Advances in Biological Chemistry, 2011, 1, 65-73
doi:10.4236/abc.2011.13009 Published Online November 2011 (http://www.SciRP.org/journal/abc/ ABC ).
Published Online November 2011 in SciRes. http://www.scirp.org/journal/ABC
Biological and physiological parameters of Bulinus truncatus
snails exposed to methanol extract of the plant
Sesbania sesban plant
Wafaa Salim Hasheesh1, Ragaa Taha Mohamed2*, Sayed Abd El-Monem1
1Zoology Department, Faculty of Science, Cairo University, Gizo, Egypt;
2Zoology Department, Faculty of Science, Fayoum University, Fayyum, Egypt.
Received 22 August 2011; revised 27 September 2011; accepted 8 October 2011.
ABSTRACT
The effects of sublethal concentrations of methanol
extract of Sesbania sesban plant on survival rate, egg
laying of Bulinus truncatus snails, hatchability of
their eggs, infection rate with Schistosoma haemato-
bium miracidia, cercarial production and certain
physiological parameters of treated snails were stu-
died. The sublethal concentrations of the tested plant
extract (LC0, LC10 and LC25) caused considerable
reduction in survival rates; egg production of B.
runcates snails; hatchability of eggs as well as in the
infectivity of Schistosoma haematobium miracidia to
the snail. Also, the tested concentrations reduced the
cercarial production per snail and the period of cer-
carial shedding. The glucose level in haemolymph of
exposed snails was elevated while the glycogen, pro-
tein content and the activities of hexokinase (HK),
pyruvatekinase (PK) and lactate dehydrogenase (LDH)
showed a decrease in soft tissues when compared
with the control group. It was concluded that the app
lication of sublethal concentration of methanol ex-
tracts of Sesania sesban may be helpful in snail con-
trol as it interferes with the snails’ biology and phy-
siology.
Keywords: Bulinus truncates; Schistosoma haemato-
bium Miracidia; Susana sesban Plant
1. INTRODUCTION
Schistosomiasis is a public health problem of social and
economic importance in many d eveloping co untries call-
ing for international cooperation [1]. There is no doubt
that schistosomiasis is one of the major communicable
diseases and it is second to the malaria with socio-eco-
nomic and health importance in the developing world [2].
Controlling of the snail intermediate hosts of this parasite
by molluscicides (synthetic and/or of natural origin) is
still one of the most promising means in the battle a-
gainst this parasitic disease [3].
There is a great interest in the use of molluscicid es of
plant origin by local communities in self-sup porting sys-
tem of schistosomiasis control program. Such mollus-
cicides seem to be less expensive, readily available, rep-
idly biodegradable, have low toxicity to non-target or-
ganisms and probably easily applicable with simple te-
chniques appropriate to developing countries [4,5].
The plant Sesbania aegyptiaca proved to have a mol-
luscicial activity against Biomphalaria alexandrina snails
as water suspensions from its dry powder [6]. Thereafter,
S. sesban exhibited a marked toxic effect against the
snail’s Biomphalaria pfeifferi and B. truncatus [7]. The
methanol extract of Datura innoxia showed a promising
molluscicidal potency against B. alexandrina, B. trun-
catus and Lymnaea caillaudi snails [8]. In addition, me-
thanol extract of Datura stramonium has a strong anti-
fungal property against Fusarium mangiferae fungus
[9].
In order to promote energy production gastropods
categorize primarily carbohydrates, which are stored in
certain tissues as glycogen and transported in the
haemolymph as glucose [10]. The molluscicides greatly
affect the metabolic activities of the snail intermediate
hosts [11]. Also, they act on different enzymes chiefly
those of respiration and carbohydrate metabolism [12].
The present work was planned to study the mollus-
cicidal activity of methanol extract of Sesbania sesban
plant against Bulinus truncatus snails. As well, the ef-
fects of sublethal concentrations of this extract on the
snails mortality rates, longevity, egg laying , hatchability
of their eggs, infection rate with S. haematobium mirac-
idia, cercarial production and certain physiological pa-

W. S. Hasheesh et al. / Advances in Biological Chemistry 1 (2011) 65-73 66
rameters of treated snails were evaluated.
2. MATERIALS AND METHODS
2.1. Snails
Bulinus truncatus snails (6 - 8 mm) from laboratory bred
colony in Medical Malacology Dept., Theodor Bilharz
Research Institute (TBRI), and Giza, Egypt were used.
