Basic HTML Version
International Journal of Aquaculture, 2014, Vol.4, No.11 67
-
72
http://ija.biopublisher.ca
69
Smoked samples of the fish species (
Clarias gariepinns
)
were obtained from smoked fish market stall at Oja
oba market, Owo, Ondo State, Nigeria. The fish
samples showed no visible presence of neither
adult or larvae of
D. maculatus
infestation. The
cured fish species were sterilized thermally by
heating at 10
℃
for one hour in a hot air oven
(Gallenkamp Oven) in the laboratory in order to
kill any insect pests that may be present (Atijegbe,
2004), and allow to cool at room temperature in the
laboratory.
1.4 Effect of
P. fraternus
powder on larvae and
adult emergence of
D
.
maculatus
The toxic effect of
P. fraternus
on larvae
D. maculatus
was carried out using 250ml plastic containers
containing 15g of smoked fish with concentration of
1.0g 2.0g, 2.5g and 3.0g for set A experiment, while
set B experiment were admixed with concentration of
3.5g, 4.0g, 4.5g and 5.0g.
The smoked fish in control
dish contained no plant powder. The containers were
gently shaken for 2 min to ensure homogenous
mixture (Adesina et al. 2012) of the smoked fish and
treatment powder. Ten newly emerged (0-72h old)
larvae of
D. maculatus
were introduced into each
treated and control dish and covered. Each treatment
was in triplicate. Larvae mortality was counted every
24hours for 5days. The insects were confirmed dead
when there was no response to probing with sharp pin
at the abdomen (Adedire et al.., 2011). Daily
observations were made until adult emergence. The
number reaching adult stages was recorded and
percentage weight was also recorded. The percentage
reduction in adult emergence of F1 progeny was
calculated using the formula:
Percentage adult emergence reduction = 100 ×(No. of
adult insect emerged in control dish
－
No. of adult
insect emerged in treated dish) / No. of adult insect
emerged in control dish.
The % loss in weight was determined and recorded
using the method described by Odeyemi and
Daramola (2000).
% Weight loss = 100 ×(initial weight of fish sample
－
final weight of fish sample) / initial weight of fish
sample.
1.5 Phytochemical Analysis of
P. fraternus
Sample of the plant leaf powder was chemically tested
for qualitative phytochemical constituents using
standard procedures recommended by Trease and
Evans (1989); Harbone (1984); Mehta et al. (2013)
and Umoh et al. (2013). For tannin, 5 g of each
portion of plant extract was stirred with 10 ml of
distilled water and filtered as described by Trease and
Evans (1998). Blue black, green, or blue-green
precipitate formed following the addition of few drops
of 5% ferric chloride was taken as evidence for the
presence of tannins. Deposition of a red precipitate
when aqueous solution of leaf extract was boiled with
1% (v/v) HCl was taken as evidence for the presence
of phlobatannin. Salkowski’s test, as described by
Sofowora (1993), was used to test for cardiac
glycosides. Leaf extract (0.5 g) was dissolved in 2 ml
of chloroform prior to the careful addition of 1% (v/v)
H
2
SO
4
to form a lower layer. A reddish-brown colour
at the interface was taken as evidence for the cardiac
glycoside. Borntrager’s test was used for the detection
of anthraquinones (Heyde et al., 1984). Plant material
(5 g) was shaken with 10 ml benzene and filtered.
Ammonia solution (5 ml, 10%) was added to the
filtrate and a pink, red, or violet colour which was
formed in the ammoniacal (lower) phase was recorded
as an indication of the presence of free
anthraquinones.
1.6 Experimental Design and Data Analysis
The experiment was laid out in Complete Randomised
Design (CRD) and each treatment was replicated three
(3) times. Data were subjected to analysis of variance
and where significant differences existed, treatment
means were separated using Least Significant
Difference (LSD) at 5% probability level. Data in
percentage were arcsine transformed before analysis.
2 Results
Table 1 shows the mortality rate of
D. maculatus
larva
over a period of 120h after infestation. The results
revealed that the plant powder exert significant
(P<0.05) larva mortality with increase in application
rate over time exposure; except for 24h after
infestation in treatment A. In all the experiments
dishes treated with 3g and 5g
P. fraternus
had the
highest larval mortality, while fish protected with 1g
and 3.5g had the lowest mean values of larval
mortality respectively in both treatments.