CIRCANNUAL VARIATION IN THE FATTY-ACID COMPOSITION OF HIGH-DENSITY-LIPOPROTEIN PHOSPHOLIPIDS DURING ACCLIMATIZATION IN TROUT

A circannual variation in the fatty acid composition of plasma and hig h-density lipoprotein (HDL) phospholipids occurs in rainbow trout (Onc orhynchus mykiss) in response to seasonal alterations in environmental water temperature. The compensatory mechanisms employed in cold adapt ation include a decrease in the level of saturated fatty acids and of monoenes of the oleic acid (n-9) family and an increase in the level o f unsaturated fatty acids of the linolenic acid (n-3) family, especial ly in docosahexaenoic acid (22:6(n-3)). The present study demonstrates that in trout, a poikilothermic vertebrate, the weight percentage of 22:6(n-3) in HDL phospholipids is inversely correlated (r=-0.88, P<0.0 001) with water temperature.