Marine lipids
Les résultats montrent que :
• L'affinage pendant six semaines avec Skeletonema costatum améliore
l’indice de condition des huîtres (x 2) en augmentant de la teneur en
glycogène (x 5). La teneur en lipides reste stable chez les huîtres témoins
et augmente légèrement chez les huîtres affinées (8,4 % contre 10,4 %
de la matière sèche) ;
• Des changements importants dans la composition en acides gras des
lipides totaux sont observés. Certains acides gras caractéristiques de
Skeletonema costatum. comme le 16:1 (n-7) et le 20:5 (n-3) s’accumulent
directement dans les lipides des huîtres ;
• Le 16:1 (n-7) est converti en 18:1 (n-7) montrant que les huîtres sont
capables de transformer les acides gras monoinsaturés à 16 C apportés
par Skeletonema costatum en leurs acides gras homologues à 18 C ;
• Les acides gras typiques de Skeletonema costatum (16:4 (n-1), 16:2 (n-4),
16:3 (n-4) ne s’accumulent que faiblement dans les lipides totaux des
huîtres, suggérant que les huîtres discriminent ces acides gras.
Introduction
In France, a large part of the annual production of oysters is consumed
during Christmas and New Year celebrations. However, during this
seasonal period the quality of oysters is highly variable. This is related
to the food availability (mainly unicellular algae) which is influenced
by environmental conditions such as water temperature in the area of
production. Commercial farms routinely promote growth and fattening
performances of oyster stock by supplemental feeding with specially reared algae ro compensare the seasonal variations of naturally occurring
algae in sea water (De Pauw, 1984). Several studies have been devoted
to studying the effect of supplemental feeding of unicellular algae on
oysters but most of them concentrated on larvae and juvenile oysters
(Waldock & Nascimento, 1979; Langdon & Waldock, 1981). These
studies have established that this practice improved the growth of larvae
and juveniles and that fatty acid composition of oysters come to reflect
that of unicellular algae. However, there is little data available on similar
work conducted on adult oysters. To date, only one study was performed
but the period of feeding was too short (6 hours) to reliably observe
large changes in proximate composition of oyster flesh (Watanabé &
Ackman, 1974). However rhe authors indicated that the fatty acids of
the unicellular algae were stored in oyster tissues without changes in
their chain length or degree of unsaturation.
In France, adult oysters are fattened in land ponds (termed “claires”)
for several weeks before they are harvested and sold (Robert, 1990). This
periocl is highly suitable for supplying unicellular algae to oyster stock
as they were kept in a limited area under controlled conditions. In the
bay of Bourgneuf, recent studies evaluated the economical interest of
supplying unicellular algae to adult oysters during the fattening in
“claires”. A diatom Skeletonema costatum has been chosen for this purpose
112
Les résultats montrent que :
• L'affinage pendant six semaines avec Skeletonema costatum améliore
l’indice de condition des huîtres (x 2) en augmentant de la teneur en
glycogène (x 5). La teneur en lipides reste stable chez les huîtres témoins
et augmente légèrement chez les huîtres affinées (8,4 % contre 10,4 %
de la matière sèche) ;
• Des changements importants dans la composition en acides gras des
lipides totaux sont observés. Certains acides gras caractéristiques de
Skeletonema costatum. comme le 16:1 (n-7) et le 20:5 (n-3) s’accumulent
directement dans les lipides des huîtres ;
• Le 16:1 (n-7) est converti en 18:1 (n-7) montrant que les huîtres sont
capables de transformer les acides gras monoinsaturés à 16 C apportés
par Skeletonema costatum en leurs acides gras homologues à 18 C ;
• Les acides gras typiques de Skeletonema costatum (16:4 (n-1), 16:2 (n-4),
16:3 (n-4) ne s’accumulent que faiblement dans les lipides totaux des
huîtres, suggérant que les huîtres discriminent ces acides gras.
Introduction
In France, a large part of the annual production of oysters is consumed
during Christmas and New Year celebrations. However, during this
seasonal period the quality of oysters is highly variable. This is related
to the food availability (mainly unicellular algae) which is influenced
by environmental conditions such as water temperature in the area of
production. Commercial farms routinely promote growth and fattening
performances of oyster stock by supplemental feeding with specially reared algae ro compensare the seasonal variations of naturally occurring
algae in sea water (De Pauw, 1984). Several studies have been devoted
to studying the effect of supplemental feeding of unicellular algae on
oysters but most of them concentrated on larvae and juvenile oysters
(Waldock & Nascimento, 1979; Langdon & Waldock, 1981). These
studies have established that this practice improved the growth of larvae
and juveniles and that fatty acid composition of oysters come to reflect
that of unicellular algae. However, there is little data available on similar
work conducted on adult oysters. To date, only one study was performed
but the period of feeding was too short (6 hours) to reliably observe
large changes in proximate composition of oyster flesh (Watanabé &
Ackman, 1974). However rhe authors indicated that the fatty acids of
the unicellular algae were stored in oyster tissues without changes in
their chain length or degree of unsaturation.
In France, adult oysters are fattened in land ponds (termed “claires”)
for several weeks before they are harvested and sold (Robert, 1990). This
periocl is highly suitable for supplying unicellular algae to oyster stock
as they were kept in a limited area under controlled conditions. In the
bay of Bourgneuf, recent studies evaluated the economical interest of
supplying unicellular algae to adult oysters during the fattening in
“claires”. A diatom Skeletonema costatum has been chosen for this purpose
112