2.2. Miracidia
Schistosoma haematobium ova were obtained from Schi-
stosomiasis Biological Supply Center (SPSC), TBRI. Th e y
were left in clean dechlorinated water for hatching under
a desk lamp then fresh hatch miracidia were used in bio-
assay and infection tests.
2.3. Plants
The plant species used in this study are Sesbania sesban
(Fabaceae) from from Al-Orman garden, Giza, Egypt
(spring 2007). They were kindly identified by Botany
Dept., Faculty of Agricultu re, and Cairo University. Their
leaves were shade dried, then powdered by an electric
mill. The dry powder was stored in clean dry dark glass
bottle till use in biological tests.
Plant’s Extract
The dry powder of S. sesban plant was extracted by
Soaking with 95% methanol (0 .5 kg/liter) for seven d ays.
Then the solvent was filtered and distilled off under
vacuum and the crude extract residues were stored in
clean dry dark vessel till use [13].
2.4. Bioassay Tests
2.4.1. Mollu sc i c i dal Screening
A series of concentrations that would permit the compu-
tation of LC50 and LC90 was prepared on the basis of
weight/volume as water suspensions. Three replicates
(each of 10 snails/L) were prepared. Another 3 replicates
in dechlorinated water were used as control. Exposure
and recovery periods were 24 hours each at 25˚C ± 1˚C
[14,15]. Then, snails’ mortality was recorded and cor-
rected according to Abbots’ formula [16]. The LC0 was
estimated as 1/10 LC50 [14].
2.4.2. Effect on Snails’ Egg-Laying Capacity
For studying the mortality, longevity and egg laying of B.
truncatus, specimens of 120 adult snails (8 - 10 mm)
were randomly divided into 4 groups (30 snails each).
Three groups were continuously exposed to LC0, LC10
and LC25 of methanol extract of S. sesban plant, respec-
tively. The fourth group was left unexposed under the
same laboratory conditions as control. The tested plant
solutions were changed every 24 hours with new pre-
pared ones to avoid the effect of storage.
After each exposure period, snails were washed by
dechlorinated tap water. The snails were daily fed on
boiled lettuce leaves. Each aquarium was provided with
polyethylene sheets for ov iposition. The egg masses and
eggs laid on these sheets were counted using a binocular
steriomicroscope. Dead snails were removed daily from
aquaria and the mortality rate was calculated [17].
2.4.3. Effect on Egg Hatchability
For studying egg h atch a bility o f B. truncatus eggs of one,
three and six days age were used to examine the effect of
the tested plant on the different stages of egg develop-
ment. Each group of eggs was continuously exposed to
100 ml of plant extract solution of LC0, LC10 and LC25 in
a Petri dish till hatching. Another group of 50 eggs was
maintained in dechlorinated water as control.
2.4.4. Effect on Infection of B. truncatus Snails with
S. haematobium Miracidia
The effects of these sublethal concentrations on infection
rate of B.truncatus (5 mm - 7 mm in shell diameter) with
S. haematobium miracidia and cercarial production were
examined by exposing 3 groups, each of 50 snails, indi-
vidually to Schistosoma miracidia with a dose of 10 mi-
racidia/snail and maintained in each concentration of
plant extract (LC0, LC10 and LC25) for 24 hours under
room temperature (24˚C ± 1˚C) and ceiling illu mination.
After exposure to miracidia, snails were maintained in
their corresponding sublethal concentrations. Another
group of 50 snails was exposed to miracidia in the ab-
sence of the tested plant solutions and maintained under
the same conditions (control group). Examination of
snails for cercarial shedding was carried out twice week-
ly, 25 days post exposure, and the cercarial suspension
was poured in a graduated Petri dish, then few drops of
Bouin’s fluid were added and all cercariae were counted,
using a dissecting microscope. Shedding snails were the n
isolated and kept in special aquaria in complete dark-
ness.
2.5. Effect on Biochemical Parameters in Snails’
Hemolymph and Tissues
For studying the effect LC0, LC10 and LC25 of S. sesban
plant on some physiological parameters of B. truncatus
snails, four identical groups of B. truncatus (each of six
replicates) of which three groups were exposed to one
month to LC0, LC10 and LC25 of the tested plant, respec-
tively. The fourth group was maintained as con trol under
the same laboratory conditions, without exposure to
plant extract.
