LIPIDS OF THE EARTHWORM LUMBRICUS-TERRESTRIS

The lipid composition of the earthworm Lumbricus terrestris has been reexamined under conditions intended to avoid enzymatic and chemical alterations during storage, extraction, and fractionation procedures. The simple lipids included aliphatic hydrocarbons, steryl esters, glycerides, and at least nine different sterols, all thought to be derived from the diet. Free fatty acids, previously considered to be major components of worm lipids, comprised only 0.3% of the total lipid weight. Phospholipids included (in order of relative abundance) phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidylinositol, as well as sphingomyelin. Glycolipids included cerebrosides and sulfatides containing both glucose and galactose, and gangliosides containing glucosamine and sialic acid. The fatty acid compositions of these lipid classes appeared to be a mixture of what are considered typical plant, bacterial, and animal acids. Several fatty acids found in the worms, including cis-vaccenic and eicosapentaenoic acids, were essentially absent from the dietary components, and it is concluded that these acids were synthesized in the worms. The earthworm derives much of its lipid adventitiously, but exerts at least some control over its tissue lipid composition.