Membrane lipids of red muscle mitochondria from land-locked and sea-run Arctic char, Salvelinus alpinus

Abstract

Although laboratory studies of the effects of temperature, salinity, and diet on biological membranes of fish indicate substantial alterations in phospholipid and fatty acid composition to maintain functional properties, there are few parallel studies of wild populations. We, therefore, examined the red muscle, mitochondrial phospholipids and phospholipid fatty acids in two fish populations differing in their environmental temperature, salinity, and diet. Sea-run and freshwater (land-locked) Arctic char (Salvelinus alpinus L.) were collected from Igloolik Island, Northwest Territories, Canada, in the summer of 1991. Several differences between the phospholipids of these fish, and those reported for red muscle mitochondria in other fish species, included a higher cardiolipin content and a higher proportion of short-chain monoenes, especially 16:1. In congruence with previous studies of changes in cardiolipin fatty acids in other species of cold-acclimated fish, the fatty acid content of cardiolipin of both Arctic char groups was more saturated and less polyunsaturated than in warm-acclimated fish. Other aspects of the lipid composition of these membranes were not consistent with laboratory studies of cold-acclimated fish. For example, the fatty acids comprising phosphatidylethanolamine and phosphatidylcholine were more saturated than would be predicted based on laboratory studies of cold-acclimated fish. Some of these differences may be attributable to differences in the proportions of dietary n3 and n6 fatty acids in freshwater and marine environments. A strategy common to both groups of Arctic char is the maintenance of a similar relationship between phospholipid fatty acid chain length and degree of unsaturation in both 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 function in these different environments.