2.5.1. Ass ay Methods
Hemolymph samples were collected according to Mi-
chelson [18] by removing a small portion of the shell
and inserting a capillary tube into th e heart. The haemo-
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W. S. Hasheesh et al. / Advances in Biological Chemistry 1 (2011) 65-73 67
ABC
lymph pooled from 10 snails were collected in a vial
tube (1.5 ml) and kept in an ice-box. For preparation of
tissue homogenates of both exposed and unexposed snails,
one gram of snails soft tissues from each group was ho-
mogenized in 5 ml d istilled water pH 7.5. A glass homoge-
nizer was u sed and the homogenate was cen trifuged for 10
minutes at 3000 rpm, fresh supernatant was used .
Biochemical parameters were determined analyzed
spectrophometrically, using kits purchased from BioMe-
rieux Company, France. Total protein content was de-
termined according to Lowry et al. [19]. Determination
of tissues glycogen was evaluted according to Carrol et
al. [20]. Haemolymph glucose concentrations were de-
termined according to the glucose oxides method of
Trinder [21]. Hexokinase (HK) was assayed according to
the method of Yueda & Racker [22] in which glucose-6-
phosphate formed by the hexokinase reaction is mea-
sured by adding glucose-6-phosphate dehydrogenase and
NADP and following NADPH formation.
2.5.2. Pyruvate Kinase (PK)
PK relative activity was measured spectrophometrically
by the method of McManus and James [23]. Lactate de-
hydrogenase (LDH) as measured spectrophotometrically
according to Cabaud and Wroblewski [24].
2.6. Satistical Analysis
Snails’ mortality and infection rates were analyzed by
Chi-square values of contingency tables [25]. The mean
values of prepatent and patent periods, cercarial produc-
tion/snail and life span of infected snails in the tested
and control groups were compared using student “t” test
[26]. Statistical analysis was performed with the aid of
the SPSS comput er program (version 13.0 windows).
3. RESULTS
The molluscicidal activity of methanol extract of S. ses-
ban plant on B. truncatus snails after 24 hours of expo-
sure is presented in (Table 1). The data indicate that
LC50 and LC90 values for plant extract were 18 ppm and
31 ppm respectively. The sublethal concentrations (LC0,
LC10 & LC25) were found to be 1.8, 8 and 14 ppm re-
spectively.
The presen t results in Table 2 showed that a rapid in-
crease in mortality rate of exposed snails to sublethal
Table 1. Molluscicidal activity of methanol extract of Sesbania
sesban on Bulinus truncatus snails after 24 hours of exposure
under laboratory conditions.
Sublethal
Concentrations
LC50 ppm
(Confidence
limit) LC90 ppm Slope
function LC0 LC10 LC25
18
(15 - 21.6) 31 1.5 1.8 8 14
Table 2. Longevity of Bulinus truncatus snails exposed con-
tinuously to sublethal concentrations of methanol extract of
Sesbania sesban.
Longevity Bulinus tru nca tus sn ails (days)
Concentration Ppm Range Mean
LC0 2 - 40 22.5 ± 6.2
LC5 2 - 28 15.6 ± 6.4
LC10 2 - 22 11.8 ± 4 .2
Control 2 - 75 52.6 ± 11.5
concentrations of S. sesban methanol extract which is
significantly higher than that of control group. The data
revealed that no B. truncatus snails could survive more
than 40, 28 and 22 days in groups maintained at LC0,
LC10 and LC25 respectively with a mean life span of
22.5 ± 6.2, 15.6 ± 6.4 and 11.8 ± 4.2 days respectively
(Table 3). The death rate of B. truncatus snails in
groups treated with LC0 was highly significant as com-
pared with those in groups treated with LC10 and LC25
(p < 0.01).
Regarding the egg production of B. truncatus snails
exposed continuously to the sublethal concentrations of
S. sesban extract, Table 4 showed that control snail’s
proeeded the experimental ones in egg lying by 2 days.
Snails stopped egg lying after 28 days being exposed to
LC25 of plant extract, while snails treated with LC0 and
LC10 ceased to deposit eggs after 18, 9 days respectively.
