Fatty acids in the lipids of Drosophila heads: effects of visual mutants, carotenoid deprivation and dietary fatty acids.
Lipids of Drosophila heads were extracted and separated by high-performance thin-layer chromatography. Fatty acid compositions of major phospholipids as well as of triglycerides were analyzed by gas-liquid chromatography. Proportions of the major fatty acids (14:0, 16:0, 16:1, 18:0, 18:1, 18:2, 18:3) varied depending on the lipid analyzed. Docosahexaenoic acid (22:6), common in vertebrate photoreceptors and brain, and arachidonic acid (20:4), a precursor of eicosanoids, were lacking. A comparison of the fatty acid composition of the diet vs. the head suggested that Drosophila can desaturate but may not be able to elongate fatty acid carbon chains. Fatty acid analyses were carried out after the following visual system alterations: i) the transduction mutant where no receptor potential results from a deficit in phospholipase C; ii) an allele of eyes absent; iii) the mutant outer rhabdomeres absent which lacks visual pigment and rhabdomeres in the predominant type of compound eye receptor, rhabdomeres 1 through 6; and iv) carotenoid deprivation which reduces opsin and rhabdomere size. We also evaluated aging by comparing newly-emerged vs. aged wild-type flies. Alterations in fatty acid composition based on some of these manipulations were found. Based on comparisons between flies reared on media differing in C16 and C18, there is an indication that diet readily affects tissue fatty acid composition.