males and three embryo-bearing females were transferred to each of four containers and fed treatment diets to excess. Survival of the adult copepods was monitored daily. After
exactly 96 h, nauplii and adult copepods were preserved for later enumeration. Produc- tions, expressed as nauplii
rfemalerday, were compared using one-way ANOVAs and Tukey’s W procedure.
Prosome length of females used in the nauplius production trial were measured using an ocular graticule. Results were analysed in the same manner as above.
3. Results
3.1. Fatty acid analyses of copepod diet Ž
. Table 1 shows that Isochrysis contained the greatest proportion of DHA 22:6 n
y 3 , followed by Chaetoceros. This fatty acid was not detected in the other diets. EPA
Ž .
20:5n y 3 was the most abundant fatty acid in Nannochloropsis and Chaetoceros.
Isochrysis contained only a small proportion of this fatty acid. The high proportion of EPA resulted in Nannochloropsis recording the largest proportion of HUFAs, followed
by Chaetoceros and Isochrysis. DHA:EPA ratio was greatest in Isochrysis. In contrast, Dunaliella and yeast recorded negligible HUFA content. The most abundant fatty acids
in these diets were 18:3n
y 3 and 18:1n y 9, respectively.
Table 1 Ž
. Fatty acid content of total fatty acids of diets used to rear copepods. Means of 3 replicatesSD
Fatty acid Isochrysis
Chaetoceros Dunaliella
Nannochloropsis Yeast
C14:0 15.560.42
22.981.43 0.40.19
4.570.38 0.630.06
C15:0 0.430.03
0.320.04 –
0.310.02 0.230.04
C16:0 13.080.53
7.950.25 13.480.14
17.030.4 8.830.28
C16:1 6.050.44
18.120.65 1.720.01
16.20.28 34.254.6
C16:2 0.390.03
– 1.160.07
0.250.05 –
C16:3 –
14.160.3 3.960.39
– –
C16:4 –
– 21.170.52
– –
C18:0 0.380.06
0.410.03 0.720.45
0.440.08 2.860.12
C18:1n y7
2.480.06 0.510.15
– –
1.850.22 C18:1n
y9 16.690.61
0.630.01 –
5.480.26 43.392.75
C18:2 n y6
2.250.23 0.690.08
4.220.05 1.730.03
6.91.59 C18:2 n
y8 –
– 2.240.06
– –
C18:3n y3
– –
47.250.49 –
– C18:3n
y6 –
1.740.25 3.20.09
0.420.08 –
C18:4 n y3
26.030.74 0.840.12
– –
– C20:4 n
y6 –
3.720.14 –
7.580.32 –
C20:5n y3
0.310.21 25.152.65
– 44.260.53
– C22:0
0.10.03 –
– –
– C22:6 n
y3 16.20.93
2.440.49 –
– –
C24 –
0.350.08 0.430.16
1.130.69 0.90.31
Total HUFA 16.510.75
31.312.1 tr
52.450.49 DHA:EPA
52.3 0.1
Ž .
Ž .
Fig. 1. Copepod G. imparipes survival meanSD to maturity fed different diets at 208C and 258C. Ž
. Different letters denote a significant difference between values at the same temperature P - 0.05 .
3.2. Copepod surÕiÕal Fig. 1 shows that, at both temperatures, survival was generally greatest on a diet of
Isochrysis, followed by Dunaliella, Chaetoceros and Nannochloropsis. At 208C, sur- vival was significantly greatest on a diet of Isochrysis and lowest on a diet of
Nannochloropsis. Other results were not significant. Copepods did not survive to maturity on a diet of Nannochloropsis at 258C or on a diet of yeast at either
temperature. However, some copepods survived 9 days longer than unfed controls on a diet of yeast at 208C.
3.3. Maturation Fig. 2 shows that at 208C, the time taken for 50 of female copepods to mature was
significantly shortest with a diet of Isochrysis. Time to maturity increased with a diet of
Ž .
Ž .
Fig. 2. Cumulative maturation logit transformed over time of female copepods G. imparipes fed Isochrysis Ž .
Ž .
Ž .
Ž .
e , Chaetoceros , Dunaliella ` and Nannochloropsis \ at 208C. Dotted lines represent time
Ž .
Ž .
Ž .
x-axis taken for 50 cumulative maturation y-axis . Days and gradients b with different superscripts are
1
Ž .
significantly different P - 0.05 .
Ž .
Ž .
Fig. 3. Cumulative maturation logit transformed over time of female copepods G. imparipes fed Isochrysis Ž .
Ž .
Ž .
Ž .
e , Chaetoceros and Dunaliella ` at 258C. Dotted lines represent time
x-axis taken for 50 Ž
. Ž
. cumulative maturation y-axis . Days and gradients b
with different superscripts are significantly different
1
Ž .
P - 0.05 .
Chaetoceros. Copepods fed Dunaliella and Nannochloropsis took the longest time to Ž
. mature. The same trend occurred at 258C although copepods matured faster Fig. 3 .
However, results were not significantly different at this temperature and no copepod maturation was recorded on a diet of Nannochloropsis.
Ž .
Fig. 4. G. imparipes nauplius production per female per day and female prosome length both meanSD fed different diets at 208C and 258C. Letters show significance of data at the same temperature, different letters
Ž .
indicate a significant difference P - 0.05 .
Copepod maturation rate, as indicated by the regression gradients, was the same for Ž
. animals on different diets at 208C Fig. 2 . At 258C, this rate was significantly greater
Ž .
for Isochrysis fed copepods compared to those with the other diets Fig. 3 . 3.4. Nauplius production and female length
Fig. 4 shows that at both 208C and 258C, daily nauplius production was greatest for females on a diet of Isochrysis. At 208C, there was no difference in production on the
other diets, whereas at 258C, production on a diet of Chaetoceros was greater than on a diet of Dunaliella.
Prosome length was greatest for females reared at 208C with a diet of Isochrysis and least with a diet of Dunaliella. At 258C, copepods fed Isochrysis and Chaetoceros were
longer than those fed Dunaliella. For those copepods fed Isochrysis, Chaetoceros and Dunaliella, there appeared to be a positive correlation between female prosome length
and nauplius production at each temperature. In these copepods, length and nauplius production appeared to be determined more by diet than by temperature.
4. Discussion