The total mean number of eggs laid by treated snails
with LC0, LC10 and LC25 of plant extract throughout
their life span were 21.07, 10.39 & 5.62 versus 81.19
(No. of eggs/snail) in the control group. Regarding the
net reproductive rate (Ro), the results showed that all
experimental group s showed highly significan t reduction
(p < 0.01) in reproductive rate. This reduction was
74.05%, 87.2% and 93.08% for snails exposed to LC0,
LC10 and LC25 of plant extract respectively.
The eggs hatchability of snails exposed to sublethal
concentrations of S. sesban extract was decreased by
increasing their age after deposition (Table 5). Thus, hat-
chability rates of eggs exposed to LC25 of the tested
plant were 36%, 28% & 20% for 1, 3 and 6 days old
eggs respectively. The hatchability of eggs in the differ-
ent groups treated with sublethal concentrations was
significantly lower than that of control group (p < 0.001).
The effect of the tested sublethal concentrations of of
S. sesban extract on infection of B. truncatus with S.
haematobium miracidia was presented in (Tab le 6). The
infection rate was significantly lower than that of control
snails (75%), being 47.37%, 35.71% and 30% for snails
exposed to LC0, LC10 and LC25 respectively with a re-
duction rate 36.8 4%, 52. 39% and 60% respectively.

W. S. Hasheesh et al. / Advances in Biological Chemistry 1 (2011) 65-73 68
Table 3. Mortality percentage of Bulinus truncatus snails exposed continuously to sublethal concentrations of methanol extract of
Sesbania sesban plant.
Sublethal concentrations of methanol extract of Sesbania sesban (ppm)
LC0 LC10 LC25
Control
Duration of
experiment
(days) Cumulative
number of
dead snails
Cumulative
% mortality
Cumulative
number of
dead snails
Cumulative
% mortality
Cumulative
number of
dead snails
Cumulative
% mortality
Cumulative
number of
dead snails
Cumulative
% mortality
0 0 0 0 0 0 0 0
2 4 8 6 12 10 20 0 0
4 8 16 12 24 15 30 1 2
6 10 20 15 30 18 36 2 4
9 14 28 18 36 24 48 4 8
13 18 36 28 56 32 64 5 10
18 22 44 36 72 42 84 6 12
22 26 52 44 88 50 100 8 16
28 30 60 50 100 10 20
32 36 72 - - 14 28
36 42 84 - - 16 32
40 50 100 18 36
44 - 20 40
48 22 44
Table 4. Egg production of Bulinus truncatus snails exposed continuously to sublethal concentration of methanol extract of Sesbania
sesban.
Mean eggs number/snails
LC0 ppm LC10 ppm LC25 ppm Control
6
No. of
surviving snails Mean No. of eggs/snail No. of surviving snailsMean No. of eggs/snailNo. of surviving snailsMean No. of eggs/snail No. of surviving snails Mean No. of eggs/snail
0 50 0 50 0 50 0 50 3.1
2 48 2.1 44 1.2 40 2.8 50 10.8
4 42 3.8 38 2.1 35 3.8 49 12
6 40 5.8 35 4.5 32 1.2 48 8.6
9 36 4.2 32 2.2 26 0 46 10.2
13 32 2.1 22 1.2 18 45 15.2
18 28 2.2 14 8 44 7.2
22 24 1.2 6 50 42 6.5
28 20 0 50 40 4.2
32 14 36 4.2
36 8 34 4.7
40 0 32
Total 21.4 11.2 5.62 87.7
% Reduction 75.6% 87.23% 93.6%
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Table 5. Effect of methanol extract of Sesbania sesban on hatchability % of Bulinus truncatus ggs.
Mean eggs number/snails
LC0 ppm LC10 ppm LC25 ppm Control
6
No. of
surviving snails Mean No. of eggs/snail No. of surviving snailsMean No. of eggs/snail No. of surviving snailsMean No. of eggs/snail No. of surviving snails Mean No. of eggs/snail
0 50 0 50 0 50 0 50 3.1
2 48 2.1 44 1.2 40 2.8 50 10.8
4 42 3.8 38 2.1 35 3.8 49 12
6 40 5.8 35 4.5 32 1.2 48 8.6
9 36 4.2 32 2.2 26 0 46 10.2
13 32 2.1 22 1.2 18 45 15.2
18 28 2.2 14 8 44 7.2
22 24 1.2 6 50 42 6.5
28 20 0 50 40 4.2
32 14 36 4.2
36 8 34 4.7
40 0 32
Total 21.4 11.2 5.62 87.7
% Reduction 75.6% 87.23% 93.6 %
Table 6. Effect of sublethal concentrations of methanol extract of Sesbania sesban on infectivity of Schistosoma haematobium mirac-
idia to Bulinus truncatus snails.
