Enhancement of diapausing flesh fly puparia with additional hydrocarbons and evidence for alkane biosynthesis by a decarbonylation mechanism

Abstract

Puparia of diapausing flesh flies, Sarcophaga crassipalpis, are lined with twice as much hydrocarbon as their nondiapausing counterparts ( ca 15 vs 7 μg). The quantity of epicuticular hydrocarbon increases throughout the life of the fly, but it is only in the pupal stage that a distinction can be made between diapausing and nondiapausing cohorts. Though some of the additional hydrocarbon is deposited on the exterior surface of the puparium, the bulk of the additional hydrocarbon is on the interior surface of the puparium. The few flies that fail to diapause when reared under short day conditions also produce puparia enhanced with an abundance of hydrocarbon, thus implying that the increase in production of hydrocarbons is not invariably linked to the expression of diapause. Elevation of temperature can increase the quantity of hydrocarbon produced in puparia from nondiapausing flies, but this effect is modest in comparison to the effect of short-day (diapause) programming. In addition, we demonstrate that flesh flies convert fatty acid to alkane utilizing a mechanism that first involves reduction of fatty acid to aldehyde (with ATP, CoA and NADH as required cofactors), then carbonyl removal from aldehyde (no cofactors needed). Thus, we provide the first evidence that hydrocarbon synthesis in insects involves decarbonylation.