﻝﺍ ﺓﺭﺸﺒﻝﺍ ﻯﻭﺘﺴﻤ ﺩﻨﻋ ﺱﻤﺎﺨﻝﺍ ﺭﻭﻁﻝﺍ ﻲﻓ ﺔﻗﺭﻴﻝﺍ ﺩﻨﻋ ﻲﻤﺎﻤﻷﺍ ﻲﻌﻤﻝﺍ
،ﺩﻫﺎﺸﻝﺍ
ﺩﻨﻋ ﺔﻅﺤﻼﻤﻝﺍ ﺔﻤﻴﻤﺤﻝﺍ ﺓﺭﺸﺒﻝﺍ
ﺭﻭﻬﻅ ﻥﻭﺩﺒ
ﻥﻜﻝﻭ لﺌﺎﺴﻝﺍ ﻥﻭﻜﺘ ﺃﺩﺒ ،ﻊﺴﺎﺘﻝﺍ ﻡﻭﻴﻝﺍ لﻭﻠﺤﺒﻭ
. ﺔﻠﻤﺎﻌﻤﻝﺍ
ﻥﻤ ﻊﺒﺎﺴﻝﺍ
ﺕﺎﻨﺌﺎﻜﻝﺍ ﻲﻝﺎﺠﻝﺍ ﻙﺴﻤﻝﺍ لﺍﺯﺃ ،ﻁﺴﻭﻷﺍ
ﻲﻌﻤﻝﺍ
ﻯﻭﺘﺴﻤ ﻰﻠﻋﻭ
. ﺔﻴﻠﻀﻌﻝﺍ ﺔﻘﺒﻁﻝﺍ ﺔﻜﺎﻤﺴﻭ
ﺔﻴﺌﻼﻁﻝﺍ ﺎﻴﻼﺨﻝﺍ ﻭﻠﻋ ﺽﻔﺨﻨﺍ
،ﺱﻤﺎﺨﻝﺍ ﻡﻭﻴﻝﺍ ﻲﻔﻓ
. ﹰﺍﺭﻜﺒﻤ ﻲﺌﻼﻁﻝﺍ ﺞﻴﺴﻨﻝﺍ ﻑﺭﻁ ﻥﻤ ﻲﺌﺍﺫﻐﻝﺍ ﻊﻠﺒﻝﺍ ﻡﻀﻫ ﻊﻗﻭﻭ
،ﻡﻤﺴﺘﻝﺍ
ﺔﺠﻴﺘﻨ ﺎﻴﻼﺨﻝﺍ ﺝﺭﺎﺨ ﺔﻘﻴﻗﺩﻝﺍ
ﻡﻜﺍﺭﺘ ﺭﺜﺇ
ﻊﺴﺎﺘﻝﺍ ﻡﻭﻴﻝﺍ ﻲﻓ ﺕﻔﺘﺨﺍﻭ ﻊﺒﺎﺴﻝﺍ ﻡﻭﻴﻝﺍ ﻲﻓ ﺎﻫﺩﺍﺩﻋﺃ ﺽﺎﻔﺨﻨﺍ ﻡﺜ ﺎﻴﻼﺨﻝﺍ لﺨﺍﺩ ﺔﻘﻴﻗﺩﻝﺍ
ﺕﺎﻨﺌﺎﻜﻝﺍ ﺭﺎﺸﺘﻨﺍ ﻅﺤﻭﻝ
. ﻊﺴﺎﺘﻝﺍ ﻡﻭﻴﻝﺍ ﻲﻓ ﻻﺇ ﺩﻫﺎﺸﻝﺍ ﺩﻨﻋ ﺎﻴﻼﺨﻝﺍ لﺨﺍﺩ
ﻡﺘ
ﺎﻤﻜ
ﺔﻘﻴﻗﺩﻝﺍ ﺕﺎﻨﺌﺎﻜﻝﺍ ﺭﺎﺸﺘﻨﺍ ﺔﻅﺤﻼﻤ ﻡﺘﺘ ﻡﻝ ﻥﻴﺤ ﻲﻓ ،ﺔﻴﺘﺎﺒﻨﻝﺍ ﻡﻭﻤﺴﻝﺍ
Schistocerca gregaria Cestrum ، parquii ،ﺔﻘﻴﻗﺩ
ﺕﺎﻨﺌﺎﻜ ،ﺀﺎﻌﻤﺃ : ﺔﻴﺤﺎﺘﻔﻤ ﺕﺎﻤﻠﻜ
___________________________________________________________________________
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