ENDOGENOUS LIPIDS OF THE EARTHWORM LUMBRICUS-TERRESTRIS

Earthworms (Lumbricus terrestris) were given 1-C-14!-labeled palmitic acid by gavage on days 0 and 3, and sacrificed on day 7. The distribu tion of label among lipid classes indicated that glycerides, sterol es ters, cerebrosides, sulfatides, phosphatidylethanolamine, phosphatidyl serine and (or) phosphatidylinositol, phosphatidylcholine, and sphingo myelin turn over in, or are synthesized by, the earthworm. Free fatty acids still had the highest specific radioactivity of any lipid class at the end of the experiment. Incorporation of label into sterol and h ydrocarbon fractions was insignificant and there was no detectable lab el incorporated into gangliosides. Phosphatidylethanolamine apparently turned over quite slowly compared with other lipid classes, while the cerebroside fraction became highly labeled. Elongation of palmitic ac id to stearate and oxidation to CO2 occurred extensively, but there wa s no evidence for desaturation.