Figure 1.

Representative mirrored gas chromatograms of hexane extracts of two individual female flies resulting from the hsp70-GAL4 × UAS-tra cross. The Upper signal comes from a fly that was subjected to a 37°C heat shock for 60 minutes at 6 hours old, the Lower signal from a fly that was not heat shocked. The profile of the non-heat-shocked fly is qualitatively similar to those of most wild-type D. melanogaster females (30). The two chromatograms are to the same scale: they were aligned and calibrated by using an added standard of hexacosane on each chromatogram (removed for the sake of clarity, and indicated by two vertical lines). Peaks marked with ∗ have been suggested to have a pheromonal function (3–7). Peaks are labeled with a number and were identified by comigration with the results of mass spectrum studies on pools of 10 flies. Peak 1, 7-T; peak 2, n-tricosane; peak 3, 9-pentacosene; peak 4, 7-pentacosene; peak 5, n-pentacosane; peak 6, 7,11-HD; peak 7, 2-methyl hexacosane; peak 8, 7-heptacosene; peak 9, n-heptacosane; peak 10, 7,11-nonacosadiene; peak 11, 2-methyl octacosane. The five substances found on both hs-tra and non-hs-tra females were present in far higher mean levels on non-heat-shocked flies: n-pentacosane, 14 ± 3 ng for hs-tra, (128 ± 5 ng for non-hs tra); 2-methyl hexacosane, 21 ± 3 (262 ± 12); 7-heptacosene, 14 ± 6 (91 ± 12); n-heptacosane, 16 ± 2 (68 ± 3); 2-methyl octacosane, 70 ± 6 (93 ± 3). In all other respects (morphology, locomotor activity), hs-tra flies were normal. Viability at 24 hours was normal, but at 4 days old, hs-tra females showed 40% mortality as opposed to 2% for non-hs-tra flies (data not shown). This result may indicate the importance of cuticular hydrocarbons in protecting flies from dessication (31).