177
Table 1. Effect of light, DMSO and glycerol on cyst hatching: one way
analysis of variance
Factor
1500 lux
Light
Continuous
light
Glycerol
DMSO
Source of variation
12hUDVs
continuous light
1500 lux Vs
2500 lux
control Vs 0.0125%
error
control Vs 0.025%
error
control Vs 0.0375%
error
control Vs 0.05%
error
control Vs 0.0625%
error
control Vs 0.125%
error
control Vs 0.1875%
error
control Vs 0.0125%
error
control Vs 0.025%
error
control Vs 0.0375%
error
control Vs 0.05%
error
control Vs 0.0625%
error
control Vs 0.125%
error
control Vs 0.1875%
error
df
1
8
8
8
I
8
8
8
8
8
8
1
8
1
8
1
8
8
8
8
8
SS
MS
Fs
176.4
176.4
10.14*
139.2
17.4
739.6
739.6
22.01**
268.8
33.6
435.6
435.6
9.99*
348.8
43.6
90.0
90.0
2.08 ns
345.6
43.2
176.4
176.4
3.59 ns
393.6
49.2
102.4
102.4
1.23 ns
665.6
83.2
384.4
384.4
12.01 **
256.0
32.0
360.0
360.0
7.26*
396.6
49.6
360.0
360.0
27.27***
105.6
13.2
67.6
67.6
1.26 ns
428.8
53.6
160.0
160.0
3.19 ns
401.6
50.2
490.0
490.0
11.61*337.6
42.2
193.6
193.6
3.28 ns
472.0
59.0
129.6
129.6
3.50 ns
296.0
37.0
409.6
409.6
4.15 ns
788.8
98.6
547.6
547.6
10.22**
428.8
53.6
* P < 0.05, ** P < 0.01, *** P < 0.001, ns non-significant
from California (Sorgeloos, 1973) and in four strains
from different geographical regions (Vanhaecke et at.,
1981), light was found to enhance hatchability. Yet,
Artemia cysts hydrated in the dark also hatched appreciably (Van der Linden et at., 1986). In the present
study, only 8% of T. platyurus cysts hatched in total
darkness, a level similar (7%) to that reported in Streptocephalus macrourus Daday under dark incubation
by Mitchell (1990). A change in the duration of light
exposure, from 12 h LID to continuous light increased
hatching from 39.6% to 48% in T. platyurus. In parallel, Mitchell (op. cit.) also got 66.6% hatching of
S. macrourus under 12 h LID, and 84% in continuous
light. Hatching inhibition in the dark might be an adaptation for hydrated cysts, burried in mud, not to attempt
hatching. The more light a cyst receives, the better the
chances for a nauplius to hatch in water, not in mud.
Though optimal light intensity for maximal hatching
Table 1. Effect of light, DMSO and glycerol on cyst hatching: one way
analysis of variance
Factor
1500 lux
Light
Continuous
light
Glycerol
DMSO
Source of variation
12hUDVs
continuous light
1500 lux Vs
2500 lux
control Vs 0.0125%
error
control Vs 0.025%
error
control Vs 0.0375%
error
control Vs 0.05%
error
control Vs 0.0625%
error
control Vs 0.125%
error
control Vs 0.1875%
error
control Vs 0.0125%
error
control Vs 0.025%
error
control Vs 0.0375%
error
control Vs 0.05%
error
control Vs 0.0625%
error
control Vs 0.125%
error
control Vs 0.1875%
error
df
1
8
8
8
I
8
8
8
8
8
8
1
8
1
8
1
8
8
8
8
8
SS
MS
Fs
176.4
176.4
10.14*
139.2
17.4
739.6
739.6
22.01**
268.8
33.6
435.6
435.6
9.99*
348.8
43.6
90.0
90.0
2.08 ns
345.6
43.2
176.4
176.4
3.59 ns
393.6
49.2
102.4
102.4
1.23 ns
665.6
83.2
384.4
384.4
12.01 **
256.0
32.0
360.0
360.0
7.26*
396.6
49.6
360.0
360.0
27.27***
105.6
13.2
67.6
67.6
1.26 ns
428.8
53.6
160.0
160.0
3.19 ns
401.6
50.2
490.0
490.0
11.61*337.6
42.2
193.6
193.6
3.28 ns
472.0
59.0
129.6
129.6
3.50 ns
296.0
37.0
409.6
409.6
4.15 ns
788.8
98.6
547.6
547.6
10.22**
428.8
53.6
* P < 0.05, ** P < 0.01, *** P < 0.001, ns non-significant
from California (Sorgeloos, 1973) and in four strains
from different geographical regions (Vanhaecke et at.,
1981), light was found to enhance hatchability. Yet,
Artemia cysts hydrated in the dark also hatched appreciably (Van der Linden et at., 1986). In the present
study, only 8% of T. platyurus cysts hatched in total
darkness, a level similar (7%) to that reported in Streptocephalus macrourus Daday under dark incubation
by Mitchell (1990). A change in the duration of light
exposure, from 12 h LID to continuous light increased
hatching from 39.6% to 48% in T. platyurus. In parallel, Mitchell (op. cit.) also got 66.6% hatching of
S. macrourus under 12 h LID, and 84% in continuous
light. Hatching inhibition in the dark might be an adaptation for hydrated cysts, burried in mud, not to attempt
hatching. The more light a cyst receives, the better the
chances for a nauplius to hatch in water, not in mud.
Though optimal light intensity for maximal hatching