ENERGY VS. essential fatty
acids: what do scallop larvae (Argopecten purpuratus) need most?
N.
Nevejan, I. Saez, G. Gajardo, P. Sorgeloos-2003
Comparative Biochemistry and Physiology Part B, 134:
599-613
Abstract:
Larvae of the Chilean-Peruvian scallop Argopecten
purpuratus were fed a Dunaliella tertiolecta diet (Dun-diet) supplemented
with lipid emulsions, rich in 20:5n-3 (EmEPA), 22:6n-3 (EmDHA) or in
saturated fatty acids (EmCOCO). A mixed algal diet of Isochrysis galbana
(T-iso) and Chaetoceros neogracile served as a positive control (St-diet).
Lipid supplementation to the Dun-diet improved the larval growth and
increased the percentage of eyed larvae significantly, compared to the
non-supplemented Dun-diet because of the extra energy supplied and not
because of its fatty acid composition. No significant differences were
observed between supplementation with EmEPA, EmDHA or EmCOCO. A mixture of
20% EmEPA + 20% EmDHA (40% EmHUFA) was more efficient in raising the total
lipid content in larvae than 40% EmCOCO. Both emulsions increased the
triacylglycerol content in larvae compared to the non-supplemented Dun-diet.
The best results, however, was obtained with the St-diet, probably because
of a more suitable 18:2n-6/18:3n-3 ratio and a higher level of arachidonic
acid. A positive relationship between the 18:2n-6/18:3n-3 ratio and the
larval performance was found. No significant difference was observed in
post-settlement larval size or percentage of metamorphosed larvae between
the St-diet and the St-diet supplemented with 20% EmHUFA or 20% EmCOCO. The
metamorphosed larvae had a constant DHA/EPA ratio of 3.7, independent from
the diet, which suggested a metabolic control of the two fatty acids and a
species-dependency of the ratio.
(Universidad de Los Lagos, Laboratory of Genetics and
Aquaculture, P.O. Box 933, Osorno, Chile, e-mail: N. Nevejan@inve.be)