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International Journal of Marine Science 2013, Vol.3, No.40, 319-332
http://ijms.sophiapublisher.com
322
the creek and pond sediments, their abundance was far
lesser varying between non-detectable levels to 0.10 × 10
3
CFU g
-1
. Counts of LB were found to be below detectable
levels in hepatopancreas between 105 to 135-doc.
1.3 Correlation analysis
None of the measured environmental variables
(temperature, salinity, pH, DO) showed any significant
correlation with bacterial abundance either in rearing
water and/or in the pond sediments.
1.4 Bacterial characterization
A total of 114 and 42 bacterial isolates from shrimp
pond components and source water respectively were
retrieved from TCBS plates. The representative
isolates were identified according to cultural,
morphological and biochemical characteristics.
Species composition of
Vibrio
communities recovered
from shrimp pond components and source water have
been presented in Table 2. Among the pond
components, maximum isolates were retrieved from
rearing water (42%), followed by pond sediment (18%)
and shrimp hepatopancreas (13%).
The
Vibrio
community remained fairly diverse
throughout the culture period. Within the shrimp
culture system, closely related
Aeromonas
spp.,
V.
fluvialis,
and
V. metschnikovii
were most dominant
(Table 3). Species such as
V. mimicus
,
V. mediterranei
,
V. gazogenes, V. harveyi
and
V. hollisae
contributed
less than 10% of the total isolates. Relatively low
species diversity was noticed in source water with a
dominance of
Aeromonas
spp
.
,
V. fluvialis,
and
V.
metschnikovii
. In rearing water,
Aeromonas
spp.
showed complete dominance at 34% although
V.
fluvialis
(15%) and
V. metschnikovii
(12%) were
consistently present during the culture period. In
pond sediment,
Aeromonas
spp. dominated followed
by
V. fluvialis
(13%) and showed a greater species
diversity in the middle and later stages of the culture.
The
Vibrio
community in the hepatopancreas had
limited diversity through the culture period with
V.
metschnikovii
and
V. salmonicida
being some of the
dominant strains. The presence of
V. logei
and
V.
marinus
was also observed in the hepatopancreas.
Table 2 Composition of vibrios and closely related pathogenic species isolated from shrimp pond components during cultivation of
Penaeus monodon
Species
Number of isolates
Source water
Pond water
Pond sediment
Shrimp hepatopancreas
Aeromonas spp.
9 (23)
23 (35)
12 (41)
5 (25)
Phenon 10/85
2 (5)
-
-
1 (5)
Phenon 21
2 (5)
-
-
-
Plesiomonas shigelloides
-
-
3 (10)
-
V. fluvialis
6 (15)
8 (12)
4 (14)
1 (5)
V. furnissii
-
-
2 (7)
-
V. gazogenes
1 (2)
2 (3)
1 (3)
1 (5)
V. harveyi
-
2 (3)
-
-
V. hollisae
-
2 (3)
1 (3)
-
V. logei
-
-
-
1 (5)
V. marinus
-
-
-
2 (10)
V. mediterranei
2 (15)
4 (6)
1 (3)
1 (5)
V. metschnikovii
11 (28)
10 (15)
3 (10)
5 (25)
V. mimicus
6 (15)
6 (9)
2 (7)
-
V. natriegenes
-
1 (2)
-
-
V. ordalii
1 (2)
2 (3)
-
1 (5)
V. salmonicida
-
4 (6)
-
2 (10)
V. splendidus II
-
1 (2)
-
-
Total no. of isolates
42
65
29
20
Percentage of isolates
27
42
18
13
Note:
Isolates retrieved from shrimp pond components = 114 and source water = 42; total isolates = 156. Percentage of isolates is
given in parenthesis