236 M
.H.S. Santos et al. J. Exp. Mar. Biol. Ecol. 247 2000 233 –242
of filter paper in their mouths within 2 min after presentation and swallowing it or, rejecting it only after, at least, 4 min in their mouths’’. Data were submitted to the
Kolmogorov-Smirnov two-sample test.
2.3. Oxygen consumption experiments Acclimated PL
N 5 5–8; Table 3 non pre-exposed to the metals were exposed to
17
the different concentrations of copper and zinc, singly or in mixture, in a static respirometer containing 7.5 ml of experimental medium, for 15 min. In this case, saline
water was previously filtered 1 mm mesh and autoclaved 20 min at 1208C. The respirometer was mounted on a magnetic stirrer and provided with an O
electrode
2
connected to an oxymeter Digimed, Brazil. Each 5 min, dissolved O was measured
2
and the oxygen consumption calculated, taking into account the respirometer volume. Previous experiments indicated that by 15 min constant consumption rates were
obtained. So, after 15 min the PL oxygen consumption was measured, in duplicate.
17
PL were then isolated and weighed wet weight. Results were expressed in mg
17 21
21
O .g .h
and submitted to ANOVA followed by Duncan’s multiple range test. In the
2
control group, a possible effect of PL weight on the oxygen consumption was analysed by means of linear regression.
All statistical analysis were performed with ‘‘Statistica for Windows’’ StatSoft, Inc., 1995 and the significance level adopted was 5
a 50.05.
3. Results
The 96h-CL and the corresponding 95 intervals for copper and zinc were
50 21
estimated as 1.4 0.9–1.9 and 3.5 3.0–4.6 ppm mg.l . Chronic exposure 35 days
to sub-lethal concentrations of copper and zinc, singly or in mixture, caused important and significant reductions in PL
growth. These reductions were observed on both total
17
length and wet or dry weight Table 1. Some mortality was also registered after 35 days of experiment, but only in the highest concentrations of metals. At 212 ppb of copper or
zinc and in the mixture of 851212 ppb of copper1zinc, mortality was about 50. At 525 ppb of zinc and in the mixture of 2121525 ppb of copper1zinc, it was about 85.
In the food consumption experiments, results from the control group showed no significant correlation between food consumption and wet weight P .0.05; r 50.04;
N 513. However, acute exposure to copper or zinc significantly reduced the number of nauplii predated by PL . Concentrations of 43 and 212 ppb of copper caused reductions
17
of 28.3 and 27.1 in food consumption, respectively. For zinc, only the highest concentration tested 525 ppb affected food consumption. In this case, 25.0 inhibition
was observed. In the other hand, no significant effect on food consumption was observed when copper–zinc mixtures were tested P .0.05 Table 2.
Acute exposure to copper 212 ppb reduced PL feeding response induced by
17
L-isoleucine. Despite a lower positive feeding response when PL were exposed to
17
zinc, a significantly difference from control condition cannot be registered Fig. 1.
M .H.S. Santos et al. J. Exp. Mar. Biol. Ecol. 247 2000 233 –242
237 Table 1
Total length and weight wet and dry of Farfantepenaeus paulensis postlarvae 17 days old before T group and after copper, zinc and copper1zinc groups exposure to sub-lethal concentrations of copper
a
CuSO .5H O and zinc ZnSO .7H O, either singly or in mixture 1:2.5, for 35 days
4 2
4 2
Group Concentration
Total length Wet weight
Dry weight N
ppb cm
mg mg
T 0.9260.01
2.960.2 0.9060.04
43 Copper
Control 2.0060.02 a
59.662.4 a 11.460.5 a
100 17
2.0160.03 a 61.162.5 a
11.260.5 a 108
43 1.9660.03 a
54.862.2 b 10.360.4 a
103 85
1.7860.02 b 42.261.6 c
7.760.3 b 129
212 1.4860.02 b
22.561.1 d 4.360.2 c
61 Zinc
Control 2.0060.02 a
59.662.4 a 11.460.5 a
100 41
1.9860.03 a 58.262.6 a
11.060.5 ac 104
106 1.8760.03 b
49.562.4 b 9.360.5 b
108 212
1.8760.03 b 48.362.5 b
9.160.5 c 49
525 1.5960.09 c
34.166.4 b 5.761.2 d
13 Copper
Control 2.0060.02 a
59.662.4 a 11.460.5 a
100 1
17141 1.8860.02 b
47.261.9 b 8.860.4 b
116 Zinc
431106 1.7560.02 c
38.261.6 c 7.360.3 c
106 851212
1.6460.03 d 32.662.4 d
6.560.5 c 52
2121525 1.2760.04 e
15.061.9 e 2.460.3 d
18
a
Data are means6S.E. Same letters indicate equal means P .0.05 in the same group for each parameter.
