Most living organisms use pheromones for inter-individual communication. In Drosophila melanogaster flies, several pheromones perceived either by contact/at a short distance (cuticular hydrocarbons, CHs), or at a longer distance (cis-vaccenyl acetate, cVA), affect courtship and mating behaviours. However, it has not previously been possible to precisely identify all potential pheromonal compounds and simultaneously monitor their variation on a time scale. To overcome this limitation, we combined Solid Phase Micro-Extraction with gas-chromatography coupled with mass-spectrometry. This allowed us (i) to identify 59 cuticular compounds, including 17 new CHs; (ii) to precisely quantify the amount of each compound that could be detected by another fly, and (iii) to measure the variation of these substances as a function of aging and mating. Sex-specific variation appeared with age, while mating affected cuticular compounds in both sexes with three possible patterns: variation was (i) reciprocal in the two sexes, suggesting a passive mechanical transfer during mating, (ii) parallel in both sexes, such as for cVA which strikingly appeared during mating, or (iii) unilateral, presumably as a result of sexual interaction. We provide a complete reassessment of all Drosophila CHs and suggest that the chemical conversation between male and female flies is far more complex than is generally accepted. We conclude that focusing on individual compounds will not provide a satisfactory understanding of the evolution and function of chemical communication in Drosophila.

Recognition of conspecifics and mates is based on a variety of sensory cues that are specific to the species, sex and social status of each individual. The courtship and mating activity of Drosophila melanogaster flies is thought to depend on the olfactory perception of a male-specific volatile pheromone, cis-vaccenyl acetate (cVA), and the gustatory perception of cuticular hydrocarbons (CHs), some of which are sexually dimorphic. Using two complementary sampling methods (headspace Solid Phase Micro-Extraction [SPME] and solvent extraction) coupled with GC-MS analysis, we measured the dispersion of pheromonal CHs in the air and on the substrate around the fly. We also followed the variations in CHs that were induced by social and sexual interactions. We found that all CHs present on the fly body were deposited as a thin layer on the substrate, whereas only a few of these molecules were also detected in the air. Moreover, social experience during early adult development and in mature flies strongly affected male volatile CHs but not cVA, whereas sexual interaction only had a moderate influence on dispersed CHs. Our study suggests that, in addition to their role as contact cues, CHs can influence fly behavior at a distance and that volatile, deposited and body pheromonal CHs participate in a three-step recognition of the chemical identity and social status of insects.

Diet quality is critical for animal development and survival. Fungi can provide nutrients that are essential to organisms that are unable to synthetize them, such as ergosterol in Drosophila melanogaster. Drosophila studies examining the influence of yeast quality in the diet have generally either provided the diet over the whole life span (larva to adult) or during the adult stage and have rarely focussed on the juvenile diet. Here, we tested the effect of yeast quality in the larval diet on pre-adult development and adult weight, survival, reproduction and food preference. The yeast Saccharomyces cerevisiae was added in three forms in three treatments—live, heated or dried—to food used as the juvenile diet or was not added (empty treatment). Adults resulting from the larvae raised on these four juvenile diets were all maintained on a similar standard laboratory food diet. Our data indicate that yeast quality in the juvenile diet affects larva-to-pupa—but not pupa-to-adult—development. Importantly, adult survival, food preference, mating behaviour and cuticular pheromones strongly varied with the juvenile diet. Therefore, the variation of yeast quality in the pre-adult Drosophila diet affects key adult life traits involved in food search, reproduction and survival.

The presence and the amount of specific yeasts in the diet of saprophagous insects such as Drosophila can affect their development and fitness. However, the impact of different yeast species in the juvenile diet has rarely been investigated. Here, we measured the behavioural and fitness effects of three live yeasts (Saccharomyces cerevisiae = SC; Hanseniaspora uvarum = HU; Metschnikowia pulcherrima = MP) added to the diet of Drosophila melanogaster larvae. Beside these live yeast species naturally found in natural Drosophila populations or in their food sources, we tested the inactivated “drySC” yeast widely used in Drosophila research laboratories. All flies were transferred to drySC medium immediately after adult emergence, and several life traits and behaviours were measured. These four yeast diets had different effects on pre-imaginal development: HU-rich diet tended to shorten the “egg-to-pupa” period of development while MP-rich diet induced higher larval lethality compared to other diets. Pre- and postzygotic reproduction-related characters (copulatory ability, fecundity, cuticular pheromones) varied according to juvenile diet and sex. Juvenile diet also changed adult food choice preference and longevity. These results indicate that specific yeast species present in natural food sources and ingested by larvae can affect their adult characters crucial for fitness.

Food and host-preference relies on genetic adaptation and sensory experience. In vertebrates, experience with food-related cues during early development can change adult preference. This is also true in holometabolous insects, which undergo a drastic nervous system remodelling during their complete metamorphosis, but remains uncertain in Drosophila melanogaster. We have conditioned D. melanogaster with oleic (C18∶1) and stearic (C18∶0) acids, two common dietary fatty acids, respectively preferred by larvae and adult. Wild-type individuals exposed either during a transient period of development–from embryo to adult–or more permanently–during one to ten generation cycles–were affected by such conditioning. In particular, the oviposition preference of females exposed to each fatty acid during larval development was affected without cross-effect indicating the specificity of each substance. Permanent exposure to each fatty acid also drastically changed oviposition preference as well as major fitness traits (development duration, sex-ratio, fecundity, adult lethality). This suggests that D. melanogaster ability to adapt to new food sources is determined by its genetic and sensory plasticity both of which may explain the success of this generalist-diet species.

Pheromones are chemical signals that induce innate responses in individuals of the same species that may vary with physiological and developmental state. In Drosophila melanogaster, the most intensively studied pheromone is 11-cis-vaccenyl acetate (cVA), which is synthezised in the male ejaculatory bulb and is transferred to the female during copulation. Among other effects, cVA inhibits male courtship of mated females. We found that male courtship inhibition depends on the amount of cVA and this effect is reduced in male flies derived from eggs covered with low to zero levels of cVA. This effect is not observed if the eggs are washed, or if the eggs are laid several days after copulation. This suggests that courtship suppression involves a form of pre-imaginal conditioning, which we show occurs during the early larval stage. The conditioning effect could not be rescued by synthetic cVA, indicating that it largely depends on conditioning by cVA and other maternally-transmitted factor(s). These experiments suggest that one of the primary behavioral effects of cVA is more plastic and less stereotypical than had hitherto been realised.