Environmental Engineering Reference
In-Depth Information
Our results showed that the development time fluctuate between 55 and 42 days
approximately, at 9 and 15ºC, respectively. The sustained even increasing respiration rate
throughout the zoeal stages is interpreted as a confirmation of lecithotrophic development,
otherwise a drop in metabolic rate in starved larvae were expected (Fig. 7a). Megalopa
showed at lower temperatures a decreasing respiration rate attributed to a behavioral change
in the swimming activity, while at higher temperature the metabolic rate increased (Fig. 7a).
A similar pattern was observed for the nitrogen excretion rate (Fig. 7b). The atomic
proportion of consumed oxygen and excreted nitrogen (O:N) is considered as an estimator of
the metabolized substratum; values between 3 and 16 would indicate protein metabolism, an
O:N ratio between 50 and 60 corresponds to similar proportion of lipid and protein
catabolism and higher values than 60 represents lipid metabolism Mayzaud & Conover,
(1988).
L. santolla
larvae reared at 12ºC, in general showed a combined protein and lipid
catabolism, but, at 9 and 15ºC the Zoea I showed an evident lipid metabolism (Fig. 7c).
Respiration rate, independent to temperature, contributed principally on the energy losses,
ranging between 93 and 96% at 9 and 15ºC. Although the shortest development time was at
15ºC, low survival suggests unsuitable rearing conditions. Indeed, the highest energy losses
expressed as excretion and respiration rate (Figs. 7 a and b) occurred at 15ºC. Multiplying the
energy losses of respiration and excretion rates by the respective developmental time, the
cumulative energy losses were estimated. Similar energy losses during Zoea I and II were
observed for the different temperatures, while an evident impact of higher temperature on
the megalopa stage was observed (Fig 7d). The results suggest that elevated temperature
≥15ºC could generate a mismatch on the larval metabolism of
L. santolla
due the increasing
energy losses and the restriction in the limited stored energy in the form of yolk remaining
a)
b)
0.08
2.5
0.07
2
0.06
ZI
ZII
ZIII
Megalopa
ZI
ZII
ZIII
Megalopa
0.05
1.5
0.04
1
0.03
0.02
0.5
0.01
0
0
9
12
15
9
12
15
Temperature (ºC)
Temperature (ºC)
c)
d)
ZI
ZII
ZIII
Megalopa
180
70
160
60
140
50
ZI
ZII
ZIII
Megalopa
Total
120
40
100
Lipid
80
30
60
Protein-Lipid
20
40
10
20
Protein
0
0
9
12
15
9
12
15
Temperature (ºC)
Temperature (ºC)
Fig. 7. Temperature effect on a) the respiration rate; b) the excretion rate (J*ind
-1
*day
-1
); c)
O:N ratio; d) the cumulative energy losses (J) during larval development of
Lithodes santolla
.
Search WWH ::
Custom Search