Lipid droplets of C. elegans are characterized by a phospholipid monolayer membrane. (A) Lipid droplets in wild-type animals were electron-translucent structures (asterisks). (B and C) A typical lipid droplet (boxed area) was shown to be delimited by a phospholipid monolayer membrane (arrowhead) as opposed to a phospholipid bilayer membrane (arrows) of a nearby organelle. (D-F) Lipid droplets were not eliminated by glo-4 mutation. (G-I) Lipid droplets in daf-22 mutants were not eliminated by glo-4 mutation.