EFFECT OF VITAMIN B6 AND MELATONIN ON THE
BIOASSAY OF VARIOUS ECONOMIC CHARACTERS OF
SILKWORM, BOMBYX MORI L.
(LEPIDOPTERA: BOMBYCIDAE)
1
IBRAHIM A. I. SAAD1 AND USAMA M. GHAZY2
Department of Sericulture, Plant Protection Institute, Agricultural
Research Center, Sakha, Egypt
2
Department of Sericulture, Plant Protection Institute, Agricultural
Research Center, Giza, Egypt
(Received 30-11-2008)
INTRODUCTION
Much research has been done on the diet supplementation of mulberry leaves fed to
silkworms in order to improve the commercial characters of silkworm including vitamins,
sugars, proteins, amino acids, minerals etc. which are responsible for the proper growth and
development of the silkworm, B. mori. The vitamins such as ascorbic acid, thiamin, niacin,
folic acid and multi-vitamins were studied by (Etebari 2002 and Etebari et al., 2004.) It has
been reported that the vitamins of B-complex group and certain essential sugars, proteins,
amino acids, minerals etc. are responsible for the proper growth and development of the
silkworm, B. mori (Khan and Saha, 1997 and Faruki, 1998).
Melatonin (N-acetyl-5-methoxytryptamine) is an indoleamine originally identified in
the pineal gland, where it is synthesized enzymatically from serotonin (5- hydroxytryptamine)
(Namboodiri et al., 1987; Sugden et al., 1987). The activity of Melatonin was studied in the
mulberry silkworm, B. mori by some researchers (Sehadová et al., 2004). The present study
was attempted to supplement the mulberry leaves with Melatonin and Vitamin B6 at different
concentrations to determine their effect on the different biological aspects of silkworm B.
mori.
MATERIAL AND METHODS
The mulberry silkworm used for the present study was the Chinese hybrid (9F7X).
The larvae were reared under the laboratory hygrothermic conditions of 25±2°c and 65-70%
R.H., according to the conventional method in trays and provided with suitable amounts of
fresh mulberry leaves.
Bull. Ent. Soc. Egypt, 86, 2009 (109-1 14)
110
The experimental study was performed on the last larval instar. All larvae which
molted to the last instar at the same time were grouped and used for the experimentation. The
last larval instar was determined by (0 hour) from the last larval ecdysis (Peferoen and
Deloof, 1980). Tablets of commercial compound (Viva-Max) were used in this study. Each
Tablet Contain: N-Acetyl 5 Methoxy Tryptamine (Melatonin 3mg) and Pyridoxine
hydrochloride (Vitamin B6 10mg) manufactured by Amoun Pharmaceutical Co.(APIC) S.A.E,
Egypt. Tablets were offered to the larvae by feeding method after dissolved in distilled water
at different concentrations i.e. 3, 6, 9, 12, 15 and 18 ppm. The clean mulberry leafs were
dipped in different concentrations for 5 minutes and left to dry then provided to larvae, while
untreated larvae fed on clean mulberry dipped in distilled water only . Each treatment and
control has 20 replicates. The daily mean weight of larvae was recorded. The silk glands,
fresh pupae, fresh cocoons and cocoon cortex's mean weight were also recorded.
RESULTS AND DISCUSSION
1- Effect of Melatonin and Vitamin B 6 on the larval growth.
Data in Fig (1) show a gradual daily increase in the mean weights of last larval instar
during the feeding period from the beginning of the first day until reaching to its maximum
mean weights at 8th day (mature larva), then the larval weights showed a gradual decrease in
weights after the 8th day (beginning of spinning period) and during the pre pupal stage.
Table (1) showed that larvae treated with Melatonin and Vit.B6 presented an
increase in the mean weights of mature larvae at all concentrations, but the only significant
increase was 10.3% in the mean weight of treated larvae at concentration of 6 ppm compared
with untreated one. The present results are in agreement with the findings of Saha and Khan
(1996) who determined that mulberry silkworm reared on food supplemented with Vita-Plus
(a multivitamin + multimineral capsule) enhanced the larval growth.
2- Effect of Melatonin and Vitamin B6 on the silk gland.
Data in table (2) showed also that larvae treated with Melatonin and Vit.B6
presented a significant increase in the silk glands mean weight at concentration of 6 ppm
(17%) in comparison to control. These results are in agreement with the findings of ELKaraksy et al., (1983) who observed that B. mori silk glands were highly affected by
supplementing mulberry leaves by B-complex vitamins; and Saad (2005) who studied that
111
mulberry silkworm reared on food supplemented with minerals at low concentrations gave the
highest mean weight of silk glands.
Table (I)
Effect of Melatonin and Vitamin B6 on the mean weights of mature larvae.
Treatments
Mean Weight (gm) ± SD
2.5989 ± 0.380568
2.7306 ± 0.189169
2.8655 ± 0.160516
2.6948 ± 0.365655
2.6325 ± 0.275986
2.6685 ± 0.231983
2.6433 ± 0.233524
Control
3ppm
6ppm
9ppm
12ppm
15ppm
18ppm
Increase Or Decrease %
b
ab
a
b
b
b
b
5.1
10.3
3.7
1.3
2.7
1.7
There are no significant differences among the means with the same litters at
5% level according to LSD test.
