Sex- and age-related changes in the biophysical properties of cuticular lipids of the housefly, Musca domestica.

We examined the biophysical properties of cuticular lipids isolated from the housefly, Musca domestica. Melting temperatures (Tm) of surface lipids isolated from female houseflies decreased from 39.3 degrees C to 35.3 degrees C as the females attained sexual maturity and produced sex pheromone, whereas those prepared from males did not change with age. Lipids melted over a 10-25 degrees C temperature range, and their physical properties were a complex function of the properties of the component lipids. The Tm of total cuticular lipids was slightly below that of cuticular hydrocarbons (HC), the predominant lipid fraction. Hydrocarbons were further fractionated into saturated, unsaturated, and methyl-branched components. The order of decreasing Tm was total alkanes > total HCs > methyl-branched alkanes > alkenes. For 1-day-old flies, measured TmS of hydrocarbons were 1.3-5.5 degrees C lower than TmS calculated from a weighted average of TmS for saturated and unsaturated components. For 4-day-old flies, calculated TmS underestimated Tm by 11-14 degrees C.