Effect of lipid emulsions on production and fatty acid composition of eggs of the scallop Argopecten purpuratus
N.
Nevejan, V. Courtens, M. Hauva, G. Gajardo, P. Sorgeloos-2003
Marine Biology, 143(2): 327-338
Abstract:
The impact of supplementing lipid emulsions rich in
eicosapentaenoic acid (EmEPA), docosahexaenoic acid (EmDHA) or saturated
fatty acids (EmCOCO) to a standard algal diet [3:1 mixture of Isochrysis
galbana (T-iso) and Chaetoceros neogracile, St-diet] on Argopecten
purpuratus broodstock was evaluated. Broodstock fecundity was compared
as well as the egg quality in terms of lipid content, fatty acid composition
and lipid class distribution. Fecundity was defined as the number of eggs
released in the spawning process, since spawning was virtually complete.
Results indicated that the total lipid content of the eggs of A. purpuratus
was diet independent. A greater energy reserve was spent on a larger number
of oocytes and not on bigger sized oocytes with a higher lipid content. The
lipids supplied through the emulsions were at least partially allocated to
the eggs, demonstrating that the fatty acid composition of the eggs could be
manipulated, especially the neutral lipid fraction. Levels of EPA changed
more rapidly than DHA levels, supporting the observation that they fulfilled
an energetic and structural role, respectively. The St-diet supplemented
with 50%EmCOCO resulted in a significantly higher fecundity compared to the
algal diet supplemented with 25%EmEPA+25%EmDHA and the non-supplemented
algal diet. It would seem that saturated fatty acids (SAFA) were more easily
or preferentially incorporated in the female gonads of A. purpuratus.
The relative content of SAFA and 18:2( n-6) in these eggs rose
significantly. The relative content of the highly unsaturated fatty acids,
EPA and DHA, on the other hand was substantially lower in the neutral lipid
fraction, but hardly affected in the polar lipid fraction. It appeared that
the maintenance of an adequate DHA/EPA ratio (approximately 1.2) was more
important than the absolute levels of the two fatty acids, as long as a
threshold value was reached.
(Ghent University, Laboratory of Aquaculture &
Artemia Reference Center, Rozier 44, 9000 Ghent, Belgium; E-mail: n.nevejan@inve.be)