MEMBRANE-LIPIDS OF RED MUSCLE MITOCHONDRIA FROM LAND-LOCKED AND SEA-RUN ARCTIC CHAR, SALVELINUS-ALPINUS

Although laboratory studies of the effects of temperature, salinity, a nd diet on biological membranes of fish indicate substantial alteratio ns in phospholipid and fatty acid composition to maintain functional p roperties, there are few parallel studies of wild populations. We, the refore, examined the red muscle, mitochondrial phospholipids and phosp holipid fatty acids in two fish populations differing in their environ mental temperature, salinity, and diet. Sea-run and freshwater (land-l ocked) Arctic char (Salvelinus alpinus L.) were collected from Iglooli k Island, Northwest Territories, Canada, in the summer of 1991. Severa l differences between the phospholipids of these fish, and those repor ted for red muscle mitochondria in other fish species, included a high er cardiolipin content and a higher proportion of short-chain monoenes , especially 16:1. In congruence with previous studies of changes in c ardiolipin fatty acids in other species of cold-acclimated fish, the f atty acid content of cardiolipin of both Arctic char groups was more s aturated and less polyunsaturated than in warm-acclimated fish. Other aspects of the lipid composition of these membranes were not consisten t with laboratory studies of cold-acclimated fish. For example, the fa tty acids comprising phosphatidylethanolamine and phosphatidylcholine were more saturated than would be predicted based on laboratory studie s of cold-acclimated fish. Some of these differences may be attributab le to differences in the proportions of dietary n3 and n6 fatty acids in freshwater and marine environments. A strategy common to both group s of Arctic char is the maintenance of a similar relationship between phospholipid fatty acid chain length and degree of unsaturation in bot h Arctic char populations in spite of differences in diet and thermal regimes. The observed differences in membrane composition between land -locked and sea-run fish presumably act to maintain mitochondrial func tion in these different environments.