Biology Reference
In-Depth Information
Table 15.11.
Activity of extracts from
C. microphylla
on pupation and emergence parameters of
S. frugiperda
(after 21 days of incubation)
a
.
Mean time
pupation
(days)
b
Mean
emergence
(days)
d
Conc.
(ppm)
Pupation
SP (%)
e
Mean weight
pupae (mg)
c
Emergence
(%)
f
Female
(%)
Treatment
Male (%)
Control
22.0
88.2
309.5 ± 15.47a
33
77.50
35
42.5
n
-hexane
2.0
22.0
60.6
190.5 ± 11.43a
31
8.3
8.3*
-
10.0
22.5
22.8
180.9 ± 9.78b
33
8.3
8.3*
-
25.0
24.0
16.8
122.7 ± 8.79b
-
0.0
-
-
50.0
n.d.
0
n.d.
-
0.0
-
-
Ethyl
acetate
2.0
21.5
68.3
227.6 ± 11.38a
33
16.7
8.3
8.3
10.0
24.0
25.7
150.8 ± 7.54b
36
8.3
8.3*
-
25.0
25.0
12.5
148.8 ± 7.44b
-
0.0
-
-
50.0
25.0
6.3
n.d.
-
0.0
-
-
MeOH
2.0
22.0
52.3
205.3 ± 10.26a
32
16.6
8.3*
8.3
10.0
25.0
26.3
119.9 ± 5.49b
35
8.3
8.3*
-
25.0
25.0
6.3
109.0 ± 4.44b
-
-
-
-
50.0
25.0
0
n.d.
-
-
-
-
Gedunin
10.0
22.5
49.8
111.5 ± 5.57b
34
16.6
8.3
8.3
25.0
23.0
24.2
67.1 ± 3.35c
35
15.6
5.2
10.4
50.0
24.0
4.17
d
55.1 ± 2.75c
36
4.17
4.17*
-
Me-Ced
2.0
21.5
78.4
235.9 ± 1179a
33
33.3
11.1
22.2
10.0
22.0
56.2
148.2 ± 7.41b
33
30.5
10.2
20.3
25.0
23.5
29.5
124.3 ± 6.21b
34
20.8
10.4
10.4
50.0
24.5
18.2
119.2 ± 5.54b
34
16.7
-
16.7
a
The values for growth bioassay were from weight, values taken at 22 ± 1 days before pupation, the criteria followed
were to account for larvae that formed pupae; the larvae that did not form pupae were counted as dead larvae.
b
Values
taken after pupation. The values for aqueous extract were omitted because they are irrelevant, and this extract did not
show any effect at all assayed concentrations.
c
Means followed by the same letter within a column after ± standard error
values are not significantly different in a Student-Newman-Keuls (SNK) test at
p
<0.05 (treatments are compared by
concentration to control), 95% confidence limits.
d
Percentage with respect to control.
e
SP: survival pupation = number of
surviving pupae × 100/total larvae for pupation.
f
% = Number of adults emerged × 100/total number of pupae. The
asterisks indicate deformities.
(2.0 and 10 ppm, 83.4 and 91.7%, respec-
tively), and at these concentrations deformi-
ties could be also observed. Moreover, at
concentrations between 2.0 ppm and 0.5 ppm
this extract from
C. microphylla
signifi-
cantly blocked the percentage of adult emer-
gence, because no viable adults can emerge
from pupae in this step.
In this study, analysis of the test insect
fed with
C. microphylla
extracts revealed a
developmental disruption in which the
insects died (between 10 and 25 ppm) dur-
ing pharate conditions after initiation of
moulting (the apolysis step), without com-
pletion of morphogenesis. These last sub-
stances act in concert to trigger insect
ecdysis during the final stages of the moult.
Thus, the
n-
hexane extract of
C. microphylla
may disrupt several steps of ecdysteroid
metabolism to result in an inhibition of
emergence behaviour, or alternatively may
act directly by inhibiting the release of ETH
(Hesterlee and Morton, 1996). In our case,
and based on toxicological information, the
accumulation of long-chain
n-
alkanes as
hentriacontane, for instance, by means of an
unknown mechanism of action, could be
affecting the complete morphogenesis of
the insects used in our study. Because the
hydrophobic environment prevents the
action of enzymes, which require an aqueous
medium for action (Jung and Deetz, 1993),
all these considerations are supported under
the evidence shown in Table 15.12, where
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