Influence of egg
lipids and fatty acids on egg viability, and their utilization during
embryonic development of spotted wolf-fish, Anarhichas
minor Olafsen
H. Tveiten, M. Jobling, I. Andreassen-2004
Aquaculture
Research, 35(2): 152-161
Abstract:
The changes in egg lipids and fatty acid
compositions that occur during embryonic development of spotted wolf-fish, Anarhichas
minor, were examined by monitoring individual egg batches from the time
of spawning (egg stripping) until hatching. The lipids, present as 3.7±0.1%
of the wet mass of the freshly stripped eggs, contained high percentages of
monoenes (monounsaturated fatty acids (MUFAs), ca. 33%) and polyenes (ca.
43%) and approximately 20% saturated fatty acids (SFAs). The fatty acid
profiles were dominated by a small number of fatty acids. The major SFA was
16:0 (ca. 14%), the dominant MUFA was 18:1 n-9 (ca. 21%), and among the
polyenes, the n-3 highly unsaturated fatty acids (HUFAs) 22:6 n-3
docosahexaenoic acid (DHA) and 20:5 n-3 eicosapentaenoic acid (EPA) were
present in the highest concentrations (EPA, ca. 16%; DHA, ca. 19%). The n-6
HUFA 20:4 n-6 arachidonic acid (AA) was present as ca. 1% of the total fatty
acids in the freshly stripped eggs. This resulted in an AA:EPA of ca. 0.07,
which is lower than reported for eggs of many other fish species. As
embryonic development progressed, the percentage contribution of AA to the
total fatty acids almost doubled. There were also increases in the relative
proportions of SFAs (due mainly to an increase in the percentage of 16:0 to
ca. 16% at hatch) and DHA (to ca. 23%), and there was a corresponding
decrease in the percentage of MUFAs (mostly brought about by a decrease in
the percentage of 18:1 n-9 to ca. 18% at hatch). The most marked changes
occurred towards the end of incubation. The percentage of EPA changed little
during incubation. This implies that there was selective retention of DHA,
16:0 and AA, and these fatty acids were probably incorporated into cell
membranes. MUFAs, particularly 18:1 n-9, seem to have been catabolized to
provide energy for the developing embryo, and some EPA also seems to have
been utilized as an energy source. Survival of eggs to the eyed stage (range
ca. 10-80%) and to hatch (ca. 5-75%) was negatively correlated with the %AA,
%EPA and AA:DHA of the freshly stripped eggs. There was also a negative
correlation between AA:EPA and egg survival, which implies that there is not
a universal requirement for a high AA:EPA to ensure high rates of survival
of fish eggs.
(NFH, University of Tromsų, 9037 Tromsų,
Norway. E-mail of M. Jobling: malcolmj@nfh.uit.no)