Survived snails at first shedding Infected snails
Treatment Number of
exposed snails Number % Number %
%
Reduction
Control 50 46 92 36 75
LC0 (3ppm) 50 38 76 18 47.37 36.84*
LC10 (12ppm) 50 28 56 10 35.71 52.3 9**
LC25 (18ppm) 50 20 40 6 30 60***
*p < 0.05, **p < 0.01, ***p < 0.00.
Prepatent period (Table 7) of exposed snails to LC0,
LC10 and LC25 of tested plant was prolonged to be 29.5 +
1.6, 30.4 + 1.1and 32.1 + 4.2 days compared to 30.8 +
2.1days for the control group. Meanwhile, the duration
of cercarial shedding was significantly shortened among
these snails, being 11.6 + 2.2, 9.2 + 3.4 and 6.2 + 2.6
days for LC0, LC10 and LC25, respectively, compared
with 18.2 + 5.8 days for control snails. Highly signifi-
cant reductions of total cercarial production per snails
and per stimulant were also detected in experimental
snails in comparison with the con trol group.
The results in (Ta b le 8) show a significant reduction
(24.5 ± 2.2*, 16 ± 2.6** and 11 ± 2.8 mg/g tissue) in the
protein content in snails exposed to LC0, LC10 and
LC25, respectively of the tested plant, compared to their
corresponding control (38.23 ± 4.12 mg/g tissue). The
glycogen contents in tissues of the treated snails were
Table 7. Effect of sublethal concentrations of methanol extract
of Sesbania sesban on cercarial production of Schistosoma
haematobium from infected Bulinus truncatus snails.
Concentration
(ppm) Number of cercariae/snail Prepatent period (days) Duration of shedding (days)
LC0 (3ppm) 411.23 ± 651.1* 29.5 ± 1.6 11.6 ± 2.2**
LC10 (12ppm)284.11 ± 6,3** 30.4 ± 1.1 9.2 ± 3.4**
LC2 (18ppm)216.2 ± 14.2*** 32.1 ± 4.2* 6. 2 ± 2.6***
Control 111.2 ± 3 2 0 30.8 ± 2.1 18.2 ± 5.8
*p < 0.05, ** p < 0.01, *** p < 0.001.

W. S. Hasheesh et al. / Advances in Biological Chemistry 1 (2011) 65-73 70
Table 8. Effect of a month continuous exposure to metha nol ex-
tract of Sesbania sesban on glucose level in haemolymph, total
protein and glycogen content in soft tissues of Bulinus truncatus.
In soft tissue In haemolymph
Sublethal
concentrations
(ppm)
Protein content
(mg/g tissue)
Glycogen
content
(mg/g tissue)
Glucose level
in (mg/ml)
Control 38. 2 3 ± 4.12 30 ± 2 .4 27 ± 4.1
LC0 (ppm) 24.5 ± 2.2* 21 ± 1.2* 32 ± 1.2*
LC10 (ppm) 16 ± 2.6** 18 ± 2.6** 38 ± 1.8**
LC25 (ppm) 11 ± 2.8*** 12 ± 3.5*** 44 ± 2.5***
X ± SD mean of 4 experiment. *p < 0.05, **p < 0.01, ***p < 0.001.
significantly lower (p < 0.01) than in the control group.
On the other hand, glucose levels increased in snails ex-
posed to these concentrations of the tested plant in com-
parison with control ones. The results in (Table 9) showed
that the levels of Hexokinase (HK), Pyruvatekinase (PK)
and lactate dehydrogenase (LDI) in the soft tissues of
normal and treated snails were also significantly reduced
in repose to treatment with these concentrations of the
tested plant. The HK activity in snails exposed for one
month was 18.21 u/mg ± 2.2 u/mg, 14.14 u/mg ± 1.4
u/mg & 10.12 u/mg ± 2.1 u/mg tissue respectively. Such
reduced values were significant than those of the corre-
sponding control s (2 2 u/ m ± 1.4 u/m g t i ssue).
4. DISCUSSION
The methanol extract of the plant S. sesban showed con-
siderable molluscicidal effect against B. truncatus. The
LC50 and LC90 were found to be 18 ppm & 31 ppm re-
spectively. This agrees with the findings of Shoeb et al.
