Discrimination of C18 fatty-acids by Drosophila melanogaster larvae and adults (wild-type strain, Dijon 2000)

Fatty acids (FAs) are involved in many metabolic pathways in animals and greatly influence their physiology. In most, if not in all cases, animals need a minimal supply of essential fatty acids in their diet to survive: for example, intake of ω3- and ω6-FAs is necessary to human body which cannot synthesize them. The biological basis of fat perception and preference remains poorly understood. Recent studies have shown that both vertebrates and insects share elaborate olfactory and gustatory sensory systems to respectively decrypt the volatile and the solubilised compounds present in their chemical environment and suggest that the genes underlying the metabolic pathways regulating food intake are very well conserved between Drosophila and vertebrates. To locate food sources and sample food quality, animals need acute chemoperception abilities. Our data show that larvae of Drosophila melanogaster (Dijon 2000 strains) are repulsed by the saturated C18:0 acid - stearic acid - whereas they are more or less attracted to the unsaturated ones, depending on the number and positions of the double bounds. Linolenic acid (C18:3) remains the most attractive one. Stimulation tests (Proboscis extension Reflex, PER) reveal that only adult females present an inhibitory response when confronted to linolenic acid. For the first time, our data suggest that Drosophila larvae and adults are able to discriminate between various concentrations of the commonly encountered C18 FAs