160
......
ro
>
.~
>
":::J
U)
60 :' 1
:\. ,
.'
,
40 :.:
\j
.'
,
. .
,
".",
\
20
'.
5
10
15
20
25
30
35
Time (days)
Fig. 1. Survival (mean±S.D.) of S. proboscideus as a function
of algal concentration. Symbols represent algal levels (x 1000 cells
ml- 1 ) asterisk: 0.5; filled square: 1; unfilled circle: 5; unfilled
square: 10; unfilled diamond 50; filled triangle: 100, and unfilled
triangle: 500.
14
12
10
E B
E
Cl>
ffi 6
5
10
15
20
25
30
35
Age (days)
Fig. 2. Size (length) (mean±S.D.) of S. proboscideus, fed different
concentrations of algae. (Symbols as in Fig. 1).
tubes were covered with a perforated transparent lid
to avoid evaporation. Medium was renewed (20-50%)
on alternative days. Gentle bottom aeration was provided. A photoperiod of 12D: 12L and a light intensity
of 1600 lux was maintained. Food was supplied two
times a day.
Separate experiments were conducted on growth,
maturation and survival in S. proboscideus using different algal concentrations at one temperature (27±1 0c)
and different temperatures at one food concentration
(5 x 10 4 cells ml- I ).
40,-------------------------.
(j) 30
>ro
E
ClJ
E
.~
...., 20
c
a
.~
....,
co
":::J
...., 10
ro
::iE
5
10
50
100
500
Algal density (x 1000 cells ml- 1)
Fig. 3.
Maturation time (mean±S.D.) of S. proboscideus, fed
different concentrations of algae.
......
ro
>
.~
>
"- :::J
U)
5
10
15
Time (days)
20 • C
.. 25 'c
o
30' C
35 'c
20
25
30
Fig. 4. Survival (mean±S.D.) of S. proboscideus reared at different
temperatures as a function of time.
The effect of food density was studied (with
30 nauplii) using a mixture of Scenedesmus acutus
and S. obliquus. Seven food concentrations (5 x 10 2 ,
1 X 10 3 , 5 x 103, 1 X 10 4 , 5 X 10 4 , 1 X 10 5 and 5 x 10 5
cells ml- 1 ) were used. The selection of algal concentrations was based on a study by Brendonck (l993b).
Algae were cultured in 1.5 1 transparent containers at
20± 1 °C under light illumination of 4000-6000 lux.
Log phase algae were centrifuged and resuspended
in test medium. Their density was estimated using a
Burker counter.
For the temperature experiments, 20 nauplii 1-1
were used. They were reared at 20±1, 25±1, 30±1
and 35± 1 dc. The choice of these temperatures seemed
......
ro
>
.~
>
":::J
U)
60 :' 1
:\. ,
.'
,
40 :.:
\j
.'
,
. .
,
".",
\
20
'.
5
10
15
20
25
30
35
Time (days)
Fig. 1. Survival (mean±S.D.) of S. proboscideus as a function
of algal concentration. Symbols represent algal levels (x 1000 cells
ml- 1 ) asterisk: 0.5; filled square: 1; unfilled circle: 5; unfilled
square: 10; unfilled diamond 50; filled triangle: 100, and unfilled
triangle: 500.
14
12
10
E B
E
Cl>
ffi 6
5
10
15
20
25
30
35
Age (days)
Fig. 2. Size (length) (mean±S.D.) of S. proboscideus, fed different
concentrations of algae. (Symbols as in Fig. 1).
tubes were covered with a perforated transparent lid
to avoid evaporation. Medium was renewed (20-50%)
on alternative days. Gentle bottom aeration was provided. A photoperiod of 12D: 12L and a light intensity
of 1600 lux was maintained. Food was supplied two
times a day.
Separate experiments were conducted on growth,
maturation and survival in S. proboscideus using different algal concentrations at one temperature (27±1 0c)
and different temperatures at one food concentration
(5 x 10 4 cells ml- I ).
40,-------------------------.
(j) 30
>ro
E
ClJ
E
.~
...., 20
c
a
.~
....,
co
":::J
...., 10
ro
::iE
5
10
50
100
500
Algal density (x 1000 cells ml- 1)
Fig. 3.
Maturation time (mean±S.D.) of S. proboscideus, fed
different concentrations of algae.
......
ro
>
.~
>
"- :::J
U)
5
10
15
Time (days)
20 • C
.. 25 'c
o
30' C
35 'c
20
25
30
Fig. 4. Survival (mean±S.D.) of S. proboscideus reared at different
temperatures as a function of time.
The effect of food density was studied (with
30 nauplii) using a mixture of Scenedesmus acutus
and S. obliquus. Seven food concentrations (5 x 10 2 ,
1 X 10 3 , 5 x 103, 1 X 10 4 , 5 X 10 4 , 1 X 10 5 and 5 x 10 5
cells ml- 1 ) were used. The selection of algal concentrations was based on a study by Brendonck (l993b).
Algae were cultured in 1.5 1 transparent containers at
20± 1 °C under light illumination of 4000-6000 lux.
Log phase algae were centrifuged and resuspended
in test medium. Their density was estimated using a
Burker counter.
For the temperature experiments, 20 nauplii 1-1
were used. They were reared at 20±1, 25±1, 30±1
and 35± 1 dc. The choice of these temperatures seemed