(1994) on the high toxicity of V. tinus against B. alexan-
drina, B. truncatus and L. caillaudi snails. The plant S.
sesban exhibited and acceptable toxic effect to B. alex-
andrina snails according to WHO, [1] recommendations
on plant molluscicides. Th is is coinciding with the activ-
ity of S. sesban against B. pfeifferi and B. trancatus
snails [7]. This effect could be due to the presence of 3
glucuronide derivatives of oleanolic acid in this plant
Table 9. Effect methanol extract of Sesbania sesban on hexo-
kinase (HK), Pyruvate Kinase (PK) and lactate dehydrogenase
(LDH) in the soft tissues of Bulinus truncatus snails.
PK (U/mg tissue)
× ± SD HK (U/mg tissue) × ± SD
LDH (U/mg
tissue)
× ± SD
Control 2.15 ± 2.9 22 ± 1 .4 1.8 ± 2.14
LC0 (ppm) 1.22 ± 2.40* 18. 21 ± 2.2* 1.15 ± 0.21*
LC10 (ppm) 0.82 ± 1. 4 ** 14.14 ± 1.4** 0.72 ± o.14**
LC25 (ppm) 0.62 ± 3. 1* ** 10.12 ± 2.1* ** 0.21 ± 0.81***
X ± SD mean of 4 experiment. *p < 0.05, **p < 0.01, p < 0.00 1.
species that have a high molluscicidal activity [6,28]. As
well, methanol extract from D. innoxia exhibited a re-
markable toxic effect against the snails B. alexandrina, B.
trancatus and L. caillaudi, and this could be due to the
presence of a compound from the coronaridine glycoside
derivatives [8] .
The results showed that there was a significant in-
crease in the mortality rates of snails exposed to sub-
lethal concentrations of the tested plant compared to the
control group. This finding agrees with those of Rawi et
al. [29,30], Bakry and Sharaf El-Din [31,32], Gawish et
al. [33]. They showed marked reduction in the survival
rate of snails treated with sublethal concentrations of
different plant species compared to the control.
Concerning the effect of sublethal concentrations of
the tested plant on egg production, it was found that B.
truncatus snails exposed to LC0, LC10 and LC25 of the
tested plant laid few eggs, then they stopped egg laying
from 28 to 9 days of experiment. Similar observations
were recorded on suppressing egg laying capacity of B.
alexandirna snails after 4 weeks of continuous exposure
to the dry powder of the plants Solanum nigrum and
Dizygotheca kerchoveana [5].
The authors attributed this to severe histological da-
mages to the snail’s hermaphrodite gland cells and eva-
cuations of some of its tubules from various gametoge-
netic stages. The same phenomenon was stated on the
plants Agave filifera and Agave attenuate [34] Ambrosia
maritime [35], Lantana camara and Salvia officinalis [36]
and Spiroli na pl atensi s [17] ag ai nst B. al exan drina snails.
Moreover, the present study showed that hatchability
of B. truncatus eggs exposed to sublethal concentrations
of the tested plant was decreased by increasing their age
and the plant concentrations. This is in agreement with
Gawish [17] who reported that the older embryonic
stages of B. truncatus eggs were more susceptible to the
experimental molluscicides than freshly laid ones. This
may be due to the thicker yolk layer surrounding the
embryo in freshly laid eggs than in older ones. This layer
and the egg membrane act as a mechanical barrier a-
gainst the molluscicides or other pesticides that could
not penetrat e t hese b ar ri e rs [37].
The present result also showed that LC25 of the tested
plant was significantly more effective against the hat-
chability of all developmental stages of eggs than LC0
and LC10. This result agrees with that reported by Tan-
tawy et al. [38] who found that hatchability of B. alex-
andrina eggs exposed to sublethal concentrations of So-
lanum dubium was decreased by increasing its concen-
trations.
In this study, the infectivity of S. haematobium mirac-
idia to B. truncatus was greatly reduced by the tested
sublethal concentrations of S. sesban. The reduction of
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W. S. Hasheesh et al. / Advances in Biological Chemistry 1 (2011) 65-73 71
infection rate was found to increase with the increase of
sublethal concentrations. These results are in once acc-
ords with many authors working on various chemical
and plant molluscicides [11,12,32,39,40]. This was re-
corded b y Ibr ahim et al. [5] on significant reduction of B.
alexandrina infection rates with S. mansoni miracidia
post their exposure to LC25 of P. repens dry powder.
