Role of eicosenoic and docosenoic fatty acids in fresh water and marine lipids

The isomeric compositions of the eicosenoic and docosenoic fatty acids of four freshwater fish oils (from sheepshead Aplodinotus grunniens, tullibee Coregonus artedii, maria Lota lota and alewife Alosa pseudoharengus, respectively) were examined by open-tubular gas—liquid chromatography. The 22:1ω11 isomer, usually the dominant isomer in marine-fish oils, was unimportant relative to 22:1ω9. The unsaponifiables lacked fatty alcohols and pristane and were mostly cholesterol. The probability that the 22:1ω1 in marine fish oils is strictly of an exogenous origin (primarily originating as the fatty alcohol in copepod wax esters) is reviewed and it is proposed that docosenoic acids have no obligatory role in the lipid biochemistry of either marine or freshwater fish.