Mean Weight (gm)
Fig:1 The Mean weights of mulberry silkworm after treatment with Melatonin and
Vitamin B6 during the last larval instar.
3.5
3
2.5
2
control
3ppm
1.5
6ppm
9ppm
1
12ppm
15ppm
0.5
18ppm
0
1
2
3
4
5
6
7
8
9
10
11
12
Days
3- Effect of Melatonin and Vitamin B 6 on the Silk Production.
Data in table (3) showed that larvae treated with Melatonin and Vit.B6 presented an
increase in the fresh cocoon mean weights at all concentrations except at 12 ppm where an
insignificant decrease (0.6%) was observed. Larvae treated with Melatonin and Vitamin B 6 at
concentrations of 3 ppm gave an insignificant increase of fresh cocoon mean weights (4.2%),
while significant increases of 11.6, 9.0 and 6.7% were observed at the concentrations of 6, 9
and 15 ppm respectively. An increase in the cocoon shell mean weight were also observed
when larvae were treated with Melatonin and Vit.B6, these increases ranged from 2.5 to
112
7.9%, but the only significant increase 7.9 % occurred in larvae treated with Melatonin and
Vit.B6 at the concentration of 6 ppm. The percentage of cocoon shell mean weight to the
pupal mean weight (Cocoon Shell Ratio) was calculated as 21.6 % in larvae treated with
Melatonin and Vit.B6 at concentration of 6 ppm without significant difference in comparison
to control larvae. These results are in agreement with the findings of ELKaraksy and Idriss
(1990) who observed that B. mori silk production was highly affected by supplementing
mulberry leaves by B-complex vitamins.
Table (II)
Effect of Melatonin and Vitamin B6 on the mean weights of Fresh Silk Glands.
Increase Or Decrease
Treatments
Mean Weight (mg)±SD
%
653 ± 11
d
Control
700 ± 11
bc
7.2
3ppm
764 ± 15
a
17.0
6ppm
716 ± 10
b
9.7
9ppm
648 ± 33
d
-0.8
12ppm
665 ± 17
c
1.8
15ppm
655 ± 23
d
0.3
18ppm
There are no significant differences among the means with the same litters
at 5% level according to LSD test.
Table (III)
Effect of Melatonin and Vitamin B6 on the mean weights of Fresh Cocoon and Cocoon Shell.
Treatments
Fresh Cocoon Mean
Weight (gm)±SD
Increase
Or
Decrease
%
Cocoon Shell
Mean Weight
(mg)±SD
Increase
Or
Decrease
%
Cocoon
Shell
Ratio %
Control
3ppm
6ppm
9ppm
12ppm
15ppm
18ppm
1.2424 ± 0.042535 c
1.2945 ± 0.148988 bc
1.3869 ± 0.077913 a
1.3541 ± 0.132362 ab
1.2352 ± 0.086138 c
1.3255 ± 0.227839 ab
1.29545 ± 0.05872 bc
4.2
11.6
9.0
-0.6
6.7
1.0
278 ± 16 b
293 ± 40 ab
300 ± 16 a
289 ± 40 ab
287 ± 25 ab
285 ± 19 ab
289 ± 25 ab
5.4
7.9
4.0
3.2
2.5
4.0
22.4
22.6
21.6
21.3
23.2
21.5
22.3
* There are no significant differences among the means with the same litters at 5% level
according to LSD test.
113
4- Effect of Melatonin and Vitamin 86 on the pupal weight.
As shown in table (4), larvae treated with Melatonin and Vit.B6 at all concentrations
except at 12 ppm presented an increase in the pupal mean weights. The highly and significant
increase of pupal weights were 12.7 and 10.4 % when larvae were treated with the
concentrations of 6 and 9 ppm, respectively.
Table (IV)
Effect of Melatonin and Vitamin B6 on the mean weights of Pupae.
Treatments
Control
3ppm
6ppm
9ppm
12ppm
15ppm
18ppm
Mean Weight (gm)±SD
0.9643 ± 0.039313
1.0015 ± 0.126277
1.0866 ± 0.075798
1.0647 ± 0.132776
0.9481 ± 0.084865
1.0407 ± 0.236365
1.0063 ± 0.060512
cd
bcd
a
ab
d
abc
bcd
Increase Or Decrease %
3.9
12.7
10.4
-1.7
8.0
4.4
* There are no significant differences among the means with the same litters at 5% level
according to LSD test.
These results are in agreement with the findings of Saha and Khan (1996) who
determined that mulberry silkworm reared on leaves supplemented with Vita-Plus (a
multivitamin + multimineral capsule) enhanced the pupal weight.
The present study showed that mulberry leaves supplemented with 6ppm of
Melatonin and Vitamin B6 had great effect on growth of the silkworm larvae and silk
production.
SUMMARY
Addition of Melatonin 3mg and Vitamin B6 10mg to mulberry leaves of silkworm,
Bombyx mori L. at 3, 6, 9, 12, 15 and 18 ppm concentrations was studied during the last larval
instar. The results indicated that larvae treated with low concentration (6 ppm) gave the
highest parameters and improvement in larval weight, cocoon weight, cocoon shell weight
and pupal weight. The significance of Melatonin and Vitamin B6 in the development of
silkworm with the economic characters is discussed.
114
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