Comparable results were obtained by Bakry [41] using
the plants Euphorbia splendens, Atriplex stylosa and
Guayacum officinalis and by Gawish et al. [33] on the
plant Callistemon citrinus against B. truncatus snails in-
fected with S. haematobium. The low production of cer-
cariae from snails treated with the present plants could
attribute, also, to initiation of certain componen ts in their
internal defense system. This was recorded by El-Emam
and Ebid [42] who found that treatment of B. alexan-
drina with the plant Calendula micrantha officinalis
increased the activity of acid phosphatase in snail’s tis-
sues, that has an important role in their defense system
and may has a negative reflect on cercarial production.
The same phenomenon was recorded by Mahmoud and
El-Sayed [43] on increasing AcP activity in tissues of S.
mansoni infected B. alexandrina snails treated with the
molluscicide niclosamide.
However, there was no significant difference between
the prepatent period of the snails exposed to LC25 of
methanol extract of the tested plants and the control.
Despite that, a highly significant reduction in the dura-
tion of cercarial shedding and total cercarial production
per infected snails were detected. This reduction in cer-
carial shedding period and total cercarial production per
snail is probably du e to rupture of snails’ tissues through
miracidial penetration in the presence of those mollus-
cicides which increased the harmful effects of these
plants on the subsequent development of the parasite
within snail’s tissues [44]. These observations are in
accordance with many authors using different plant spe-
cies as molluscicides. Thus, El-Ansary et al. [35] re-
ported that A. maritime caused a remarkable decrease in
cercarial shedding and cercarial production in B. alex-
andrina snails treated with this plant powder. Sharaf El-
Din et al. [32] obtained similar reduction in cercarial
shedding and cercarial production from B. alexandrina
treated with sublethal concentrations of aqueous suspen-
sion of Zygophyllum simplex.
In the present investigation, a significant decrease has
been recorded in the tissue protein in snails treated with
the concentrations of plant extract. This decrease may be
due to interference of the plant active substances with
protein synthesis. Similar results were reported by Ab-
del-Kader and Tantawy [34] and Bakry et al. [45] in B.
alexandrina using plant molluscicides.
The present study also indicated that LC25 of the
tested plant significantly decreased the glycogen content
in soft tissues while the glucose in hemolymph increased.
Consequently, the snail tries to obtain its energy re-
quirements through increasing the rate of glycolysis that
resulted in reduction of the glycogen and increase the
glucose in hemolymph. This finding was reported by
Bakry et al. [46] using Agave franzosini plant against B.
alexandrina, and Bakry [41] using Furcraea gigantean
and Lampranthus spectabilis plants.
In the present study the glycolytic enzymes, hexo-
kinase (HK), pyruvate kinase (PK) and lactate dehydro-
genase (LDH) in the snails tissues showed variable de-
crease between significant and highly significant on ap-
plying the tested plant. The depletion in HK activity in
the soft tissues causes an alteration of glycolytic mecha-
nism which in turn induces a state of anoxia .A similar
effect was detected by Bakry et al. [45] using plant ex-
tract and Mohamed et al. [47] using Abamectin as a mol-
luscicide. Another explanation for the reduction in PK
activity is may be due to the toxic effect of the tested
plant that minimizes ATP level by disturbing the enzy-
matic pathways contributing to ATP generation and hen-
ce depression of energy of the snails, metabolism .This
agreed with Bakry et al. [45] using plant extract. The
decrease in LDH activity in the soft tissues of B. alex-
andrina exposed to LC25 of tested plant may be attri-
buted to the release of the enzyme from the tissues as a
result of cellular damage caused by the toxic of the
tested plant. A similar result was detected by Aboul-
Zahab & El-Ansary [48].
From the above data, it can be concluded that the de-
pletion in tissue protein, glycogen, and activity of gly-
colytic enzymes (HK, PK & LDH) of B. truncatus snails
treated with the tested plant is mostly responsible for
reduction of egg production and the high rate of mortal-
ity in treated snails. Thus, the application of sublethal
concentrations of the methanol extract of Sesbania ses-
ban plant may play an important role in reducing the use
of chemical molluscicides without severe degree of en-
vironmental damage.
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