Losses of
lipid, protein and n-3 fatty acids in enriched Artemia franciscana starved
at different temperatures
J.O. Evjemo, T.L. Danielsen, Y. Olsen-2001
Aquaculture, 193 (1-2): 65-80
Abstract:
The loss rates of protein and lipids were determined
for enriched Artemia franciscana starved at different temperatures after
enrichment. Following 12-h enrichment with DHA Selco (0.2 g l-1)
at 28°C, the nauplii were temperature acclimated and transferred to
starving condition (0--96 h; 5°C to 30°C).
The total lipid content during enrichment increased
from 145 mg g-1 dry weight (DW) (newly hatched nauplii) to 222 mg
g-1 DW after 12 h. The DHA/EPA ratio reached an optimum after 12
h (1.85), where DHA and EPA constituted 12% and 6.7% of total fatty acids,
respectively.
When the nauplii were transferred to starving
conditions the contents of all lipid components became reduced. The specific
loss rate was found to be exponential for all components and significantly
higher for DHA than for EPA and the sum of the other n-3 fatty acids. A.
franciscana starved at the highest temperature (30°C) showed a loss rate of
92% day-1 (of DHA). Nauplii starved at 12°C had a loss rate of
51% day-1 (of DHA). At the same temperature (12°C) the
corresponding loss rate of EPA, the sum of the other n-3 fatty acids and for
the total lipid content was 15%, 30% and 11% day-1, respectively.
The protein content was relatively stable in the
nauplii kept at the lowest temperatures (5°C and 8°C), but as temperature
increased, the loss rate of protein gradually increased reaching a loss rate
of 28% day-1 in nauplii starved at 26°C. The survival of the
nauplii was >67% throughout the starvation period (96 h), but at
temperatures below 8°C and above 19°C, the survival was <13% after 96
h.
Results show that the when Artemia nauplii are
starved the lipid and protein content decreases as a function of
temperature. This might affect the nutritional value of A. franciscana quite
strongly if the nauplii reside in the fish tanks before being eaten by the
larvae, or stored at ambient temperature before they are transferred to the
fish tanks.