Table 2 Mean number 6S.E. of Artemia sp. nauplii predated by F
. paulensis postlarvae 17 days old during 30 min. Postlarvae were acutely exposed to different concentrations of copper CuSO .5H O and zinc ZnSO .7H O
4 2
4 2
a
either isolated or in mixture 1:2.5 Metal
Concentration Food consumption
Inhibition N
ppb number of nauplii
Copper Control
8.2360.43 a –
13 17
7.9060.84 a 4.0
10 43
5.9060.92 b 28.3
10 85
7.2060.53 ab 12.5
10 212
6.0060.91 b 27.1
10 Zinc
Control 8.2360.43 a
– 13
41 8.6760.31 a
– 12
106 8.4260.50 a
– 12
212 8.0960.31 ab
1.7 11
525 6.1760.71 b
25.0 12
Copper Control
8.2360.43 a –
13 1
17141 7.7060.62 a
6.4 10
Zinc 431106
8.0060.58 a 2.8
10 851212
7.4060.43 a 10.1
10 2121525
7.6060.69 a 7.7
10
a
Data are means6S.E. Same letters indicate homogeneous groups P .0.05.
238 M
.H.S. Santos et al. J. Exp. Mar. Biol. Ecol. 247 2000 233 –242
Fig. 1. Feeding response of Farfantepenaeus paulensis postlarvae 17 days old acutely exposed to copper 212 ppb as CuSO .5H O and zinc 525 ppb as ZnSO .7H O, either singly or in mixture. Indicates group
4 2
4 2
significantly different from control group P ,0.05. Table 3
Oxygen consumption of F . paulensis postlarvae 17 days old acutely exposed to different concentrations of
a
copper as CuSO .5H O and zinc as ZnSO .7H O, either singly or in mixture
4 2
4 2
Metal Concentration
Oxygen consumption Inhibition
N
21 21
ppb mg O .g
.h
2
Copper Control
1.7760.10 a –
8 17
1.1860.25 b 33.5
5 43
1.1760.17 b 34.0
5 85
1.1460.11 b 35.6
5 212
1.3460.10 b 24.2
7 Zinc
Control 1.7760.10 a
– 8
41 1.2760.29 ab
28.0 5
106 1.2360.19 b
30.5 5
212 1.0660.13 b
40.3 5
525 1.2460.15 b
30.0 5
Copper Control
1.7760.10 a –
8 1
17141 1.7860.28 a
– 5
Zinc 431106
1.5260.18 a 14.4
5 851212
1.6260.17 a 8.4
5 2121525
1.1660.24 a 34.7
5
a
Data are means6S.E. Same letters indicate homogeneous groups P .0.05.
M .H.S. Santos et al. J. Exp. Mar. Biol. Ecol. 247 2000 233 –242
239
PL oxygen consumption was significantly reduced by all copper and zinc con-
17
centrations tested, except 41 ppb of zinc. For both metals, the effect was not dose dependent, and the mean reduction registered was of approximately 32. As observed
above for feeding experiments, the copper–zinc mixture did not significantly modify the PL
oxygen consumption, despite the fact that a reduction of 34.7 was observed in
17
the higher concentration tested Table 3. It is important to note that in the control group, no significant correlation could be established between oxygen consumption rate
and PL wet weight P .0.05; r 50.15; N 58.
17
4. Discussion
