Fatty acid composition of brain and body phospholipids of the anadromous salmon, Oncorhynchus nerka, From fresh-water and marine habitat

1. 1. The fatty acid composition of individual phospholipids of brain, muscles and liver was studied in the sockeye salmon ( Oncorhynchus nerka) during marine and fresh-water periods of its life. Samples were taken: (1) from adult fish caught in the sea; (2) during their spawning migration up the river; (3) in the lake during spawning; (4) from 2–3-year-old young (smolt) in the lake; (5) from “resident” fish in the lake; (6) from “resident” fish during spawning. Fishes (1), (2) and (3) do not feed. They may be regarded as “marine” stages, as the fatty acid composition of their tissue lipids was performed when they fed on marine plankton. Groups (4), (5) and (6) are fresh-water stages as these fish never lived in sea water. 2. 2. Fatty acid composition of basic phospholipids of muscles and liver revealed differences which are characteristic of the so-called “marine” and “fresh-water” type of lipids. 3. 3. On the contrary, the fatty acid composition of brain phospholipids remained fairly constant and did not reveal any noticeable changes depending upon a marine or fresh-water habitat. Probably the fundamental role of the membrane phospholipids of the brain cells is incompatible with fluctuations of the apolar side-chain constituents which largely determine the physico-chemical properties of phospholipids.