Chemical communication of emigration behavior of Drosophila melanogaster. II. Identification of chemical substances

Fatty-acid preference changes during development in Drosophila melanogaster

Fatty-acids (FAs) are required in the diet of many animals throughout their life. However, the mechanisms involved in the perception of and preferences for dietary saturated and unsaturated FAs (SFAs and UFAs, respectively) remain poorly explored, especially in insects. Using the model species Drosophila melanogaster, we measured the responses of wild-type larvae and adults to pure SFAs (14, 16, and 18 carbons) and UFAs (C18 with 1, 2, or 3 double-bonds). Individual and group behavioral tests revealed different preferences in larvae and adults. Larvae preferred UFAs whereas SFAs tended to induce both a strong aversion and a persistent aggregation behavior. Adults generally preferred SFAs, and laid more eggs and had a longer life span when ingesting these substances as compared to UFAs. Our data suggest that insects can discriminate long-chain dietary FAs. The developmental change in preference shown by this species might reflect functional variation in use of FAs or stage-specific nutritional requirements, and may be fundamental for insect use of these major dietary components.

Intraspecific variation in the effects of mating on emigration activity and fecundity in a natural population of Drosophila melanogaster

Intraspecific variation in the effects of mating on the emigration response behavior and fecundity of Drosophila melanogaster was investigated using isofemale lines of the Himeji population in Japan. The emigration activities of the mated and unmated females were examined with Sakai's population system. The isofemale lines were classified into two groups with respect to the effect of mating on emigration activity; 1) copulation decreased the emigration activity in 26 out of 28 isofemale lines, and 2) higher emigration activity was noted in the mated than in the unmated females in two lines. The percentage of expressed genotypic variance on emigration activity was higher in the unmated females than in the mated ones. Gregarious oviposition did not seem to be related to the decrease of emigration activity in the mated females.